Abstract
Municipal sludge is a by-product of urban sewage treatment; it has high water content and contains many hydrophilic extracellular polymeric substances (EPS). It is difficult to achieve deep dewatering of sludge. Therefore, it is necessary to find an efficient method to treat sludge. In this study, an acid-microwave treatment method was proposed to improve the dewatering ability of sludge. A vacuum filtration test and particle size analysis test were used to explore the improvement effect of dehydration performance. After centrifugation, the concentrations of soluble proteins and polysaccharides in the supernatant were measured to explore the disintegration of acid-microwave treatment on EPS. Finally, the microstructure of sludge treated by acid-microwave was studied via the SEM test. The results showed that short-term microwave radiation was conducive to sludge dewatering. However, the sludge dewatering performance deteriorated significantly when the treatment time was too long. The optimal microwave treatment condition was 700 W for 180 s, and the SRF of sludge was the lowest, which was 10.11 × 10 12 m / kg . After acid-microwave treatment, sludge particle size increased significantly. The concentration of protein and polysaccharide in supernatant increased with the increase of microwave treatment time. Acid-microwave treatment could significantly improve the release efficiency of the polysaccharide. Through the SEM test, it can be verified that the bulk floc structure of sludge is broken after microwave treatment, and acid-microwave treatment is beneficial to the aggregation of floc fragments to form large particles, which can provide larger pores for drainage.
Highlights
Municipal sludge is the product of municipal sewage and industrial wastewater treatment by wastewater treatment plants (WWTPs)
Many suspended substances are usually trapped in the wastewater treatment process, and sludge is composed of these suspended substances after settling
Municipal sludge was obtained from the Wusong Wastewater Treatment Plant in Shanghai
Summary
Municipal sludge is the product of municipal sewage and industrial wastewater treatment by wastewater treatment plants (WWTPs). Bougrier et al [16] studied the treatment of sludge by ultrasonic, heat, and ozone, and the results showed that heat treatment could significantly reduce the apparent viscosity of sludge and improve the filtration capacity, which was the most effective method to improve the sludge dewatering ability. Compared with traditional treatment methods of sludge, microwave conditioning does not pollute the environment and can transfer energy directly into the sludge to avoid wasting energy [17]. Acidmicrowave treatment was proposed as a new composite conditioning method to improve sludge dewatering ability. To explore the mechanism of acid-microwave treatment improving sludge dewatering capacity, the particle distributions of sludge and soluble protein and polysaccharide in the supernatant were analyzed. The results obtained from this study can provide guidance for the actual engineering
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