State Environmental Protection Key Laboratory of Drinking Water Source Management and Technology, Shenzhen Key Laboratory of Drinking Water Source Safety Control, Shenzhen Key Laboratory of Emerging Contaminants Detection & Control in Water Environment, Shenzhen Academy of Environmental Sciences, Shenzhen 518001, China
The sludge disintegration under different pH conditions in alkaline treatment of PAC excess sludge was investigated. In addition, the phosphorus release mechanism was identified with both releasing process of phosphorus and aluminum, including the distribution and variation of phosphorus forms. Finally, phosphorus recovery was carried out. The results demonstrated that more DNA release and higher cell cracking rate (96.9% after 240min alkaline treatment) was found from PAC sludge treated with pH 13, compared with results of pH 11 and 12. Meanwhile, the addition of alkali caused obvious release of SOP (soluble orthophosphate, measured as PO43--P), most of which was from the dissolution of aluminum phosphate and aluminum hydroxide. 91.2% of NAIP (non-apatite inorganic phosphorus) and 69.2% of OP (organic phosphorus) in the sludge was dissolved after 240min alkaline treatment with the original pH 13 of sludge. 82.4% of phosphorus recovery from dewatering filtrate of alkali-treated sludge was obtained with the pH=9.5, Ca/P=3after 30min reaction. Results indicated that the substantial SOP was released from PAC sludge treated by alkali and the efficient phosphorus recovery was achieved with simple procedure, which displayed application potential.
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