Land Application of Water Plant Sludges
Most municipal and industrial waters are produced by conventional treatment processes, which include the addition of a coagulant during a rapid mixing period, flocculation of solids during a slow mix period, and then separation of the solids by means of sedimentation and filtration processes. Two decades ago most of the sludges produced during conventional water treatment were returned to a watercourse without further treatment. This often resulted in severe detrimental impact to the watercourse, since the sludges contained both the original solids from the watercourse plus new solids generated during treatment and also because the disposal was irregular, with large flows during backwash of the filter or from intermittent cleaning of sedimentation basins. In many cases the sludge was disposed into a smaller watercourse than the source of the water. As a result, the EPA decided that the sludges from municipal and industrial water treatment must be treated in a responsible fashion.