Influence analysis for the behavior of dewaterability of excess sludge in a two-stage vermifilter.
To improve excess sludge dewaterability, a two-stage vermifilter was developed to qualitatively and quantitatively analyze sludge physico-chemical properties (fractal dimension, zeta potential, extracellular polymeric substances (EPS), particle size distribution, etc.) and to correlate them with sludge dewatering characteristics (specific resistance to filtration (SRF) and capillary suction time (CST)). Results demonstrated that sludge dewatering performance was significantly improved after the primary vermifilter VF1and the second-stage vermifilter VF2. In addition, the further VF2treatment exhibited higher effects on sludge dewatering performance. The particle boundary of sludge after VF2treatment was clearer and smoother than VF1sludge (VF1S), apart from the fact that sludge morphological structure got denser and more compact. Comparing with VF1S, the fractal dimension D1calculated within 1D topological space was closer to 1 after VF2treatment, and the fractal dimension D2within 2D topological space closer to 2, indicating a better dewatering performance after VF2treatment. Additionally, the changes of sludge floc surface properties (such as zeta potential and EPS) resulted in small particles agglomerating into larger ones and then the increase of particle diameter. In summary, the two-stage vermifilter got a better sludge dewatering performance, and thus beneficial for subsequent processing of sludge.
Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China. xingmeiyan@tongji.edu.cn.
Meiyan
M
Xing
Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China.
Cenran
C
Li
Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China.
Jinzhou
J
Jiang
Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China.
Yin
Y
Wang
Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China.
Jian
J
Yang
D012722:Sewage; D014865:Waste Disposal, Fluid
D012722:Sewage
Dewaterability; Fractal dimension; Sludge morphology; Two-stage vermifilter