Sewage treatment (sewage treatment, wastewater treatment): in order to make the sewage to meet the water quality requirements for discharge into a body of water or re-use of its purification process. Sewage treatment is widely used in construction, agriculture, transportation, energy, petrochemicals, environmental protection, cityscape, medical, food and beverage and other fields, but also more and more into the daily life of ordinary people. On the topic of water pollution is constantly being raised, especially groundwater pollution, Hangzhou, Zhejiang Province, Wenzhou and other places have farmers or entrepreneurs funded to ask the environmental protection bureau chief to swim in the river, as a way to draw attention to the seriousness of water pollution, although the various environmental protection bureau chiefs chose to remain silent or refused, but the awakening of the people's awareness of environmental protection, the degree of concern for water pollution has reached an unprecedented level.