Study On The Characteristics Analysis Of Organic Pollutants In The Ethylene Production Wastewater

As one of the major chemical raw materials, ethylene was mainly utilized for producing polyethylene, dichloroethane and epoxyethane and etc. Large amount of ethylene alkaline sewage with complex composition and a nasty odor, was discharged during the ethylene-producing process. Moreover, the buffer produced by alkaline-washing tower not only have an impact on the tower operation and alkaline-washing effect, but also result in a severe environmental pollution. A fast detection and analysis method was established for analysis of organic pollutants in ethylene wastewater. In order to lay a foundation for the upgrade of ethylene-producing system and the selection of advanced treatment technology, a follow-up test was required for obtaining the information of ethylene-producing wastewater treatment system.Ethylene-producing wastewater(including oxidation influents and effluents) were analyzed for COD, BOD and concentration of sulfide. The results show that the oxidation of COD in the wastewater of ethylene production plant reaches 20000mg/L above, Sulfide concentrations close to 4000mg/L, It has poor biodegradability; the effluent COD is above 3000mg/L, and the sulfide concentration is about 101.5 mg/L, Its biochemical property is good. Combining with ethylene production process, Ethylene-producing wastewater were analyzed for three-dimensional fluorescence and UV absorption spectra.it was indicated that ethylene wastewater with refractory organic pollutants, mainly contained humic-like substa and petroleum type substances.For semi-volatile organic compounds in ethylene-producing wastewater, a liquid-liquid extraction- gas chromatography/mass spectrometry monitoring method was then developed for analysis of alcohols, olefins, aromatics and other 24 kinds of semi-volatile organic compounds. In this method, standard curve equation for each component has a good linear relationship in a linear range. R2 ranged from 0.9975 to 0.9997, while relative standard deviation(n=7) was <5.535%; And the method detection limit ranged from 1.2 to 1485μg/L; Recovery rate ranged from 90.6 to 138%.A PT-GC/FID analysis method was developed for monitoring volatile organic compounds in ethylene wastewater, while alcohols, olefins, aromatics and other 16 kinds of volatile organic compounds were monitored simultaneously. In this method, standard curve equation for each component has good linear relationship in a linear range. R2 ranged from 0.9789 to 0.9999, while relative standard deviation(n=7) was < 8.866. And the method detection limit ranged from 0.006~0.6μg/L. Recovery rate ranged from 72.6% ~134%.Ethylene-producing wastewater were analyzed for conventional water quality indexes, i.e. COD, BOD, TOC, TN, concentration of sulfide and etc. It was indicated that alkaline oxidation units achieved a good performance for especially COD and sulfide removal. COD and sulfide removal rate reached 83% and 97%, respectively. Therefore, after-treated wastewater owned a better biodegradability. It can be concluded by the comparison of ethylene wastewater treatment technology home and abroad that high temperature and pressure wet oxidation treatment process obtained the best removal efficiency with 99% for both COD and S2- when compared to low temperature and pressure wet oxidation process and catalytic oxidation process. Because of high temperature and pressure wet oxidation treatment process is easy to induce accidents.In order to prevent accidents better, it is necessary to put forward high requirements for equipment. To the petrochemical enterprise of this paper, the treatment process of waste alkali oxidation unit is more reasonable.Ultimate aerobic biodegradation research was conducted aiming for oxidation emissions from alkaline wastewater oxidation unit, which showed that ultimate aerobic biodegradation rate of oxidation emission was 60.86% with good biodegradation performance. In addition, Benzene homologues, alcohols, olefins in wastewater can all be utilized as a carbon source by microorganisms, while 2,4-dichlorobenzoic acid, 2-methyl-thiazolidine and other organic matters were difficult to degrade.