Behaviour Of Nonylphenol Ethoxylates In A Sewage Treatment Plant

Endocrine disrupting chemicals (EDCs) are a kind of chemical substance which can enter into the human body, play the roles of estrogen and endanger humankind's healthy. EDCs are artificial synthesization and exist widely in the environment accompanying with the discharge of industrial and municipal wastewater. EDCs which have brought out abroad attention in the world become a hot research area in the field of environmental sciences due to their harmful effects to animals and human beings.Nonylphenol polyethoxylates (NPnEO) is a widely used nonionic surfactant in the world.NPnEO can be degraded into intermediates, such as NP1EO, NP2EO and NP (NP0-2EO for short) via microbial degradation after they enter into water bodies. These intermediates exhibit bioaccumulation, hydrophobic and lipophilic properties, have been proved as Environmental Hormones.During sewage treatment process, NP0-2EO existing in wastewater can be easily adsorbed onto organic particles and accumulated in sludge at last. NP0-2EO residued in the wastewater and sludge can be discharged into environment along with the effluent of STPs and sludge disposal.In this study, the occurrence and transportation of nonylphenol ethoxylates in a full-scale municipal wastewater plants equipped with anoxic/oxic (A/O) process and biological aerated filter (BAF) processes in different seasons were investigated using a solid phase extraction-gas chromatography-mass spectrometry (SPE-GC-MS). Removal efficiency NP1EO,NP2EO and NP in A/O and BAF processes were also compared.The study led several results. The concentration of NP, NP1EO and NP2EO ranged (ng/L) from 1000 to 6900, 1000 to 4800 and 1000 to 7200ng/l in influent, while 200 to 500, 150 to 1100 and 160 to 1600 in the effluent, respectively. The concentrations of NP0-2EO in the influent had apparent correlation to seasons with the highest in winter and lowest in spring. NP0-2EO entering into STPs were removed mainly by two pathways: biodegradation of microorganisms and adsorption into sludge in each unit and the latter may play the dominant role in this study. Comparing with the characteristics of different techniques to erase NP0-2EO,we can draw a conclusion that biological secondary treatment process has certain effect to erase NP0-2EO and the best removal efficiency can achieve 90%. A/O process showed better performance than BAF process. Large amount of target compounds were migrated into sludge after treated. The removal efficiency of NP0-2EO in activated sludge treatment was influenced by temperature. However, no significant correlation was found between temperature and the concentration in the influent. The trend of removal efficiency varied from season was summer> spring, autumn>winter. This study appears important to investigate the details of discharge situation of nonylphenolic compounds in northeast China and is vital to risk assessment in this district.