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Enhancing Sewage Sludge Dewaterability by a Skeleton Builder: Biochar Produced from Sludge Cake Conditioned with Rice Husk Flour and FeCl3

Wu, Yan, Zhang, Panyue, Zeng, Guangming, Ye, Jie, Zhang, Haibo, Fang, Wei, Liu, Jianbo
ACS sustainable chemistry 2016 v.4 no.10 pp. 5711-5717
biochar, ferric chloride, filtrates, filtration, flour, iron, pH, pyrolysis, rice, rice hulls, sewage sludge, temperature, turbidity
Biochar produced from sludge cake conditioned with rice husk flour and FeCl₃ (biochar-conditioned) was used to enhance sewage sludge dewaterability. The pyrolysis temperature and dosage of biochar-conditioned were optimized, and the effect of biochar produced from raw sludge cake (biochar-raw) and biochar-conditioned on the sewage sludge dewaterability was compared. Moreover, the mechanisms of biochar-conditioned improving sludge dewaterability as a skeleton builder were analyzed. The optimal pyrolysis temperature of biochar-conditioned was 400 °C. The biochar-conditioned contained the sludge-based biochar with a high content of iron and rice husk-based biochar. Compared with biochar-raw, biochar-conditioned prepared at 400 °C was more effective at enhancing the sludge dewaterability, and the optimal biochar-conditioned dosage was 70% dry sludge (DS). Compared with adding FeCl₃ alone, the sludge specific resistance to filtration decreased by 63.9%, the net sludge solids yield increased by 39.2%, and the net percentage sludge water removal increased to 98.36%. Large cracks made the sludge cakes permeable, so that more sludge moisture was filtered from the sludge cake. In addition, adding biochar-conditioned reduced the turbidity and SCOD of sludge filtrate and adjusted the sludge pH to neutral. Using biochar-conditioned to condition the sewage sludge as a skeleton builder is promising.