Microbial community of Biological Oxygen-dosed Activated Carbon (BODAC) whole granules prior to backwashing procedure
Biological oxygen-dosed activated carbon (BODAC) filters in an Ultrapure water plant were demonstrated to have the potential to further treat secondary wastewater effluent. The BODAC filters were operated for 11 years without carbon regeneration or replacement while still functioning by actively removing OMPs and foulant as a pre-treatment step to reverse osmosis (RO) membranes. In this study, a holistic approach by analyzing granules and water samples of BODAC filters was conducted for two years to understand the mechanisms behind the long-term operation of the BODAC filters. The results showed that the BODAC granules' surface area was reduced by ~70% of what is in virgin carbon granules and covered by biofilm and inorganic depositions. The BODAC filters removed soluble organics, mainly protein, performed as an effective nitrification system, and almost completely removed manganese. During the two years of observation, the filters consistently removed some OMPs such as hydrochlorothiazide, metoprolol, sotalol, and trimethoprim by at least 70%. Finally, through microbial community analysis, we found that nitrifying and manganese-oxidizing bacteria were detected in high relative abundance on BODAC granules, supporting BODAC performance in removing OMPs and manganese as well as converting nitrogenous species in the water.