STUDIES ON BIODEGRADATION KINETICS OF CYANIDE BY USING AN ISOLATED MICROORGANISM

S13:WASTEWATER MANAGEMENT: RECYCLING AND REUSE STUDIES ON BIODEGRADATION KINETICS OF CYANIDE BY USING AN ISOLATED MICROORGANISM FROM STEEL PLANT WASTEWATER

PRESENTED BY RAHUL SINGH NATIONAL INSTITUTE OF TECHNOLOGY, DURGAPUR ANUJ KUMAR, DALIA DASGUPTA, TAMAL MANDAL NATIONAL INSTITUTE OF TECHNOLOGY, DURGAPUR, WEST BENGAL, INDIA SIDDARTHA DATTA JADAVPUR UNIVERSITY, KOLKATA 32, INDIA

INTRODUCTION Large amount of cyanides was used in industrial activities involved metal plating, aluminum electrolysis, coal gasification, coal coking, ore leaching, pharmaceuticals, synthetic fibers, and plastics.  Replacement of cyanide has been sought for many decades, but it remains the exclusive chemical for applications because of its availability, effectiveness, and economics . Cyanide was highly toxic to living organisms, particularly in inactivating the respiration system by tightly binding to terminal oxidase. To protect the environment and water bodies, wastewater containing cyanide must be treated before discharging into the environment. Although the physical and chemical processes are frequently used for cyanide removal, biological methods are gaining support as potentially inexpensive and environmental friendly alternatives.

Various Cyanide removal technologies : Alkaline chlorination Advantages- (1) The cyanate is relatively less toxic and further oxidized to CO2 and nitrogen.

Disadvantages – (1) Chlorine can react with organics to form chlorinated compounds. Iron cyanide precipitation Advantages – (1) Used suitably for mining industry.

Disadvantages – (1) Works only with a low conc. Of cyanide.

(2) Disposal of precipitate again a problem

Activated carbon Advantage – (1)Used as a polishing process.

Disadvantages – (1) Cost is high.

(2) Used only for low conc. of cyanide.

(3) Sometimes pretreatment is required. Photolysis Advantages - (1) Complete removal process.

(2) No undesirable by product.

Disadvantages – (1) Requires high energy.

(2) Difficult to operate.

(3) Cost is high. Biological oxidation/Biodegradation Advantages – (1) Can treat cyanides without generating another waste stream.

(2) Cost is fixed (3) Environmental friendly

Biodegradation :  Biodegradation is the process by which living organisms degrade or transform hazardous organic contaminants. Microorganisms that can degrade various pollutants have been isolated with the eventual goal of exploiting their metabolic potential for the bioremediation of contaminated sites. Process in which biological agents play the vital role in the detoxification of the toxic pollutant into nontoxic simpler form under aerobic and anaerobic condition. Microorganisms have the ability to biodegrade the cyanide to nontoxic end products and using cyanide as a sole nitrogen source.  Biodegradation kinetics result may be useful in the design and optimization of the biological reactors treating cyanide waste water.

Biodegradation kinetics:

.

Monod Kinetics: The growth of bacteria, which does not exhibit any inhibition to their growth upon the increased substrate despite of the toxicity of contaminant, can often described by the Monod [Monod ,1949].

µg =

µmax S

Ks +S

Where, µg = specific growth rate (per hour). µmax = Maximum specific growth rate (per hour). ks = Half saturation constant (milligram per litre).

S = initial substrate concentration (milligram per litre).

Haldane Model: when bacterial growth exhibits any inhibition due to toxicity can be described by a kinetic model [Haldane 1930].

µg = (mg/L)

µmax S 2  K s + S +  S ÷ K i  

whereas Ki = inhibition constant

Objectives:  Isolation of bacteria from steel plant wastewater.  To study biodegradation potential of Cyanide using bacterial strain CB-1.  To investigate the cell growth in Cyanide containing wastewater.  To study the degradation kinetics using the bacterial strain CB 1 with the help of Monod and Linearized Haldane growth kinetics model.

Description of Work Bacterial strain CB-1 has been isolated from cyanide contaminated Coke-oven wastewater by serial dilution method and used for biodegradation of cyanide. The bacterium has been grown in an enrichment medium prepared by adding Part A and Part B with the following compositions Part A- K2HPO4, KH2PO4, FeSO4·7H2O PartB-MgCl2·6H2O,MnCl2·4H2O,CaCl2·2H2O, Na2MoO4·2H2O These two parts and Cyanide has been mixed in appropriate proportions at the start of any batch experiment.

The pH of the medium thus obtained is 7.0±0.1. Cyanide electrodes (Orion 94-06 and Orion 96-06 ionplus) has been used for detection of cyanide concentration in wastewater samples. The cyanide electrode has been calibrated by their standard solutions.

Afterwards, cyanide electrode was used for direct cyanide detection.  For measuring biomass, the samples were centrifuged at approximately 8,000 rpm for 10 min. The biomass attached to the walls of tubes was re-suspended in distilled water and optical density of this suspension was measured against media as reference at 600 nm using UV-vis double beam spectrophotometer

Results:

+VE

Pure culture of CB 1

Bacterial Culture CB 1 Gram –ve, Bacillus (Rod shape)

Biochemical Test (IMVIC Test)

Effect of initial cyanide concentration:

Cyanide degradation by CB-1 in batch reactor

Growth of bacteria CB-1 in Cyanide

Cyanide conc (mg/L) Biomas OD (600 nm)

Removal (%) of CN

0.34 60

0.32

100

0.30

50

Cyanide conc. (mg/L)

40

% Removal of cyanide

60

40

20

0.26

30

0.24 0.22

20

0.20 10

0.18

Biomass (OD at 600 nm)

0.28

80

0.16

0 0

0.14

35mg/L 60mg/L 100mg/L120mg/L150mg/L200mg/L250mg/L300mg/L

0

10

20

30

40

50

60

70

80

Time (h)

% Removal of Cyanide

Cyanide degradation by CB1 in batch reactor [initial conc. = 60 mg/L, temperature = 35.0±2 ºC, pH = 7.0].

Growth kinetic parameters: The kinetic parameters µmax, Monods coefficient (kS) and inhibition constant (kI) were determined. We obtained the values of µmax and ks as are 0 .015(hr -1) and 21.47 mg/L for Monod’s model and µmax and KI of 0.1344(hr -1) and 1.66 mg/L for Haldane’s model(Table2). The coefficient of correlation R2 was found to be 0.986 in Monod’s model and 0.614 in Haldane’s model. The growth of these bacteria thus reasonably is in conformity with Monod’s model.

Compound

cyanide

Monod’s Model µmax (h-1)

Ks (mg/l)

0.015

21.47

Linearized Haldane model µmax (h-1) 0.1344/hr

KI (mg/l) 1.66 mg/L

Conclusions : The isolated strain CB-1 degraded cyanide up to 200 mg/L quite comfortably but the rate declined thereafter. The duration taken up by the bacteria to degrade cyanide of concentration 200 mg/L was about 144 hrs as shown by the results of shake-flask experiments. The degradation potential can be increased by acclimatization process. The organism shows a short lag phase at high substrate concentration, whereas in the low concentrations the lag phase was absent. Cyanide exhibited inhibitory behaviour and their growth kinetics could be correlated well by the simple Haldane’s inhibitory growth kinetics model. I It is our view that above information would be useful in modeling and designing of units treating wastewater.

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Baxter, J. and Cummings, S.P.( 2006): The Current and Future Applications of Microorganism in the Bioremediation of Cyanide Contamination, School of Applied Sciences,North Umbria University, Newcastle upon Tyne, NE1 8ST, UK, pp. 1–17.

Dash, R.R., Majumder, C.B. and Kumar, A. (2008): Treatment of metal cyanide bearing wastewater by simultaneous adsorption biodegradation (SAB), J. Hazard. Mater, 152, pp. 387–396.

Dursun, A.Y., Alik, A. C. and Aksu, Z. (1999): Degradation of ferrous (II) cyanide complex ions by Pseudomonas fluorescens, Process Biochemical, 34, pp. 901–908.

Eddy, Metcalf (1991): Wastewater Engineering Treatment Disposal and Reuse, third edition, McGrawHill, Singapore, pp. 197-567.