Wastewater includes all sources of household discharges into sewers, industrial effluent discharge and stormwater inflows. A typical wastewater treatment plant is therefore required to treat a variety of constituents including pathogenic microorganisms, suspended matter, dissolved metals, fats and oils, organic compounds that may be volatile, hazardous or carcinogenic and nutrients that may stimulate the growth of a variety of nuisance algae and plants. In addition the odour and colour of wastewater may require a treatment regime.
Modern treatment plants deliver performance to the tertiary level of treatment standards. This standard indicates compliance in the removal of both nutrients and suspended solids to a low level and the removal of biodegradable organics. Odorous constituents such as Ammonia compounds are also converted in the process.
Through disinfection of the treated wastewater, re-use strategies have been adopted for water to be distributed to downstream users including irrigation, farming, energy and industrial applications.
The re-cycling of treated and disinfected wastewater back into the potable water distribution system is being adopted in many cities. The combination of advanced biological treatment of wastewater coupled with Reverse Osmosis membrane treatments and disinfection provides a multiple barrier approach in the risk management strategies for the delivery of safe re-useable water.