Anaerobic Immobilization Biotechnology for Treating Low Strength Synthetic Wastewater: Effect of HRT and COD Concentration on Treatment Performance
Date Issued
2016
Date
2016
Author(s)
Tien, Chun-Yen
Abstract
Anaerobic biological treatment processes (ABTPs) can produce methane as biogas during wastewater treatment, and consume less energy and waste less sludge compared with aerobic biological processes. As a result, ABTPs show promise in treating domestic wastewater. However, the slow growth rate of microorganism, the requirement of longer hydraulic retention time, and the easily washed-out biosolids have been found while ABTPs treat low-strength domestic wastewater. Therefore, this study employed an immobilization biotechnology of entrapped mixed microbial cell (EMMC) to ABTPs. The immobilization biotechnology was used to enhance biomass concentration, highly increase sludge retention time, and shorten hydraulic retention time which overcome the restraints of ABTPs when treating low-strength domestic wastewater. A laboratory-scale anaerobic immobilization bioreactor system (AIBS) which contained single continuous stirred-tank with 24 L volume was constructed and used to treat low-strength synthetic wastewater of non-fat dry milk (NFDM) at 35℃.The operation parameters including organic loading rate (0.6, 1.2 kg/m3/d), hydraulic retention time (4, 8, 16, 32 h), and influent COD concentration (200, 400, 800, 1600 mg/L) were used to evaluate the effect of each parameter on carbon removal and methane production of AIBS. After continuous operation of more than 381 day, total COD removal rate and methane recovery efficiency were higher than 80% and 44.7%, respectively, over the range of values tested HRT and COD. When HRT operated above 16 h, the COD removal rates were stably higher than 90%. When HRT operated below 8 h, the COD removal rates significantly decrease. Methane production during the AIBS operation was affected by influent COD concentration. At a constant of HRT, methane content and methane production rate decreased with decreasing of influent COD concentration. However, the methane content was stably higher than 59% when influent COD concentration of 200 mg/L. Hence, the methane recovery efficiency was higher than 44.7% when HRT operated below 4 h. An increase in OLR improved the efficiency of carbon removal and methane production, and OLR has a positive correlation with both VRE and methane production rate. In conclusion, the performance of anaerobic immobilization bioreactor system is better than typical anaerobic treatment process. The advantage of higher SRT improves AIBS. From experimental results, AIBS performs higher COD removal rate, methane content, and methane recovery under different operating conditions. Therefore, the combination of immobilization biotechnology and anaerobic biological treatment process could be potentially used for treatment of low-strength domestic wastewater under appropriate operating conditions.
Subjects
anaerobic treatment
immobilized microorganism
domestic wastewater
methane production
hydraulic retention time
organic loading rate
Type
thesis