Promotion of Ammonium Removal by a Synergistic System of Acinetobacter baumannii AL-6 and Modified Walnut Shell Biochar

Some severe conditions, such as acid conditions or high ammonium concentration, always inhibited biological ammonium removal in water. This study constructed a novel synergistic system of Acinetobacter baumannii AL-6 and modified walnut shell biochar (MBC), which achieved an excellent promotion for ammonium removal under severe conditions. The application of MBC could help the growth of microbe under pH 5 and show a high removal efficiency to ammonium of 79.9%, which is 3.7 times higher than that of individual MBC adsorption. Moreover, the biodegradation capability of strain AL-6 had been enhanced by the application of MBC. The average ammonium removal rate reached 5.02 mg·L −1 ·h −1 at initial NH 4 + –N concentration of 300 mg·L −1 , which is 6.84 times high than that of single strain AL-6 and 2.37 times MBC adsorption. The biomass on the biochar indicated that the MBC was loaded with a large number of living bacteria. The OUR results suggested that the strain AL-6 could maintain high biological activity continuously on MBC. The SEM and FTIR shown that the large number of irregular pores, specific surface areas and hydrophilic functional groups on the surface of MBC, which could promote the loading of strain AL-6 on MBC and the biodegradation of strain AL-6. Besides, in the sequence batch reactor (SBR) inoculating with the microbe–biochar composite, more than 98.12% of NH 4 + –N was removed. Hence, biochar-immobilized AL-6 has great potential and can be applied to degrade NH 4 + –N polluted wastewater. Graphical Abstract