COD: COD in water means chemical oxygen demand. It represents the amount of oxygen required to decompose oxidizable compounds present in a waste water sample. COD is an important parameter of water quality. To detect this, a special chemical (potassium dichromate in sulfuric acid solution) is used in the water sample. The acceptable range of COD is 250 to 500 parts per million (PPM). COD test is used to detect the amount of organic matter in waste water. COD testing can also test highly toxic waste water for BOD testing. The higher the COD value of water, the more serious the pollution. COD testing is also used to assess the impact of waste water on the environment .