Composite functional particle enhanced gravity driven ceramic membrane bioreactor for simultaneous removal of nitrogen and phosphorus from groundwater

Abstract

Recently, the emergency of ammonia (NH3-N) and phosphorus (TP) in groundwater becomes the serious environment problem. Herein, a composite functional particle enhanced gravity driven ceramic membrane bioreactor (GDCMBR) was developed to ensure the safety of potable water. After the composite granulation of bentonite and steel slag, the specific surface area, pore diameter and pore volume of particles increase continuously via specific surface area and pore size distribution analyses (BET-BJH analysis), thus providing more adsorption sites for the adsorption of ammonia nitrogen and phosphorus. Moreover, using SEM-EDS-Mapping, X-ray Diffraction (XRD) and Fourier Transform Infrared Spectrometer (FTIR), PO43− presented a precipitation reaction with steel slag, and NH4+ could replace metal ions inside bentonite. Besides, in the 60 days operation, GDCMBR enabled to enhance the bacteria enrichment, shorten the ripening period (10 ∼ 15d) of nitrogen and phosphorus removal, and then achieved the desirable effluent quality (TP: below 0.05 mg/L, NH3-N: no detected). During long-term continuous operation, the intensity biological activity within bioreactors was demonstrated by Total Organic Carbon (TOC) measurement, Excitation-Emission Matrix (EEM) spectrum and Confocal laser scanning microscope (CLSM). At the same time, the nitrifying bacteria (i.e., Nitrospira) and denitrifying phosphorus accumulating bacteria (i.e., Exiguobacterium and Pseudomonas) existed in the biofilter for removing nitrogen and phosphorus. Afterwards, the GDCMBR flux dropped to 9.8 L·m−2·h−1 and kept it stable after 14 days’ operation, due to the microorganism accumulation on membrane. Finally, the particles of GDCMBR could be transferred quickly to promote the flux and obtain a sustainable water purification efficiency. The composite functional particle enhanced GDCMBR combines the advantages of adsorption and biological process, and is expected to become an effective water treatment technology.