Seasonal changes and spatial distributions of nonylphenol ethoxylates in sewage treatment plant with BAF process

Recently, there has been growing concern over the prevalence of Nonylphenol ethoxylates (NPnEOs) in the natural environment as these compounds are known endocrine disruptors. This study focuses on the seasonal variation and spatial distribution of NPnEOs in the wastewater of a full scale sewage treatment plant, operating a Biological Aerated Filter (BAF), in Harbin, a city in Northeast China. Water samples were collected seasonally from 2009 to 2010, with the findings revealing remarkable seasonal variations in the concentrations of NPnEOs. The total influent concentrations of short-chain NPnEOs (NP, NP1EO and NP2EO) measured during winter was 16 mg L−1, with decreasing concentrations observed during autumn, summer and spring of 89, 67 and 41 mg L−1, respectively. The concentrations of the short-chain NPnEOs measured during autumn become higher (89 mg L−1), with summer becoming the lowest (16 mg L−1). Although the removal efficiencies of short-chain NPnEOs in STP showed various trends in different seasons, they all achieve relatively good performance during summer and winter. The BAF process plays the main role in the elimination of short-chain NPnEOs compounds; however, the ambient temperatures were not found to significantly influence the removal efficiency of short-chain NPnEOs compounds from the STP.