Abstract
Volatile fatty acids (VFAs) from waste activated sludge (WAS) via alkaline fermentation have been shown to provide an effective alternative carbon source for biological nutrient removal in wastewater treatment plants (WWTPs) that promotes the subsequent release of phosphorus (P) and refractory dissolved organic matter. The dewatering ability of fermented sludge is known to decrease during alkaline fermentation. Here, a novel strategy of initiating fermentation at a pH of 10 was developed to improve VFA purity, P removal efficiency, and fermented sludge dewaterability during WAS fermentation. Although VFAs concentration was lower (1.69 ± 0.09 g COD/L) when the pH was only initially adjusted to pH 10 (RIA) relative to when the pH was maintained at 10 on a daily basis (RDC), the purity of VFAs in the fermented liquid was improved (58.48%). Furthermore, the release of total phosphorous (TP) in RIA was 5.90 times lower than that in RDC (139.37 mg/L). The normalized capillary suction time and specific resistance to filtration in RIA decreased to 42.23% and 40.70%, respectively, suggesting that the dewaterability of fermented sludge also improved. The amount of alkali needed was 17.44 kg for each ton of total solid (TS) in RIA, which was 5.49 times lower than that in RDC. Thus, approximately 45.44 USD was saved in operational costs for each ton of TS processed in RIA. These results indicated that VFAs production via initial pH 10 fermentation was a robust and cost-efficient way for providing carbon resources in WWTPs.
Published Version
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