EMERGING CHEMICALS OF CONCERN IN BIOSOLIDS

Wastewater treatment is a complex process providing a crucial line of defense for the aquatic environment against anthropogenic pollution contained in industrial and residential discharges and urban runoff. Continuing improvements in industrial pretreatment have diminished these risks by reducing the levels of many toxic chemicals before they enter the wastewater treatment plant (WWTP). Technological improvements in the treatment processes have also contributed to achieving higher pollutant removal efficiencies. Enhanced biodegradation and partitioning of hydrophobic chemicals into sewage sludge has greatly decreased the levels of known pollutants discharged to receiving waters. But, recent studies indicate that new environmental contaminants of concern may be released through WWTPs. Some of these emerging contaminants have shown preferential partitioning into sewage sludge, reducing their concentrations in WWTP effluents. However, sewage sludge recycling (using stabilized sewage sludge as soil amendment, referred to as biosolids) has placed additional challenges on the wastewater industry, as they must assure that biosolids do not adversely effect the environment. Since the 1988 National Sewage Sludge Survey (NSSS), few attempts have been made to characterize new environmental pollutants of concern within biosolids. Here we examined 12 U.S. biosolid samples for contaminants, which were not included in the original EPA Part 503-risk assessment or NSSS. These emerging chemicals of concern are polybrominated diphenyl ethers, alkylphenols and their associated polyethoxylates, polycyclic musks, and Triclosan. Although their route of exposure is not fully understood, these emerging contaminants have been detected in fish tissue and human breast milk, indicating a need to further evaluate their presence and environmental fate associated land-applied biosolids before the occurrence of detrimental effects.