Fate and Behaviour of Alkylphenols and their Poly-ethoxylates in an Activated Sludge Plant

Alkylphenol polyethoxylates (APEOs) are commercially important non-ionic surfactants used in industrial and domestic detergent and emulsifier formulations (Ferugerson et al. 2001), and nonylphenol ethoxylates (NPEO) and octylphenol ethoxylates (OPEO) are some of the most commonly used surfactants. The exposure of wildlife to these chemicals is mainly through water by discharge through wastewater treatment plant effluents and possibly sewage disposal (Montgomery-Brown and Reinhard 2003;Ying et al. 2002). It has been reported that partial biodegradation of NPEO in wastewater treatment plants generates more persistent nonylphenol (NP) and shorter-chain mono- to triethoxylates (NP1-3EO) (Giger et al. 1984). NPEOs and their degradation products have been detected in effluents of many municipal sewage treatment works (STWs) and their concentrations demonstrate spatial variation from below detection limits to 343 μg l-1 (Ying et al. 2002). Laboratory studies have also demonstrated the build up of NP in biological sludge due to its recalcitrance and hydrophobic nature (Langford et al. unpublished data). The wide-spread occurrence of NP1-3EO in th