Chemical Oxygen Demand (COD)

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Chemical oxygen demand (COD)
This is a measurement of the oxygen needed to oxidize soluble and particulate organic matter in water. It similar to BOD, it supplies an index to evaluate the effect discharged wastewater will have on the receiving environment. It is usually expressed in mass of oxygen consumed over volume of solution which in SI units is milligrams per litre (mg/L) and accepted standard measurement by the International Organization for Standardization is ISO 6060. Also this test can be used to easily quantify the quantity of organics in water and most common implementation of COD is in quantifying the amount of oxidizable pollutants available in surface water such as lakes and rivers or wastewater and is useful for water quality
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Physical Test on water
The physical characteristics of water are paramount as they are the first visibly perceptible factors. Ideally water should be colourless as well odourless with a neutral pH. Presence of dissolved components such as silt, clay, algal materials and so on makes water turbid and change in a pH make it corrosive.

3.1 Conductivity
Conductivity is the estimation of water’s capability to pass electrical flow. Conductive ions come from dissolved salts and inorganic materials like sulfides, alkalis, chlorides and carbonate compounds. The more ions available, the higher the conductivity of water, likewise fewer ions present lesser conductivity of water, distilled or deionized water can act as an insulator because of its very low conductivity value but sea water contain a very high conductivity. Conductivity usually measured in micro- or millisiemens per centimeter (uS/cm or mS/cm), also it can be reported in micromhos or millimhos/centimeter (umhos/cm or mmhos/cm), though these units not common, one siemen is equal to one mho, standard unit for freshwater measurements is Microsiemens per
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The rate of chemical reactions normally increases at higher temperature.

3.5 Total Dissolve solid
Total dissolved solids (TDS) integrate sum of all ion particles that are smaller than 2 microns (0.0002 cm). This comprises all of the disassociated electrolytes that formed salinity concentrations and other compounds like dissolved organic matter. In “clean” water, TDS is approximately equal to salinity but in wastewater or polluted areas, TDS can encompass organic solutes like hydrocarbons and urea in addition to the salt ions. This can be reported in mg/L as well estimated by calculated by multiplying a conductivity value by an empirical factor or gravimetry that is with an evaporation dish.

4. Carbondioxide
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