VPE 511: Environment and Environmental Hygiene (2+1)

REDUCING POWDER OR "OXYGEN ABSORBED"

• The pollution of natural waters is invariably accompanied by an increase in the amount of organic matter present in solution. This dissolved organic matter is easily oxidised and the amount of available oxygen absorbed by the water from a oxidising solution gives a measure of it.
• The ability of water to reduce a dilute solution of acid potassium permanganate referred to as the Reducing Powder or Oxygen Absorbed figure, and is reported as parts of available oxygen absorbed per 1000,00 parts of water.
• Many natural waters contain dissolved organic watter that is innocuous . Moorland waters, for example, contain peat acids, and if the reducing powder of such waters is not in excess of about 0.1 parts per 100,000, they may be regarded as satisfactory.
• In the case of other waters the reducing power should not normally be in excess of 0.05 parts per 100,000.
• In all cases the reducing power should be considered in the light of the other estimations, e.g. free ammonia and chloride, that indicate possible contamination.