Chemical Oxygen Demand (COD) is a test that measures the amount of oxygen required to chemically oxidize the organic material and inorganic nutrients, such as Ammonia or Nitrate, present in water. COD is measured via a laboratory assay in which a sample is incubated with a strong chemical oxidant for a specified time interval and at constant temperature (usually 2 h at 150°C). The most commonly used oxidant is potassium dichromate, which is used in combination with boiling sulphuric acid. It is important to note that the chemical oxidant is not specific to organic or inorganic compounds, hence both these sources of oxygen demand are measured in a COD assay. Furthermore, it does not measure the oxygen-consuming potential associated with certain dissolved organic compounds such as acetate. Thus, measurements are not directly comparable to Biochemical Oxygen Demand (BOD) but can be used to compliment (though is sometimes used as surrogate measure). Suspended solids present in the industrial wastewater can cause problems in the sewer system or in subsequent treatment units where they may settle out or cling to pipe or on reactor walls. Sedimentation is the process of removal of suspended solids from wastewater utilizing their ability to settle under the influence of gravity. The settling characteristics of suspended particles may be classified into one of the following types. Discrete settling—Type 1, Flocculent—Type 2, Zone settling—Type 3, Compression Settling—Type 4.