Phosphorous release from activated sludge containing ferric phosphate using sodium sulfide
LU Xiao, SUN Jing, LI Yong-mei
State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
This work aims to study the enhancement of phosphorous (P) release from the waste activated sludge containing ferric phosphate (FePO4) by adding sodium sulfide (Na2S). First, effects of Na2S dosage and temperature on P release from FePO4 precipitation were investigated. Then, anaerobic fermentation of the sludge containing FePO4 was studied with different Na2S dosage, focusing on P release. The results showed that adding more Na2S could increase P release, and 100% of P can be released from iron phosphate when S/Fe molar ratio was 5:1 or more. Temperature mainly affected the reaction rate. During the anaerobic fermentation of the mixed sludge containing FePO4, when S/Fe molar ratio was 1:1, 3:1 and 5:1, P release efficiency was 60%, 93% and 100%, respectively; compared to the sludge without Na2S addition, the efficiency was increased by 26%, 59% and 73%, respectively. In addition, Na2S addition could promote volatile fatty acids production. When the S/Fe molar ratio was 3:1 and after 7days fermentation, the total VFA concentration was 4.3times of that without Na2S addition. However, Na2S addition has negative effect on methane production.
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