Abstract
Volatile fatty acids (VFAs) are preferred valuable resources, which can be produced from anaerobic digestion process. This study presents a novel technology using β-cyclodextrins (β-CD) pretreatment integrated alkaline method to enhance VFAs production from codigestion of food waste and sewage sludge. Experiment results showed that optimized ratio of food waste to sewage sludge was 3 : 2 because it provided adequate organic substance and seed microorganisms. Based on this optimized ratio, the integrated treatment of alkaline pH 10 and β-CD addition (0.2 g/g TS) performed the best enhancement on VFAs production, and the maximum VFAs production was 8631.7 mg/L which was 6.13, 1.38, and 1.57 times higher than that of control, initial pH 10, and 0.2 g β-CD/g TS treatment, respectively. Furthermore, the hydrolysis rate of protein and polysaccharides was greatly improved in integration treatment, which was 1.18–3.45 times higher than that of other tests. Though the VFAs production and hydrolysis of polymeric organics were highly enhanced, the primary bacterial communities with different treatments did not show substantial differences.
Highlights
Food waste (FW) is becoming a serious concern for the developed countries due to its environmental impacts
The main objective of this study is to evaluate the feasibility of β-CD addition integrated into alkaline pretreatment for enhancing Volatile fatty acids (VFAs) production from codigestion of food waste and sewage sludge
The VFAs production at ratios of 2 : 3 and 1 : 1 was almost the same (1277.4 versus 1237.9 mg/L), which were both higher than the test at ratio of 1 : 2 (1014.7 mg/L)
Summary
Food waste (FW) is becoming a serious concern for the developed countries due to its environmental impacts. As the byproduct of wastewater treatment plants (WWTPs), 6.25 million tons of dry excess sludge has been produced in China in 2013 and is still showing a rapid increasing rate [1]. The main component of food waste and excess sludge is organic matter (e.g., proteins, polysaccharides, and lipid), and anaerobic digestion is preferred as an efficient pathway for treatment of these highly organic solids [3]. Efficient digestion of such organics can generate soluble organic products that assist in recovery of valuable resources [4]. Volatile fatty acids were valuable products as alternative carbons for nutrients removal, polyhydroxyalkanoates (PHA) production, and methane production processes [5,6,7]
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