Chapter 9 - Treatment and disposal of sludge solids

Abstract

Waste engineers spend more time and money removing the solids than finally treating and disposing of them, so often a poor solid disposal program will cause trouble in an otherwise properly designed and operated waste treatment plant. When the solids disposal system is poor, the solids tend to build up in the flow-through treatment units, and overall removal efficiencies then begin to decrease. Therefore, proper sludge handling enhances the overall treatment of all wastes. The most commonly used methods to deal with sludge solids are as follows: anaerobic and aerobic digestion, vacuum filtration, elutriation, drying beds, sludge lagooning, wet combustion, atomized suspension, drying and incineration, centrifuging, sludge barging, landfill, transporting to an acceptable landfill, and miscellaneous methods. Anaerobic digestion is a common method of readying sludge solids for final disposal. Two main groups of microorganisms, hydrolytic and methane, carry out digestion. Aerobic digestion is applied in small plants, as it requires less-skilled workers. “Vacuum filtration” has become popular because the volume of solids for ultimate disposal is reduced and the sludge is drier than it would otherwise be. Elutriation improves filtration by washing the sludge. The Zimpro process is a relatively innovative treatment for sludge.