IntroductionWhile various types of pollution share common attributes, important differencesare apparent as well. These differences form the basis for the elements of policyunique to each pollutant. We have seen, for example, that although the types ofpollutants emitted by mobile and stationary sources are often identical, the policyapproaches differ considerably.Water pollution control has its own unique characteristics as well. The followingstand out as having particular relevance for policy:1. Recreation benefits are much more important for water pollution controlthan for air pollution control.2. Large economies of scale in treating sewage and other wastes create thepossibility for large, centralized treatment plants as one control strategy,while for air pollution, on-site control is the standard approach.3. Many causes of water pollution are more difficult to trace to a particularsource. Runoff from streets and agriculture as well as atmospheric depositionof pollutants are major diffuse sources of water pollution. Control of thesesources adds additional complexities for water pollution control.These characteristics create a need for yet another policy approach. In thischapter we explore the problems and
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