Advanced nitrogen and phosphorus removal from groundwater by a composite functional particle-ceramic membrane bioreactor

Abstract

Nutrients are the main environment pollution issue in groundwater, while the efficient and sustainable membrane technology is the key to solving this problem. In this work, a composite functional particle-ceramic membrane bioreactor (CFP-CMR) was developed for advanced nitrogen and phosphorus removal from groundwater. Under the condition of moderate flux (5–15 L·m−2·h−1), CFP-CMR is able to sustain the preferable water purification performance (effluent: TP < 0.1 mg/L, NH3-N < 0.5 mg/L) for long-term stable operation (>100 days) via the synergy of membrane, adsorption, and microorganism. Composite functional particle could enrich and provide the carbon source for microorganism, as well as combine with the P in the water to form the crystals. The adsorption effect of composite functional particles in the early stage and the biological phosphorus removal in the later stage could synergistically improve the TP removal. Similarly, the CFP-CMR could ensure that the NH3-N in effluent reached the Chinese drinking water standard through the synergy of adsorption and microbial. However, the excessive gel layer with high C/N (i.e. Rhodobacter) on the ceramic membrane surface brought about the dissimilation reduction of nitrate to ammonium and affected the ammonia nitrogen removal. Besides, as the main membrane fouling, the biological gel layer could be effectively removed by hydraulic backwashing, so as to reduce the TMP and restore the permeability. Whereas, the re-startup after membrane cleaning clearly reduced the microbial and organics in the system, then weakened the nitrogen and phosphorus removal efficiency. In general, the findings of this work verify the reliability of CFP-CMR for the effective and sustainable operation of groundwater purification. The CFP-CMR combines the advantages of adsorption and biological processes, and is expected to become an effective technology for nitrogen and phosphorus removal.