Abstract:
Anaerobic treatment has widely been used especially for treatment of medium and high strength industrial wastewaters such as brewery wastewater. Expanded Granular Sludge Bed (EGSB) reactor is considered a desirable treatment option for the brewery wastewaters and other high strength organic wastewaters produced by industries. The reactor performance is usually evaluated in terms of process efficiency and stability through estimation of organic matter removal, VFA levels, quantity and composition of biogas produced, etc. The specific methanogenic activity (SMA) test has been used to determine the maximum methanogenic activity. In addition, non-methanogenic activity tests can explain each biodegradation phase of anaerobic treatment processes. For accurately describing microbial populations, rRNA-based approaches utilizing the techniques of fluorescent in situ hybridization (FISH) with nucleic acid probes, together with other genetic analyses, have dramatically increased our knowledge of many ecosystems and have yielded a clearer overall picture of microbial diversity. In this study, methanogenic and non-methanogenic activities and archaeal population dynamics in a full-scale EGSB reactor treating a brewery wastewater were determined for a three months period (April, May and June 2007), using SMA Test and FISH, respectively. The SMA tests showed that the maximum acetoclastic methanogenic activity was found to be 457 mL CH4 /g VSS.d in April sample. In addition, the maximum specific methanogenic activity with butyrate and propionate were 460 mL CH4 /g VSS.d and 250 mL CH4 /g VSS.d in June and April samples, respectively. Finally, maximum overall methanogenic activity using a VFA mixture (2000 mg/L acetate, 500 mg/L butyrate and 500 mg/L propionate) was found to be 400 mL CH4/g VSS.d in April sample. Regarding to non-methanogenic activity measurements, a method based on substrate utilization rate was adopted. June sample had the maximum acidogenic activity of 2.84 mg COD/mg VSS.d. The hydrolytic step was dominant in 3000 and 4000 mg/L sucrose concentrations in the three samples. FISH results supported activity test results particularly acetoclastic methanogenic activity tests results. Methanosaeta spp. were found to be the predominant methanogens in the EGSB reactor at all heights. However, predominance of Methanosaeta spp. tended to change to hydrogenotrophic methanogens along the reactor during the three months sampling.
