Reduction of Emerging Contaminants Through Conventional and Advanced Wastewater Treatment Processes

To better understand the extent to which secondary treatment removes emerging contaminants from wastewater, a reconnaissance study of six full-scale treatment facilities was used to sort twenty target pharmaceutical and personal care products (PPCPs) into a three-by-three matrix of nine categories of secondary influent occurrence and activated sludge treatment reduction. Plots of the percentage removal of each compound versus the solids retention time (SRT) of the treatment process were used to define a critical SRT80% representing the minimum SRT value needed to consistently achieve compound removal greater than 80 percent. The SRT80% values for the target compounds ranged from 15 days. Equivalent removal was observed for a pilot MBR operated in parallel with a conventional sludge system and little additional removal of target compounds was evident through full-scale media filters. Microfiltration reverse osmosis (MF/RO) was effective in reducing the remaining target compounds in the filter media effluent to below detection limits. Previous studies of reverse osmosis membrane process trains (e.g.MBR/RO, UF/RO) for the removal of endocrine disrupting compounds (EDCs) and PPCPs have demonstrated the effectiveness of membrane treatment, but trace detects of some compounds can still occur. The effectiveness of UV and peroxide treatment, frequently used after RO to provide one-log reduction of N-nitrosodimethylamine (NDMA) for indirect potable reuse applications, was investigated under the dose conditions needed to achieve a one-log reduction of NDMA. All but one of eight target EDC and PPCP compounds investigated exhibited lower dose requirements than NDMA.