To establish the COD:BOD ratio for your wastewater, simply have both COD and BOD run on several wastewater samples. Divide the COD concentration by the BOD concentration for each sample and average the results.
How do you analyze COD in water?
COD testing typically involves digestion of the water sample in a sealed vial with potassium dichromate and sulfuric acid at 150C for 2 hours. Vials are read in a spectrophotometer to determine results. Of the two tests, COD analysis is more commonly performed as it takes less time and is more replicable.
How can we determine COD?
In the titration method for determining COD, the excess dichromate is reacted with a reducing agent, ferrous ammonium sulfate. As the ferrous ammonium sulfate (FAS) is added slowly, the excess dichromate is converted into its trivalent form. As soon as all the excess dichromate reacts, an equivalence point is reached.
What are the two methods of determining the COD value of a water sample?
There are two methods available for COD determination namely open reflux and closed reflux.
Which titration method is used to determine COD in water?
Learn how to determine the COD in waste water to know the pollution quantity in water by the titration method using Ferrous ammonium sulfate and Ferroin solution as indicator.
What is a good COD level?
Greenfield CET Plant Pvt. Ltd. According to standards of Central Pollution Control Board, permissible value of BOD is 30 mg/l and COD is 250 mg/l.
What is COD and How Is It measured?
COD is an indicative measure of the amount of oxygen that can be consumed by reactions in a measured solution. It is commonly expressed in mass of oxygen consumed over volume of solution, which in SI units is milligrams per liter (mg/L). A COD test can be used to easily quantify the amount of organics in water.
What is the principle of COD test?
The principle behind the COD testing method is that, under acidic conditions, a strong oxidising agent will oxidise almost any organic compound to carbon dioxide. COD analysis will measure the equivalent amount of oxygen that is required to chemically oxidise organic compounds in water.
Which instrument is used for determination of COD test?
COD Test Procedures
A COD reactor/heating (150°C) block and a colorimeter are turned on so that both instruments are allowed to stabilize. Pre-prepared low-range (3-50 ppm) or high-range (20-1500 ppm) vials are selected for the COD test based on expected results.
Why is h2so4 used in COD test?
Chemical Oxygen Demand (COD) 1% Silver Sulphate in Sulphuric Acid (conc.) provides the primary and secondary digestion catalysts for oxidation of carbon during chemical oxidation.
What causes high COD in wastewater?
COD increases as the concentration of organic material increases. It also increases if inorganic compounds susceptible to oxidation by the oxidant (typically dichromate) are present. Water with high COD typically contains high levels of decaying plant matter, human waste, or industrial effluent.
Why do we measure COD?
Chemical oxygen demand (COD) is the amount of dissolved oxygen that must be present in water to oxidize chemical organic materials, like petroleum. COD is used to gauge the short-term impact wastewater effluents will have on the oxygen levels of receiving waters.
What happens if COD is low?
A Low concentration of Dissolved Oxygen is harmful life forms which oxygen to live. Therefore it’s best to reduce COD levels, thus increasing DO concentrations, in wastewater before releasing it. Luckily, there are several ways to reduce COD.
What causes low COD in wastewater?
High chemical oxygen demand in water indicates greater levels of oxidizable organic matter and consequently, a lower amount of Dissolved Oxygen (DO). Critical DO depletion due to organic contamination can kill off aquatic life forms.
How is high COD wastewater treated?
You can reduce COD and BOD by adding hydrogen peroxide to the wastewater solution. The hydrogen peroxide will chemically attack the organics in the wastewater, degrading them and reducing the measured COD and BOD.
What is COD reagent?
The most general COD determination uses potassium dichromate (K2Cr2O7) in excess in an acidic medium with the aid of silver sulfate (Ag2SO4) as a catalyst, and mercuric sulfate (HgSO4) added to remove interference of chlorides.
What is the difference between BOD and COD?
Biochemical oxygen demand (BOD) is the amount of oxygen required by the microorganisms to break down the organic materials, whereas chemical oxygen demand (COD) is the amount of oxygen required to break down the organic material via oxidation.
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