Strategies for selecting optimal sampling and work-up procedures for analyzing alkylphenol polyethoxylates in effluents from non-activated sludge biofilm reactors

Abstract

Trace-level analysis of alkylphenol polyethoxylates (APEOs) in wastewater containing sludge requires the prior removal of contaminants and preconcentration. In this study, the effects of the types of alkylphenols present, their degree of ethoxylation, the biofilm-wastewater treatment and sample matrix were investigated on optimal work-up procedures for these purposes. The spot for sampling APEO-containing specimens from an industrial wastewater treatment plant was optimized, and boxed round the tubing carrying the wastewater to prevent sedimented sludge contaminating the collected samples. Following these changes, the sampling precision (in terms of dry matter content) at a point just under the tubing leading from the biofilm reactors was 0.7 % RSD. The findings were applied to develop a work-up procedure for use prior to a high-performance liquid chromatography-fluorescence detection analysis method capable of quantifying nonylphenol polyethoxylates (NPEOs) and poorly investigated dinonylphenol polyethoxylates (DNPEOs) at low μg L−1 concentrations in effluents from non-activated sludge biofilm reactors. The selected multistep work-up procedure includes lyophilization and pressurized fluid extraction (PFE) followed by strong ion exchange solid phase extraction (SPE). The yields of the combined procedure, according to tests with NP10EO-spiked WWTP-derived wastewaters, were in the 62–78 % range.