A new flowsheet is proposed to achieve energy-neutral wastewater treatment (even better, electricity-neutral) while removing nitrogen using the proven nitrification-denitrification metabolic pathway. It is compatible with solid-liquid separation by conventional clarification or membrane filtration.
The new flowsheet is based on a hybrid membrane-aerated biofilm reactor process which uses hollow fiber membranes arranged in modules and cassettes deployed in a way similar to immersed hollow fiber filtration membranes used for MBR (e.g., the ZeeWeed1 500 product). Atmospheric air is fed down the lumen of hollow fibers and oxygen is transferred to the biofilm growing on the outer surface of the membrane without the formation of bubbles.
The new energy-neutral flowsheet is compared to a conventional activated sludge (CAS) flowsheet including complete wastewater and sludge treatment with anaerobic digestion and combined heat and power energy recovery. The new flowsheet has an electricity consumption 40% lower and energy production 18% higher as compared to the CAS flowsheet and is overall electricity-neutral.