Screening And Combined Toxicity Evaluation Of Organic Pollutants In A Typical Municipal Wastewater Treatment Plant

Organic pollutants in municipal wastewater were often detected,but were not currently included in routine monitoring programs.These substances came from a wide range of complex sources,such as personal care products,plasticizers,pharmaceutical intermediates,drugs,antioxidants and pesticides,etc.Their migration,transformation and ecotoxicological effects had not been fully understood.Toxic organics in particular had posed a serious threat to human health and ecosystems.In order to contain the threat of water pollution to human health and ecological security as soon as possible,it was urgent to strengthen the control of toxic pollutants and ecological risk management.It was urgent to establish a screening and toxicity research system for organic pollutants.The study combined with the treatment process of typical municipal wastewater plants,the removal of acute toxicity of wastewater and extracted organic pollutants was evaluated through conventional indexes,spectral characteristics and toxicity analysis,and the correlation between water quality indexes and acute toxicity was established.The microorganic pollutants in municipal sewage were screened by concentration and gas chromatography-mass spectrometry,and the characteristic organic pollutants in municipal sewage were screened by comprehensive score.The toxicity of the screened organic pollutants was evaluated based on luminescent bacteria.The main results were as follows:(1)The results of conventional index,spectral analysis and toxicity test at each treatment stage showed that:the biological toxicity of wastewater was effectively reduced after the treatment process.By evaluating each period of the sewage biological toxicity of organic matter,conventional index,UV₂₅₄,humus index and extraction of organic pollutants in wastewater average luminous inhibition rate and the corresponding mercuric chloride equivalent concentration showed significant positive correlation,and biological index,fluorescence index extracting organic pollutant and sewage average luminous inhibition rate of mercuric chloride and corresponding equivalent concentration showed significant negative correlation.(2)The results of GC-MS screening showed that:the screening system established through the enrichment of organic components of wastewater samples at each treatment stage with GC-MS analysis.The primary list of 64 organic pollutants was determined,and the removal rate of different organic pollutants in the Influent was analyzed.The comprehensive scoring method was used to prioritize the organic pollutants in the preliminary list,and finally selected six kinds of organic matter such as dioctyl phthalate and methyl stearate were characteristic organic pollutants of municipal wastewater.(3)The mixed toxicity study of characteristic toxic organic pollutants showed that:the acute toxicity of the six characteristic organic pollutants was ranked as follows:Dioctyl Phthalate>Dibutyl phthalate>Dimethyl phthalate>Methyl stearate>Antioxidant 2246>2,4,6-tritert-butylphenol.The combined toxicity evaluation of dibutyl phthalate,methyl stearate and 2,4,6 tertbutyl phenol was carried out under the condition of equal toxicity ratio,the combined effects showed partial addition or antagonism.In summary,the comprehensive application of simple and easy-to-obtain conventional and spectral indicators had great potential for quick and convenient prediction of acute toxicity;the generated list of characteristic organic pollutants provided information support for the source control of municipal wastewater plants;Single low concentration characteristic organic pollutants had high n-octanol water partition coefficient,and had high bioaccumulation potential in aquatic organisms,which had certain risks to water ecological security.