Saline short-term shock and rapid recovery on anammox performance

Anaerobic ammonia oxidation (anammox) is an environmental-friendly biological nitrogen removal process, which has been developed as a promising technology in industrial wastewater treatment. However, anammox nitrogen removal under high saline conditions still faces many challenges. This study investigated the perfor-mance of anammox sludge under saline short-term shock and the strategy of rapid recovery. Salinity concen-tration, saline exposure time, and NaCl/Na2SO4 ratio were selected as three critical factors for short-term shock. The activity inhibition of anammox sludge were tested by using response surface methodology (RSM). Our results showed that, compared with the NaCl/Na2SO4 ratio, the salinity concentration and saline exposure time were the significant factor causing the anammox inhibition. The addition of glycine betaine (GB) in moderate amounts (0.1-5 mM) was found to help anammox to resist in relative low saline shock intensities (e.g., IC25 and IC50), with the activity retention rate of 94.7%. However, glycine betaine was not worked effectively under relatively high saline shock intensities (e.g., complete inhibition condition). Microbial community analysis revealed that Bro-cadiaceae accounted for only about 7.6% 13.2% at inhibited conditions. Interestingly, 16S rRNA analysis showed that the abundance of activated Brocadiaceae remarkably decreased with time after high-level saline shock. This tendency was consistent with the results of qPCR targeted hzsA gene. Finally, based on quorum sensing, the anammox activity was recovered to 93.5% of original sludge by adding 30% original sludge. The study realized the rapid recovery of anammox activity under complete inhibition, promoting the development and operation of salt-tolerant anammox process.

Automated summary

This study investigated the challenges of anammox nitrogen removal under high saline conditions and found that adding moderate amounts of glycine betaine (GB) could help resist relative low saline shock intensities.