Applicability of a Sequencing Batch Membrane Biofilm Reactor for Simultaneous Nitrogen and Phosphorus Removal from Low C/N Ratio Wastewater

Abstract

A sequencing batch membrane biofilm reactor (SBMBfR) was developed towards simultaneous carbon, nitrogen and phosphorous removals from a low carbon/nitrogen (C/N) ratio wastewater. The SBMBfR is composed of two functional parts in a single-reactor vessel: (1) a fibrous-composite matrix of a gas-permeable hollow-fiber membrane on which a nitrifying biofilm grows and (2) activated sludge in which denitrifying polyphosphate-accumulating organisms (DNPAOs) are predominant. The reactor was operated in a batch manner with the turning on and off of the membrane aeration. Anaerobic period (without membrane aeration) allowed consumption of organic carbon by DNPAOs. They further took phosphate in the bulk with nitrite/nitrate produced via nitrification at the nitrifying biofilm during membrane aeration period. A higher nitrogen removal efficiency was obtained with the nitrifying biofilm formed on a gas-permeable membrane at various C/N ratios in synthetic wastewaters than without the biofilm, corroborating the significance of the biofilm as a region for ammonia oxidation. Continuous operation of the SBMBfR achieved average nitrogen and phosphorus removal efficiencies of 90% and 92%, respectively, at a C/N ratio of 2.0 indicating the effectiveness of the SBMBfR for nutrient removal from low C/N ratio wastewater.