January 2000

APE Research Council: Safety of APs and APEs in Biosolids

Alkylphenols (APs) are chemical compounds used primarily to manufacture alkylphenol ethoxylates (APEs), which have been used widely for more than 50 years as cleaning agents or surfactants.

Biosolids (sewage sludge) are the solid remains produced by modern sewage treatment plants that often are used as a soil conditioner or fertilizer. Residual APEs may be present in biosolids because the wastes from some products containing these substances are directed to sewers for treatment and disposal. Residual APs also may be present as a minor degradation product of APEs. This document summarizes the available research on the safety of these residual levels of APs and APEs in biosolids.

APs and APEs are effectively biodegraded in well-functioning sewage treatment plants.

A recent study of two Canadian treatment plants showed that AP and APE levels in sewage were reduced significantly during treatment - the resulting biosolids contained less than 15% of the levels of APs and APEs in the untreated sewage. The levels of APs and APEs in the treated wastewater were even lower, demonstrating that most of the APs and APEs in the sewage were biodegraded during treatment.

A study of a U.S. treatment plant showed that nonylphenol (the major AP) levels in sewage sludge were only 0.1% of the nonylphenol and nonylphenol ethoxylate levels entering the plant.

Environmental monitoring shows that levels of APs and APEs in soils amended with biosolids are insignificant.

Recent data from Canada and Europe indicate that AP and APE concentrations in soils amended with biosolids are below those that may harm earthworms and other terrestrial organisms. Other studies indicate that APs and APEs from biosolids applied to soils are unlikely to be transported into subsurface soils or to migrate into groundwater, due to their extensive biodegradability.

Residual APs and APEs from biosolids do not build up in soil.

Numerous studies show that APs and APEs rapidly and extensively biodegrade (mineralize) when biosolids are mixed with soil. Consequently, there is no build up in soils even when biosolids containing APs and APEs are applied every year.

Biosolids containing residual APs and APEs have been beneficially used as a soil conditioner or fertilizer for over thirty years.

Application to soil generally is considered the environmentally preferred use of biosolids. Biosolids provide nutrients to soil and recycle carbon back to nature rather than release it during incineration as carbon dioxide, a greenhouse gas.

For more information or copies of studies referenced above, please contact the APE Research Council.
The APE Research Council, composed of manufacturers, processors, users and raw material suppliers, is working with government and academic scientists to further the understanding of the human health and environmental profile of APs, APEs and APE biodegradation intermediates.

                                                                                                                             

 

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