Sludge Treatment Technologies

Sewage sludge is generated as a result of treating municipal wastewater to remove organic and inorganic impurities from dilute solutions. The treatment results in concentrating the impurities into a smaller volume of liquid, called sludge. The main processes involve sludge stabilisation, dewatering and incineration. The major objective of stabilisation is to make the sludge less odorous and putrescible, and to reduce the pathogenic organisms. The processes of stabilisation include aerobic digestion, anaerobic digestion, thermo-chemical treatment and chemical treatment. Dewatering of sludge plays a crucial role, both operationally and economically, particularly when the methods of disposal involve landfill disposal or heat treatment combined with subsequent disposal of the residues. There are different types of dewatering processes namely cntrifugal dewatering, centripress, centridry, belt filter dewatering, chamber filter press, membrane chamber filter press. Incineration of sludge is becoming an acceptable treatment alternative, due to a high volume reduction, possible energy recovery, and some toxic destruction or reduction. This option is gaining more attention with the advent of proper air pollution control devices and highly effective flue gas cleaning systems.