Over the past decade, the concept of anaerobic processes for the treatment of low temperature domestic wastewater has been introduced. This paper uses a developed wastewater flowsheet model and experimental data from several pilot scale studies to establish the impact of integrating anaerobic process into the wastewater flowsheet. The results demonstrate that, by integrating an expanded granular sludge blanket reactor to treat settled wastewater upstream of the activated sludge process, an immediate reduction in imported electricity of 62.5% may be achieved for a treated flow of c. 10,000 m3 d−1. This proposed modification to the flowsheet offers potential synergies with novel unit processes including physico-chemical ammonia removal and dissolved methane recovery. Incorporating either of these unit operations can potentially further improve the flowsheet net energy balance to between +0.037 and +0.078 kWh m−3 of produced water. The impact of these secondary unit operations is significant as it is this contribution to the net energy balance that facilitates the shift from energy negative to energy positive wastewater treatment.
Keywords: dissolved methane, EGSB, energy balance, MBR, nutrient removal, psychrophilic