精选优质文档-倾情为你奉上Unit 13Text: Water Treatment ProcessesOne of the great achievements of modern technology has been to drastically reduce the incidence of waterborne of diseases such as cholera and typhoid fever. These diseases are no longer the great risks to pubic health that they once were. The key to this advance was the recognition that contamination of pubic water supplies by human wastes was the main source ci infection, and that it could be eliminated by more effective water treatme
