Retention and recycling of granules in continuous flow-through system to accomplish denitrification and perchlorate reduction.

ABSTRACT

This study employed a completely anoxic reactor and a gravity-settling design for continuously capturing and separating granules from flocculated biomass, and recycling granules back to the main reactor. The average chemical oxygen demand (COD) removal in the reactor was 98%. Average nitrate (NO3--N) and perchlorate (ClO4-) removal efficiencies of 99% and 74 ± 19% were observed, respectively. Preferential utilization of NO3- over ClO4- led to COD limiting conditions, which resulted in ClO4- in the effluent. The average granule diameter in continuous flow-through bubble-column (CFB) anoxic granular sludge (AxGS) bioreactor was 6325 ± 2434 µm, and the average SVI30/SVI1 was >90 % throughout its operation. 16s rDNA amplicon sequencing revealed Proteobacteria (68.53%-88.57%) and Dechloromonas (10.46%-54.77%) to be the most abundant phylum and the genus present in reactor sludge representing the denitrifying and ClO4- reducing microbial community. This work represents a pioneering development of CFB-AxGS bioreactor.