Wastewater comprises a mixture of domestic sewage (waste from household toilets, sinks, showers and washing machines), industrial effluent, occasional run-off of surface water and ground water which has infiltrated into the sewers. Wastewater is 99.99% water, with a small amount of dissolved or suspended solid matter. At our treatment plants the wastewater undergoes a multi-stage treatment process to clean it before discharge or reuse.