Biological activated carbon (BAC) combined the adsorption and biologic degradation consuming low power energy and chemicals without concern of DBPs production as well as no frequent updates for activated carbon media. The BAC biofilter can remove the PPCPs pollutants, and then the followed UF can reject microorganisms and particles flowing out from the biofilter to ensure the quality of drinking water. Thus, the BAC-UF process makes up for the defects of the respective operations of BAC biofilter and UF. Although many pilot-scale setups were used to treat secondary wastewater effluent for water reclamation, this type of raw water quality was different from the river water, causing the potential of biofilm growing differently. As far as we investigated, the lack of enough attention to long-term pilot study is present. Therefore, in this study, a BAC-UF system was carried out for several months with a pilot scale.
What is the main challenge? Why author choose this material? Please highlight in the introduction part.