New research suggests that large quantities of a popular ingredient in antibacterial soap could be entering the environment through recycled sewage sludge.
Researchers looking for emerging contaminants in wastewater treatment plants (WWTPs) face a formidable challenge—to “find the needle in the haystack,” says Rolf Halden, an assistant professor of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health. In a study posted today to ES&T’s Research ASAP website (DOI: 10.1021/es052245n), Halden and his coauthors report that approximately 75% of the mass of a popular antiseptic called triclocarban that enters a typical WWTP persists in the treated sludge.
Halden and his coauthors found that triclocarban was almost entirely removed from the WWTP’s effluent after activated sludge treatment—with an average efficiency of 97%. The compound tends to attach itself to particles in the sludge because of its hydrophobic nature. Therefore, it remains in the sludge; even after 19 days of anaerobic digestion, levels were as high as 51 milligrams per kilogram (mg/kg). According to Snyder, the concentration of triclocarban in treated sludge is higher than he would have expected.
