Study On VOCs Emissions From Wastewater Treatment In Petrochemical Industry Based On RWET Model

Volatile Organic Compounds(VOCs)are one of the key precursors for the formation of fine particulate matter(PM_2.5)and ozone(O₃).Due to the great harm to the environment and the human health,they have received widespread attention from air pollution researchers at home and abroad at present.The petrochemical industry is one of the first important industries for VOCs control in our country.VOCs emissions include organized and unorganized sources.Due to the complex pollutant composition of waste water treatment units in unorganized emission sources,organic matter may volatilize from water to the atmosphere depending on its physical properties.At the same time,chemical reactions may occur between organic matter to generate new pollutants,so it is difficult to quantify VOCs emissions scientifically.At now,our country draws on foreign estimation methods and proposes the actual measurement method,the material balance algorithm,the model method,the emission coefficient method,etc.Among them,the Water 9 model is advocated in the model method.However,as a novel calculation method,the RWET model has not been studyed and applied in our country.Firstly,this article conducted an in-depth theoretical study of the RWET model,understood the estimation method,masted the operation steps,and organized the data required for model calculation;secondly,applied it to the wastewater treatment process of a domestic petrochemical company,and compare it with the estimated results of the current mainstream Water 9 model to verify its reliability;finally,the impact of key paramenters in the RWET model on VOCs emissions is discussed,and gave recommendations for reducing VOCs.Which shows:(1)The RWET model is used to estimate the VOCs emissions of a domestic petrochemical company's wastewater treatment process to be 634.03 t/a.Regarding the discharge volume of various wastewater treatment operation facilities,the regulation tank discharge accounted for the largest proportion of 85.057%;the secondary settling tank discharge accounted for the smallest proportion of 0.002%;for the discharge volume of VOCs components,the xylene discharge amount was the largest,which is 229.91 t/a,and the 1,1-biphenyl emission is the smallest,which is 3.46 t/a.(2)Substituting the data in the literature into the RWET model,the VOCs emissions from the wastewater treatment of petrochemical company A are calculated to be 341.42 t/a,which is close to the 285 t/a estimated by the Water 9 model;the VOCs emissions from the wastewater treatment of petrochemical company B are calculated to be 431.77 t/a,which is close to the 398t/a estimated by the Water 9 model.The RWET model has high reliability.(3)Parameters such as wastewater flow rate,VOCs influent concentration,turbulence area,wastewater temperature,air-to-water ratio,and wind speed in the RWET model will affect the VOCs emissions.When applying the RWET model,these parameters should be as detailed as possible to improve the accuracy of the results.