The fate of various alkylphenolic compounds during wastewater treatment was studied at full scale in thirteen plants, selected in order to cover a wide range of treatment processes, sizes and countries. In-depth investigations consisted in the analysis of nonylphenols, short chained (n = 1, 2) but also long chained polyethoxylates in raw wastewaters, effluents, raw and treated sludges. The degradation of long chained polyethoxylates (APnEO) was shown, resulting in significant production of alkylphenols that concentrate in the sludges. Results show however that the pending Directive on spreading of sludge on land would be complied with in all cases. For the effluent, the EQS established within the WFD might not be satisfied in very critical situations where the dilution factor of the effluent in the river would be too small.