Enhancing the dewaterability of the municipal sludge by flocculant combined with skeleton builder

Abstract

In order to cope with the problems that the sludge cannot be treated by incineration directly, a treatment process for conditioning sludge by flocculant (aluminum ammonium enhancer) combined with skeleton builder (sawdust) has been proposed, which is beneficial to the final sludge incineration. In this work, the effects of flocculant combined with skeleton builder on sludge conditioning were evaluated. When the addition amount of aluminum ammonium enhancer and sawdust was 2% and 20% of the dry weight of sludge respectively, the conditioning effect was the best. Under this condition, the specific resistance to filtration of the sludge and the capillary suction time decreased by 89.9% and 73.1% respectively compared with the raw sludge. The organic matter content of the best combination of sludge cake was 9.12% and the calorific value was 13,972 kJ/kg. The surface of the sludge cake became rough. The holes and cracks appeared due to the formation of large flocculating masses in the sludge, which allowed water to flow out smoothly. The determination of protein and polysaccharide in extracellular polymer combined with Fourier transform infrared spectrometer analysis showed that the extracellular polymers structure was changed after the sludge conditioning. The conditioning mechanism of the combined conditioning agent was proposed. The conditioning cost accounting showed the operation cost pretreated by aluminum salt enhancer combined sawdust was just 40 $/ton. These results showed the combination of flocculant and skeleton construction can not only effectively enhance the sludge dewatering performance, but also facilitate the final incineration disposal.