Effect of Different Inorganic Salts on Dewatering Performance of Municipal Anaerobic Sludge

In order to achieve efficient deep dewatering, harmless and resource utilization of municipal anaerobic sludge, three inorganic salts were tested to treat municipal anaerobic sludge in this study, and the effects on anaerobic sludge dewatering performance and extracellular polymer were investigated. The results showed that both FeCl₃ and AlCl₃ could significantly improve the dehydration performance of anaerobic sludge. When the dosage was 60 mg·g^-1 (mass ratio of inorganic salt to dry sludge), the TTF of the sludge treated with FeCl₃ and AlCl₃ was shortened by 81.03% and 80.00% respectively compared with the original anaerobic sludge. However, the PAC improvement effect was not obvious. Further experiments showed that the moisture content and specific resistance of sludge decreased after using different concentrations of inorganic salt. Among them, the improvement of sludge after FeCl₃ and AlCl₃ conditioning was the most significant. The higher the inorganic salt concentration was, the lower the sludge moisture content and sludge specific resistance would be. After treatment with FeCl₃ and AlCl₃, the content of polysaccharide and protein in the sludge became higher. When the dosage of FeCl₃ was 40mg·g^-1, the content of polysaccharide and protein reached the highest. When the dosage of AlCl₃ was 20mg·g^-1 and 40mg·g^-1, the polysaccharide and protein contents reached the highest respectively.