Impact of salinity and time on structure and functional potential of wastewater treatment biofilms in intermittent sand bioreactors.

High salt wastewater is produced in industries, including seafood and pickling processing. The salinity in such wastewaters has been shown to negatively impact biological treatment efficacy. Little is known about the changes in the microbial community structure in the mature biological 2 treatment systems, the impacts of salinity on community composition, and the shifts over time during operation. This study aimed to identify the changes in the microbial community due to both salt and days of operation through 16s rRNA sequencing and KEGG functional predictions. Intermittent sand bioreactors (ISBs) with a focus on ammonia treatment were utilized. Results showed that the overall community structure and diversity were distinct as wastewater salinity varied from 0%-1.3%. At 1.3% salinity Zoogloea, a common genus in wastewater treatment plants, was not present and Aequorovita, Thauera and Dokdonella became the dominant genera. Nitrosomonas, an important ammonia oxidizing bacteria, increased in abundance with days of operation but was not significantly impacted by an increase in salinity. This finding was further supported by an increase in predicted nitrification potential with time of operation within all intermittent sand bioreactors tested. These results provide a deeper understanding of the impacts of salinity on microbial community development in biological treatment systems and elucidate the shifts in community structure occurring during early operations and into system maturity.