Fast start-up of partial nitrification for high-ammonia wastewater treatment using zeolite with in-situ bioregeneration

Partial nitrification (PN) has been successfully applied in treating wastewater with medium or low concentrations of ammonia, whereas the treatment of high-concentration ammonia wastewater remains a great challenge due to the inhibition of ammonia-oxidizing bacteria (AOB) by excessive free ammonia (FA). In this study, the zeolite adsorption and bioregeneration synergy were utilized to enhance the PN of sequencing batch reactors (SBRs) for treating high-ammonia wastewater (500- 1000 mg NH4+-N/L). The SBRs with natural zeolite (NZeolite) and modified zeolite (M-zeolite) could successfully start-up within 8 days (90 % ammonia nitrogen removal (ANR) and 71 % nitrite accumulation rate (NAR) for SBR with N-Zeolite, and 81 % ANR and 84 % NAR for SBR with M-Zeolite), while the SBR without adding zeolite failed to start-up (40 % ANR). The PN enhancement may be attributed to the rapid adsorption of NH+4 by zeolite and the subsequent bioregeneration in an SBR cycle, which allowed a lower ammonia level in the bulk solution and alleviated the inhibition of FA on AOB, thus enabling a sustainable PN. Compared with M-zeolite, N-zeolite may be more practical for highammonia wastewater treatment owing to its fair performance, low cost, and simple maintenance. These results revealed that the "adsorption"-"saturation"-"desorption" process of zeolite was favored to construct a virtuous cycle of nitrification-pH-FA equilibrium in SBRs, which broadens the knowledge of biotransformation in high-ammonia wastewater and in-situ regeneration mechanism of zeolite and provides a highly efficient and practical method for treating high-ammonia wastewater.