DEWATERING CHARACTERISTICS OF WASTE WATER TREATMENT SLUDGES AND EFFECT OF FLOCCULANTS

Abstract

Sludge handling and ' its ` disposal, is ; one of the major constraints in any chemical industry, pulp and paper industry in particular. The restraints are imposed very recently due to the growing awareness of people. for creating clean environment. The major problem relating to sludge handling can be overcome by efficient sludge dewatering techniques for which understanding of sludge characteristics and conditioning of the sludge by flocculants is very much needed. In Indian paper mills, there is no data available on dewatering characteristics of sludge obtained from their Waste Water Treatment plant with and without chemical conditioning by flocculants. It is also a fact that thea is no+enough information regarding the parametric influence on water drainability from sludge particularly the effect of conventional parameters like pH ,mixing time temperature, pressure, speed of mixing etc. An attempt has been made in this present investigation to study indepth, the dewatering characteristics of both primary and secondary sludges of two different mills using different kind of raw materials. Laboratory scale experiments have been carried out at large scale with various sludges with varying consistencies. The influence of various flocculants, organic and inorganic in nature, as well as their optimum doses on specific resistance to filteration (SRF) values have been also studied at room temperature. Further , the effect of various parameters like, pH, time of agitation, storage time, pressure on dewaterability of sludge during conditioning with flocculants in terms of specific cake resistance values have been investigated. To evaluate the various parameters like, SRF, compressibility factor, air suction rate, various mathematical correlations have been attempted based on phenomenological concepts available in classical chemical engineering literature. • A non detailed economical feasibility has been studied based on the cost items of the flocculants followed by balancing it against the benefits achieved by fixed charges, power cost and other cost parameters related to reduction of SRF values. The preliminary evaluation of economic viability studies indicates a good promise in near future. Pilot plant/commercial plant application will bring out the success of the project in real sense.