Improvement in biomass characteristic and degradation efficiency in modified UASB reactor treating municipal sewage: A comparative study with UASB reactor

摘要

Low Strength Wastewaters (LSW) are difficult to degrade efficiently in the upflow anaerobic sludge blanket (UASB) reactor. The possible reason for poor treatment of low strength wastewaters in UASB are: (i) low mixing due to low biogas production (ii) frequent biomass washout at higher hydraulic loading rate due to low settleability of biomass. In the present study, lab scale UASB reactor and modified upflow anaerobic sludge blanket (MUASB) reactor were operated with municipal sewage COD (180-210 mg/L) as LSW at three different HRTs (8, 6 and 4h) and changes in the biomass characteristics as well as degradation efficiency were compared with respect to time. During this operation, samples of biomass were taken from both reactors to measure TSS, settling velocity, granular size and specific methanogenic activity (SMA). The overall COD removal in MUASB reactor was higher compared to UASB (84 and 67% respectively). After 150 days of operation,the settling velocity and SMA of MUASB biomass increased, but no significant change in settling velocity and SMA of UASB biomass was observed. The study shows that MUASB could be preferred over UASB for the treatment of municipal sewage as LSW.