Raw sewage indudea waste from ainks. Lollets, and industrial procaoc. Treatment of the eawage is required before it can be safety buried. Or reieesad back into focal water systems. In a treatment plant, the waste is passed through a aeries of screens,Chambers, and chemicalprocesses to reduce its bulk and toxicity. The three general phases of treatment are primary. Secondary and tertiary. During primary treatment, a large parentage of the suspended soilda and inorganic material is removed from the sewage. The focus of secondary treatment, is reducing organic material by accelerating natural biological processes. Tertiary treatment is necessary whenthe water will be reused; 99 percent of solids. Are removed and various chemical processes are used to ensure the water is as free from impurity as possible.