Effect of psychrophilic temperature shocks on a gas-lift anaerobic membrane bioreactor (Gl-AnMBR) treating synthetic domestic wastewater

Municipal wastewater is a renewable resource containing energy, nutrients and water. These valuables can be recovered via new, innovative technologies such as the gas-lift anaerobic membrane bioreactor (Gl-AnMBR), which is especially suitable for decentralized wastewater treatment. To better understand the effects of fluctuating environmental conditions on the treatment performance, the impact of short-term temperature shocks was studied. We present a laboratory study of a 10 L Gl-AnMBR equipped with an external tubular ultrafiltration membrane treating synthetic domestic wastewater at mesophilic (35 °C) conditions with a series of short-term (12-48 h) cold (15 °C) shocks applied prior to switching to psychrophilic (15 °C) conditions. The average COD removal under mesophilic conditions was as high as 94 ± 2%, even during the temperature shocks. Under psychrophilic conditions, more than 80% of the influent COD accumulated in the reactor (compared to 39% under mesophilic conditions). The results suggest that an abrupt and short-term temperature decrease from 35 to 15 °C can largely be absorbed by our system with no negative effect on effluent quality.