A simultaneous removal of beryllium and ammonium–nitrogen from smelting wastewater in bench- and pilot-scale biological aerated filter

Abstract

Heavy metal and NH4+–N co-contaminated wastewater are frequently found, and the presence of NH4+–N makes it extremely difficult to treat. In the present study, bench-scale and pilot-scale experiments were conducted to investigate the simultaneous removal of beryllium and NH4+–N from smelting wastewater by biological aerated filter (BAF) reactors. The results of the five-stage BAF reactors showed that the system could endure shock loadings. The average removal efficiency for beryllium and NH4+–N was 92.6% and 95.0%, respectively. Sequence extraction indicates that the primary removal mechanism in the first two reactors was precipitation, whereas the organic-bound fraction was predominant in the last three reactors due to the high accumulation rates of beryllium inside the microbial cells. Polymerase chain reaction and denaturing gradient gel electrophoresis (PCR–DGGE) and sequence analysis of 16S rDNA gene fragments showed that N-oxidizing bacteria (Nitrosomonas sp. and Beta proteobacterium CH24i) were primarily detected in the first two BAF reactors, in accordance with their high NH4+–N removal efficiencies, and metal-resistant bacteria (Actinobacteria sp.) were found in all BAF reactors.