Application of a synthetic zeolite as a storage medium in SBRs to achieve the stable partial nitrification of ammonium

Abstract

Free ammonia (FA) is the growth substrate for ammonia-oxidizing bacteria (AOB), but a high concentration of FA could also inhibit AOB activities. Since ammonium can be adsorbed by zeolite and desorbed by microorganisms, a unique attempt to use zeolite synthesized from coal fly ash (ZCFA) as a storage medium for supplying ammonium concentrations in SBRs was conducted, leading to an appropriate FA range. After confirming the excellent adsorbent properties, the SBR was set up with an added amount of 10 g L⁻¹ synthetic zeolite (ZSBR). According to the Haldane model, the inhibition concentrations of the effluent FA in the ZSBR and the blank SBR were calculated as 58.52 mg L⁻¹ and 25.66 mg L⁻¹, respectively, suggesting that the ZSBR can adapt to higher FA concentrations. Inhibition of nitrite-oxidizing bacteria and the dominance of AOB can lead to an excellent nitrite accumulation rate (up to 96%) in the ZSBR. High-throughput sequencing analysis further presented the enrichment of AOB in the ZSBR, which accounted for 49.58% of the operational taxonomic units at the family level. These results showed that the application of ZCFA for realizing the stable partial nitrification of ammonium in the ZSBR was successfully achieved.