Descriptions on some parameters of hydrochemistry by abu khairul bashar

Descriptions on Some Parameters of Hydrochemistry

Submitted By

Submitted To

Abu Khairul Bashar

Dr. Syed Hafizur Rahman

Class Roll: 584

Professor

Session 2011-12

Department of Environmental Sciences

Department of Environmental Sciences Jahangirnagar University Savar, Dhaka-1342

Hydrochemistry is the process of measuring the condition of water according to the requirements of more than one biotic species or any human purpose. It is most commonly used to refer to a set of standards which compliance is tested against. Hydrochemistry is the subdivision of hydrogeology that deals with the chemical characteristics of water. In Hydrochemistry, there are needed so many parameters. Such as-

DO BOD COD TDS TSS TOC Iron(Fe) Heavy Metal Trace Element Microorganism Chlorination Hardness

Dissolved Oxygen refers to the volume of oxygen that is contained in water. Oxygen enters the water by photosynthesis of aquatic biota and by the transfer of oxygen across the air-water interface. The amount of DO in water is dependent on the water temperature. DO is a very important indicator of a water body’s ability to support aquatic life. Oxygen is more easily dissolved into water at low altitudes than high altitudes because of higher atmospheric pressure. DO concentrations are higher in the winter than in the summer. The colder the water, the more oxygen can be dissolved water.

Biochemical oxygen demand is a measure of the oxygen used by microorganisms to decompose the organic matter. When BOD levels are high, DO levels decrease because the oxygen that is available in the water is being consumed by the bacteria. Since less DO is available in the water, fish and other aquatic organisms may not survive. The BOD test takes 5days to complete and is performed using a DO test kit.

BOD level(in ppm)

Water Quality

1-2

Very good

3-5

Fair: Moderately clean

6-9

Poor: somewhat polluted

100 or greater

Very poor: very polluted

The amount of oxygen needed to consume the organic and inorganic materials is called chemical oxygen demand (COD). COD has the advantage over BOD in that the analysis can be completed within a few hours whereas BOD requires 5 days. The major drawback of the COD test is the presence of hazardous chemicals toxic waste disposal. The UV absorption can be considered as an alternative method for COD. The COD is a rapid and precise method for determination of aggregate organic matter. COD value can be related to TOC value also which is a measure of organic carbon atoms in a sample.

The expression of ‘’total dissolved solid’’ (TDS) refers to the total amount of all inorganic and organic substances including minerals, salts, cat ions, anions, metals that are dispersed within a volume of water. TDS concentrations are the cat ions and anions in water.

Sources for TDS include agricultural run-off, urban runoff, industrial wastewater, sewage and natural sources such as leaves, silt, plankton and rocks. Piping and plumbing also release metals in water.

Total Suspended Solids (TSS) are solids in water that can be trapped by a filter. TSS can include a wide variety of material, such as silt, decaying plant and animal matter, industrial wastes, and sewage. High concentrations of suspended solids can cause many problems for stream health and aquatic life. High TSS can block light from reaching submerged vegetation. As the amount of light passing through the water is reduced, photosynthesis slows down. Reduced rates of photosynthesis causes less dissolved oxygen to be

released into the water by plants. If light is completely blocked from bottom dwelling plants, the plants will stop producing oxygen and will die. As the plants are decomposed, bacteria will use up even more oxygen from the water. Low dissolved oxygen can lead to fish kills. High TSS can also cause an increase in surface water temperature, because the suspended particles absorb heat from sunlight. This can cause dissolved oxygen levels to fall even further (because warmer waters can hold less DO), and can harm aquatic life in many other ways, as discussed in the temperature section.

Total organic carbon (TOC) is the amount of carbon bound in an organic compound and is often used as a non-specific indicator of water quality or cleanliness of pharmaceutical manufacturing equipment. A typical analysis for TOC measures both the total carbon present and the so-called "inorganic carbon" (IC), the latter representing the content of dissolved carbon dioxide and carbonic acid salts. Subtracting the inorganic carbon from the total carbon yields TOC. Another common variant of TOC analysis involves removing the

IC portion first and then measuring the leftover carbon.

TOC detection is an important measurement because of the effects it may have on the environment, human health, and manufacturing processes. TOC is a highly sensitive, non-specific measurement of all organics present in a sample. It, therefore, can be used to regulate the organic chemical discharge to the environment in a manufacturing plant. In addition, low TOC can confirm the absence of potentially harmful organic chemicals in water used to manufacture pharmaceutical products. TOC is also of interest in the field of potable water purification due to disinfection of byproducts. Inorganic carbon poses little to no threat.

Typically, iron exists in water in two different forms, soluble ferrous or insoluble ferric. Soluble ferrous iron is dissolved in the water and thus clears, while insoluble ferric iron will be very visible. Excessive amounts of iron in water (more than ten parts per million) will give food and drink a very unpleasant, metallic flavor.

Additionally, water with too much iron could stain clothing and appliances if spilled. Iron is not a hazard to health, so there are no health-related risks involved

when water contains too much iron. After doing a water test to determine that there is a problem with iron, there are many treatment options available, such as aeration, filtration, softening and zonation.

A heavy metal is any one of a number of elements that exhibit metallic properties, which includes transition metals lanthanides actinides as well as the metalloids Arsenic and Antimony. Typically the term refers to elements of atomic number 21 or higher (e.g. Scandium or above) the term heavy metal chiefly arose with discussions of pollutants discharged to the environment in the form of air, water or soil contaminants. While many heavy metals have considerable toxicity, others are considered not deemed to possess significant toxic properties, and, in fact, several of these elements including zinc, iron, copper, chromium and cobalt are necessary for metabolic function for a large class of organisms.

A trace element is a chemical element whose concentration is less than 1000 ppm or 0.1% of a rock's composition. The term is used mainly in igneous petrology. Trace elements will either prefer liquid or solid phase. If compatible with a mineral, it will prefer a solid phase (e.g., Ni compatible with Olivine). If it is incompatible with an element it will prefer a liquid phase. The measurement of this ratio is known as the partition coefficient. Trace elements can be substituted for network-forming captions in mineral structures.

Minerals do not have to contain trace elements, i.e., they do not have to appear in the mineral's chemical formula. When practicing biodynamic farming it is important to utilize the trace elements of the soil, in order to give strength to the roots. Hydroponic practices however are decreasing the seed germination rate, causing an increase in pollution and waste. Trace element analysis is a technique that measures very small concentrations of specific elements present in a sample to understand alteration of the host rocks under investigation, with the greater purpose of reconstructing fluid circulation of a hydrothermal system.

Microorganisms are vital to humans and the environment, as they participate in the Earth's element cycles such as the carbon cycle and nitrogen cycle, as well as fulfilling other vital roles in virtually all ecosystems, such as recycling other organisms' dead remains and waste products through decomposition.

The majority of all oxidative sewage treatment processes rely on a large range of microorganisms to oxidize organic constituents which are not amenable to sedimentation or flotation. Anaerobic microorganisms are also used to reduce sludge solids producing methane gas (amongst other gases) and a sterile mineralized residue. In potable water treatment, one method, the slow sand filter, employs a complex gelatinous layer composed of a wide range of microorganisms to remove both dissolved and particulate material from raw water.

Water chlorination is the process of adding chlorine to water as a method of water purification to make it fit for human consumption as drinking water. Water that has been treated with chlorine is effective in preventing the

spread of waterborne disease. Chlorides are present both in fresh and salt water and are essential elements for life. A normal adult human body contains approximately 81.7g chloride. Chloride increases the electrical conductivity of water.

As a halogen, chlorine is a highly efficient disinfectant, and is added to public water supplies to kill diseasecausing pathogens, such as bacteria, viruses and protozoans, that commonly grow in water supply reservoirs, on the walls of water mains and in storage tanks.[1] The microscopic agents of many diseases such as cholera, typhoid fever, and dysentery killed countless people annually before disinfection methods were employed routinely. Chlorine is obtained from salt (NaCl). It is a gas at atmospheric pressures but liquefies under pressure. The liquefied gas is transported and used as such. As a strong oxidizing agent, chlorine kills via the oxidation of organic molecules. Chlorine and its hydrolysis product hypochlorous acid are neutrally charged and therefore easily penetrate the negatively charged surface of pathogens. It is able to disintegrate the lipids that compose the cell wall and react with intracellular enzymes and proteins, making them nonfunctional. Microorganisms then either die or are no longer able to multiply.

Water hardness is a natural feature and is a result of the geology of the area, being primarily limestone.

Minerals such as calcium and magnesium dissolve into the water as moves over and through the ground. The level of these minerals in the water determines the water hardness. The information in the table below provides a general rule for classifying water hardness.

Hardness description Soft Hard Very Hard

Total Hardness in mg/l Calcium carbonate < 150 150 â&#x20AC;&#x201C; 300 > 300