This leaflet is designed to look at the complex processes involved in treating liquid wastes at North Shore City's Wastewater Treatment Plant. For a general overview of the treatment plant and information on the mechanical process of screenings and grit removal see leaflets 1 and 7.
Wastewater is largely the communities water supply after it has been fouled by various uses.
In appearance raw wastewater is a turbid liquid containing solids in suspension and is generally brown in colour and has a musty but not unpleasant odour. These are solids which are inert and not subject to decay, and include sand, gravel, silt and mineral salts. Generally, they are not combustible. Wastewater also contains countless numbers of living organisms, most of them too small to be visible except under a microscope. These include bacteria, fungi, algae, protozoa, rotifers, etc.