A semi-industrial scale AnMBR for municipal wastewater treatment at ambient temperature: performance of the biological process.

A semi-industrial scale AnMBR plant was operated for more than 600 days to evaluate the long-term operation of this technology at ambient temperature (ranging from 10 to 27 ○C), variable hydraulic retention times (HRT) (from 25 to 41 h) and influent loads (mostly between 15 and 45 kg COD·d-1). The plant was fed with sulfate-rich high-loaded municipal wastewater from the pre-treatment of a full-scale WWTP. The results showed promising AnMBR performance as the core technology for wastewater treatment, obtaining an average 87.2 ± 6.1 % COD removal during long-term operation, with 40 % of the data over 90%. Five periods were considered to evaluate the effect of HRT, influent characteristics, COD/SO42--S ratio and temperature on the biological process. In the selected periods, methane yields varied from 70.2±36.0 to 169.0±95.1 STP L CH4·kg-1 CODinf, depending on the influent sulfate concentration, and wasting sludge production was reduced by between 8 % and 42 % compared to conventional activated sludge systems. The effluent exhibited a significant nutrient recovery potential. Temperature, HRT, SRT and influent COD/SO42--S ratio were corroborated as crucial parameters to consider in maximizing AnMBR performance.