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AMMONIUM REMOVAL AND ELECTRICITY GENERATION BY USING MICROBIAL DESALINATION CELLS

Han Wang

October 2011

TRITA-LWR Degree Project ISSN 1651-064X LWR-EX-11-29


Han Wang

TRITA LWR Degree Project 11:29

© Han Wang 2011 Master of Science Degree Project Water System Technology Department of Land and Water Resources Engineering Royal Institute of Technology (KTH) SE-100 44 STOCKHOLM, Sweden Reference should be written as: Han, W (2011) “Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells”

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Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

S AMMANFATTNING Biokemiska bränsleceller har blivit ett intressant alternativ för uthållig energiteknik för avloppsvattenbehandling under de senaste åren. Tekniken kombinerar avloppsvattenrening med produktion av elektricitet för att uppnåen positiv elektricitetsbalans. Genom att tillföra mikroorganismer till anoddelen och användning av en katoddel och mellan dessa delar ett membran för transport av vätejoner kan energi alstras i form av elektricitet och värme. Biokemiska bränsleceller för avsaltning kan genomföras genom att tillföra ytterligare en mellandel försett med ett membran för utbyte av anjoner. Denna studie fokuserar påavlägsnande av ammonium kombinerat med system med biokemiska bränsleceller. Främst två vatten studerades det ena med tillsats av hjorthornssalt (ammoniumvätekarbonat) och det andra med filtrerat rejektvatten från avvattning av rötslam. Experimenten genomfördes vid försöksanläggningen vid Hammarby Sjöstadsverk och vattenkemiska laboratoriet vid inst. för Mark- och vattenresurser, KTH, Stockholm. Genomfört arbete består av ett förberedelsesteg följt av experiment med avsaltning och med elektricitetskälla från biokemisk bränslecell. Som första del i den experimentella delen utvecklades en biofilm på anoden i anoddelen. Därefter studerades effekten av olika koncentrationer av hjorthornssalt (1,5, 2,5, 5 och 15 g/L) och sedan även rejektvatten från avvattning av rötslam. Hastigheten för avlägsnande av ammonium kan erhållas utifrån initialhalt och sluthalt för en viss tidsperiod och alstring av elektricitet utifrån mätning av volt som kontinuerligt mättes med en elektrisk multimeter. Experimentella resultat visade att biokemiska bränsleceller i kombination med avsaltning är en lämplig teknik både för hjorthornssalt och rejektvatten. Avlägsnandet av hjorthornssalt i avsaltningsdelen (mellandelen) uppgick till 53,1%, 52,7%, 60,3% och 27,3% för initialhalterna av ammoniumkväve på 341, 376, 376 respektive 2220 mg/L. För rejektvatten var procentuella avlägsnandet 53,4% och 43,7% för en drifttid på 21 respektive 71 timmar. Utifrån produktion av elektricitet producerade den biokemiska bränslecellen högsta spänningen när permanganat användes i katoddelen (217 mV). Erhållen effekt vid användning av hjorthornssalt var relativt låg (46,7 – 86,6 mW/m3) och var betydligt högre för rejektvatten (190,8-227,7 mW/m3).

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Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

A CKNOWLEDGEMENTS First of all, I would like to thank my supervisor Bengt Hultman, who changed my mind and guided me into this interesting field. His wisdom and strong faith about MFC and MDC always inspired me to rethink what already exists and explore un-known things. I also want to thank professor Elzbieta Plaza and associate professor Erik Levlin for sharing their theoretical knowledge and encouragement to my thesis work. Thanks Dr. Ann Fylkner for the kindly guidance when I had my first step experiment in LWR laboratory. Moreover, I would like to express my sincere thanks to Mila Harding, Lars Bengtsson and Christian Baresel in Hammarby Sjรถstad research station. They spent a lot of time to help me familiarize with the equipment and for their extreme patience in clearing my doubts. My appreciation to be conveyed to Junli Jiang and Pegah Piri for they sparing no effort to help me build up the structure. Without their selfless support, I could not have moved smoothly with my thesis work. A lot of help came from Michelle Maria Jose, who is always encouraging me and gave useful suggestions in the thesis. My specials thank goes to Jingjing Yang, who gave me the most of supports and encouragement at the experimental stage. From the start point till the end of experiment, she guided me on the operation procedures and also gave many critical comments and suggestions about MDC. Finally, to my lovely parents for your immense love and support and without you both I could never succeed.

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Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

T ABLE OF CONTENT Sammanfattning ......................................................................................................................... iii Acknowledgements ......................................................................................................................v Table of content ......................................................................................................................... vii Acronyms and abbreviations...................................................................................................... ix Abstract ........................................................................................................................................ 1 1. Introduction ....................................................................................................................... 1 1.1.

General background .................................................................................................... 1

1.1.1. 1.1.2.

1.2. 1.3.

Risks caused by excessive ammonia nitrogen supply and eutrophication.............. 3 Ammonium removal methods .................................................................................... 3

1.3.1. 1.3.2. 1.3.3. 1.3.4. 1.3.5.

2.

General description of fuel cells.................................................................................. 5

2.1.1. 2.1.2.

2.2.

2.3.

Enzymatic fuel cells............................................................................................................ 5 Microbial fuel cells ............................................................................................................. 6

Working principle of microbial fuel cells ................................................................... 6

2.2.1. 2.2.2. 2.2.3.

pH effects in the MFC ....................................................................................................... 6 Mediator MFCs and MFCs without mediators .................................................................... 7 Thermodynamic theory of MFCs ....................................................................................... 8

Literature review of microbial desalination cells ....................................................... 9

2.3.1. 2.3.2. 2.3.3. 2.3.4.

Working principle of MDCs ............................................................................................... 9 Microorganisms involved in MDC experiments ................................................................ 10 Commonly used media/substrates and operational conditions .......................................... 11 Hjorthorn salt in MDC experiment .................................................................................. 11

Purpose of present study................................................................................................. 11 Materials and methods.................................................................................................... 13 4.1. 4.2.

Framework of whole experiment .............................................................................. 13 Laboratory equipment involved and parameter measurements ............................. 13

4.2.1. 4.2.2. 4.2.3. 4.2.4. 4.2.5. 4.2.6. 4.2.7.

4.3.

Electronic balance ............................................................................................................ 13 Multimeter ....................................................................................................................... 14 Conductivity meter ........................................................................................................... 14 Spectrophotometer .......................................................................................................... 15 Incubator ......................................................................................................................... 17 Resistance decade box ...................................................................................................... 17 Air pump ......................................................................................................................... 18

Process description of MFC and MDC experiments .............................................. 18

4.3.1. 4.3.2. 4.3.3.

5.

Break-point chlorination method........................................................................................ 3 Selective ion exchange method ........................................................................................... 4 Air stripper......................................................................................................................... 4 Biological method .............................................................................................................. 4 Chemical precipitation........................................................................................................ 5

Microbial fuel cells and microbial desalination cells ...................................................... 5 2.1.

3. 4.

Mechanism of water eutrophication ................................................................................... 2 Sources of nitrogen ............................................................................................................ 3

Preparation stage .............................................................................................................. 18 MFC stage ........................................................................................................................ 20 MDC stage ....................................................................................................................... 21

Results and discussion from MFC to MDC stage ........................................................ 24 5.1. 5.2.

MFC stage .................................................................................................................. 24 MDC stage ................................................................................................................. 25

5.2.1. 5.2.2. 5.2.3. 5.2.4.

Scenario 1 ........................................................................................................................ 25 Scenario 2 ........................................................................................................................ 27 Scenario 3 ........................................................................................................................ 28 Scenario 4 ........................................................................................................................ 29

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5.2.5. 5.2.6. 5.2.7. 5.2.8. 5.2.9. 5.2.10. 5.2.11.

6. 7. 8.

TRITA LWR Degree Project 11:29 Scenario 5 ........................................................................................................................ 30 Scenario 6 ........................................................................................................................ 31 Scenario 7 ........................................................................................................................ 32 Scenario 8 ........................................................................................................................ 33 Scenario 9 ........................................................................................................................ 34 Scenario 10 ...................................................................................................................... 36 Comparison and discussion .............................................................................................. 38

Conclusions...................................................................................................................... 41 Limitations of the study .................................................................................................. 41 Suggestions for further research ..................................................................................... 42

Specific suggestions for the used MDC system ...................................................... 42 Use of MDC system as a part of a treatment system .............................................. 43 Development of theoretical concepts ....................................................................... 43 9. References ........................................................................................................................ 45 10. Other references .............................................................................................................. 47 Appendix I.................................................................................................................................. 48 Appendix II ................................................................................................................................ 58 8.1. 8.2. 8.3.

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Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

A CRONYMS AND ABBREVIA TIONS AEM CEM COD DI water DO H_Salt MDC MFC N OCV OM ORR P PEM S SS TN WWTP

Anion Exchange Membrane Cation Exchange Membrane Chemical Oxygen Demand Distilled water Dissolved Oxygen Hjorthorn Salt Microbial Desalination Cells Microbial Fuel Cells Nitrogen Open Circuit Voltage Organic Matter Oxidize-Reduction Reaction Phosphorus Proton Exchange Membrane Scenario Suspended Solids Total Nitrogen Wastewater Treatment Plant

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Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

A BSTRACT Microbial fuel cell (MFC) has become one of the energy-sustainable technologies for wastewater treatment purpose in the recent years. It combines wastewater treatment and electricity generation together so as to achieve energy balance. By inoculating microorganism in the anode chamber and filling catholyte in the cathode chamber, and also with the help of a proton exchange membrane (PEM) between them, the MFC can transfer protons and produce power. Microbial desalination cells (MDC) are based on MFC’s structure and can fulfill desalination function by the addition of a middle chamber and anion exchange membrane (AEM). This study focuses on ammonium removal and electricity generation in MDC system. Mainly two types of liquid were tested, a solution of Hjorthorn Salt and filtrated supernatant. The experiments were performed at Hammarby SjÜstad research station and laboratory of Land and Water Resources department, Stockholm. It consists of a preparation stage, a MFC stage and a MDC stage. Until the end of MFC stage, biofilm in the anode chamber had been formed and matured. After that, solutions of different initial concentrations (1.5, 2.5, 5, 15 g/L) of Hjorthorn Salt and also filtrated supernatant have been tested. Ammonium removal degree can be obtained by measuring the initial concentration and cycle end concentration, while electricity generation ability can be calculated by voltage data which was continuously recorded by a multimeter. Results showed that this MDC system is suitable for ammonium removal in both of Hjorthorn Salt solutions and supernatant. The removal degrees in Hjorthorn Salt solution at desalination chamber were 53.1%, 52.7%, 60.34%, and 27.25% corresponding to initial NH4+ concentration of 340.7, 376, 376 and 2220 mg/L. The ammonium removal degrees in the supernatant were up to 53.4% and 43.7% under 21 and 71 hours operation, respectively. In power production aspect, MDC produced maximum voltage when potassium permanganate was used in the cathode chamber (217 mV). The power density in solutions of Hjorthorn Salt was relative low (46.73 - 86.61 mW/m3), but in the supernatant it showed a good performance, up to 227.7 and 190.8 mW/m3. Key words: Microbial desalination cell, microbial fuel cell, ammonium removal, power production, digested sludge

1. I NTRODUCTION 1.1. General background Today, in this 21th century, we are facing more and more challenges in the aspect of population explosion, natural resource exhaustion and global environment deterioration. In the environmental field, the main problems of public concern include fresh water scarcity and water pollution, greenhouse effect and global warming, acid rain and forest deterioration. It can be noted that the largest proportion of contributor to the water body pollution belongs to insufficiently treated wastewater from domestic households and industries and this phenomenon appeared severely in developing countries such as China and India. For instance, 70% of surface water in India is polluted and 82.3% in China as well (Baidu website, 2011). This situation may reflect the truth that, in most of the developing countries, governments lack in scientific water 1


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TRITA LWR Degree Project 11:29

Figure 1. Eutrophication process (Biosphere, atmosphere and hydrosphere, 2011) resource management experience. To some extent, water scarcity is caused by immature water cleaning technology and low-efficiency water consumption rate. Moreover, ammonia nitrogen problem is especially important and it is always linked to eutrophication. It is well known that high contents of NH4+ and phosphorus could cause eutrophication, which leads to interruption of water body balance. Eutrophication can only happen in the slow-flow water bodies (lakes, estuaries or bays.) when large proportions of nitrogen and phosphorus are injected. Algae and plankton grow rapidly in a rich nutrient environment thereby reducing the dissolved oxygen in the water body and finally causing the death of fishes and other living beings. 1.1.1. Mechanism of water eutrophication In the surface fresh water system, phosphate is the limiting factor of plant growth. However, in the seawater system, the factors are ammonia nitrogen and nitrate because seawater has enough phosphate content. In fact sea water contains only limited contents of ammonia nitrogen and nitrate and thus, if pollutants containing ammonia nitrogen and nitrate are injected into seawater, the restricted balance will be eliminated and some special plants will grow rapidly (Figure 1). The most common dominant species in the seawater are diatoms and chlorella. But after domestic waste water, food and chemical fertilizer industrial wastewater and agricultural drainage are injected into natural water body, with these plenty nutrients, the autotrophic organisms start to grow fast. As time goes by, blue algae will finally be the dominating species. They have a short life-cycle and get easily decomposed by microorganism. The dissolved oxygen in the water will be consumed and hydrogen sulfide is produced; both reactions will deteriorate water quality. Finally, the fishes and other organisms die. When their bodies decay, nitrogen and phosphate elements are released into the water again and the vicious circle begins. Even cut off external nutrient supply, water body is still difficult to recover to normal conditions.

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Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

1.1.2. Sources of nitrogen Agriculture runoff is the main source of nitrogen. It brings large proportions of ammonia nitrogen into the water body and change the original nitrogen balance. A recent study on nitrogen circle conducted by USA Agriculture ministry (China environmental impact assessment, 2011) shows that domestic wastewater and excrement which contain lots of carbamide and ammonia nitrogen may significantly interrupt the nitrogen cycle, Flagellates and Gonyaulax calenella species will be replaced by Nannochloris Genus and Stichococcus Genus (Brett et al., 2010).

1.2. Risks caused by excessive ammonia nitrogen supply and eutrophication Harmful to aquatic animals, mainly fishes Eutrophication will lead to lower transparency of water body, photosynthesis restriction due to the difficulty of sunlight to reach the aquatic plants and gradual reduction in the dissolved oxygen content. At the same time, plankton grows fast and consumes a large proportion of DO. All of these phenomena will be harmful to the aquatic animals, especially the fishes. Moreover, accumulated organic matters at the bottom layer will produce hydrogen sulfide under anaerobic condition, which also cause damage to fishes. Harmful to the human body and livestock when use it as drinking purpose in a longterm basis Water in the eutrophication area contains nitrite and nitrate. If consumed, it might be toxic and harmful to the body.

1.3. Ammonium removal methods Ammonia nitrogen wastewater can be defined as 3 classes based on the concentration: NH3-N > 500 mg/L as high concentration, NH3-N between 50 to 500 mg/L as middle concentration, NH3-N < 50 mg/L as low concentration. Removal methods generally include physical, chemical and biological methods (Table 1), and the most common methods are break-point chlorination method, selective ion exchange method, air stripper method, biological methods and chemical precipitation methods. 1.3.1. Break-point chlorination method This method uses chlorine or sodium hypochlorite which is injected into the wastewater and the NH3-N gets oxidized to N2. When supplied with appropriate volume of chlorine gas, the ammonia concentration will be zero and free chlorine concentration will be the lowest. After the supply volume exceeds this point, the free chlorine concentration will increase and thus it is called break-point (Baidu website, 2011).

Table 1. List of different approaches for NH4+ removal Physical method Chemical method Biological method

Reverse osmosis; Distillation; Soil irrigation and so on. Ion exchange; Air stripper; Break-point chlorination; Incineration; Chemical precipitation; Electro-osmosis and so on. Algal culture; nitrification and so on.

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Cl2  H 2O  HOCl  H   Cl  NH 4  HOCl  NH 2Cl  H   H 2O

NHCl2  H 2O  NOH  2H   2Cl  NHCl2  NaOH  N2  HOCl  H   Cl  The advantage of break-point chlorination method is effective ammonia nitrogen removal rate as well as disinfection. It will be economy efficient if applied to low NH3-N concentration wastewater. However, for higher concentration wastewater, the addition of chlorine will be a large amount. Moreover, chloramine as by-product may cause secondary pollution. 1.3.2. Selective ion exchange method Ion exchange occurs between solid interface and liquid interface. Zeolite in most cases has been chosen as exchange resin because of higher adsorption effect to un-ionized ammonia as well as exchange effect to ionized ammonia. It is a simple and reliable technology, with high efficiency and low cost. It is suitable for treating middle and low concentrated (< 500 mg/L) wastewater (Baidu website, 2011). 1.3.3. Air stripper By using gas to supply wastewater, ammonia nitrogen can be transferred from the liquid phase to gas phase. It takes advantage of the difference between real concentration and balance concentration in both phases. When pH is adjusted to alkalinity, ionized ammonia (NH4+) turns to free ammonia (NH3). With an air stripper, NH3 can be removed at the efficiency of 60-95% (Baidu website, 2011). After that, ammonia gas can be collected by hydrochloric acid and produce ammonium chloride which could be used to soda ash production process. The advantage of the process is that it is simple and stable. However, it is of low efficiency if wastewater temperature is low, and thus it might be not be suitable for operation in winter period. 1.3.4. Biological method The biological method to remove ammonia nitrogen is a process where various bacterial reactions take place and by passing through nitrification and denitrification processes, finally nitrogen gas is formed. Generally, the nitrification process should be under aerobic condition. The aerobic nitrifying bacterium oxidizes ammonia nitrogen into nitrite or nitrate using carbon source in the wastewater. The reaction contains two parts; the first step is the transformation of ammonia nitrogen to

Figure 2. Nitrogen conversion circle 4


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

nitrite by nitrosomonas bacteria and the second step is the transformation of nitrite to nitrate by the participation of nitrobacteria. Nitrosobacteria and nitrobacter bacteria are autotrophic bacteria and by taking part in the redox reaction they gain energy.

2 NH 4  3O2  2 NO2  2H 2O  4H  2 NO2  O2  2 NO3 After this, denitrification takes place and nitrate is transformed into nitrogen gas by denitrifying bacteria (Figure 2). The biological treatment method can be applied to remove various nitrogen compounds and the efficiency of 70-95% can be achieved. It also has limited secondary pollution and is economical. Thus, biological method is the most used technology all over the world, despite its large land occupation. 1.3.5. Chemical precipitation Chemical precipitation method mainly relies on the chemical reaction to remove ammonia nitrogen compounds. Based on appropriate temperature, pH value, pressure, residence time etc., pollutants will form sparingly soluble compounds or insoluble gas, so as to purify wastewater. The principle behind chemical precipitation is that NH4+, Mg2+, PO43react with pollutants and form a precipitate. This method can be used to recycle ammonia nitrogen as agriculture fertilizer.

2. M ICROBIAL FUEL CELLS AND MICROBIAL DESALINATI ON CELLS

2.1. General description of fuel cells Fuel cell in general refers to a device that directly can convert chemical energy into electrical energy. It produces electricity in the anode chamber while at the same time transfer electrons from anode to cathode. The anode chamber and cathode chamber is separated by an ion or proton exchange membrane and this membrane plays a critical role in closing the circuit and electricity generation. It is a passive device that only allows protons to pass through the membrane so that an electrical circuit is formed. Fuel cells are different from batteries because it is sustainable if energy rich compounds are continuously supplied, whereas, batteries consume the limited volume of energy stored by chemical compounds in a closed system (Brett et al., 2010). Biofuel cells are one of the most important type of fuel cells. It is defined mainly by way of electron formation. In a biofuel cell, electrons are generated by the use of biocatalysts. Based on the biocatalyst that has been used, biofuel cells can be characterized as enzymatic fuel cells (EFC) or microbial fuel cells (MFC). The EFC and MFC use enzymes and bacteria respectively (Brett et al., 2010). 2.1.1. Enzymatic fuel cells Immobilized enzymes, especially redox enzymes are commonly used as catalysts in enzymatic fuel cells. It is efficient to accelerate the specific reactions. One of the advantages of EFC is high turnover rate because of small size of enzymes as well as high specificity of the reactions from the anode and cathode. Thus, EFC provides the possibility to construct low energy power supply units for small electrical equipment.

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2.1.2. Microbial fuel cells Microbial fuel cells are almost the same as enzymatic fuel cells, but the main difference is the use of bacteria as a power source. The oxidation reactions happen inside the bacteria, and then electrons are transferred to the anode via cell membrane. With the biomass as substrate and microorganisms as the catalyst, microbial fuel cells can work continuously under stable nutrient supply conditions.

2.2. Working principle of microbial fuel cells A standard MFC should consist of two chambers, anode chamber and cathode chamber respectively (Figure 3). The anode chamber is used to inoculate liquid media. In many cases of wastewater treatment process, activated sludge or digested sludge is inoculated as bacteria source. By feeding with specific nutrients and ensuring anaerobic conditions in anode chamber, advantage bacteria are growing up and metabolism take place. The most important step, which is the electricity generation, occurs in this chamber. In the metabolism process, carbohydrate glucose is oxidized under anaerobic condition and electrons are released by enzymatic reactions. Those electrons are to be reduced after transferring to the cathode chamber (Wikipedia, 2011). The simplified anode half-cell reaction of oxidation of glucose is as follows.

C6 H12O6  6H 2O  6CO2  24H   24e While in the cathode chamber, oxygen is required so as to reduce electrons and maintain pH neutral.

6O2  24H   24e  12H 2O 2.2.1. pH effects in the MFC In the MFC, it is vital to maintain the pH in the anode chamber and feed substrate to ensure the target bacteria groups grow. The microorganisms prefer neutral pH rather than acidic or basic condition. Thus, monitoring pH value in the MFC is necessary so as to avoid wide variations. If the interval time of substrate replacement stands too long, pH value in the anode chamber may drop. The growth and metabolism of the microorganism can be inhibited or even halted. An explanation of this inhibition phenomenon is the change in the shape of proteins due to the presence of more H+ ions.

Figure 3. MFC structure and internal reactions (Brett et al., 2010) 6


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Moreover, ion exchange membrane can be another important factor in pH maintenance. By placing membrane between the anode chamber and cathode chamber, different aquatic environments occur and different pH ranges arise. The membrane inhibits oxygen transfer from cathode chamber to anode chamber, which is vital to ensure anaerobic condition and also to the corresponding pH range. Also, the bacteria that take part in the biological reactions in the anode chamber cannot move freely. With the membrane, the bacteria in the anode chamber can have a relatively stable environment for favorated group growth. More importantly, membrane plays the role as that of a bridge, to transport ions through the membrane and continue with cathode chamber reactions. Movement of protons from the anode chamber can make an ionic equilibrium, and thus the movement efficiency mainly depends on ionic concentration gradient and membrane material. If protons cannot be transported at a sufficient rate, the pH will surely drop at the anode chamber and rise at the cathode chamber while charge balance can still make equilibrium because of other ions complement (Brett et al., 2010). 2.2.2. Mediator MFCs and MFCs without mediators Mediator MFCs uses some specific mediators to help electrons transfer from the inside of the microbial cell membrane to the outside, so the electrons can reach the electrodes. Since the electrodes are solid entities, they are impossible to reach the inside of the microbial cells. Therefore, mediators play a role of a bridge to work effectively. Thionine, methyl blue, humic acid, methyl viologen, neutral read belong to the group of mediators that can help to transfer electrons and cope with the problem of electrochemically inactive microbial cells (Wikipedia, 2011). Mediatorless MFCs are basically divided into two different types, one is direct oxidation of secondary fuels at the anode, and the other one is to use biofilm. Direct oxidation of secondary fuels at the anode is a reliable MFC method based on the catalyst usage at the anode. Those fermentative microorganisms take advantage of molecular hydrogen as nutrients and with the addition of a catalyst (such as platinum) on the anode, the conversion efficiency can be extremely high. Nevertheless, the catalyst may also cause problems like low stability and high costs of platinum.

Figure 4. MFC without mediator using biofilm to produce electricity (Brett et al., 2010) 7


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Thus, it would be difficult to put this approach into large-scale practice at present research level. The more commonly used approach is biofilm MFC (Figure 4). It is based on the direct physical and electronic interaction between the anode and bacteria. By continuous feeding and replacing substrates to the anode, the bacteria colony will slowly grow on the electrode in the anode chamber. It may take a few days or a few weeks according to different articles, but after that it becomes stable, the biofilm will adhere to the electrode surface and produce electricity. The internal mechanism of power production is still unclear and requires further research, and three theories have been proposed (Brett et al., 2010): i. Iron molecules exist on the surface of electrochemically active redox enzymes membrane. These iron molecules play a role as a bridge to enable electrons transfer to external materials (anode electrode) and do not require any chemical assistance to complete the transfer process. ii. The pili or protein appendages may be conductive and can transfer electrons when the pili have physical contact with the electrode in the anode chamber. iii. Some of the microorganisms can self-produce micromolar amounts of their own redox mediators and these products can be directly used as mediators to conduct electrons. Moreover, when microorganisms oxidize the organic matter dissolved in the substrate, the protons are released into the water and are transferred to the cathode via proton exchange membrane. In the cathode chamber, oxygen will be supplied and the protons then combine with water. If platinum is coated to cathode surface, the electricity generation efficiency will be higher compared to bare electrode because platinum is able to donate electrons during oxygen reduction to produce water. While using it as the anode electrode, platinum can also work well as electron acceptor in the oxidation reaction. Based on what has been discussed above, biofilm MFC has been chosen as an experimental subject and will be described later. 2.2.3. Thermodynamic theory of MFCs In a reversible chemical reaction, the Gibbs free energy equation can be written as (Bard 1985, Newman 1973):

G  G0  RT ln() Where:

G = Gibbs free energy

G 0 = Gibbs free energy under standard conditions R = universal gas constant T = absolute temperature

 =reaction quotient of the product divided by the reactants Logan and his research group indicate that the Gibbs free energy under standard conditions is derived from the tabulated energies linked to the formation for OC (Logan 2006). If give a negative sign to the value of G , it then means maximum theoretical work and electromotive force (emf) can also be deduced (Logan, 2006).

Gr  Wmax  Eemf  (Q)  Eemf  (n  F ) where

Wmax =

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Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Eemf =

Q = n = F =

potential difference between the cathode and anode charge

number of electrons per reaction Faraday’s constant Rearrangement of equations above,

Eemf  

Gr (n  F )

0 Eemf 

Gr0 (n  F )

At the standard conditions,

Therefore, the overall electromotive force in all conditions can be described as, 0 Eemf  Eemf 

RT ln() nF

Finally, the MFC second law efficiency is given as the ratio between actual work output and maximum theoretical work. The formula is valid under the assumption that simple reactions evaluated at the anode and cathode are treated as parallel as more complicated reactions in biodegradable wastewater (Zielke, 2006).

MFC 

Wactual Vmeasured  (n  F ) Vmeasured   Wmax Eemf  (n  F ) Eemf

where

MFC = Wactual = Vmeasured =

MFC second law efficiency Actual work output Measured voltage potential

2.3. Literature review of microbial desalination cells 2.3.1. Working principle of MDCs Microbial desalination cells are based on the MFC structure and functions, but with 3 chambers and separated by cation exchange

Figure 5. Simplified MDC structure (Cao et al., 2009) 9


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TRITA LWR Degree Project 11:29

membrane (CEM) and anion exchange membrane (AEM) (Figure 5). It is a new technology that can be used in wastewater treatment and potable water production from brackish water or seawater by means of transfer of different ions from middle chamber (desalination chamber) to anode and cathode chamber. As shown in Figure 5, the AEM is closed to the anode chamber while CEM is closed to the cathode chamber. When the MDC starts to work, the microorganisms oxidize substrate in the anode chamber and release the same amount of protons into the water. The protons cannot pass through AEM (AEM only allows anions across the membrane; the primary species are Cl-, HCO3- and HPO4-). Based on the pH neutrality principle, the anions in the middle chamber have to be transferred to the anode chamber. While the similar situation happens in cathode chamber, the reaction in this chamber results in the reduction of protons. CEM prevents anions in the cathode chamber transfer to the middle chamber, the membrane mainly allows Na+, K+ and H+ in the middle chamber to pass through (Cao et al., 2009). Therefore, the result is transportation of protons and anions in the middle chamber (desalination chamber) and the purpose of desalting can be achieved. Compared with traditional approaches, the MDC method does not require water pressure or electrical energy (oxygen aeration in the cathode chamber is selectable and will be discussed later). Instead, by using MDC approach, electricity can be generated during proper operation process. (Cao et al., 2009) 2.3.2. Microorganisms involved in MDC experiments In the sediments many kind of metal-reducing bacteria are easily found. They utilize insoluble electron acceptors (Fe3+ and Mn4+) in the surroundings. Shewanella putrefaciens is one type and its specific cytochromes at the outer membrane make the cell active (Kornell et al., 2005). Another bacteria family called Geobacteraceae can form biofilm on the anode electrode after feeding with some days, and then the biofilm transfers electrons from acetate (Bond and Lovley, 2003). Based on Chaudhuri and Lovleyâ&#x20AC;&#x2122;s research, Rhodoferax species can take glucose as substrate and convert it to CO2. The conversion efficiency is quite high and can reach as much as 90%. The rest groups of bacteria perform similarly at 1-17 mW/m2 graphite surfaces (Table 2). Even though these bacteria all show high electron transfer efficiency, they still have drawbacks. Most of them require specific substrates such as acetate or lactate. They grow slowly and to obtain a stable output. It requires lots of time, few days or even few weeks, depending on the feeding approach and laboratory conditions etc. Moreover, compared to

Table 2. Microorganism in MFC/MDC (Kornell et al., 2005) Microorganism References Desulfuromonas acetoxidans Bond et al., 2002 Geobacter metallireducens Bond et al., 2002 Bond and Lovley 2003, Kim et al., Shewanella putrefaciens 1999a, Kim et al. 1999b, Kim et al., 2002, Schroder et al., 2003 Geobacter sulfurreducens Bond and Lovley 2003 Rhodoferax ferrireducens Chaudhuri and Lovley 2003 Clostridium beijerincki Park, et al., 2001 10


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

the mixed culture, the axenic bacterial culture holds a relatively low position because of low energy transfer efficiency. The mixed bacterial cultures are easily adaptable to different substrates and environments, with very high power output (Rabaey et al., 2004a, b). Active mixed cultures can be gained from many places such as sediments or wastewater treatment plant (WWTP). Kim et al., (2004) and Rabaey et al., (2004) indicated nitrogen fixing bacteria (such as Azospirillum) and facultative anaerobic bacteria (such as Pseudomonas and Enterococcus), respectively. 2.3.3. Commonly used media/substrates and operational conditions The substrates most commonly used in MDC are acetate, lactate and glucose. They are easily dissolved in water and play a role as nutrient supplier. In the MDC, before the set-up of the chambers, electrodes and wire, it is vital to fix which type of chamber or electrode should be used. For the anode part, the electrode material to be selected should meet requirements like adequate surface for the formation of biofilm; conductive surface. If the MDC uses recycle system, it is better to make sure the electrode will not affect the free flow of influent and effluent. Generally, anode electrode has several options such as graphite felt, graphite granules and plate shaped plain graphite. On the other hand, electrodes in the cathode chamber can be basically divided into two situations, with or without oxygen. The cathodes are often either platinum-coated carbon electrodes with extra oxygen supply or plain carbon electrodes immersed in ferricyanide solution. From up-to-date experiment results, it can be concluded that the addition of ferricyanide works better than the others. For instance, Sangeun et al., (2004) and Logan (2004) inoculated wastewater sludge with 20 mM acetate and got a maximum of 0.097 mW within 120h after inoculation. 2.3.4. Hjorthorn salt in MDC experiment Hjorthorn salt is a Swedish name of deer horn salt. It has its name because it was obtained from deer horns. It mainly consists of ammonium hydrogen carbonate (NH4HCO3). Usually it is used for food purpose: bakery. It is easily decomposed by heating, and the product will be ammonia and carbon dioxide. In the MDC system, Hjorthorn salt can be used to simulate ammonium removal. As AEM and CEM applied and biofilm formed, protons will be released into water in the anode chamber while cation will be required in the cathode reaction. Thus, NH4+ and HCO3- in the Hjorthorn salt solution will be attracted by cathode and anode chamber respectively. By this way, the NH4+ can be removed from the desalination chamber.

3. P URPOSE OF PRES ENT ST UDY This MDC research study was performed in two main stages. The first stage is incubation period and aims at formation of biofilm and stable output of electricity; the second stage is test period and the goal of ammonium removal by using different ammonium concentration solutions. With this experiment, it is possible to have a clear idea of “what is MDC?”, “how to operate a simple small scale MDC?” and “Can we use MDC to remove ammonium?”. Till date, MDC is still at its beginning stages and very limited attention has been put on ammonium removal by using MDC. Thus, it might be interesting to test many different parallel samples under short periods. 11


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TRITA LWR Degree Project 11:29

1. Preparation stage/MFC stage: Setting up of two parallel MFCs, inoculating different kinds of sludge and then feeding with different nutrients (sugar sold in the supermarket and acetate solution) so as to find out biofilm formation times, maximum voltages and open circuit voltages and efficient nutrients. 2. Ammonium removal stage/MDC stage: Combining the two MFC’s into one MDC and keeping the previous anode electrodes (with biofilm on the electrode), AEM and CEM are inserted adjacent to the anode chamber and cathode chamber respectively. By changing test solutions in desalination chamber and catholyte, it is possible to collect these data:  Ammonium removal degree from the addition of artificial solution (Hjorthorn salt) under different replacement times;  Internal resistance at different running stages in MDC (start-up phase, rise phase, peak phase, decline phase, low stable phase);  Energy aspect: Maximum voltage, maximum power and power density;

Figure 6. Flow chart of experiment 12


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Table 3. Equipment list in the MFC and MDC experiment Name Air pump Mixer Multimeter Conductivity meter Spectrophotometer Electronic balance Incubator Resistance decade box

No. 302S WM/220/F BS1901W Cond 330i XION 500 LA-110

Country of origin Sweden England Sweden Germany Germany Germany Germany

Description Christian Berner AB Fisons Scientific Apparatus Caltek Industrial (H.K.) Ltd. WTW 82362 Wellheim DR LANGE ACCULAB MEMMERT

RBOX-408

Taiwan

Lutron Electronic CO., LTD.

4. M ATERIALS AND METHODS 4.1. Framework of whole experiment The experiment process (Figure 6) is divided into 3 stages: preparation stage, MFC stage and MDC stage. It was started from 29th, June and ended on 17th, August. Details will be explained in later 4.3.

4.2. Laboratory equipment involved and parameter measurements During the 2 month of experiment process, the equipment been used are listed as Table 3 shown. 4.2.1. Electronic balance The electronic balance used during the whole experiment is LA-110, ACCULAB Corporationâ&#x20AC;&#x2122;s product, made in Germany.

Figure 7. Electronic balance used in this experiment 13


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TRITA LWR Degree Project 11:29

Figure 8. Multi-meter to test voltage data LA-110 is an analytical balance with high performance. The display update only requires 0.1 to 0.4 second and also with selectable weighing units (g, kg, GN, mg, ct, lb, oz, thl, tlt, dwt etc.). The maximum capacity is 110 g, which means it is only for small scale experiment usage. The readability and reproducibility specifications are 0.0001 g and ±0.0001 g, respectively. LA-110 is frequently used in the experiment (Figure 7). It was mainly responsible for weighing chemical compounds in addition to be added to MFC/MDC as nutrient solutions. In this whole experiment, chemical compounds includes sugar, potassium chloride, sodium chloride, disodium hydrogen phosphate, potassium hydrogen phosphate, sodium acetate, ammonium chloride, magnesium chloride hexahydrate and calcium chloride hexahydrate etc. 4.2.2. Multimeter Multimeter is a hand-held electronic measuring device that can be applied in many circumstances. It has lots of basic functions such as voltage, current and resistance measurement. Usually it provides measurement function of both alternating current/voltage and direct current/voltage. In this experiment, all of the measurements are set as direct current/voltage. BS1901W series has been chosen as the voltage measurement device (Figure 8). It is a 3 1/2 Digits all-ranges protection meter with battery test. The measuring range is between 200 mV to 600 V and DC current from 20 mA to 200 mA. Due to limitation of present lab conditions (no data logger is available), it is possible to record voltage data by connecting multimeter to the circuit 24 hours together with video monitoring (for instance, open video monitoring software before the lab is closed, and on return the next morning, voltage data at every moment can be seen from the software “YouCam”). 4.2.3. Conductivity meter Conductivity is important in MFC/MDC test. Previous research (Cao, 2009) has been shown that with a higher conductivity, the MFC/MDC performs more efficient and gives higher maximum voltage output. Conductivity meter is such a device that can measure conductivity in solutions. It is widely known that salt content reflects the 14


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Figure 9. Conductivity meter in use strength of conductivity, the higher salt concentration, the higher conductivity the solution has. Cond 330i meter (Figure 9) is a robust and waterproof handheld device with parallel temperature display. It also provides manual temperature compensation with linear temperature function and non-linear function for ultrapure water and natural waters. The working temperature is between -5 â&#x201E;&#x192; to 105 â&#x201E;&#x192; and resolution is 0.00 ď ­ S / cm . In this experiment, due to the small volume of MFC and MDC (8.4 mL volume in each chamber), it is difficult to measure conductivity by using Cond 330i meter (The normal procedure of measurement is to use probe immersed in the solutions, but in this situation there is not enough solution). Therefore, as a parameter, conductivity value will only appear occasionally in the text. 4.2.4. Spectrophotometer Spectrophotometer is one kind of photometer that makes it possible to test the intensity based on the light source wavelength. Spectral bandwidth and linear range of absorption are two vital characteristics of

Figure 10. Spectrophotometer in the Lab 15


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TRITA LWR Degree Project 11:29

Figure 12. Cuvettes used in the measurement spectrophotometer. Due to the fast speed and high precision, it is widely used for measurement of transmittance/reflectance of solutions. Spectrophotometer used in the laboratory is XION 500, DR LANGE Corporation, made in Germany (Figure 10). Simply attach ProID clips to the cuvette containing the sample, read the identification with the scanner and read out the right measurement procedure. It ranges from 340 to 900 nm, wavelength accuracy is Âą2 nm with automatic zeroing. In this MFC/MDC experiment, it might be the most crucial device because all of the ion concentrations are measured by spectrophotometer. The concentration tested in this device included ammonium and COD. The process of ammonium measurement is: Firstly, the rough value of solution was estimated; secondly, the solution was diluted in a 50 mL flask and mixed; thirdly, 0.2 mL solution was extracted from flask and

Figure 11. Incubator in Hammarby SjĂśstadsverk Lab 16


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Figure 13. Resistance decade box been added to the cuvette (LCK 302 cuvette ranging from 47 -130 mg/L of NH4-N, Figure 12) and been shacked; fourthly, 15 minutes was for cooling and then tested in the spectrophotometer. The value will be finally shown in the screen and NH4+ concentration can be calculated. 4.2.5. Incubator Incubator is a container that provides a constant temperature (adjustable) so as to ensure a stable growing environment for microorganism. Usually the incubator used in the laboratory is electric heating, but the old method of using hot water may also achieve the heating function. At the Hammarby SjĂśstadsverk Laboratory (as shown in Figure 11), electrical heating made by MEMMERT, Germany is used. During the experiment, incubator was used when membrane required to be soaked in DI water before 24 hours of usage. 4.2.6. Resistance decade box Resistance decade box is a device that can change external resistance and at the same time the resistance value can be displayed. By connecting it to the MFC/MDC circuit, external resistance can be adjusted to test internal resistance. In this MDC experiment, internal resistance is required to be measured not only because it is a key factor that affects electricity generation, but also reflects the advantages/drawbacks of MFC/MDC structures and membrane block effect. Generally, when the external resistance equals to the internal resistance, the value of maximum power density Pm will reach the peak.

Pm ď&#x20AC;˝

E2 4 Ri

where

Pm =

Maximum power density

E = Ri =

Electromotive force Internal resistance 17


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TRITA LWR Degree Project 11:29

2 1

Figure 14. Air pump Thus, it can be seen that MFC/MDC power output is restricted by E and Ri. E is the driving force of the cell, due to the reactions that happens in the MFC/MDC, it is difficult to enhance E. However, the internal resistance is closely linked to MFC/MDC structure and there is a great space for improvement. Thus, it is vital to reduce internal resistance in the MFC/MDC. The first part is to measure true internal resistance by adjusting external resistance to draw a polarization curve VS power density-current curve. In this case, RBOX-408 (LUTRON Electronic Enterprise CO., LTD) has been chosen as external resistance. It is able to provide a wide range of resistance from 1 ohm to 11111110 ohm (Figure 13). The working temperature is between 0 to 50 degrees and accuracy is Âą1%. The operation is simple: by switching the button with different combinations, the preferred resistance value can be obtained. 4.2.7. Air pump The only purpose of using air pump is to provide air in the cathode chamber. The cathode chamber with mixed catholyte continuously requires oxygen for water formation purpose. The soft pipe is across the pump and on one side (No.1 in the Figure 14) the pipe is exposed to air while the other side (No. 2 in the Figure 14) is connected to a well-sealed probe which is inserted to catholyte. Due to the rotation of the pump, air is continuously transferred to the catholyte and catholyte is almost saturated.

4.3. Process description of MFC and MDC experiments As mentioned in Figure 6, the whole experiment process is divided into 3 parts: preparation stage, MFC stage and MDC stage. 4.3.1. Preparation stage At the first stage, it is interesting to see which sludge (activated sludge or digested sludge) is able to produce more electricity. Thus, in the preparation stage, both activated sludge and digested sludge were fed by sugar or mixed nutrients in order to screen out suitable microorganism. The process was carried out in the following way: Activated sludge and digested sludge were obtained from Hammarby SjĂśstadsverk by using the container (No. 1) shown in Figure 15. 18


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

2

3

1

Figure 15. Preparation stage: container Preparation stage: container. Sludge was supplied to a 50 mL volume bottle (No. 2) for feeding purpose. Sugar (No. 3) was fed every 24 hours and continuously for 5 days as mentioned in the Table 4. The process of adding sugar should be as quick as possible to ensure anaerobic conditions. The dosage operation was carried out by electronic balance. During 7th July to 12th July, digested sludge was extracted and stored in two different bottles. As parallel samples, these two bottles were fed by mixed nutrients and sugar, respectively. The sludge volume and dosage can be seen in Table 4.

Table 4. Nutrient solution contents Period Nutrient

Activated sludge 06.29 - 07.04 Sugar

Digested sludge Food 1 07.07 - 07.12 Mixed solution

Digested sludge Food 2 07.07 - 07.12 Sugar

CH 3COONa  3H 2O  1.6 KH 2 PO4  4.4 K 2 HPO4  3H 2O  3.4

Conc. (g/L)

1

NH 4Cl  1.5

1

MgCl2  6H 2O  0.1

Sludge volume

30 mL

CaCl2  2H 2O  0.1 KCl  0.1 22 mL (17 mL sludge+5 mL DI water) 0.0352g

24 mL (19+5)

0.0968g 0.0748g

Dosage

0.03 g

0.033g 0.0022g 0.0022g 0.0022g

19

0.024 g


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TRITA LWR Degree Project 11:29

Figure 16. CEM and a new assembled MFC 4.3.2. MFC stage Two sets of MFC package were ordered from Reading University, UK. They required to be assembled before usage. When building MFC together with cation exchange membrane inside, the whole container should be soaked in the DI water for 24 hours. The purpose of this is to moist the carbon paper electrodes as well as CEM (Figure 16). This MFC (Reading University, made in UK) is small scale and sealed by rubber. Electrodes were cut into suitable size and placed into the chambers, and most importantly, the electrodes were crossed through the hole and can be linked to the outside. While at the same time, measuring the dimension of each chamber, it was found that (Figure 17): Chamber volume = Length * Width * Height = 4 cm * 3 cm * 0.7 cm = 8.4 mL Electrode area = Length * Width = 4 cm* 2.7 cm = 10.8 cm2 After being soaked in DI water for 24 hours, the container would be empty and then have to wait a few minutes to dry naturally. A 2.5 g of activated sludge (fed with sugar in the previous 5 days) and injected into anode chamber, and the rest space was occupied by supernatant in the fed bottle. The holes were sealed properly by PTFE and adhesive tape as soon as possible. After the anode chamber has been done, the next step was injecting catholyte in the cathode chamber. The catholyte was made by 4 chemical compounds as shown in Table 5. As a matter of convenience, 500 mL of catholyte was made and stored in the fridge. The final step was to connect the circuit by simple electric wires and clamps. The external resistance was set to 220 ohm with a multimeter to measure its voltage, the measuring range set to 200 mV. After the circuit was connected, voltage change was recorded. The room temperature was checked was checked and 23Âą1â&#x201E;&#x192;. The evaporation effect is significant due to the capillarity action. Liquid in the cathode chamber gets evaporated easily through the exposed part 20


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Figure 17. Structure of MFC in use of carbon paper electrode. Thus, for bacteria safety and membrane performance, it is necessary to keep liquid level and supply catholyte every 24 hours (anode chamber does not have these problems since it was blocked and has no air contact). The anode chamber, however, requires substrate replacement. As microorganism in the anode chamber lives on nutrients and uses them to form biofilm, the nutrient solution (Table 4) should be replaced every day. The ideal condition is to extract all substance from the anode chamber and put it into centrifuge, and then replace the liquid supernatant. However, since there was no centrifuge available at the lab, liquid was kept stable and liquid from the upper layer was extracted as an alternative way for replacement purpose. Most importantly, after 7 days of running, MFC with activated sludge could not produce detectable electricity (resolution: 1 mV) and two bottled digested sludge fed by different nutrients were taken over by it. They followed the same operation procedures but slight difference in the substrate constitute. The NH4+ concentration and COD measurement were not proceeding in this stage and the value will be absent in the result tables. This stage was focused on biofilmâ&#x20AC;&#x2122;s formation and electricity generation. 4.3.3. MDC stage MDC stage is the core component in the whole thesis work. It has two main tasks, ammonium removal and electricity generation. MDC build-up: When two MFCs are stabilized to produce electricity, then it could be possible to consider MDC construction. The small size of container may cause difficulties to replace substrate, therefore two anode chambers instead of one (Figure 19) maybe considered wisely. Before constructing

Table 5. Catholyte composition in MFC process Chemical component KCl NaCl Na2HPO4 KH2PO4

Concentration (g/L) 0.1 1.0 2.75 4.22 21


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TRITA LWR Degree Project 11:29

Figure 18. Anion exchange membrane soaked in salt solution before usage the MDC, another membrane called anion exchange membrane (Membrane international, US), requires to be soaked in NaCl solution for 24 hours. Here I weighed 12.5 g of NaCl powder and dissolved it into 250 mL DI water (Figure 18). The biofilm already formed in both of the anode electrodes was moved to the new structured MDC. AEM was closed to anode chamber and CEM was closed to cathode chamber (Figure 19). The gaps were sealed by rubber and electrodes were connected to resistance box by wire lines. The external resistance first chosen was 440 ohm and which was replaced by resistance box purchased on 27th, July. Moreover, after the digested sludge is injected in the anode chamber, use nitrogen gas to expel oxygen for 3 minutes. After the MDC construction finished, it was shown as Figure 21. MDC operation: With a probe supplying oxygen continuously, the MDC started to work. It tested 10 scenarios during 22 days (from 26th, July to 17th, August) and basically followed the same procedure (Figure 22).

HCO3-

Figure 19. MDC construction plan 22

NH4+


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Figure 21. Real product of MDC The normal procedure is firstly to measure the input NH4+ concentration and COD value, and then after several hours’ reaction measure the output NH4+ and COD value and finally calculate the ammonium removal degree and COD change. Measurement method has been described in 4.2.4 Spectrophotometer. During the cycle time, it is required to record voltage data continuously. As mentioned before, as there was no data logger of voltage parameter in the lab, laptop camera with the software called “YouCam” was applied as substitution (Figure 20). Set the photo interval time as 10 seconds and put the multimeter in front of camera, it can be totally the same effect as data logger.

Figure 20. “YouCam” software’s interface of video monitoring 23


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Figure 22. Working conditions of MDC system There are totally 10 scenarios that has been tested (Table 6). No. 1 to No.5 scenarios were designed to test pure and simple chemical solution performance in MDC system, since the Hjorthorn salt mainly contains NH4HCO3. No.6 to No. 8 scenarios were more valuable to provide data that was more closed to reality (filtrated supernatant and even wastewater with low NH4+ concentration). No. 9 and No. 10 were designed to see the influence of different catholyte, based on the previous catholyte composition, 20 mg/L KMnO4 was added to the original catholyte and tested the NH4+ removal rate and power generation ability. It is necessary to mention that the resistance box purchased on 27th, July. Therefore, experiments performed before that day could not measure the internal resistance.

5. R ESULTS AND DISCUSSIO N FROM MFC TO MDC STAGE The MFC stage, as mentioned in Figure 6, is mainly responsible for biofilmâ&#x20AC;&#x2122;s formation while in the MDC stage, the attention is more focused on ammonium removal and electricity generation. Therefore, voltage data in both of the MFC stage and MDC stage will be presented in the Appendix and core data and voltage-time figures will be shown in the text.

5.1. MFC stage During 12th July to 26th July with 334 hours of running, two sets of MFC have been successfully launched with different nutrient solutions.

24


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Table 6. Scenarios tested in MDC stage No

Desalination chamber

1

H_Salt 1.5 g/L

2

H_Salt 2.5 g/L

3

H_Salt 2.5 g/L

4

H_Salt 5 g/L

5

H_Salt 15 g/L

6

Filtrated supernatant

7

Filtrated supernatant

8

Filtrated influent wastewater

9

H_Salt 15 g/L

10

H_Salt 15 g/L

Process description Test the removal degree as well as electricity generation under 48 hours. Test the NH4+ removal degree as well as electricity generation under 22 hours. Test the NH4+ removal degree as well as electricity generation under 45 hours. Test the NH4+ removal degree as well as electricity generation under 67 hours. Under the high NH4+ concentration condition, test NH4+ removal degree as well as electricity generation under 24 hours. Test the filtrated supernatant sample in 21 hours. Sample was taken from Hammarby Sjöstadsverk. Test the filtrated supernatant sample as comparison in 71 hours. Sample was taken from Hammarby Sjöstadsverk. Test the filtrated influent wastewater sample under 24 hours. Sample was taken from Hammarby Sjöstadsverk. Under the high NH4+ concentration condition, add the KMnO4 to the former catholyte, test the electricity generation performance under 24 hours. Under the high NH4+ concentration condition, add the KMnO4 to the former catholyte, test the electricity generation performance under 92 hours. NH4+

The MFC of FOOD 2 produced maximum voltage of 13.4 mV and OCV of 233.5 mV under 400 ohm resistance condition. In the MFC stage, the MFC of FOOD 1 performed generally better than the MFC of FOOD 2 (Table 11 in the appendix). While it is admitted that due to lack of operation experience and monitoring video, the biofilm formation time can only be roughly estimated, ~50 hours. Compared to many other researches, this result does not even reach the average power production level (ranging from 200 mV to 600 mV). However it is still reasonable due to the container size, lack of stirrer and centrifuge, oxygen diffusion from cathode chamber to anode chamber, which will be discussed in 5.2.11.

5.2. MDC stage 5.2.1. Scenario 1 During the 48 hours, the MDC produced maximum voltage of 26.3 mV, maximum power of 0.00157 mW, maximum power density of 1.45 mW/m2 (based on 10.8 cm2 electrode area) and 46.73 mW/m3 (based on 33.6 mL volume) under 440 ohm condition (Table 13 and Table 12). The time for MDC to reach maximum voltage is 27 hours (Figure 23). However, as the curve rises slowly after 2.03 h, it is possible to use 2.03 as the “arrival time”. It is necessary to state that, the voltage data measured by multimeter was lost during 2011/08/02 14:15 to 2011/08/03 10:00.due to the laptop

25


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TRITA LWR Degree Project 11:29

Voltage - time curve 35

Voltage (mV)

30 Voltage (mV)

25

Data

20 15 10

(48.35, 3.3)

5 0 0

5

10

15 20 Time (h)

25

48

Figure 23. Voltage generated by using 1.5 g/L H_Salt crash (Figure 23). Since the voltage - time curve is still rising before 14:15, the real maximum voltage value may not be known. However, based on the predictions and Scenario 2-10, the value should be in the range of 26.3 to 30 mV. The ammonium removal degree is 53.1% based on the original NH4+ concentration of 340.7 mg/L. The ammonium concentration (430.5 mg/L) in cathode chamber was even higher than for fresh H_Salt solution. This phenomenon could be explained either by evaporation effect or by ammonium ion residual, or both. The internal resistance can be roughly measured by resistance box. When the peak voltage appears, test a series of resistance value (from 1 ohm to 100000 ohm) and record the data of voltage. Based on the voltage and resistance value, parameters such as current, current density, power and power density could be figured out (Appendix II). In this experiment, the MDC showed a maximum power density of 2.32 mW/m2 at ~3000 ohm and 0.100 mW/m2 at ~5500 ohm, in high and low efficiency respectively (Table 20 and Table 21). The maximum power production was 0.00250 mW at current of 0.029 mA, where the voltage was 86.6 mV correspondingly (Figure 24). 0.003

250 Power (mW) Voltage (mV)

200

0.002 150 0.0015 100

Voltage (mV)

Power (mW)

0.0025

0.001 50

0.0005 0 0.000 0.068 0.063 0.053 0.035 0.017 0.008 Current (mA)

0

Figure 24. Voltage and power generated as a function of current in Scenario 1 26


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Voltage - time curve

35 30 25 20 15 10 5 0

Voltage (mV)

Voltage (mV)

0

4

8

12 Time (h)

16

20

Figure 25. Voltage generated by using 2.5 g/L H_Salt

0.0006

Power (mW)

120

0.0005

Voltage (mV)

100

0.0004

80

0.0003

60

0.0002

40

0.0001

20

0 0.000 0.020 0.020 0.019 0.015 0.007 0.003

Voltage (mV)

Power (mW)

5.2.2. Scenario 2 During the 22 hours, the MDC produced maximum voltage of 29.6 mV, maximum power of 0.00199 mW, maximum power density of 1.84 mW/m2 and 59.23 mW/m3 (based on 33.6 mL volume) under 440 ohm condition (Table 14). The time for MDC to reach maximum voltage is 3 hours (Figure 25). The ammonium removal degree is 52.7% based on the original NH4+ concentration of 376 mg/L. The ammonium concentration in cathode chamber (452.4 mg/L) was even higher than fresh H_Salt solution. This phenomenon could be explained either by evaporation effect or by ammonium ion residual, or both. The internal resistance can be roughly measured by resistance box as described in Scenario 1. In this experiment, the MDC showed a maximum power density of 0.514 mW/m2 at ~6000 ohm in low efficiency condition (Table 22). The peak performance in high efficiency condition was missed. Due to miss of high efficiency data, the maximum power production in low efficiency was 0.00056 mW at current of 0.0096 mA, where the voltage was 57.7 mV correspondingly (Figure 26).

0

Current (mA)

Figure 26. Voltage and power generated as a function of current in Scenario 2 27


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Table 7. Basic information and critical data of scenario 3 Time 2011/7/26 14:14 â&#x20AC;&#x201C; 2011/7/28 11:26 Duration 45 hours Anode chamber Mixed acetate solutions (Same as FOOD 1 in Table 4) Desalination chamber Hjorthorn salt 2.5 g/L Cathode chamber Catholyte shown in Table 5 + NH4 concentration comparison(mg/L) Before After Middle chamber 376 149.1 Cathode chamber 0 409.4 Removal degree 60.3% Internal resistance (Ohm) Peak performance / Stable low performance / Power production under 440 ohm Maximum voltage 28.8 mV Maximum power 0.00178 mW 1.65 mW/m2 Maximum power density 52.98 mW/m3 5.2.3. Scenario 3 During the 45 hours, the MDC produced maximum voltage of 28.8 mV, maximum power of 0.00179 mW, maximum power density of 1.65 mW/m2 (based on 10.8 cm2 electrode area) and 52.98 mW/m3 (based on 33.6 mL volume) under 440 ohm condition (Table 7). The time for MDC to reach maximum voltage is 34.3 hours (Figure 27). The ammonium removal degree is 60.3% based on the original NH4+ concentration of 376 mg/L. The ammonium concentration in cathode chamber (409.4 mg/L) was even higher than fresh H_Salt solution. This phenomenon could be explained either by evaporation effect or by ammonium ion residual, or both. The internal resistance value could not be measured due to lack of resistance box (still in delivery). Without these data, V-P curve cannot be produced.

Voltage (mV)

Voltage - time curve 35 30 25 20 15 10 5 0

Voltage (mV)

0

10

20 Time (h)

30

Figure 27. Voltage generated by using 2.5 g/L H_Salt

28

40


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Voltage - time curve 30

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(3984, 4.1)

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Figure 28. Voltage generated by using 5 g/L H_Salt 5.2.4. Scenario 4 During the 67 hours, the MDC produced maximum voltage of 27.8 mV, maximum power of 0.00176 mW, maximum power density of 1.630 mW/m2 (based on 10.8 cm2 electrode area) and 52.4 mW/m3 (based on 33.6 mL volume) under 440 ohm condition (Table 15). The time for MDC to reach maximum voltage is 1.43 hours (Figure 28). The ammonium removal degree is 20.2% based on the original NH4+ concentration of 536 mg/L. The ammonium concentration in cathode chamber (558 mg/L) was even higher than fresh H_Salt solution. This phenomenon could be explained either by evaporation effect or by ammonium ion residual, or both. The internal resistance can be roughly measured by resistance box as described in Scenario 1. In this experiment, the MDC showed a maximum power density of 2.5 mW/m2 at ~2000 ohm in high efficiency condition (Table 23). The peak performance in low efficiency condition was missed. The maximum power production in high efficiency was 0.00269 mW at current of 0.0367 mA, where the voltage was 73.4 mV correspondingly (Figure 29).

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Figure 29. Voltage and power generated as a function of current in Scenario 4

29


Han Wang

TRITA LWR Degree Project 11:29

Voltage - time curve

40

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Figure 30. Voltage generated by using 15 g/L H_Salt 5.2.5. Scenario 5 During the 24 hours, the MDC produced maximum voltage of 35.8 mV, maximum power of 0.00291 mW, maximum power density of 2.7 mW/m2 (based on 10.8 cm2 electrode area) and 86.60 mW/m3 (based on 33.6 mL volume) under 440 ohm condition (Table 16). The time for MDC to reach maximum voltage is 2.4 hours (Figure 30). The ammonium removal degree is 27.3% based on the original NH4+ concentration of 2220 mg/L. The ammonium concentration in cathode chamber was 965 mg/L. The internal resistance can be roughly measured by resistance box as described in Scenario 1. In this experiment, the MDC showed a maximum power density of 4.15 mW/m2 at ~2100 ohm under high efficiency condition and 0.15 mW/m2 at 6000 ohm under low efficiency condition (Table 24 and Table 25). The maximum power production was 0.00448 mW at current of 0.0462 mA, where the voltage was 97 mV correspondingly (Figure 31).

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Figure 31. Voltage and power generated as a function of current in Scenario 5

30


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Voltage - time curve 70

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Figure 32. Voltage generated by using filtrated supernatant 5.2.6. Scenario 6 During the 21 hours, the MDC produced maximum voltage of 58 mV, maximum power of 0.00765 mW, maximum power density of 7.08 mW/m2 (based on 10.8 cm2 electrode area) and 227.68 mW/m3 (based on 33.6 mL volume) under 440 ohm condition (Table 17). The time for MDC to reach maximum voltage is 8.08 hours (Figure 32). The ammonium removal degree is 53.4% based on the original NH4+ concentration of 993 mg/L. The ammonium concentration in cathode chamber (712 mg/L) was even higher than fresh H_Salt solution. This phenomenon could be explained either by evaporation effect or by ammonium ion residual, or both. The internal resistance can be roughly measured by resistance box as described in Scenario 1. In this experiment, the MDC showed a maximum power density of 7.86 mW/m2 at ~1250 ohm under the high efficiency condition and 0.700 mW/m2 at ~5500 ohm under low efficiency (Table 26 and Table 27). The maximum power production was 0.00849 mW at current of 0.0824 mA, where the voltage was 103 mV correspondingly (Figure 33).

0.008

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0

Figure 33. Voltage and power generated as a function of current in Scenario 6 31


Han Wang

TRITA LWR Degree Project 11:29

Voltage - time curve 60 Voltage (mV)

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Figure 34. Voltage generated by using filtrated supernatant 5.2.7. Scenario 7 During the 71 hours, the MDC produced maximum voltage of 53.1 mV, maximum power of 0.00641 mW, maximum power density of 5.94 mW/m2 (based on 10.8 cm2 electrode area) and 190.8 mW/m3 (based on 33.6 mL volume) under 440 ohm condition (Table 18). The time for MDC to reach maximum voltage is 5.42 hours (Figure 34). The ammonium removal degree is 42.7% based on the original NH4+ concentration of 1221 mg/L. The ammonium concentration in cathode chamber was 801 mg/L after the cycle. The internal resistance can be roughly measured by resistance box as described in Scenario 1. In this experiment, the MDC showed a maximum power density of 6.93 mW/m2 at ~1600 ohm under high efficiency condition and 0.0677 mW/m2 at ~6500 ohm under low efficiency (Table 28 and Table 29). The maximum power production was 0.00748 mW at current of 0.0684 mA, where the voltage was 109.4 mV correspondingly (Figure 35).

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Figure 35. Voltage and power generated as a function of current in Scenario 7

32


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Voltage - time curve

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Figure 36. Voltage generated by using filtrated wastewater

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5.2.8. Scenario 8 During the 24 hours, the MDC produced maximum voltage of 19.7 mV, maximum power of 0.00088 mW, maximum power density of 0.817 mW/m2 (based on 10.8 cm2 electrode area) and 26.25 mW/m3 (based on 33.6 mL volume) under 440 ohm condition (Table 19). The time for MDC to reach maximum voltage is 12.8 hours (Figure 36). The ammonium removal degree is insignificant based on the original NH4+ concentration of 40.7 mg/L. The ammonium concentration in cathode chamber was 226 mg/L after the cycle. This phenomenon reflected the truth that ammonium residual existed in both of desalination chamber and cathode chamber. It means chambers didnâ&#x20AC;&#x2122;t washed well by DI water before this scenario started. But if combine the power generation data, it might be not satisfied using MDC to treat influent wastewater due to low ammonium concentration. The internal resistance can be roughly measured by resistance box as described in Scenario 1. In this experiment, the MDC showed a maximum power density of 0.398 mW/m2 at ~3000 ohm under high efficiency condition and 0.0226 mW/m2 at ~6000 ohm under low efficiency (Table 30 and Table 31). The maximum power production was 0.00043 mW at current of 0.0120 mA, where the voltage was 35.9 mV correspondingly (Figure 37).

Figure 37. Voltage and power generated as a function of current in Scenario 8 33


Han Wang

TRITA LWR Degree Project 11:29

Table 8. Basic information and critical data of scenario 9 Time 2011/8/10 13:31 â&#x20AC;&#x201C; 2011/8/11 13:31 Duration 24 hours Test the Hjorthorn salt at 15 g/L by using KMnO4. Description Oxygen supplied. Mixed acetate solutions (Same as FOOD Anode chamber 1 in Table 4) Desalination chamber Hjorthorn salt 15 g/L KMnO4 (200 mg/L) + Catholyte shown Cathode chamber in Table 5 + NH4 concentration comparison(mg/L) Before After Middle chamber 2220 1425 Cathode chamber 0 1125 Removal degree 35.81% COD test Before After Anode chamber / / Middle chamber 33.3 99.8 Cathode chamber / / Internal resistance (Ohm) Peak voltage happened when KMnO4 was injected into the chamber. It is unstable and impossible to test the Peak performance internal resistance. The internal resistance at medium efficiency is around 4000 - 5000 ohm. Stable low performance Around 11500 (Voltage at 13.8 mV) Power production under 440 ohm Maximum voltage 217 mV Maximum power 0.107 mW 99.1 mW/m2 Maximum power density 3185 mW/m3 5.2.9. Scenario 9 During the 24 hours, the MDC produced maximum voltage of 217 mV, maximum power of 0.107 mW, maximum power density of 99.1 mW/m2 (based on 10.8 cm2 electrode area) and 3185 mW/m3 (based on 33.6 mL volume) under 440 ohm condition (Table 8). The time for MDC to reach maximum voltage is less than 1 second (immediately) (Figure 38).

34


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Voltage - time curve 250 Voltage (mV) Voltage (mV)

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4

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Figure 38. Voltage generated by using KMnO4 as catholyte

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The ammonium removal degree is 35.8% based on the original NH4+ concentration of 2220 mg/L. The ammonium concentration in cathode chamber was 1125 mg/L after the cycle. The internal resistance in scenario 9 can hardly be measured because the maximum voltage appeared immediately when the catholyte injected. Instead, internal resistance has been tested at medium efficiency. The MDC showed a maximum power density of 7.12 mW/m2 at ~5000 ohm under high efficiency condition and 3.79 mW/m2 at ~11500 ohm under low efficiency (Table 32 and Table 33). The maximum power production was 0.00769 mW at current of 0.0392 mA, where the voltage was 35.9 mV correspondingly (Figure 39).

0

Current (mA)

Figure 39. Voltage and power generated as a function of current in Scenario 9

35


Han Wang

TRITA LWR Degree Project 11:29

Table 9. Basic information and critical data of scenario 10 Time 2011/8/11 13:30 â&#x20AC;&#x201C; 2011/8/15 09:24 Duration 92 hours Test the Hjorthorn salt at 15 g/L by using KMnO4. Description Without oxygen. Mixed acetate solutions (Same as FOOD Anode chamber 1 in Table 4) Desalination chamber Hjorthorn salt 15 g/L KMnO4 (200 mg/L) + Catholyte shown Cathode chamber in Table 5 + NH4 concentration comparison(mg/L) Before After Middle chamber / / Cathode chamber / / Removal degree / COD test Before After Anode chamber / 225 Middle chamber 33.3 114 Cathode chamber / / Internal resistance (Ohm) Peak voltage happened when KMnO4 was injected into the chamber. It is Peak performance unstable and impossible to test the internal resistance. The voltage continuously decreased. Stable low performance 6000 Power production under 440 ohm Maximum voltage 31.7 mV Maximum power 0.00228 mW 2.12 mW/m2 Maximum power density 68.0 mW/m3 5.2.10. Scenario 10 During the 92 hours, the MDC produced maximum voltage of 31.7 mV, maximum power of 0.00228 mW, maximum power density of 2.12 mW/m2 (based on 10.8 cm2 electrode area) and 68.0 mW/m3 (based on 33.6 mL volume) under 440 ohm condition (Table 9). The time for MDC to reach maximum voltage is less than 1 second (immediately) (Figure 38). The ammonium removal degree cannot obtain due to lack of cuvettes. Thus, the ammonium removal ability will not show in the later comparison and discussion part.

36


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Voltage - time curve

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Figure 40. Voltage generated by using KMnO4 as catholyte The internal resistance at peak performance in scenario 10 can hardly be measured because the maximum voltage appeared immediately when the catholyte injected and decreased continuously. Instead, internal resistance has been tested at medium efficiency. The MDC showed a maximum power density of 7.65 mW/m2 at ~23000 ohm under medium efficiency condition (21 mV under 440 ohm at that time) and 1.17 mW/m2 at ~6000 ohm under low efficiency (Table 34 and Table 35). The maximum power production was 0.00827 mW at current of 0.0190 mA, where the voltage was 436 mV correspondingly (Figure 41). 0.009

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Figure 41. Voltage and power generated as a function of current in Scenario 10 37


TRITA LWR Degree Project 11:29

80

2500

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Running time (h) & removal

Han Wang

Figure 42. Comparison of running time & removal degree and initial concentration 5.2.11. Comparison and discussion Ammonium removal ability analyze From Figure 42 it can be easily found that:  S2 and S3: runtime difference Under the same experimental conditions, ammonium removal efficiency is improved by runtime. The removal degree increased from 52.7% to 60.34% by adjusting the running time from 22 hours to 45 hours.  S5 and S9: big role of catholyte Under the same experimental conditions, ammonium removal efficiency is improved by changing catholyte. The removal degree increased from 27.25% to 35.81% by adding KMnO4 into original catholyte.  S8, S2, S5: concentration level Under almost the same experimental conditions, ammonium removal efficiency in this MDC system depends on concentration level of target solution. The removal degree is relatively high when the NH4+ concentration in S2 is 376 mg/L and the removal degree is 52.7%, compared to removal degree at 0% and 27.25% when the NH4+ concentrations are 40.7 mg/L (S8) and 2220 mg/L (S5), respectively. There is an optimum concentration of ammonium which gives the best removal performance.  S4: runtime isn’t “the longer, the better” Under the same experimental conditions, ammonium removal efficiency is disappointed when running it for 67 hours. As discussed above, S4 has a concentration of 536 mg/L which is in the high efficiency range but it only obtained 20.15% removal degree. Although lack of equipment and funds to examine the phenomenon called “back diffusion” (mentioned by many papers that ions in the anode and cathode chamber will diffuse back to the desalination chamber), it is still reasonable to associate to concentration gradient among these three chambers. After a long term period, with the lower metabolism speed as well as accumulated ion concentration in side chambers, the back diffusion could happen. The same situation happened in S7 compared to S6. Once the NH4+ concentration in cathode chamber increased to a 38


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

higher level (by both of ion transfer and evaporation effect), the concentration gradient may lead to back diffusion. S6: a good example of supernatant treatment Under the same experimental conditions as others, ammonium removal efficiency is 53.4% in 21 hour cycle. As described above, this MDC system can be applied to deal with most of supernatant generated from domestic wastewater as a pretreatment method.

Power generation ability analyze From Figure 43 it can be easily found out that S6, S7 and S9 perform much better than the others. S6 and S7 belong to one group and S9 belongs to another group:  S6 and S7: filtrated supernatant Consistent with the results of ammonium removal ability comparison, filtrated supernatant continued to perform well in power density aspect. They showed the maximum voltage of 58 mV and 53.1 mV during 21 hours and 71 hours respectively. Finally maximum power densities of 227.7 ± 0.1 mW/m3 and 190.7 ± 0.1 mW/m3 were obtained. This result might reflect the truth that, abundant ions in supernatant could be more conductive, which is an essential parameter of deciding the MDC performance.  S9: repeat the importance of catholyte The huge voltage appeared on the moment of new catholyte injected. In fact, potassium permanganate is a better electrolyte which has been mentioned by previous researchers. The voltage dropped speedily but the new catholyte could still drive the MDC to hold the voltage above 50 mV level for more than 1 hour. Finally the power density was 3185 mW/m3 which is the best result until now.  S6, S7 and S9: different way but the same purpose S6, S7 and S9 all obtained relatively high power density. Compared to the others, they were using different ways to enhance electricity production. S6 and S7 focused on improve conductivity in desalination chamber while S9 focused on cathode chamber. And the common point is that they were all designed to reduce “transfer obstruction”, which refers to the parameter of internal resistance. Figure 43 has shown clearly that an example of relative higher power production always accompanied by a lower internal resistance. 300

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Figure 43. Power generation and internal resistance comparison 39

9


Han Wang

TRITA LWR Degree Project 11:29

1.8 1.6 1.4

Formula right side

1.2 1 0.8 0.6 y = -0.5685x + 4.1511 R² = 0.8485

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Figure 44. Linear correlation Data correlation As described before, the figures of voltage and power generated as a function of current from scenario 2,3,8,9 was not obtained due to lack of resistance box at that time and also impossiblities to measure within one second. Thus, the rest 6 scenarios will be analyzed (Table 10). In order to check if there are any dead pixels in the result, the maximum voltage and maximum power will be put into the empirical formula below:

 max voltage  103  3 log    f log 10  max power   max power   The parameters can be found in Table 10. Figure 44 shows that the max voltage has a strong correlation to max power since the trend line has R2 larger than 0.8. The limitation is that the samples are not enough in numbers. If the rest 4 scenarios can be included, it would be better to make a more clear and trustable probability. Thus, under this situation, it is possible to confirm that the data from 1,4,5,6,7,10 are reliable.

Table 10. Raw data and correlation No. 1 4 5 6 7 10

Max Voltage (mV) 26.3 27.8 35.8 58 53.1 31.7

Max power (mW) 0.029 0.0367 0.00448 0.00849 0.00748 0.00827

40

Formula left side 4.733502 4.680847 5.812615 5.954754 5.932956 5.440429

Formula right side 1.462398 1.564666 0.651278 0.928908 0.873902 0.917506


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

6. C ONCLUSIONS Studies on build-up and operation by feeding acetate solutions and sugar to remove ammonium and produce electricity in MFC and MDC stages were done in this master thesis. In the MFC stage, two parallel MFCs set up and the biofilm formation took approximately 50 hours. MFC fed with acetate performed better than MFC fed with sugar, the maximum voltage reached 53.5 mV and OCV reached 673 mV under 780 ohm conditions. The mixed nutrient solutions containing acetate are more efficient compare to sugar. In the MDC stage, Hjorthorn salt and supernatant were tested respectively. Ammonium removal degree in Hjorthorn salt solution was varying from 20.2% to 60.3% and the optimized running time was 45 hours in Scenario 3. Longer time will lead ammonium back diffusion from cathode chamber to desalination chamber. Internal resistances were varying from 2100 ohm to 3000 ohm at the peak performance and 5500 ohm to 6000 ohm at the low efficiency in Scenario 1 to 5. Supernatant performs almost the same with Hjorthorn salt in ammonium removal degree (42.7% and 52.4% in S6 and S7, respectively) but 2-5 times better than H_Salt in electricity generation aspect (227.7 mW/m3 and 190.8 mW/m3). Therefore, MDC is possible to apply for supernatant treatment. Moreover, catholyte plays a vital role in the MDC system. The addition of potassium permanganate in the original catholyte can improve electricity generation performance. Last but not least, the MDC is still in lab stage, it requires more effort to put it forward to the large-scale WWTP. With the characteristics of electricity generation, MDC can be one of the sustainable ways to purify wastewater.

7. L IMITATIONS OF THE STUDY The MFC and MDC experiments were performed successfully during the 50 days period. However, there are still many shortages. If improved at that time, the NH4+ removal degree and power density result could have been better.  Small volume of MFC and MDC container The container is one of the most vital components in MFC and MDC experiments. It should be well-sealed and with smooth contact with two pieces of membranes. In this experiment, container from Reading University is 8.4 mL in each chamber, which could be said as too small. Especially in the MFC period, the purpose was to cultivate as much as microorganism on the anode surface, however the anode electrode was easily closed to the CEM or even had a contact, which may have a side effect due to the diffusion of oxygen in cathode chamber.  No data logger, centrifuge and magnetic stirrer As described before, the software named “YouCam” was used for 24-hour monitoring. It had a same effect as data logger under the normal condition, however the power was cut off at two nights, which means no data was recorded during that time (Figure 23 and Figure 28). The small scale centrifuge can be very helpful at the time of daily substrate replacement. The microorganism in the anode 41


Han Wang

TRITA LWR Degree Project 11:29

chamber could be at most extent stayed there while old substrate could be replaced fully. Magnetic stirrer was not used in this experiment due to size problem. It makes sure the bacteria in the bottom layer can absorb substrate and grow rapidly. Measurement errors When measuring the ammonium concentration, there are many errors exists. One another aspect is in Scenario 8, which 0% result could be explained by the residual ammonium in the last run. Even cleaned by DI water before each cycle started, it was still a factor that interfere ammonium measurement.

8. S UGGESTION S FOR FURTHER R ESEARC H 8.1. Specific suggestions for the used MDC system The MDC system performance can be improved mainly by three aspects: anode bacteria, component of substrate and catholyte and electrode material.  Anode bacteria The digested sludge has been proved to be a suitable bacteria source. However, this study didn’t reach the microcosmic field. It could be very helpful with electron microscope to see the growth of target microorganism under different substrate.  Component of substrate and catholyte Substrate as an energy source in anode chamber is crucial for target microorganism growth. So far acetate is the most popular chemical substance being used. The other components include NaHCO3, NH4Cl, NaH2PO4*H2O, KCl, NaH2PO4, Na2HPO4, KH2PO4, K2HPO4*3H2O, NH4Cl, MgCl2*6H2O, CaCl2*2H2O and so on. Finding a suitable nutrient solution for specific bacteria is important and it may affect the start-up time and later maximum performance. The catholyte has a more direct effect on power production. Basically it is divided into two types, with or without oxygen (as mentioned in 2.3.3). Generally it is more impressive when ferricyanide is used; however it is still better to study a simpler, nontoxic and more effective chemical compounds in catholyte.  Electrode material One of the main reasons for this experiment to have not achieved high maximum voltage was related to anode and cathode electrode. A MFC without Pt-coated electrode can reduce 78% of power generation substantially as shown in a previous study (Sangeun et al., 2004). Another report (Liang et al., 2008) mentioned that compared with carbon nanotube, activated carbon and flexible graphite as anode electrode, the carbon nanotube performed better than the others (20% to 40%). Thus, developing a new type of electrode in MDC system is required and it might decide if MDC can be used as wastewater treatment in the real world. Moreover, the ammonium removal by using larger volume of middle chamber will be interesting. Personally I judge that the ammonium removal degree in supernatant can be achieved up to 90% or more based on similar principle in the “A new method for water desalination using Microbial Desalination Cells”, Cao et al., 2009. It is necessary to mention that even the salt removal degree achieved 90% and the internal resistance as low as 25 ohm in this study, the chamber volume was not 42


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

close to reality. The inside volume of anode chamber, middle chamber and cathode chamber is 27, 3, 27 mL, which means to use 18 mL water to purify 1 mL water. Thus, it would be interesting to explore how to expand the volume of middle chamber while at the same time keep the NH4+ removal degree at the relatively high level.

8.2. Use of MDC system as a part of a treatment system The studies have been focused on the use of microbial desalination cells (MDC) for removal of ammonium hydrogen carbonate as Hjorthorn salt or in digester supernatant. The same type of apparatus may after some modifications also be used for other purposes or be a part of some units for pre-treatment or post-treatment for complementary treatment of ammonium or removal of other components. A possible pre-treatment is the membrane electrodialysis of sodium chloride to give hydrochloric acids at the anode and sodium hydroxide at the cathode (Mazrou et al., 1998). The acid produced can be used for the removal of alkalinity or facilitate dissolution of precipitates while sodium hydroxide may be used for precipitation (for instance of struvite) or to increase the pH-value to facilitate the transfer of ammonium to ammonia. To facilitate removal of carbon dioxide or ammonia from the liquid phase vacuum, air stripping, electroflotation (Chen, 2004) or special equipment for degassing may be used (Maciejewski et al, 2008). Carbon dioxide may later on be used for lowering the pH-value and ammonia may be recovered as a product. A way to transfer ferric phosphate to struvite is the use of a microbial fuel cell (Fisher et al., 2011; CEEP 2011). In this case pure ferric phosphate or in digested sludge is dissolved due to supply of hydrogen supply simultaneously with electron produced. The obtained orthophosphate solution can then be precipitated as struvite. This process may be facilitated by use of hydrochloric acid and sodium hydroxide supplied from electrodialysis of sodium chloride. A possibility that may be worth to study is treatment of digested sludge in a MDC cell with the purpose to both remove ammonium hydrogen carbonate and dissolve precipitated metal phosphates. In this way both phosphate and ammonium can be recovered. Much attention is today given at release of greenhouse gases. One way to decrease greenhouse gas production driven by microbial activity is to degrade organic material at redox potentials between 0 and 200 and thereby use manganese +4 or iron + 3 as dominating oxidant (Li, 2007). Microbial fuel cell may thereby have an important role (Li et al., 2011. Jiang, 2011).

8.3. Development of theoretical concepts This thesis works had as main purpose to demonstrate the feasibility to treat supernatant by microbial desalination fuel cell (MDC). The theoretical aspects described and used in the thesis works can be developed. One important way is the use of half reactions for the used organic materials sugar and sodium acetate (as described as FOOD 1 in Table 4) and in the anodic chamber and of oxygen or permanganate in the cathodic chamber. These reactions are given by Rittman and McCarty (2001): Electron donators Acetate:

1 3 1 1 CH 3COO   H 2O  CO2  HCO3   H   e 8 8 8 8 43


Han Wang

TRITA LWR Degree Project 11:29

Glucose:

1 1 1 C6 H12O6  O2  CO2  H   e 24 4 4

Electron acceptor (illustrated for oxygen) Oxygen:

1 1 O2  H   e  H 2O 4 2

Combinations of electron donating and electron accepting reactions (redox-reactions) give: Acetate and oxygen:

CH 3COO  2O2  CO2  HCO3   4H 2O Sugar and oxygen:

C6 H12O6  6O2  6CO2  6H 2O As COD is measured in oxygen units (as “O”) it is possible to calculate the COD value of the organic compounds in FOOD 1: Sodium acetate, NaCH3COO*3H2O: 0.471 g COD/g sodium acetate (incl. 3H2O) Sugar: 1.067 g COD/g sugar A solution containing 1.6 g NaCH3COO*3H2O and 1 g sugar per L has the COD value of about 1.82 g COD/L. Added amount into the MDC was 5 ml corresponding to an added COD amount of 9.1 mg COD. The energy value of 1 g COD is about 12 kJ or 3.3 Wh. (Hultman, 2011). Thus, the added chemical energy value of added substrate was about 30 mWh. This value can then be used to compare the power output from the experiments. For an average power production of 0.002 mW during 24 h the energy produced is 0.048 mWh. A comparison between theoretical maximum energy from supplied organics and output in form of electrical energy shows that significant improvements can be made for the efficiency of the suggested process and, thus, a good basis for further research.

44


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

9. R EF ERENCES Aelterman, P., Rabaey, K., Clauwaert, P. & Verstraete, W. 2006. Microbial fuel cells for wastewater treatment. Wat. Sci. Tech. 54(8): 9-15. Brett, B., Miriam, R., Phyllis, B., Largus, T. A. 2010. A curriculum for high school science education: Microbial fuel cells: A living Battery. Cao, X,, Liang, P., Huang, X. 2006. A membrane electrode assembly typed microbial fuel cell for electricity generation. Acta Scientiae Circumstantiae, 26(8): 1252-1257. Cao, X., Huang, X., Liang, P., Xiao, K., Zhou, Y., Zhang, X., Bruce E. L. 2009. A new method for water desalination using microbial desalination cells. Environ. Sci. Technol. 43: 7148-7152. CEEP. 2011. Iron phosphate. Process to extract P from iron precipitate in sludge. SCOE Newsletter. 81: 9-10. Chen, G. 2004. Electrochemical technologies in wastewater treatment. Separation and Purification Technology. 38: 11-41. Chen, X., Xia, X., Liang, P., Cao, X., Sun, H., Huang, X. 2011. Stacked microbial desalination cells to enhance water desalination efficiency. Environ. Sci. Technol. 45: 2465â&#x20AC;&#x201C;2470. Fan, M., Liang, P., Cao, X., Huang, X. 2008. Effect of the initial anode potential on electricity generation in microbial fuel cell. Environmental Science. 29(1): 263-267. Feng, Y., Wang, X., Li, H., & Ren, N. 2007. Research on electricity generation process in microbial fuel cell based on sodium acetate. Journal of Harbin Institute of Technology. 39(12): 1890-1894. Fikret, K., Serkan, E. 2007. Electricity generation with simultaneous wastewater treatment by a microbial fuel cell (MFC) with Cu and Cu-Au electrodes. Chem Technol Biotechnol. 82: 658-662. Fischer, F., Bastian, C., Happe, M., Mabillard, E., and Schmidt, N. (2011). Microbial fuel cell enables phosphate recovery from digested sludge as struvite. Bioresource Technology. 102: 5824-5830. He, Z., Shao, H., & Angenent, L. T. 2007. Increased power production from a sediment microbial fuel cell with a rotating cathode. Biosensors and Bioelectronics. 22(12): 3252-3255. Hong, L., Bruce, E. L. 2004. Electricity generation using an air-cathode single chamber microbial fuel cell in the presence and absence of a proton exchange membrane. Environ. Sci. Technol. 38: 4040-4046. Hong, S. W., Kim, H. S., & Chung, T. H. 2010. Alteration of sediment organic matter in sediment microbial fuel cells. Environmental Pollution. 158 (1): 185-191. Huang, L., Yang, X., Quan, X., Chen, J., Yang, F. 2010. A microbial fuel cell-electro-oxidation system for coking wastewater treatment and bioelectricity generation. Chem Technol Biotechnol. 85: 621-627. Huang, X., Fan, M., Liang, P., & Cao, X. 2007. Influence of anodic characters of microbial fuel cell on power generation performance. China Water and Wastewater. 23(3): 8-13. Ieropoulos, I., Greenman, J., Melbuish, C., & Hart, J. 2005. Energy accumulation and improved performance in microbial fuel cells. Journal of Power Sources. 145(2): 253-256. Jiang, J. 2011. Use of manganese compounds and microbial fuel cells in wastewater treatment. TRITA LWR Degree project. 11(16): 5-10. 45


Han Wang

TRITA LWR Degree Project 11:29

Kiely, P. D., Cusick R., Call, D. F., Selembo, P. A., Regan, J. M., & Logan, B. E. 2011. Anode microbial communities produced by changing from microbial fuel cell to microbial electrolysis cell operation using two different wastewaters. Bioresource Technology. 102(1): 388-394. Kim, B. H., Park, H. S., Kim, H. J., Kim, G. T., Chang, I. S., Lee, J., Phung, N. T. 2003. Enrichment of microbial community generating electricity using a fuel-cell-type electrochemical cell. Microbiol Biotechnol. 63: 672-681. Kyle, S. J., David, M. D., Zhen, H., 2011. Efficient salt removal in a continuously operated upflow microbial desalination cell with an air cathode. Bioresource Technology. 102: 376–380. Li, C. 2007. Quantifying greenhouse gas emissions from soils: Scientific basis and modeling approach. Japanese Society of Soil Science and Plant Nutrition. 53: 344-352. Li, X., Hu, B., Suib, S., Lei, Y. and Li, B. 2011. Electricity generation in continuous flow microbial fuel cells (MFCs) with manganese dioxide (MnO2) cathodes. Biochemical Engineering J. 54: 10-15. Lian, J., Feng, Y., Li, H., Du, W. 2006. Progress in research on microbial fuel cells. The Chinese Journal of Process Engineering. 6(2): 334338. Liang, P., Fan, M., Cao, X., Huang, X., Peng, Y., Wang, S., Cong, Q., Liang, J. 2008. Electricity generation by the microbial fuel cells using carbon nanotube as the anode. Environmental Science. 29(8): 2356-2360. Liang, P., Fan, M., Cao, X., Huang, X., Wang, C. 2007. Composition and measurement of the apparent internal resistance in microbial fuel cell. 28(8): 1894-1898. Liu, G., Matthew, D. Y., Cheng, S., Douglas, F. C., Sun, D., Bruce, E. L. 2011. Examination of microbial fuel cell start-up times with domestic wastewater and additional amendments. Bioresource Technology. 102: 7301-7306. Maciejewski, M., Oleszkiewicz, G. & Nazar, A. 2009. Degasification of mixed liquour improves settling and biological nutrient removal. 2nd IWA Specialized Conference. Nutrient Management in Wastewater Treatment Processes. 6-9: 821-828. Mazrou, S., Kerdjoudj, H., Chérif, A.T., Elmidaouni, A. and Molénat, J. 1998. Regeneration of hydrochloric acid and sodium hydroxide with bipolar membrane electrodialysis from pure sodium chloride. New J. Chem. 355-359. Mehanna, M., Saito, T., Yan, J., Hickner, M., Cao, X., Huang, X., Bruce, E. L., 2010. Using microbial desalination cells to reduce water salinity prior to reverse osmosis. Energy Environ. Sci. 3: 1114–1120. Ozansoy, C., Heard, R. 2011. Microbial conversion of biomass: A review of microbial fuel cells. Progress in Biomass and Bioenergy Production. 21: 409-426. Patrick, D. K., Roland, C., Douglas, F. C., Priscill, A, Selembo, John, M., Bruce, E. L. 2011. Bioresource Technology. 102: 388-394. Rabaey, K., Lissens, G., Siciliano, D. S., & Verstraete, W. 2003. A microbial fuel cell capable of converting glucose to electricity at high rate and efficiency. Biotechnology Letters. 25: 1531–1535.

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Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Rittman, B. and McCarty, P. 2001. Stoichiometry and bacterial energetics. Environmental Biotechnology.2: 126-164. Sangeun, O., Booki, M. & Bruce E. L. 2004. Cathode performance as a factor in electricity generation in microbial fuel cells. Environ. Sci. Technology. 38: 4900-4904. Scott, K., Cotlarciuc, I., Hall, D., Lakeman, J., & Browning, D. 2008. Power from marine sediment fuel cells: the influence of anode material. J Appl Electrochem. 38: 1313-1319. Swades, K C. & Derek, R. L. 2003. Electricity generation by direct oxidation of glucose in mediatorless microbial fuel cells. Nature Biotechnology. 21: 1229-1232. You, S., Ren, N., Zhao, Q., Wang, J., Yang, F. 2009. Analysis of biocathode microbial fuel cell using graphite fibre brush as cathode material. FUEL CELLS. 09(5): 588â&#x20AC;&#x201C;596. You, S., Zhang, J., Jiang, J., Zhao, S. 2006. A microbial fuel cell using permanganate as the cathodic electron acceptor. Journal of Power Sources. 162: 1409â&#x20AC;&#x201C;1415. Zielke, A. E. 2006. Thermodynamic analysis of a single chamber Microbial fuel cell. The 2006 Annual Meeting. 1-17.

10. O THER REF ERENCES Biosphere, atmosphere and hydrosphere, 2011 http://05lovesgeography.blogspot.com/2011/02/eutrophication.html Baidu website, 2011: http://baike.baidu.com/view/1628677.htm http://baike.baidu.com/view/87653.htm http://zhidao.baidu.com/question/217362805.html Wikipedia, 2011: http://en.wikipedia.org/wiki/Microbial_fuel_cell#Mediator_microbial_fuel_cell Soso website, 2009: http://wenwen.soso.com/z/q171310347.htm China environmental impact assessment website, 2011: http://www.china-eia.com/xwzx/1282.htm

47


Han Wang

TRITA LWR Degree Project 11:29

A PPENDIX I Table 11. Voltage data from MFC stage (FOOD 1 and FOOD 2) Digested Sludge: Food 1 Time

Voltage (mV)

Notes

Digested Sludge: Food 2 OCV (mV)

Time

Voltage (mV)

Notes

OCV (mV)

2011/7/12 12:38

4

2011/7/12 14:50

2

2011/7/12 12:44

3

2011/7/13 14:46

1

2011/7/12 13:30

1

2011/7/13 15:54

1

2011/7/13 14:35

1

2011/7/13 16:11

1.7

2011/7/13 16:05

0.9

2011/7/14 12:27

0.6

2011/7/14 12:25

0.7

2011/7/14 14:55

0.6

2011/7/14 14:50

1.9

2011/7/14 15:09

0.9

2011/7/14 15:08

2.1

2011/7/14 15:25

0.7

2011/7/14 15:25

2.8

2011/7/14 15:35

0.8

2011/7/14 15:35

3.2

2011/7/14 15:46

0.7

2011/7/14 15:46

3.7

2011/7/14 16:15

0.7

2011/7/14 16:15

2.2

2011/7/14 16:33

2.7

2011/7/14 16:33

2.2

2011/7/14 16:40

1.5

2011/7/14 16:40

1.9

2011/7/14 16:50

4.2

2011/7/14 16:50

1.8

2011/7/14 16:53

4.1

2011/7/14 16:53

1.6

2011/7/15 10:00

13.4

2011/7/15 10:00

0.3

2011/7/15 10:30

1.5

2011/7/15 10:30

0.4

2011/7/15 10:40

1.3

2011/7/15 10:40

0.5

2011/7/15 14:30

1.1

2011/7/15 14:30

0.3

2011/7/15 16:40

4.3

2011/7/15 16:40

0.7

2011/7/15 19:10

1.3

2011/7/15 19:28

0.3

2011/7/15 23:13

1.6

2011/7/15 23:15

0.3

2011/7/16 13:30

0.5

2011/7/16 13:30

0.6

2011/7/18 11:05

0.4

73.1

2011/7/18 11:45

0.4

2011/7/18 10:35

55.1

2011/7/18 11:52

52.3

2011/7/18 10:39

77.8

2011/7/18 11:56

62.1

2011/7/18 10:40

86.2

2011/7/18 12:00

66.8

2011/7/18 10:41

88.3

2011/7/18 12:04

70.5

2011/7/18 10:42

90.8

2011/7/18 13:23

84

2011/7/18 10:49

105.4

2011/7/18 13:33

86.2

2011/7/18 10:51

106.7

2011/7/18 13:43

87.7

2011/7/18 11:08

109.1

2011/7/18 14:02

89.3

2011/7/18 13:24

119.3

2011/7/18 14:24

92.7

2011/7/18 14:01

133.3

2011/7/18 14:43

2011/7/18 14:22

124.6

2011/7/18 15:23

2.4

400 ohm

2011/7/18 14:43

121.3

2011/7/18 15:35

1.5

400 ohm

2011/7/18 15:23

115.2

2011/7/19 10:40

0.1

200 ohm

2011/7/19 11:42

Replace anode and cathode

move to hammarby Lab

2011/7/18 10:30

2011/7/19 11:00

Replace anode

38.1

Replace anode and cathode

hammarby Lab 41.1

98

2011/7/19 11:00 change cathode

Replace anode

add both

110.6

33.3

91.6

2011/7/19 11:45

1.1

400 ohm

2011/7/19 11:43

102.2

2011/7/19 14:01

3.6

400 ohm

2011/7/19 11:44

107.1

2011/7/19 14:30

2.4

400 ohm

2011/7/19 11:45

113.5

2011/7/20 10:31

0.5

400 ohm

105.3

2011/7/19 11:46

118.9

2011/7/20 11:10

1.1

400 ohm

124.5

2011/7/19 11:47

125.3

2011/7/20 11:54

1.4

48

150.1


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Time

Voltage (mV)

Notes

OCV (mV)

Time

Voltage (mV)

Notes

OCV (mV)

2011/7/19 11:59

141.3

2011/7/21 9:53

1.9

2011/7/19 12:17

148.9

2011/7/21 12:23

2.4

2011/7/19 12:28

153.4

2011/7/21 13:04

2011/7/19 12:37

178.6

2011/7/21 13:12

0.1

2011/7/19 13:55

174.5

2011/7/21 14:01

0.7

188

2011/7/19 14:15

157.3

2011/7/21 14:17

0.5

219

2011/7/19 14:32

142.3

2011/7/21 10:30

3.1

2011/7/19 14:38

138.7

2011/7/21 10:53

1.1

2011/7/21 11:27

1.2

2011/7/21 11:39

0.7

66.1

2011/7/22 12:03

1.4

43.5

2011/7/22 12:05

1.7 1.9

164

2011/7/19 14:45

53.5

2011/7/19 14:56

50.3

2011/7/20 10:27

1.1

2011/7/20 11:53

1.2

2011/7/20 12:27

2.3

73.9

2011/7/22 12:13

2011/7/20 12:49

2.5

137.4

2011/7/22 12:14

2

2011/7/20 12:53

2.7

156.9

2011/7/22 12:18

2.3

2011/7/21 9:53

0.8

2011/7/22 12:29

3.1

2011/7/21 10:53

1

2011/7/22 13:23

6.1

2011/7/22 13:29

6.6

2011/7/21 11:43

1.2

780 ohm

change anode and cathode

change substrate

2011/7/21 12:45

613

2011/7/25 10:30

2.5

2011/7/21 12:47

661

2011/7/25 10:58

2.7

2011/7/21 12:51

203

2011/7/26 10:06

2

2011/7/21 12:56

416

2011/7/21 13:00

673

2011/7/21 13:10

384

2011/7/21 13:20

174

2011/7/21 13:49

652

2011/7/21 14:20

20.1

2011/7/21 14:24

15.4

2011/7/21 14:27

14.7

2011/7/21 14:29

12.6

2011/7/21 14:39

9.9

2011/7/22 10:16

9

2011/7/22 10:52

9.5

2011/7/22 11:24

12.1

2011/7/22 11:40

11.5

2011/7/22 12:02

11.5

2011/7/22 12:29

11.7

2011/7/22 13:23

10

2011/7/22 13:29

9.7

2011/7/25 10:22

1.7

2011/7/25 13:39

0.7

2011/7/26 10:06

1

190

232 stable

299

weekend 256

49

233.5

139.5

change anode and cathode


Han Wang

TRITA LWR Degree Project 11:29

Table 12. Voltage data from MDC stage: Scenario 1

Time 2011/8/1 11:18 2011/8/1 11:55 2011/8/1 12:08 2011/8/1 12:09 2011/8/1 12:11 2011/8/1 12:13 2011/8/1 12:20 2011/8/1 12:23 2011/8/1 12:27 2011/8/1 12:33 2011/8/1 12:37 2011/8/1 12:41 2011/8/1 12:45 2011/8/1 12:50 2011/8/1 13:00 2011/8/1 13:10 2011/8/1 13:20 2011/8/1 13:30 2011/8/1 13:40 2011/8/1 13:50 2011/8/1 14:15 2011/8/1 14:27 2011/8/1 15:12 2011/8/1 15:26 2011/8/1 16:15

Voltage (mV) 8.3 8.3 18.2 19 19.4 19.7 20.5 20.9 21.3 21.9 22.3 22.6 22.8 23.2 23.7 23.9 24.4 24.7 24.8 24.9 25.1 24.9 25.1 24.7 25.1

Time 2011/8/1 16:36 2011/8/1 16:52 2011/8/1 17:10 2011/8/1 17:25 2011/8/1 18:00 2011/8/1 18:15 2011/8/1 18:35 2011/8/1 19:00 2011/8/1 19:30 2011/8/1 20:00 2011/8/1 20:30 2011/8/1 21:00 2011/8/1 21:30 2011/8/1 22:00 2011/8/1 22:30 2011/8/1 23:00 2011/8/1 23:30 2011/8/2 0:00 2011/8/2 0:30 2011/8/2 1:00 2011/8/2 1:30 2011/8/2 2:00 2011/8/2 2:30 2011/8/2 3:00 2011/8/2 3:30 2011/8/2 4:00

50

Voltage (mV) 24.9 25.3 25.4 25.5 26.3 26 25.5 25.4 25.5 25.5 25.7 26 26.3 26.1 26.2 26.7 26.4 26.2 26.3 25.9 25.9 25.6 25.5 25.3 25.4 25.3

Time 2011/8/2 4:30 2011/8/2 5:00 2011/8/2 5:30 2011/8/2 6:00 2011/8/2 6:30 2011/8/2 7:00 2011/8/2 7:30 2011/8/2 8:00 2011/8/2 8:30 2011/8/2 9:00 2011/8/2 9:30 2011/8/2 10:00 2011/8/2 10:30 2011/8/2 10:40 2011/8/2 11:00 2011/8/2 11:07 2011/8/2 11:20 2011/8/2 12:33 2011/8/2 12:45 2011/8/2 13:15 2011/8/2 13:30 2011/8/2 13:45 2011/8/2 14:00 2011/8/2 14:15 2011/8/3 10:15 2011/8/3 11:39

Voltage (mV) 25.4 25.3 25.4 25.1 25.2 25.3 25.1 25.1 25.2 25.2 25.1 24.4 25.3 24.9 25.6 25.9 26.3 24.1 23.9 27 28.8 29.3 29.6 29.8 3.5 3.3


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Table 13. Basic information and critical data of scenario 1 Time Duration

2011/8/01 11:18 â&#x20AC;&#x201C; 2011/8/03 11:39 48 hours Test the MDC performance under low ammonia Description concentration. Mixed acetate solutions Anode chamber (Same as FOOD 1 in Table 4) Desalination chamber Hjorthorn salt 1.5 g/L Cathode chamber Catholyte shown in Table 5 + NH4 concentration comparison(mg/L) Before After Middle chamber 340.7 159.8 Cathode chamber 0 430.5 Removal degree 53.1% COD test Before After Anode chamber / / Middle chamber / / Cathode chamber / / Internal resistance (Ohm) Peak performance Around 3000 Stable low performance Around 5500 Power production under 440 ohm Maximum voltage 26.3 mV Maximum power 0.00157 mW 1.45 mW/m2 Maximum power density 46.73 mW/m3

51


Han Wang

TRITA LWR Degree Project 11:29

Table 14. Basic information and critical data of scenario 2 Time Duration

2011/7/28 13:23 â&#x20AC;&#x201C; 2011/7/29 11:00 22 hours Raise the H_Salt concentration to see the cellâ&#x20AC;&#x2122;s Description performance. Mixed acetate solutions (Same as FOOD Anode chamber 1 in Table 4) Desalination chamber Hjorthorn salt 2.5 g/L Cathode chamber Catholyte shown in Table 5 + NH4 concentration comparison(mg/L) Before After Middle chamber 376 178 Cathode chamber 0 452 Removal degree 52.7% COD test Before After Anode chamber / / Middle chamber / / Cathode chamber / / Internal resistance (Ohm) Peak performance / Stable low performance 6000 Power production under 440 ohm Maximum voltage 29.6 mV Maximum power 0.00199 mW 1.84 mW/m2 Maximum power density 59.23 mW/m3

52


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Table 15. Basic information and critical data of scenario 4 Time Duration

2011/7/29 15:36 â&#x20AC;&#x201C; 2011/8/01 10:00 67 hours Mixed acetate solutions (Same as FOOD Anode chamber 1 in Table 4) Desalination chamber Hjorthorn salt 5.0 g/L Cathode chamber Catholyte shown in Table 5 + NH4 concentration comparison(mg/L) Before After Middle chamber 536 429 Cathode chamber 0 558 Removal degree 20.2% COD test Before After Anode chamber / / Middle chamber / / Cathode chamber / / Internal resistance (Ohm) Peak performance 2000 Stable low performance 6000 Power production under 440 ohm Maximum voltage 27.8 mV Maximum power 0.00176 mW 1.63 mW/m2 Maximum power density 52.4 mW/m3

53


Han Wang

TRITA LWR Degree Project 11:29

Table 16. Basic information and critical data of scenario 5 Time Duration

2011/8/09 13:15 â&#x20AC;&#x201C; 2011/8/10 13:15 24 hours Mixed acetate solutions (Same as FOOD Anode chamber 1 in Table 4) Desalination chamber Hjorthorn salt 15 g/L Cathode chamber Catholyte shown in Table 5 + NH4 concentration comparison(mg/L) Before After Middle chamber 2220 1615 Cathode chamber 0 965 Removal degree 27.25% COD test Before After Anode chamber / 345 Middle chamber 33.3 125 Cathode chamber / / Internal resistance (Ohm) Peak performance Around 2100 Stable low performance Around 6000 Power production under 440 ohm Maximum voltage 35.8 mV Maximum power 0.00291 mW 2.7 mW/m2 Maximum power density 86.60 mW/m3

54


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Table 17. Basic information and critical data of scenario 6 Time 2011/8/04 13:25 â&#x20AC;&#x201C; 2011/8/05 10:00 Duration 21 hours Test the filtrated supernatant performance in Description membrane system. Mixed acetate solutions (Same as FOOD Anode chamber 1 in Table 4) Desalination chamber Filtrated supernatant Cathode chamber Catholyte shown in Table 5 + NH4 concentration comparison(mg/L) Before After Middle chamber 993 463 Cathode chamber 0 712 Removal degree 53.4% COD test Before After Anode chamber / 444 Middle chamber 506 442 Cathode chamber / / Internal resistance (Ohm) Peak performance Around 1250 Stable low performance Around 5500 Power production under 440 ohm Maximum voltage 58 mV Maximum power 0.00765 mW 7.08 mW/m2 Maximum power density 227.68 mW/m3

55


Han Wang

TRITA LWR Degree Project 11:29

Table 18. Basic information and critical data of scenario 7 Time 2011/8/05 11:05 â&#x20AC;&#x201C; 2011/8/08 10:00 Duration 71 hours Test the filtrated supernatant performance under 3 Description day condition. Mixed acetate solutions (Same as FOOD Anode chamber 1 in Table 4) Desalination chamber Filtrated supernatant Cathode chamber Catholyte shown in Table 5 + NH4 concentration comparison(mg/L) Before After Middle chamber 1221 700 Cathode chamber 0 801 Removal degree 42.7% COD test Before After Anode chamber / 480 Middle chamber 506 351 Cathode chamber / / Internal resistance (Ohm) Peak performance 1500 - 1600 Stable low performance Around 6500 Power production under 440 ohm Maximum voltage 53.1 mV Maximum power 0.00641 mW 5.94 mW/m2 Maximum power density 190.8 mW/m3

56


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Table 19. Basic information and critical data of scenario 8 Time 2011/8/08 11:40 â&#x20AC;&#x201C; 2011/8/09 11:40 Duration 24 hours Test the filtrated wastewater performance under 1 day Description condition. Mixed acetate solutions (Same as FOOD Anode chamber 1 in Table 4) Desalination chamber Filtrated wastewater Cathode chamber Catholyte shown in Table 5 + NH4 concentration comparison(mg/L) Before After Middle chamber 40.7 46.4 Cathode chamber 0 226 Removal degree 0% COD test Before After Anode chamber / 492 Middle chamber 122 73.8 Cathode chamber / / Internal resistance (Ohm) Peak performance 2000 - 2500 Stable low performance Around 6000 Power production under 440 ohm Maximum voltage 19.7 mV Maximum power 0.00088 mW 0.817 mW/m2 Maximum power density 26.25 mW/m3

57


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

A PPENDIX II Table 20. Internal resistance measurement (high efficiency): Scenario 1 Time period Description External resistance (Ohm) 1 2 5 10 25 50 75 100 125 150 200 300 400 500 600 700 800 1000 1500 2000 3000 4000 5000 6000 7500 10000 13000 20000 30000 50000 100000

2011/8/01 11:18:00 - 2011/8/01 14:00 Electrode area= 0.00108 m2 Feed with acetate and a new 1.5 g/L H_Salt in the middle, under 440 ohm condition (25 mV), almost stable. With very high efficiency. Voltage (mV) Current (mA) Current density (A/m2) Power (mW) Power density (mW/m2) 0 0 0 0 0 0.1 0.05 0.04630 0.000005 0.004630 0.3 0.06 0.05556 0.000018 0.01667 0.6 0.06 0.05556 0.000036 0.03333 1.7 0.068 0.06296 0.0001156 0.10704 3.4 0.068 0.06296 0.0002312 0.2141 5 0.067 0.06173 0.0003333 0.3086 6.6 0.067 0.06111 0.0004356 0.4033 8.1 0.065 0.06000 0.0005249 0.4860 9.6 0.064 0.05926 0.0006144 0.5689 12.6 0.063 0.05833 0.0007938 0.7350 18 0.06 0.05556 0.001080 1 22.9 0.057 0.05300 0.001311 1.2139 27.5 0.055 0.05093 0.001513 1.4004 31.7 0.053 0.04892 0.001675 1.5508 35.6 0.051 0.04709 0.001811 1.6764 39.3 0.049 0.04549 0.001931 1.7876 45.8 0.046 0.04241 0.002098 1.9423 59.4 0.040 0.03667 0.002352 2.1780 70 0.035 0.03241 0.002450 2.2685 86.6 0.029 0.02673 0.002450 2.3147 99 0.025 0.02292 0.002450 2.2688 108.5 0.022 0.02001 0.002354 2.1800 116.4 0.019 0.01796 0.002258 2.0909 125.9 0.017 0.01554 0.002113 1.9569 137.5 0.014 0.01273 0.001891 1.7506 147.8 0.011 0.01053 0.001680 1.5559 162.7 0.008 0.007532 0.001324 1.2255 175.1 0.0058 0.005404 0.001022 0.9463 187.1 0.0037 0.003465 0.0007001 0.6483 198.4 0.0020 0.001837 0.0003936 0.3645

58


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Table 21. Internal resistance measurement (low efficiency): Scenario 1 Time period Description External resistance (Ohm) 1 2 5 10 25 50 100 150 175 200 300 400 500 600 700 800 1000 1500 2000 3000 4000 5000 5500 6000 7500 10000 13000 15000 17500 20000 30000 50000 100000

2011/8/01 14:10:00 - 2011/8/03 10:20 Electrode area= 0.00108 m2 Feed with acetate and a new 1.5 g/L H_Salt in the middle, under 440 ohm condition (3.5 mV), almost stable. With very low efficiency. Voltage (mV) Current (mA) Current density (A/m2) Power (mW) Power density (mW/m2) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.2 0.008 0.007407 0.0000016 0.001481 0.4 0.008 0.007407 0.0000032 0.002963 0.8 0.008 0.007407 0.0000064 0.005926 1.2 0.008 0.007407 0.0000096 0.008889 1.4 0.008 0.007407 0.0000112 0.01037 1.6 0.008 0.007407 0.0000128 0.01185 2.4 0.008 0.007407 0.0000192 0.01778 3.2 0.008 0.007407 0.0000256 0.02370 3.9 0.0078 0.007222 0.00003042 0.02817 4.6 0.0077 0.007099 3.5267E-05 0.03265 5.3 0.0076 0.007011 4.0129E-05 0.03716 5.9 0.0074 0.006829 4.3513E-05 0.04029 7.2 0.0072 0.006667 0.00005184 0.048 10.1 0.0067 0.006234 6.8007E-05 0.06297 12.5 0.0063 0.005787 0.00007813 0.07234 16.6 0.0055 0.005123 9.1853E-05 0.08505 19.9 0.0050 0.004606 9.9003E-05 0.09167 22.7 0.0045 0.004204 0.0001031 0.09542 24.4 0.0044 0.004108 0.0001082 0.10022 25 0.0042 0.003858 0.0001042 0.09645 27.9 0.0037 0.003444 0.0001038 0.0961 31.4 0.0031 0.002907 0.00009860 0.09129 34.6 0.0027 0.002464 9.2089E-05 0.08527 35.9 0.0024 0.002216 8.5921E-05 0.07956 37.6 0.0021 0.001989 8.0786E-05 0.07480 39.1 0.0020 0.001810 7.6441E-05 0.07078 42.8 0.0014 0.001321 6.1061E-05 0.05654 45.8 0.00092 0.000848 4.1953E-05 0.03885 49.2 0.00049 0.000456 2.4206E-05 0.02241

59


Han Wang

TRITA LWR Degree Project 11:29

Table 22. Internal resistance measurement (low efficiency): Scenario 2 Time period Description External resistance (Ohm) 1 5 10 25 50 75 100 150 175 200 300 400 500 600 700 800 1000 1500 2000 3000 5000 6000 7500 10000 13000 15000 17500 20000 30000 50000 75000 100000

2011/7/28 13:23:00 - 2011/7/29 12:20 under 440 ohm condition, already stable. With very low efficiency. Voltage (mV) Current (mA) Current density (A/m2) 0 0 0 0.1 0.02 0.01852 0.2 0.02 0.01852 0.5 0.02 0.01852 1 0.02 0.01852 1.5 0.02 0.01852 2.1 0.021 0.01944 3 0.02 0.01852 3.5 0.02 0.01852 4 0.02 0.01852 5.9 0.020 0.01821 7.7 0.019 0.01782 9.5 0.019 0.01759 11.1 0.019 0.01713 12.6 0.018 0.01667 14.3 0.018 0.01655 17.2 0.017 0.01593 24 0.016 0.01481 29.2 0.015 0.01352 38.5 0.013 0.01188 51.4 0.010 0.00952 57.7 0.010 0.00890 62.1 0.0083 0.00766 69.8 0.0070 0.006463 76.6 0.0059 0.00546 80.4 0.0054 0.004963 83.9 0.0048 0.004439 87 0.0044 0.004028 95.1 0.0032 0.002935 102.8 0.0021 0.001904 107.5 0.0014 0.001327 110.2 0.0011 0.001020

60

Electrode area= Power (mW) 0 0.000002 0.000004 0.00001 0.00002 0.00003 0.0000441 0.00006 0.00007 0.00008 0.0001160 0.0001482 0.0001805 0.0002054 0.0002268 0.0002556 0.0002958 0.000384 0.0004263 0.0004941 0.0005284 0.0005549 0.0005142 0.0004872 0.0004514 0.0004309 0.0004022 0.0003785 0.0003015 0.0002114 0.0001541 0.0001214

0.00108 m2 Power density (mW/m2) 0 0.001852 0.003704 0.009259 0.01852 0.02778 0.04083 0.05556 0.06481 0.07407 0.1074 0.1372 0.1671 0.1901 0.2100 0.2367 0.2739 0.3555 0.3947 0.4575 0.4892 0.5138 0.4761 0.4511 0.4179 0.3990 0.3724 0.3504 0.2791 0.1957 0.1427 0.1124


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Table 23. Internal resistance measurement (high efficiency): Scenario 4 Time period Description External resistance (Ohm) 1 5 10 25 50 100 125 150 200 300 400 500 600 700 800 1000 1500 2000 3000 4000 5000 6000 7500 10000 13000 15000 17500 20000 30000 50000 75000 100000

2011/7/29 15:30:00 - 2011/7/29 16:30 Electrode area= 0.00108 m2 Feed with acetate and a new 5 g/L H_Salt in the middle, under 440 ohm condition (27.1 mV), almost stable. With very high efficiency. Voltage (mV) Current (mA) Current density (A/m2) Power (mW) Power density (mW/m2) 0 0 0 0 0 0.3 0.06 0.05556 0.000018 0.01667 0.7 0.07 0.06481 0.000049 0.04537 1.9 0.076 0.07037 0.0001444 0.1337 3.8 0.076 0.07037 0.0002888 0.2674 7.3 0.073 0.06759 0.0005329 0.4934 9.1 0.073 0.06741 0.0006625 0.6134 10.7 0.071 0.06605 0.0007632 0.7067 13.9 0.070 0.06435 0.0009660 0.8945 19.7 0.066 0.06080 0.001293 1.1978 25 0.063 0.05787 0.001562 1.4468 29.8 0.060 0.05519 0.001776 1.6445 34.2 0.057 0.05278 0.001949 1.8050 38.3 0.055 0.05066 0.002095 1.9403 42.2 0.053 0.04884 0.002226 2.0612 48.9 0.049 0.04528 0.002391 2.2141 62.7 0.042 0.03870 0.002620 2.4267 73.4 0.037 0.03398 0.002693 2.4942 89.7 0.030 0.02769 0.002682 2.4834 101.8 0.025 0.02356 0.002590 2.3989 111.2 0.022 0.02059 0.002473 2.2899 119.1 0.020 0.01838 0.002364 2.1890 128.4 0.017 0.01585 0.002198 2.0354 139.7 0.014 0.01293 0.001951 1.8070 149.8 0.012 0.01066 0.001726 1.5983 154.9 0.010 0.00956 0.001599 1.4811 160.4 0.0092 0.00848 0.001470 1.3613 164.9 0.0082 0.00763 0.001359 1.2589 176.7 0.0059 0.00545 0.001040 0.9637 188.4 0.0038 0.00348 0.0007098 0.6573 195.3 0.0026 0.002411 0.0005085 0.4709 204.8 0.0020 0.001896 0.0004194 0.3884

61


Han Wang

TRITA LWR Degree Project 11:29

Table 24. Internal resistance measurement (high efficiency): Scenario 5 Time period Description External resistance (Ohm) 1 2 5 10 25 50 100 150 200 250 500 750 1000 1250 1500 1600 2000 2100 2250 2500 3000 4000 5000 6000 7500 10000 15000 20000 30000 50000 100000 300000 700000

2011/8/09 13:15:00 - 2011/8/09 15:15 Electrode area= 0.00108 m2 Feed with acetate and H_Salt 15 g/L in the middle, under 440 ohm condition (34.3 mV), almost stable. With very high efficiency. Voltage (mV) Current (mA) Current density (A/m2) Power (mW) Power density (mW/m2) 0.1 0.1 0.09259 0.00001 0.009259 0.2 0.1 0.09259 0.00002 0.01852 0.4 0.08 0.07407 0.000032 0.02963 0.9 0.09 0.08333 0.000081 0.07500 2.3 0.092 0.08518 0.0002116 0.1959 4.7 0.094 0.08703 0.0004418 0.4090 9.1 0.091 0.08425 0.0008281 0.7667 13.3 0.089 0.08209 0.001179 1.0919 17.3 0.087 0.08009 0.001496 1.3856 21.1 0.084 0.07814 0.001780 1.6489 38 0.076 0.07037 0.002888 2.6741 51.1 0.068 0.06308 0.003481 3.2237 62 0.062 0.05740 0.003844 3.5593 71.7 0.057 0.05311 0.004112 3.8081 79.8 0.053 0.04925 0.004245 3.9309 82.8 0.052 0.04791 0.004284 3.9675 93.2 0.047 0.04314 0.004343 4.0214 97 0.046 0.04276 0.004480 4.1486 98.6 0.044 0.04057 0.004320 4.0008 103.5 0.041 0.03833 0.004284 3.9675 112.1 0.037 0.03459 0.004188 3.8785 125.4 0.031 0.02902 0.003931 3.6401 135.9 0.027 0.02516 0.003693 3.4202 143.7 0.024 0.02217 0.003441 3.1867 153.1 0.020 0.01890 0.003125 2.8938 164.1 0.016 0.01519 0.002692 2.4934 178.5 0.012 0.01101 0.002124 1.9668 186.9 0.0093 0.008652 0.001746 1.6172 196.7 0.0066 0.006070 0.001289 1.1942 205 0.0041 0.003796 0.0008405 0.7782 213 0.0021 0.001972 0.0004536 0.4201 219 0.00073 0.0006759 0.0001598 0.1480 221 0.00032 0.0002923 6.9773E-05 0.06460

62


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Table 25. Internal resistance measurement (low efficiency): Scenario 5 Time period Description External resistance (Ohm) 1 5 10 50 100 150 200 500 1000 1500 2000 3000 4000 5000 5500 6000 6500 7500 10000 13000 15000 20000 30000 50000 75000 100000

2011/8/09 13:15:00 - 2011/8/10 11:30:00 Electrode area= 0.00108 m2 Feed with acetate and H_Salt at 15 g/L in the middle, under 440 ohm condition (4.2 mV), almost stable. With very low efficiency. Voltage (mV)

Current (mA)

Current density (A/m2)

Power (mW)

Power density (mW/m2)

0 0 0 0.5 1 1.4 1.9 4.7 8.7 12.2 15.3 20.4 24.4 27.8 29.4 30.8 32 34.1 38.2 42.3 43.9 47.2 50.9 54.4 57.1 59

0 0 0 0.01 0.01 0.0093 0.0095 0.0094 0.0087 0.0081 0.0077 0.0068 0.0061 0.0056 0.0053 0.0051 0.0049 0.0045 0.0038 0.0033 0.0029 0.0024 0.0017 0.0011 0.00076 0.00059

0 0 0 0.009259 0.009259 0.008641 0.008796 0.008703 0.008055 0.007530 0.007083 0.006296 0.005648 0.005148 0.004949 0.004753 0.004558 0.004209 0.003537 0.003012 0.002709 0.002185 0.001570 0.001007 0.0007049 0.0005462

0 0 0 0.000005 0.00001 1.3067E-05 0.00001805 0.00004418 0.00007569 9.9227E-05 0.0001170 0.0001387 0.0001488 0.0001546 0.0001572 0.0001581 0.0001575 0.0001550 0.0001459 0.0001376 0.0001284 0.0001113 8.6360E-05 5.9187E-05 4.3472E-05 0.00003481

0 0 0 0.004629 0.009259 0.01210 0.01671 0.04091 0.07008 0.09188 0.1084 0.1284 0.1378 0.1431 0.1455 0.1464 0.1459 0.1436 0.1351 0.1274 0.1190 0.1031 0.07996 0.05480 0.04025 0.03223

63


Han Wang

TRITA LWR Degree Project 11:29

Table 26. Internal resistance measurement (high efficiency): Scenario 6 Time period Description External resistance (Ohm) 1 5 10 25 50 75 100 150 200 250 500 750 1000 1250 1500 1600 2000 2250 2500 3000 4000 5000 6000 7500 10000 15000 20000 30000 50000 100000 300000 700000

2011/8/04 17:09:00 - 2011/8/04 17:09 Electrode area= 0.00108 m2 Feed with acetate and supernatant in the middle, under 440 ohm condition (56.1 mV), almost stable. With very high efficiency. Voltage (mV) Current (mA) Current density (A/m2) Power (mW) Power density (mW/m2) 0.2 0.2 0.1852 0.00004 0.03704 0.9 0.18 0.1667 0.000162 0.1500 1.9 0.19 0.1759 0.000361 0.3343 4.6 0.18 0.1703 0.0008464 0.7837 9 0.18 0.1667 0.00162 1.5000 13.1 0.17 0.1617 0.002288 2.1186 16.9 0.17 0.1564 0.002856 2.6445 24.2 0.16 0.1493 0.003904 3.6151 30.7 0.15 0.1421 0.004712 4.3634 36.8 0.15 0.1362 0.005416 5.0157 60.6 0.12 0.1122 0.007344 6.8007 78.2 0.10 0.09654 0.008153 7.5497 91.8 0.092 0.085 0.008427 7.8030 103 0.082 0.07629 0.008487 7.8585 112.4 0.075 0.06938 0.008422 7.7986 116 0.073 0.06712 0.00841 7.7870 127.8 0.064 0.05916 0.008166 7.5615 134.1 0.060 0.05518 0.007992 7.4003 140.1 0.056 0.05188 0.007851 7.2696 149.8 0.050 0.04623 0.007480 6.9259 165.2 0.041 0.03824 0.006822 6.3174 177.1 0.035 0.03279 0.006272 5.8082 186.8 0.031 0.02883 0.005815 5.3849 198 0.026 0.02444 0.005227 4.8400 211 0.021 0.01953 0.004452 4.1223 230 0.015 0.01419 0.003526 3.2654 242 0.012 0.01120 0.002928 2.7113 255 0.0085 0.007870 0.002167 2.0069 269 0.0054 0.004981 0.001447 1.3400 280 0.0028 0.0025925 0.000784 0.7259 290 0.00097 0.0008951 0.0002803 0.2596 293 0.00042 0.0003876 0.0001226 0.1136

64


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Table 27. Internal resistance measurement (low efficiency): Scenario 6 Time period Description External resistance (Ohm) 1 2 5 10 50 100 150 200 500 700 1000 1500 2000 3000 4000 5000 5500 6000 6500 7500 10000 13000 15000 20000 30000 50000 75000 100000

2011/8/04 13:25:00 - 2011/8/05 10:00 Electrode area= 0.00108 m2 Feed with acetate and filtrated supernatant in the middle, under 440 ohm condition (10 mV), almost stable. With very low efficiency. Voltage (mV) Current (mA) Current density (A/m2) Power (mW) Power density (mW/m2) 0 0 0 0 0 0 0 0 0 0 0.1 0.02 0.01851 0.000002 0.001852 0.2 0.02 0.01851 0.000004 0.003704 1.2 0.024 0.02222 0.0000288 0.02667 2.4 0.024 0.02222 0.0000576 0.05333 3.6 0.024 0.02222 0.0000864 0.08000 4.7 0.024 0.02175 0.0001105 0.1023 11.1 0.022 0.02055 0.0002464 0.2282 14.9 0.022 0.01970 0.0003172 0.2937 20.2 0.020 0.01870 0.0004080 0.3778 27.8 0.019 0.01716 0.0005152 0.4771 34.5 0.017 0.01597 0.0005951 0.5510 45.2 0.015 0.01395 0.0006810 0.6306 54.1 0.014 0.01252 0.0007317 0.6775 61.3 0.012 0.01135 0.0007515 0.6959 64.5 0.012 0.01085 0.0007564 0.7004 67.3 0.011 0.01038 0.0007548 0.6990 70 0.011 0.009971 0.0007538 0.6980 74.4 0.0099 0.009185 0.0007380 0.6834 83.3 0.0083 0.007712 0.0006938 0.6425 91.1 0.0070 0.006488 0.0006384 0.5911 95.6 0.0064 0.005901 0.0006092 0.5642 103.3 0.0052 0.004782 0.0005335 0.4940 112.6 0.0038 0.003475 0.0004226 0.3913 120.9 0.0024 0.002238 0.0002923 0.2707 125.8 0.0017 0.001553 0.0002110 0.1954 128.9 0.0013 0.001193 0.0001661 0.1538

65


Han Wang

TRITA LWR Degree Project 11:29

Table 28. Internal resistance measurement (high efficiency): Scenario 7 Time period Description External resistance (Ohm) 1 5 10 25 50 100 150 175 200 250 500 750 1000 1250 1500 1600 2000 2250 2500 3000 4000 5000 6000 7500 10000 15000 20000 30000 50000 100000 300000 700000

2011/8/05 11:05:00 - 2011/8/05 15:45 Electrode area= 0.00108 m2 Feed with acetate and supernatant in the middle, under 440 ohm condition (50.5 mV), almost stable. With very high efficiency. Voltage (mV) Current (mA) Current density (A/m2) Power (mW) Power density (mW/m2) 0.1 0.1 0.09259 0.00001 0.009259 0.8 0.16 0.1481 0.000128 0.11852 1.6 0.16 0.1481 0.000256 0.2370 3.9 0.16 0.1444 0.0006084 0.5633 7.8 0.16 0.1444 0.001217 1.1267 14.7 0.15 0.1361 0.002161 2.0008 21.3 0.14 0.1314 0.003025 2.8006 24.3 0.14 0.1285 0.003374 3.1243 27.2 0.14 0.1259 0.003699 3.4252 32.6 0.13 0.1207 0.004251 3.9361 55.1 0.11 0.1020 0.006072 5.6222 71.9 0.096 0.0887 0.006892 6.3822 85.1 0.085 0.07879 0.007242 6.7056 96.2 0.077 0.07125 0.007404 6.8551 105.9 0.071 0.06537 0.007476 6.9227 109.4 0.068 0.06331 0.007480 6.9261 121.1 0.061 0.05606 0.007333 6.7894 127.4 0.057 0.05242 0.007214 6.6793 133.2 0.053 0.04933 0.007096 6.5712 143.2 0.048 0.04419 0.006835 6.3291 159.1 0.040 0.03682 0.006328 5.8594 171.3 0.034 0.03172 0.005868 5.4340 180.9 0.030 0.02791 0.005454 5.0501 192.6 0.026 0.02377 0.004945 4.5796 206 0.021 0.01907 0.004243 3.9293 223 0.015 0.01376 0.003315 3.0697 236 0.012 0.01092 0.002785 2.5785 250 0.0083 0.007716 0.002083 1.9290 264 0.0053 0.004888 0.001394 1.2907 276 0.0028 0.002555 0.0007618 0.7053 286 0.00095 0.0008827 0.0002726 0.2525 288 0.00041 0.0003809 0.0001185 0.1097

66


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Table 29. Internal resistance measurement (low efficiency): Scenario 7 Time period Description External resistance (Ohm) 1 5 10 50 100 150 200 500 1000 1500 2000 3000 4000 5000 5500 6000 6500 7500 10000 13000 15000 20000 30000 50000 75000 100000

2011/8/05 11:05:00 - 2011/8/08 10:08:00 Electrode area= 0.00108 m2 Feed with acetate and filtrated supernatant in the middle, under 440 ohm condition (2.5 mV), almost stable. With very low efficiency. Voltage (mV) Current (mA) Current density (A/m2) Power (mW) Power density (mW/m2) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.2 0.004 0.003703 0.0000008 0.0007407 0.6 0.006 0.005555 0.0000036 0.003333 0.9 0.006 0.005555 0.0000054 0.005 1.2 0.006 0.005555 0.0000072 0.006667 2.8 0.0056 0.005185 0.00001568 0.01452 5.3 0.0053 0.004907 0.00002809 0.02601 7.6 0.0051 0.004691 3.8506E-05 0.03565 9.7 0.0049 0.004490 0.00004705 0.04356 13.2 0.0044 0.004074 0.00005808 0.05378 16.1 0.0040 0.003726 6.4803E-05 0.0600 18.5 0.0037 0.003425 0.00006845 0.06338 19.6 0.0036 0.003299 6.9847E-05 0.06467 20.8 0.0035 0.003209 7.2107E-05 0.06677 21.8 0.0034 0.003105 7.3114E-05 0.06770 23.4 0.0031 0.002888 0.00007301 0.06760 26.6 0.0027 0.002462 0.00007076 0.06552 29.5 0.0023 0.002101 6.6942E-05 0.06198 31.4 0.0021 0.001938 6.5731E-05 0.06086 34.3 0.0017 0.001587 5.8825E-05 0.05447 38.1 0.0013 0.001175 0.00004839 0.04480 41.5 0.00083 0.000768 0.00003445 0.03189 43.7 0.00058 0.0005395 2.5463E-05 0.02358 44.4 0.00044 0.0004111 1.9714E-05 0.01825

67


Han Wang

TRITA LWR Degree Project 11:29

Table 30. Internal resistance measurement (high efficiency): Scenario 8 Time period Description External resistance (Ohm) 1 5 10 50 75 100 150 175 200 500 750 1000 1250 1500 1600 2000 2250 2500 3000 4000 5000 6000 7500 10000 15000 20000 30000 50000 100000 300000 700000

2011/8/08 11:40:00 - 2011/8/08 16:10 Electrode area= 0.00108 m2 Feed with acetate and wastewater in the middle, under 440 ohm condition (8.9 mV), almost stable. With relatively high efficiency. Voltage (mV) Current (mA) Current density (A/m2) Power (mW) Power density (mW/m2) 0 0 0 0 0 0.1 0.02 0.01852 0.000002 0.001852 0.2 0.02 0.01851 0.000004 0.003704 1.1 0.022 0.02037 0.0000242 0.02241 1.7 0.023 0.02098 3.8533E-05 0.03568 2.2 0.022 0.02037 0.0000484 0.04481 3.3 0.022 0.02037 0.0000726 0.06722 3.8 0.022 0.02010 8.2514E-05 0.07640 4.3 0.022 0.01991 0.00009245 0.08560 9.9 0.020 0.01833 0.0001960 0.1815 14 0.019 0.01728 0.0002613 0.2420 17.4 0.017 0.01611 0.0003028 0.2803 20.6 0.016 0.01530 0.0003395 0.3143 23.6 0.016 0.01456 0.0003713 0.3438 24.6 0.015 0.01423 0.0003782 0.3502 28.4 0.014 0.01314 0.0004033 0.3734 30.5 0.014 0.01255 0.0004134 0.3828 32.5 0.013 0.01203 0.0004225 0.3912 35.9 0.012 0.01108 0.0004296 0.3978 41.3 0.010 0.009560 0.0004264 0.3948 45.6 0.0091 0.008444 0.0004158 0.3851 49.1 0.0082 0.007577 0.0004018 0.3720 53.1 0.0071 0.006556 0.0003759 0.3481 58.2 0.0058 0.005389 0.0003387 0.3136 64.3 0.0043 0.003969 0.0002756 0.2552 68.1 0.0034 0.003153 0.0002319 0.2147 72.2 0.0024 0.002228 0.0001738 0.1609 75.8 0.0015 0.001404 0.0001149 0.1064 79.1 0.00079 0.0007324 6.2568E-05 0.05793 81.5 0.00027 0.0002515 2.2141E-05 0.0205 82.6 0.00012 0.0001092 9.7468E-06 0.009025

68


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Table 31. Internal resistance measurement (low efficiency): Scenario 8 Time period Description External resistance (Ohm) 1 5 10 50 100 150 200 500 1000 1500 2000 3000 4000 5000 5500 6000 6500 7500 10000 13000 15000 20000 30000 50000 75000 100000

2011/8/08 11:40:00 - 2011/8/09 11:40:00 Electrode area= 0.00108 m2 Feed with acetate and filtrated influent wastewater in the middle, under 440 ohm condition (1.8 mV), almost stable. With very low efficiency. Voltage (mV) Current (mA) Current density (A/m2) Power (mW) Power density (mW/m2) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.2 0.004 0.003704 0.0000008 0.0007407 0.4 0.004 0.003704 0.0000016 0.001481 0.6 0.004 0.003704 0.0000024 0.002222 0.8 0.004 0.003704 0.0000032 0.002963 2 0.004 0.003704 0.000008 0.007407 3.4 0.0034 0.003148 0.00001156 0.01070 5.1 0.0034 0.003148 0.00001734 0.01606 6.1 0.0031 0.002824 0.00001861 0.01723 8.1 0.0027 0.0025 0.00002187 0.02025 9.4 0.0024 0.002175 0.00002209 0.02045 10.8 0.0022 0.002 0.00002333 0.02160 11.1 0.0020 0.001868 2.2402E-05 0.02074 12.1 0.0020 0.001867 2.4402E-05 0.02259 12.4 0.0019 0.001766 2.3655E-05 0.02190 13 0.0017 0.001604 2.2533E-05 0.02086 14.1 0.0014 0.001305 0.00001988 0.01840 14.9 0.0011 0.001061 1.7078E-05 0.01581 15.5 0.0010 0.0009567 1.6017E-05 0.01483 16.4 0.00082 0.0007592 0.00001345 0.01245 17.6 0.00059 0.0005432 1.0325E-05 0.009560 18.7 0.00037 0.0003462 6.994E-06 0.006476 19.7 0.00026 0.0002432 5.1745E-06 0.004791 19.9 0.00020 0.0001842 3.9601E-06 0.003667

69


Han Wang

TRITA LWR Degree Project 11:29

Table 32. Internal resistance measurement (medium efficiency): Scenario 9 Time period Description External resistance (Ohm) 1 2 5 10 25 50 100 150 200 250 500 750 1000 1250 1500 1600 2000 2250 2500 3000 4000 5000 6000 7500 10000 15000 20000 30000 50000 100000 300000 700000

2011/8/10 13:15:00 - 2011/8/10 15:30 Electrode area= 0.00108 m2 Feed with H_Salt 15 g/L and KMnO4 + original in the cathode, under 440 ohm condition (32 mV), almost stable. With only medium efficiency. Voltage (mV) Current (mA) Current density (A/m2) Power (mW) Power density (mW/m2) 0 0 0 0 0 0.1 0.05 0.04629 0.000005 0.004630 0.2 0.04 0.03703 0.000008 0.007407 0.5 0.05 0.04629 0.000025 0.02315 1.4 0.056 0.05185 0.0000784 0.07259 2.9 0.058 0.05370 0.0001682 0.1557 5.2 0.052 0.04814 0.0002704 0.2504 7.8 0.052 0.04814 0.0004056 0.37556 10.5 0.053 0.04861 0.0005513 0.5104 13.4 0.054 0.04962 0.0007182 0.6650 24.9 0.050 0.04611 0.001240 1.1482 39 0.052 0.04814 0.002028 1.8778 50.2 0.050 0.04648 0.002520 2.3334 61.1 0.049 0.04525 0.002986 2.7653 71.2 0.047 0.04395 0.003379 3.1293 86.1 0.054 0.04982 0.004633 4.2901 110.1 0.055 0.05097 0.006061 5.6120 119.5 0.053 0.04917 0.006346 5.8766 128.5 0.051 0.04759 0.006604 6.1156 143.6 0.048 0.04432 0.006873 6.3645 175.3 0.044 0.04057 0.007682 7.1134 196.1 0.039 0.03631 0.007691 7.1213 209 0.035 0.03225 0.007280 6.7409 236 0.031 0.02913 0.007426 6.8760 269 0.027 0.02490 0.007236 6.7001 298 0.020 0.01839 0.005920 5.4817 319 0.016 0.01476 0.005088 4.7111 340 0.011 0.01049 0.003853 3.5679 363 0.0073 0.006722 0.002635 2.4402 378 0.0038 0.0035 0.001428 1.3230 399 0.0013 0.001231 0.0005307 0.4914 405 0.00058 0.0005357 0.0002343 0.2170

70


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Table 33. Internal resistance measurement (low efficiency): Scenario 9 Time period Description External resistance (Ohm) 1 5 10 50 100 150 200 500 1000 1500 2000 3000 4000 5000 5500 6000 6500 7500 10000 11500 13000 15000 20000 30000 50000 75000 100000 500000

2011/8/10 13:31:00 - 2011/8/11 10:30:00 Electrode area= 0.00108 m2 Feed with KMnO4 and H_Salt at 15 g/L in the middle, under 440 ohm condition (13.8 mV), almost stable. With low efficiency. Voltage (mV) Current (mA) Current density (A/m2) Power (mW) Power density (mW/m2) 0 0 0 0 0 0.1 0.02 0.01851 0.000002 0.001852 0.3 0.03 0.02777 0.000009 0.008333 1.6 0.032 0.02962 0.0000512 0.04741 3.2 0.032 0.02962 0.0001024 0.09481 4.8 0.032 0.02962 0.0001536 0.1422 6.4 0.032 0.02962 0.0002048 0.1896 15.4 0.031 0.02851 0.0004743 0.4392 29.5 0.030 0.02731 0.0008703 0.8058 43 0.029 0.02654 0.001233 1.1414 56.3 0.028 0.02606 0.001584 1.4674 78.6 0.026 0.02426 0.002059 1.9068 100.8 0.025 0.02333 0.002540 2.3520 118.8 0.024 0.02200 0.002822 2.6136 130.4 0.024 0.02195 0.003091 2.8627 139.8 0.023 0.02157 0.003257 3.0161 149.6 0.023 0.02131 0.003443 3.1881 163.3 0.021 0.02016 0.003555 3.2922 199 0.020 0.01842 0.003960 3.6668 217 0.019 0.01747 0.004094 3.7914 224 0.017 0.01595 0.003859 3.5738 243 0.016 0.015 0.003936 3.6450 273 0.014 0.01263 0.003726 3.4504 312 0.010 0.009629 0.003245 3.0044 347 0.0069 0.006425 0.002408 2.2298 369 0.0049 0.004555 0.001815 1.6810 388 0.0039 0.003592 0.001505 1.3939 414 0.00083 0.0007667 0.0003428 0.3174

71


Han Wang

TRITA LWR Degree Project 11:29

Table 34. Internal resistance measurement (medium efficiency): Scenario 10 Time period Description External resistance (Ohm) 1 5 10 50 100 150 200 250 500 750 1000 1250 1500 1600 2000 2250 2500 3000 4000 5000 6000 7500 10000 15000 20000 23000 30000 50000 100000 300000 700000

2011/8/11 13:30:00 - 2011/8/12 16:30 Electrode area= 0.00108 m2 Feed with H_Salt 15 g/L and KMnO4+original in the cathode, under 440 ohm condition (21 mV), almost stable. With only medium efficiency. Voltage (mV)

Current (mA)

Current density (A/m2)

Power (mW)

Power density (mW/m2)

0 0.2 0.5 2.5 5 7.4 9.8 12.1 22.8 32.8 42 50.6 58.8 62.2 74.9 83.3 91.3 105.3 133.3 160.1 184.2 220 263 332 394 436 473 580 663 720 745

0 0.04 0.05 0.05 0.05 0.049 0.049 0.048 0.046 0.044 0.042 0.040 0.039 0.039 0.037 0.037 0.037 0.035 0.033 0.032 0.031 0.029 0.026 0.022 0.020 0.019 0.016 0.012 0.0066 0.0024 0.0011

0 0.03703 0.04629 0.04629 0.04629 0.04567 0.04537 0.04481 0.04222 0.04049 0.03888 0.03748 0.03629 0.03599 0.03467 0.03427 0.03381 0.0325 0.03085 0.02964 0.02842 0.02716 0.02435 0.02049 0.01824 0.01755 0.01459 0.01074 0.006138 0.002222 0.0009855

0 0.000008 0.000025 0.000125 0.00025 0.0003650 0.0004802 0.0005856 0.001039 0.001434 0.001764 0.002048 0.002304 0.002418 0.002805 0.003083 0.003334 0.003696 0.004442 0.005126 0.005654 0.006453 0.006916 0.007348 0.007761 0.008265 0.007457 0.006728 0.004395 0.001728 0.0007928

0 0.007407 0.02315 0.1157 0.2315 0.3380 0.4446 0.5423 0.9627 1.3282 1.6333 1.8966 2.1342 2.2389 2.5972 2.8555 3.0873 3.4223 4.1132 4.7467 5.2361 5.9753 6.4045 6.8040 7.1869 7.6528 6.9052 6.2296 4.0701 1.6 0.7342

72


Ammonium Removal and Electricity Generation by Using Microbial Desalination Cells

Table 35. Internal resistance measurement (low efficiency): Scenario 10 Time period Description External resistance (Ohm) 1 5 10 50 100 150 200 500 1000 1500 2000 3000 4000 5000 5500 6000 6500 7500 10000 11500 13000 15000 20000 30000 50000 75000 100000 500000

2011/8/15 09:30:00 - 2011/8/17 11:00:00 Electrode area= 0.00108 m2 KMnO4 and H_Salt at 15 g/L in the middle, under 440 ohm condition (14.9 mV), almost stable. With low efficiency. Only for maintenance. Voltage (mV)

Current (mA)

Current density (A/m2)

Power (mW)

Power density (mW/m2)

0 0.2 0.4 2 3.8 5.7 7.4 16.8 29.4 38.6 46.4 59.1 69.5 78.9 82.4 87.1 90.5 95.7 107.8 114.4 120.3 130.9 145.5 168.5 214 262 293 531

0 0.04 0.04 0.04 0.038 0.038 0.037 0.034 0.029 0.026 0.023 0.020 0.017 0.016 0.015 0.015 0.014 0.013 0.011 0.0099 0.0093 0.0087 0.0073 0.0056 0.0043 0.0035 0.0029 0.0011

0 0.03703 0.03703 0.03703 0.03518 0.03518 0.03425 0.03111 0.02722 0.02382 0.02148 0.01824 0.01608 0.01461 0.01387 0.01344 0.01289 0.01181 0.009981 0.009210 0.008568 0.008080 0.006736 0.005200 0.003962 0.003234 0.002712 0.0009833

0 0.000008 0.000016 0.00008 0.0001444 0.0002166 0.0002738 0.0005645 0.0008644 0.0009933 0.001076 0.001164 0.001207 0.001245 0.001234 0.001264 0.001260 0.001221 0.001162 0.001138 0.001113 0.001142 0.001058 0.0009464 0.0009159 0.0009152 0.0008584 0.0005639

0 0.007407 0.01481 0.07407 0.1337 0.2006 0.2535 0.5227 0.8003 0.9197 0.9967 1.0780 1.1181 1.1528 1.1431 1.1707 1.1667 1.1307 1.0760 1.0537 1.0308 1.0577 0.9801 0.8763 0.8481 0.8475 0.7949 0.5222

73

Han+Wang_Master+Thesis%5B1%5D  

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