Calcium peroxide pretreatment of waste activated sludge for enhancement of short chain fatty acids extraction from fermentation liquid by layered double hydroxides

In the present study, calcium peroxide (CaO2) pretreatment of waste activated sludge (WAS) was proposed to enhance the extraction efficiency of short chain fatty acids (SCFAs) from anaerobic fermentation liquid (AFL) via in situ synthesis of layered double hydroxides (LDHs). The experimental results showed that the SCFAs concentration in the AFL of the WAS with CaO2 pretreatment was significantly enhanced to 7471.7 mg chemical oxygen demand (COD)/L, which was much higher than that of the control (4982.0 mg COD/L). At the same time, phosphate and carbonate ions were simultaneously removed by calcium ions with removal rates of 85.3% and 90.8% compared with the control, respectively. With the help of a higher SCFAs concentration and the removal of interfering anions, the SCFAs content in the synthesized SCFAs-LDHs-CaO2 could be enhanced to 26.6 mg COD/g LDH, which was 39.3% higher than that of the control. The economic analysis for future applications revealed that the expense of using SCFAs-LDHs-CaO2 as an external carbon source was 0.9 Renminbi/m(3), which resulted in a savings of approximately 57.0% compared with that of the SCFAs-LDHs-Control. (C) 2019 Elsevier Ltd. All rights reserved.