Influences of volatile solid concentration, temperature and solid retention time for the hydrolysis of waste activated sludge to recover volatile fatty acids

Volatile fatty acids productions by mesophilic and thermophilic sludge fermentation: Biological responses to fermentation temperature

“…Compared with other studies which used primary or secondary sludge, or synthetic materials as substrates for fermentation (Jia et al, 2013;Wang et al, 2013;Zheng et al, 2013), the sludge used in this study had higher solids concentration, as it was reported previously that higher solids concentration could improve VFAs production (Xiong et al, 2012).…”

“…However, VFAs accumulation is very low in this case. To improve VFAs production, increasing fermentation temperature is a succinct and effective approach Xiong et al, 2012). Under thermophilic condition (50-60°C), high concentration of VFAs can be acquired, as well as good stability and economic efficiency by proper control (Lu et al, 2007;Song et al, 2004).…”

“…products (Song et al, 2004;Xiong et al, 2012). Mesophilic condition (30-40°C) has long been adopted for anaerobic digestion to recover biogas, showing good performances (Cai et al, 2004).…”

“…Up to now, large efforts have been made to convert the abundant organic matter in the sludge to methane or hydrogen (Cai et al, 2004;Palatsi et al, 2011). Recently, the production of volatile fatty acids (VFAs) is gaining increasingly attention since the produced VFAs can be provided as organic carbon source for nitrogen and phosphorus removal in wastewater treatment plant (Tong and Chen, 2007), or as raw material for bioplastic polyhydroxyalkanoates (PHAs) synthesis (Xiong et al, 2012).…”

Transformation and utilization of slowly biodegradable organic matters in biological sewage treatment of anaerobic anoxic oxic systems

“…Theoretically, 2.86 mg of COD are required to reduce 1 mg of nitrate nitrogen, approximately 2 mg/ L COD of carbon source are required for removing nitrogen through denitrification, and overall, approximately 11 mg/L COD of carbon source are consumed in the anaerobic stage. Research has shown that in the anaerobic stage, phosphorus-accumulating bacteria firstly utilize quality carbon sources, such as volatile fatty acids (VFA) and polyhydroxybutyric acid, and degrade intracellular polymeric phosphate and glycogen to increase soluble phosphorus concentrations (Xiong et al, 2012). Thus, in the anaerobic stage, RBCOD was entirely used to release phosphorus, 3.15 mg/L of SBCOD were used to release phosphorus, and all carbon sources required for nitrogen removal by denitrification were obtained from SBCOD.…”