Fermentation of Municipal Primary Sludge: Effect of Srt and Solids Concentration on Volatile Fatty Acid Production

Abstract

Laboratory bench-scale experiments were conducted to investigate the performance of primary sludge fermentation for volatile fatty acids production. Primary sludges from two major wastewater treatment plants located in Valencia (Pinedo and Carraixet) were used. Experiments were performed at solids retention times between 4 and 10 days, and total volatile solids concentrations between 0.6% and 2.8%. Operation at two temperatures (20 degrees C and 30 degrees C) was also checked. Results indicated the importance of feed sludge characteristics on volatile fatty acids yields, being approximately double for the Carraixet wastewater treatment plant sludge than for the Pinedo plant. In both cases, higher volatile fatty acids yields were observed at higher total volatile solids concentrations. Solids retention times above 6 days scarcely improve volatile fatty acids yields, while experiments conducted at 4 days of solids retention times show an important decrease in volatile fatty acids yields. On raising temperature an increase in volatile fatty acids yields was observed, mainly due to an improvement in the hydrolysis of particulate organic matter.

2,4-D removal via denitrification using volatile fatty acids

“…The digester effluent (total VFAs equalling 3153 mg/L as HAc), contained mean concentrations of 1621 mg/L HAc (51.4%), 1071 mg/L HPr (27.5%), 909 mg/L n-HBu (19.6%) and 75 mg/L i-HVa (1.4%). In general, the distribution of HAc and HPr was relatively consistent with other researchers operating at similar SRTs, where HAc ranged from 33% to 73% and HPr from 22% to 44% (Mavinic et al 2000;Bouzas et al 2002).…”

Anaerobic hydrolysis and acidification of organic substrates: Determination of anaerobic hydrolytic potential

“…Miron et al (2000) found that digestion of primary sludge at 25°C resulted in methanogenic conditions for SRT over 8 days. Bouzas et al (2002) also showed that the VFA production was reduced significantly below 4-day SRT and increased slightly over 6-day SRT. The optimum treatment time for VFA production was obtained at fermentation time of 6 days in batch fermentation experiments performed by Jiang et al (2007) for waste activated sludge.…”

Full-scale in-line hydrolysis and simulation for potential energy and resource savings in activated sludge – a case study

“…The applicability of primary sludge hydrolysis to produce volatile fatty acids (VFAs) for biological nitrogen removal and enhanced biological phosphorous removal has been demonstrated, and these methods have been applied to full-scale WWTPs [3][4][5][6]. Furthermore, previous studies at Klagshamn have shown that the production of hydrolysate with low levels of ammonium and phosphate release provides a high denitrification rate [7] and has no significant effect on the measured gas production [8].…”