Anaerobic digestion of textile industries wastes for biogas production

Abstract

Energy and nutrient recovery by anaerobic digestion of textile industry wastes (sludge) is facing challenges due to the anticipated toxicity, lower pH (6.6) and low C:N ratio (12.2). In the present study, the anaerobic co-digestion of textile aerobic sludge (ETP) generated in industry with different co-substrates (Food waste and Cow dung) was assessed through biochemical methane potential tests under mesophilic temperature (35 °C). The VS and ash content of textile sludge was observed to be 5.9 gVS/L and 41.4 g/L, respectively. In lab-scale study, the cumulative biogas and methane production from textile sludge was observed under controlled conditions (36 ± 1 °C) using CD (cow dung) as co-substrate in 1:1 ratio. It was found that the cumulative biogas and methane production were 567.3 and 244.1 mL/gVS added, respectively, during the 30-day digestion period while using the CD with textile sludge. On-site (at leading textile industry) cumulative biogas production from textile sludge with CD and FW (food waste) co-substrate was 524.4 and 288.3 mL/gTS added, respectively, during the 30-day anaerobic digestion. In the lab-scale study, the VSR (volatile solid reduction), Total Alkalinity (T. Alk.) and TVFA (Total volatile fatty acid) observed were 39.5%, 300 and 340.7 mg/L after completion of anaerobic digestion. The digestibility of the textile sludge, as reflected based on COD (chemical oxygen demand) removal, was higher with CD co-substrate (51%) as compared to FW (37%). After anaerobic digestion of CD and FW co-substrate, the TAN (Total ammoniacal nitrogen) and T. Alk. were observed as 147.5, 222.5 and 2560, 2800 mg/L, respectively. The present study provided an efficient method for textile sludge utilization coupled with biogas generation. The surplus energy generated during the process can be utilized in several operational units and also overcome the sludge disposal issued faced by leading textile industries.