Simultaneous removal of nitrate, carbamazepine, and copper by fulvic acid and ferric chloride composite modified ceramsite assembled fixed biofilter reactor: Performance and microbial community response.

The complex pollution and nutrient-poor characteristics of surface waters result in the limited ability of conventional reactors to remove pollutants. In this study, a novel modified ceramsite material, modified with trivalent iron (Fe(III)) and fulvic acid (FA) to form ceramsite@Fe(III)@FA (HC), was used for the first time as a biocarrier to immobilize strain Cupriavidus sp. W12, constructing a biofilter to enhance nitrate (NO3--N) removal in micro-polluted water. HC could accelerate electron transfer, significantly enhancing the denitrification capacity of the biofilter. When HRT was 6, pH was 7, and C/N was 2.5, the removal efficiency of NO3--N could reach 97.0%. Efficient removal of carbamazepine (CBZ) and copper (Cu2+) was achieved through adsorption by HC and precipitate. Calcium ions (Ca2+) removal (74.2%) was achieved through the microbial-induced carbonate precipitation (MICP) process. In addition, with the addition of CBZ and Cu2+, the biofilter maintained a stable microbial community and consistent expression of relevant functional genes. This research offers new perspectives on the efficient removal of complex pollutants in surface water treatment.