The problem of nutrient inputs to surface waters is reviewed. These inputs lead to eutrophication and an undesirable decrease in water quality. The origin and effects of eutrophication, and the principles of its control are described. The preferred method of control is through the reduction of phosphorus inputs. The origins of phosphorus inputs and methods of limiting these are considered, in particular through physico-chemical and biological treatment processes in sewage treatment plants. It is concluded that efficient control of eutrophication through reduction of phosphorus inputs is possible.

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