Analyses On The Fate And Evolution Of DOM In Municipal Wastewater Treatment Process With Combination Of Chromatography And Spectroscopy

Quality and efficiency improvement of municipal wastewater treatment is one of the important targets associated with environment protection during the 14^th Five Year Plan.Advanced pollutant monitoring and characterization technology will provide vital methodological support for achieving this target.Integrated DOM monitoring method based on spectroscopic and chromatographic characterization is developed in this study with the aim of overcoming the defect of conventional dissolved organic matter（DOM）monitoring method in municipal wastewater treatment process which only measures the total amount of organics.This method was used to investigate DOM evolution and fate in different municipal wastewater treatment projects in Changzhou city,on base of which mechanism of the removal of different DOM components and performance of treatment processes were deeply analyzed.Some relevant opinions and suggestions were also proposed.Based on the principles which are being economic,easy to be operated and easy to be analyzed,this study first combined high-performance size-exclusion chromatography（HPSEC）,reverse phase liquid chromatography（RPLC）and UV-vis,excitation-emission matrix（EEM）spectroscopy to form the instrumental foundation of the integrated DOM monitoring method.This method can separate DOM into components according to molecular weight or hydrophobicity with HPSEC or RPLC.It adopts ultraviolet-visible absorption ratio index（URI,ratio of ultraviolet-visible absorbance at 210 nm and 254 nm）as an important parameter in DOM component characterization to differentiate DOM components of different aromaticity through URI chromatographic peak shape and peak value comparison.This method can effectively improve the abundance and dimension of DOM characterization information in comparison with conventional DOM total amount analyses or other single advanced characterization method.It also performs better economy and operability when comparing with other high-end characterization instrumental method such as mass spectrometry.This study further applied the integrated DOM monitoring method into performance analyses,operation optimization and operational defect detection of municipal wastewater treatment project,the main conclusions are:（1）Comparison on DOM components variation characteristics of different domestic wastewater treatment plants（WWTPs）reveals that:DOM components in effluent of WWTP with conventional anaerobic-anoxic-aerobic process（Jiangbian WWTP）were mainly hydrophobic humic substances and some highly saturated organics of low molecular weight which can be further removed by adopting some specific advanced physical-chemical treatment process according to their chemical properties.WWTP with membrane bioreactor process（Binghu WWTP）had problems with violent endogenous organic matter release from activated sludge which resulted in complex DOM constitution in the process and could bring about side effects such as membrane pollution,high disinfection byproduct formation potential and so on.WWTP with oxidation ditch process（Wunan WWTP）was troubled by early and excessive addition of carbon source which made microbes in activated sludge preferably metabolize the more bioavailable carbon source.This possibly caused the low reduction of bioavailable DOM components in influent wastewater.（2）Analyses on DOM components variation characteristics of industrial WWTPs reveal that:process adjustment to fenton process of Xixiashu WWTP made no change to DOM compositional characteristics of final effluent.The process of this WWTP needs further adjustment.Even the quality of the final effluent meets corresponding standard,there was still problem with the low removal efficiency of fluorescent DOM composition in Henglin WWTP.In addition,the integrated monitoring method in this study can also be applied to characterizing pipeline breakage,measuring biodegradable organics concentration in wastewater,providing surrogate for measuring conventional indexes such as NO₃^-concentration and so on.The function of this method performs good expansibility.In conclusion,this study aims at improving DOM monitoring technique used in municipal wastewater treatment from total amount assessment to specific component evaluation.This can help to provide more abundant characteristic information on DOM occurrence and removal which can better guide the precise measures taken to achieve the goal of quality and efficiency improvement for municipal wastewater treatment.