Characterizing the Passage of Personal Care Products through Wastewater Treatment Processes
Wastewater treatment facilities utilize secondary treatment to stabilize the impact of discharged effluent on receiving waters by oxidizing biodegradable organic matter and reducing suspended solids and nutrients. The process was never specifically intended to remove trace quantities of xenobiotics such as endocrine disrupting compounds (EDCs) and pharmaceuticals and personal care products (PPCPs). Nonetheless, European studies performed at bench-scale or at small facilities have demonstrated that a critical minimum solids retention time (SRT) can achieve good reduction of many EDCs and pharmaceuticals. The objective of this study was to expand these findings to the removal performance for twenty PPCPs commonly found in the influent to full-scale facilities operating in the United States. The participating plants utilize SRT conditions ranging from 0.5 to 30 days and include facility capacities ranging from 5-mgd to greater than 300-mgd. Two pilot membrane bioreactors were also included in the study. The twenty PPCPs were categorized into nine bin combinations of occurrence frequency and treatment reduction performance. While most compounds were well removed, galaxolide (a musk fragrance) occurred frequently and was resistant to removal. A minimum critical SRT, defined as the minimum needed to consistently demonstrate greater than eighty percent removal (SRT80), was compound-dependent with most compounds removed at 5 to 15 days and a small group requiring longer SRTs. From limited data, no additional removal could be attributed to the use of membrane bioreactors, media filters, or longer hydraulic retention times. Reverse osmosis (RO) was effective in removing any remaining compounds.