Research on the Optimization of Beijing Municipal Sewage Plant Sludge Dewatering Reagent Cationic Polyacrylamide

Abstract

With Chinese continuous improvement of the urbanization and industrialization level, water pollution has becoming more and more serious, and the by-product —sludge has caught the focus of public attention. The total amount of sewage sludge produced in Beijing in 2010 is about 3,700t/d (wet base), 2,500t/d of which is from the urban area and 1,200t/d is from country side. Such a large amount of sludge with abundant water brought great difficulties to the subsequent processing. However, the cost of sludge treatment amounts to almost half of the sewage plant running cost while the consumption of drug covered more than half of the sludge treatment expenditure. Another aspect is that the water content of the dewatered sewage sludge is not stable, because of the variation of inlet amount and quality. Without knowing the relationship between the characteristics of sewage sludge and conditioning reagent, the operator just try to add more reagent, which in the end increase the cost of sludge treatment. Meanwhile, cationic polyacrylamide (C-PAM) is currently the most widely used sludge conditioning reagent. This research is to find out the relationship between the characteristics of sewage sludge and adding dosage of CPAM, which can be the first step to discuss how to adjust the conditioning reagent according to sewage sludge with different characteristics.Polyacrylamide (PAM) of different cationic (15%,35%,45%,60%), molecular weight (8 million, 10million, 12million) and dosage (2‰,3‰,4‰,5‰,6‰) are under testing in the experiment considering the index of capillary suction time (CST).Experimental material is the sludge from digestion tank in one of Beijing sewage plants. According to the experiment, it was found that the 8million-10million molecular weight, 4‰-6‰ adding dosage perform the best.