Alkaline and acid hydrolytic processes in aerobic and anaerobic sludges: effect on total EPS and fractions

Abstract

Sludge samples from an upflow anaerobic sludge blanket (UASB) reactor and four submerged aerated biofilters (BFs) of a wastewater treatment plant (1,000 inhab.) were processed at bench scale by alkaline and acid hydrolysis with the objective to evaluate the organic matter solubilization, volatile solids (VS) destruction and the effect of hydrolytic processes on the extracellular polymeric substances (EPS) fraction of the sludge samples. The results showed that alkaline hydrolysis of sludge samples treatment with 1.0% total solids (TS) using NaOH 20 meq L(-1) was more efficient on organic matter solubilization and VS destruction than acid hydrolysis. The EPS sludge content was also affected by the alkaline treatment of anaerobic sludge samples. The EPS concentrations (mg EPS/gVSS) on the anaerobic sludge after the alkaline treatment were significantly lowered according to sample height in the UASB reactor. Data indicated that the EPS sludge fraction is the main component affected by the alkaline hydrolytic process of anaerobic sludge samples.

State of the Art in Technologies of the Biogas Production Increasing During Methane Digestion of Sewage Sludge

“…According to the literature data alkali pretreatment is more effective that acid treatment [32]. Cassini et al [33] proved that the same doses of H2SO4 and NaOH (20 mmol/L) allowed for solubilisation COD in the sludge at level 11% and 60%, respectively. Banu et al [34] showed that optimal dose of NaOH for sludge pretreatment is 1600 mg/L (time of reaction 3 hours).…”

Microbial Consortium with High Cellulolytic Activity (MCHCA) for enhanced biogas production

“…Firstly, because the generated compounds are the substrates, which are converted by another group of microorganisms (e.g., syntrophic bacteria) in acetogenesis. Secondly, it was reported that weak acids such as propionic acid, can loosen the structure of lignocellulose, resulting in an improved overall hydrolysis rate, owing to the increased accessibility of the substrate for the enzymes (Cassini et al, 2006). The fact that a correlation was observed between the high hydrolytic activity and high biogas yield during anaerobic digestion suggests that the pretreatment of cellulose/lignocellulose substrates is crucial for promoting biogas productivity and biogas technology development (Haruta et al, 2002;Wongwilaiwalin et al, 2010;Guo et al, 2011).…”

Thermochemical pretreatment of meat and bone meal and its effect on methane production

“…Therefore, it is possible to use thermal pretreatment for MBM disposal without supplying extra heat input. As proteins are the main component of MBM, alkaline pretreatment would be more efficient than acid pretreatment for the solubilization of MBM, which has been demonstrated in the hydrolysis of protein-dominating activated sludge [11,12]. However, the effectiveness of alkaline pretreatment of MBM has not been determined.…”