Response of microbial interactions in hybrid biofilm system with low organic loading to micropollutant removal

Nonsteroidal anti-inflammatory drugs (NSAID) are the most frequently observed micropollutants in the effluents of conventional wastewater treatment plants and hybrid technologies could be an alternative to conventional systems. However, the effect on micropollutants' removal has not been well studied. In this study, the impact of hybrid systems on micropollutant removal, as well as the determination of the dominant microbial communities, were investigated. For this purpose, laboratory-scale control hybrid and micropollutant-amended (1 μg/L of diclofenac, ketoprofen, indomethacin, and mefenamic acid, 10 μg/L of ibuprofen, and naproxen) hybrid reactors were operated at organic loading rate of 0.3 kg COD/m³.day and ammonium concentration of 60 mg/L N with a sludge retention time of 10 days and hydraulic retention time of 24 hrs. Effluent chemical oxygen demand (COD) was below 30 mg/L in the control and micropollutant hybrid reactors. Significant removal efficiencies for ibuprofen (99.7%), indomethacin (99.0%), naproxen (97.6%), mefenamic acid (97%), and ketoprofen (91.4) were achieved. Results revealed that NSAIDs did not have a chronic inhibitory effect on the biodegradation of organic matter and nitrification process. Higher biodiversity observed in attached biomass of micropollutant hybrid reactor might contribute to enhance system stability and performance. Dominant genera detected in hybrid micropollutant reactor were Chitinophagaceae (10.1%), Ferruginibacter (7.8%), and Comamonas (6.8%) for suspended biomass, and Fimbriimonadaceae (8.7%), Parafilimonas (6.5%), and Rickettsia (5.6%) for attached biomass, which might contribute to the removal of NSAIDs. Moreover, the genera Chitinophagaceae and Comamonas which are reported as heterotrophic ammonia-oxidizing bacteria, might contribute to nitrification in hybrid biofilm reactors.