Study on the formation of aerobic granular sludge induced by Ni2+ and the removal of nitrogen and phosphorus in the treatment of high salinity wastewater

Abstract

The soil surface in the southern Xinjiang region has a high salt content, and flooding water causes salt dissolution and pollutes surface water. Therefore, it is particularly important to study the technology of nitrogen and phosphorus removal in the degradation of high salt wastewater. Activated sludge was inoculated in an SBR system with a height to diameter ratio (RH/D) of 7.5, and synthetic wastewater (containing 0.25 mg/L Ni2+) was used as influent to analyze the changes in sludge morphology, pollutant removal performance, microbial community during the sludge granulation process, as well as the ability of granular sludge to remove pollutants from high salt wastewater under salinity stress. The results showed that the mature granular sludge was yellow in multiple forms, with an average particle size of 357 μm. The average removal rates of COD, TP, and NH4+-N in wastewater were 95%,91.27%,and 94.5%, respectively. The dominant bacterial genera were Zoogloea, Flavobacterium,and Unclassified_f_Comamonadaceae. The influent water quality would change the relative abundance of microorganisms, while there was no significant impact on the microbial community structure. When the salt application rate was 15 g/L, the removal rates of COD, TP, and NH4+-N were 86.7%, 67.2%, and 62.6%, respectively. The sludge maintained good carbon removal ability. When the salt application rate exceeded 15 g/L, the removal rates of all indicators showed a downward trend. The application of low concentrations of heavy metals accelerated the start-up of granular sludge and targeted microorganisms for nitrogen and phosphorus removal, which had reference for the treatment of pollutants in high salt wastewater.

Keywords

• aerobic granular sludge
• sequencing batch reactor
• high salt wastewater