Pretreatment Of High Concentration Organic Wastewater By UV-Fenton Oxidation Process

With the acceleration of industrialization,and the rapid development of society and economy,the demand for water is increasing in social production and human life,at the same time,the waste of water resources and the pollution of water resources are becoming more and more serious.China is a water shortage country,the population of our country leads to low per capita water resources,especially with the rapid rise of China,water pollution is becoming more and more serious.In polluted water resources,industrial wastewater occupies a large proportion,many industrial wastewater are not up to national standard,some companies even let wastewater directly into the river,causing serious pollution of water resources and environment.In recent years,the treatment of industrial wastewater is becoming more and more mature,a lot of industrial wastewater can be treated in a suitable way and up to national standard,but there are still a lot of industrial wastewater with high difficulty and high processing cost can't get a good treatment,high concentration of refractory organic wastewater is a difficult problem.This kind of wastewater is complex,high concentration,highly toxic,difficult to biodegrade,and high chemical oxygen demand?COD?,the general COD is above 2000 mg/L,some even as high as tens of thousands to hundreds of thousands of milligrams per liter,and this kind of wastewater has a low biodegradability?BOD₅/COD value is below 0.3 or lower?,it is hard to biodegradable,and has obvious carcinogenic,teratogenic and mutagenic.Due to the characteristics of complete oxidation,fast reaction speed,high efficiency and no pollution,advanced oxidation process is widely used in the treatment of the high concentration of refractory organic wastewater,in this passage,the object of study is the wastewater of a factory which produces C₈H₉NO₄S,this kind of water is strongly acidic and difficult to degrade.According to the characteristics of the wastewater,select advanced oxidation pretreatment and biochemical treatment process to deal with the wastewater,because the effect of pretreatment directly affects the subsequent biochemical treatment effect,so a detailed experimental study and parameter optimization are carried out for the pretreatment stage in this passage.Using the method of control variables and H₂O₂,Fenton,UV-H₂O₂ and UV-Fenton experiments to analysis the four factors,explores the dosage of H₂O₂,pH,the dosage of Fe²⁺and the distance between liquid level and ultraviolet lamp on how to influence the rate of COD.Experiments found that with the increase of H₂O₂ dosage,due to the limited amount of H₂O₂ involved in the reaction,the removal rate of COD was not obvious;The change of pH will directly affect the removal rate of COD,and the influence is bigger,only when the pH=3 or so,the removal rate of COD was the highest,increase or decrease pH will cause a sharp decline in COD removal rate;Although ultraviolet lamp can not directly degrade organic matter in wastewater,however,ultraviolet light can promote H₂O₂ produce more of·OH,improve the removal rate of COD;With the increase of Fe²⁺dosage,the removal rate of COD was gradually rising;The ultraviolet light can improve the removal rate of COD of Fenton reaction,but the rate is not obvious,the reason is that the distance between liquid level and ultraviolet lamp is also important,when the distance and the height of liquid level are appropriate,the removal rate of COD can reach more than 55%.According to the experimental results,design sewage treatment scheme,the wastewater of the chemical plant is mainly treated by oxidation pretreatment and biochemical treatment,and give the investment and operation cost estimation.Sewage treatment facilities total investment 730 thousand yuan,including the construction investment 205 thousand yuan,the main equipment investment 393 thousand yuan and other costs 124 thousand yuan,operating costs of 3 million 453 thousand/year,tons of water running cost of 47/ton,including electricity 230 thousand/year,pharmacy fee of 3 million 40 thousand/year,labor costs of$144 thousand/year and equipment maintenance fee of 39 thousand/year.To sum up,the UV-Fenton method is the best method of pretreatment,when H₂O₂ dosage is 0.5 times theoretical value,Fe²⁺dosage is when the mass ratio of Fe²⁺and H₂O₂ dosage is 1:5,pH=3,ultraviolet lamp power is 20W,the distance between liquid level and ultraviolet lamp is 10cm,the removal rate of COD can reach more than 55%.Advanced oxidation pretreatment and biochemical treatment were used to deal with the wastewater,and the wastewater treatment scheme was designed,and given the investment and operation cost estimation.