SLUDGE PROCESSING AND DISPOSAL

The main objective of wastewater treatment is to reduce the pollution load on receiving waters.  The treatment processes concentrate some of the impurities in a sludge along with the microbial excess biomass.  Water treatment also produces a sludge from the chemical coagulation and separation of impurities.  The treatment and disposal of these sludges should be considered as an integral part of the treatment process.  The treatment processes should be regarded therefore as a low-solids stream (effluent or drinking water) and a high-solids stream (sludge).

It should be appreciated that the sludges consist mainly of water and that dewatering is the first and most important requirement in sludge processing.  The cost of treating the sludges, particularly for wastewaters, is a major component of the total cost of treatment, and the effects of the final disposal methods and return flows from sludge treatment can have significant implications for the preceding processes.