Organic Matter, Soluble or in Suspension

This is the organic matter that constitutes the bulk of the pollution in household wastewater. The pollution indices are the biochemical oxygen demand (BOD) and the chemical oxygen demand (COD). 

COD includes everything that can be oxidised, inorganic elements (sulphates, sulphites) as well as the major part of organic compounds, whether or not they are biodegradable. 

It is expressed as milligrams per litre. The COD is no longer representative when the chloride content exceeds 2 g l [1]. 

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