Waste water treatment in Melbourne involves the removal of impurities from sewage water before it reaches aquifers or natural bodies. Waste water can include contaminants from residential and commercial use. If left untreated, the chemical compounds and pathogens in waste water can harm animals, plants, and humans living near water bodies. Adequately treated waste water is a source of water for many purposes. Waste water treatment simply allows water to be reused instead of going to waste.