Treatment Of High-salinity Wastewater Containing Volatile Organic Compounds By Evaporation And Persulfate Advanced Oxidation

High-salinity wastewater is defined as wastewater containing soluble solids with a mass fraction of at least 1%.Due to a large number of inorganic salts in the presence of such wastewater that can inhibit the microorganism activity,which make it difficult to treat the high-salinity wastewater containing organic compounds by traditional biochemical methods.To seek a reasonable and efficient processing technology,A new wastewater treatment process which coupled evaporation with persulfate advanced oxidation to treat high-salinity wastewater containing volatile organic compounds was developed on the basis of combining the characteristics of evaporation desalination and persulfate advanced oxidation.The factors which could influence on the process such as the addition amount of KPS,the addition mode of KPS,solution pH,salt content and its species in the solution were evaluated in the experiment.The main intermediates were detected and analyzed by ion chromatograph or GC-MS.In the experiment of treating high-salinity wastewater containing methanol,four kinds of wastewater including methanol-NaCl,methanol-KCl,methanol-Na2SO4 and methanol-K2SO4 were studied respectively.Results showed that the COD removal rate of high-salinity wastewater containing methanol increased with the increase of KPS dosage.When 0.05 mol/L KPS was added to the reaction system,the COD removal rate of wastewater containing 500 mg/L methanol and 5% salt can reach more than 95%.Under the condition of the same amount of KPS dosage,one-off dosing of KPS in the wastewater was more favorable for the organic compound degradation than stepwise dosing method.In the whole reaction process,the removal rate of organic matter was higher when the solution pH is neutral,and the degradation rate increases firstly and then decreases with the increase of the salt concentration.Addtionally,the intermediate products of high-salinity wastewaters containing methanol were formic acid by ion chromatography.Four kinds of wastewater including ethanol-NaCl,ethanol-KCl,ethanol-Na2SO4 and ethanol-K2SO4 were studied respectively in the experiment of treating high-salinity wastewater containing ethanol.Results indicated that the increase of KPS concentration can significantly improve the removal rate of organic matter in wastewater under the condition of thermal activation,and one-off dosing of persulfate in the wastewater was more favorable for the organic compound degradation than stepwise dosing method with the same KPS adosing into the reaction system.With different kinds of salt content varied from 1% to 5%,COD removal rate showed a tendency that decrease firstly and then increase,and the degradation effect of sulfate-containing wastewater is better than that of chloride-containing wastewater.In the whole reaction process,the COD removal rate of wastewater was higher under strong alkaline conditions.The main intermediates of high-salinity wastewater containing ethanol were acetic acid and a small amount of formic acid by ion chromatograph.In the experiment of treating high-salinity wastewater containing acetic acid,the effects of different influencing factors on the treatment effect were studied by using acetic acid-NaCl,acetic acid-KCl,acetic acid-Na2SO4 and acetic acid-K2SO4 as the research object.Results showed that the treated solution with 5%salt and 1000mg/l acetic acid was heated at the presence of 0.05 mol/L of KPS,the solution COD removal rate reached more than 90%,and the degradation rate increases as the increase of the concentration of KPS.The best dosing method of KPS is one-off dosing,and a maximum removal rate of wastewater was generated at pH=11.Different types of saline were present in reaction systems would inhibit the wastewater degradation,and chloride produced more pronounced inhibitory effects on the progressive removal of acetic acid than sulfate,and the inhibition effect was weakened with the increase of salt content.Analysis of the ion chromatogram of steamed liquid generated from wastewater degradation components showed that the acetic acid component of the wastewater can be directly mineralized into CO2 and H2 O by KPS.For wastewater containing 500 mg/L tert-butanol and 5% salt,there were appeare some unsimilar experimental phenomena with other three types of wastewater during the treatment process.Under the same experimental conditions,the degradation effect of sulfate-containing wastewater and chloride-containing wastewater showed greater different.Under the condition of he pH of values were 3,the COD removal rate of sulfate-containing wastewater were above 93% by adding 0.2 mol/L KPS,and the removal rate of chloride-containing wastewater were only 51% and 64%.With the persulfate continue to increase to 0.3 mol/L,the COD removal rate of sulfate-containing wastewater had gradually stabilized,which were close to 94% ~ 95%,while chloride-containing wastewater appears the downward trend.When the same KPS concentration were added into the reaction system,one-off dosing of persulfate in the wastewater was more favorable for sulfate-containing wastewater,but stepwise dosing of persulfate in the wastewater was more favorable for chloride-containing wastewater.GC-MS is adopted to detect and analysis the main intermediates of high-salinity wastewater containing tert-butanol.The results indicatedthat the main intermediates of wastewater containing tert-butanol and sulfate were heptanoicacid,3-methylbutyle and 3-methyl-3-penten-2-ol.The degradation process of wastewater containing tert-butanol and chloride was more complicated and its intermediates were chlorinated organic compounds,lipids,ketones,alcohols,acids and olefins.