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Nitrifying aerobic granular sludge fermentation for releases of carbon source and phosphorus: The role of fermentation pH

Zou, Jinte, Pan, Jiyang, He, Hangtian, Wu, Shuyun, Xiao, Naidong, Ni, Yongjiong, Li, Jun
Bioresource technology 2018 v.260 pp. 30-37
apatite, bacteria, carbon, chemical oxygen demand, fermentation, microbial communities, pH, phosphorus, polymers, sludge, volatile fatty acids
The effect of fermentation pH (uncontrolled, 4 and 10) on the releases of carbon source and phosphorus from nitrifying aerobic granular sludge (N-AGS) was investigated. Meanwhile, metal ion concentration and microbial community characterization were explored during N-AGS fermentation. The results indicated that N-AGS fermentation at pH 10 significantly promoted the releases of soluble chemical oxygen demand (SCOD) and total volatile fatty acids (TVFAs). However, SCOD and TVFA released from N-AGS were inhibited at pH 4. Moreover, acidic condition promoted phosphorus release (mainly apatite) from N-AGS during anaerobic fermentation. Nevertheless, alkaline condition failed to increase phosphorus concentration due to the formation of chemical-phosphate precipitates. Compared with the previously reported flocculent sludge fermentation, N-AGS fermentation released more SCOD and TVFAs, possibly due to the greater extracellular polymeric substances content and some hydrolytic-acidogenic bacteria in N-AGS. Therefore, N-AGS alkaline fermentation facilitated the carbon source recovery, while N-AGS acidic fermentation benefited the phosphorus recovery.