Study On The Pretreatment Of Sorbic Acid Wastewater

Sorbic acid is antiseptic of food, nourishing drugs, tobacco and luxury cosmetics, which has good antiseptic effect. The antiseptic effect of sorbic acid is 5 to 10 multiple of the sodium benzoate. It will be absorbed and rapidly transformed into CO2 and H2O in the body without residues, has a good safety.The wastewater from the production process of sorbic acid is a high concentration of organic waste water, have the characteristics of complex composition, showing the yellow color, irritating smell. The high concentration of organic pollutants is a lot of raw materials and intermediate products, including ethanol, croton-aldehyde, acetaldehyde, sorbic acid, ketene and small amounts of benzene pollutants. The components of wastewater which can be directly used by microorganisms is less, and the sorbic acid residues in the waste water is a microbial inhibitors, which can be effective in preventing bacteria and micro-organisms survival. Because BOD/COD value of sorbic acid wastewater is below 0.3, biochemical treatment. can not be directly used in wastewater treatment process. Therefore, a practical and efficient pretreatment of sorbic acid wastewater is very necessary.In this study, the pretreatment method of three-dimensional electrode and micro-electrolysis-Fenton reagent sorbic is used in pretreatment of acid wastewater. Experimentation inspect the treatment effects which is affected by the technical parameters, in order to determine the most appropriate parameters and further discuss the change of biodegradability of treatment effect.Three-dimensional electrodes know as particle group electrode or bed electrode. Three-dimensional electrodes is rebuilt from two-dimensional electrodes by filling with granular electrode and degradation of organic pollutants react on the surface of electrode material. Compared with the two-dimensional electrode, the distance between particles of three-dimensional electrode is shorter, in degradation process of organic pollutants, the effect of contaminated material transfer has been strengthened. So it has a higher efficiency of the current, is easy to implement continuous operation in the low current density, have the advantages of handling simple, small area, large treatment capacity, managing easily.The process of micro-electrolysis which use scrap iron and other metal debris as anode materials and activated carbon as cathode material in acid battery, use lots of micro-batteries to erode the anode and lead to a series of reactions.The micro-batteries appear in acidity by making use of the mixture of the anode material and cathode material. So the process of micro-electrolysis is a result by some actions including flocculation, adsorption, deposition, etc. The iron and [H], Fe2+ produced in the reaction are lively, that could change the structures and characteristics of the organic in wastewater, leading to degrade easily. The process of micro-electrolysis has many advantages, such as less investment, low running cost, simple process operation, and high efficiency, etc.The water from the actor of micro-electrolysis contains lots of Fe2+,and its pH is improved. So it is advantaged to reaction of Fenton process. If added H2O2 to the water, the more organic could be degraded, which leading to enhancement of treatment effect. So the Fe2+ and Fe3+ can deposit in the form of alkali after adjusting pH. Various inorganic and organic colloidal particles are adhered and settled out in a reasonable time. All of them can reduce the concentration of contaminationThe conclusions of the researches:(1)The method of three-dimensional-electrode was used to study the pretreatment of sorbic acid waster water. The operational parameters that affected the efficiencies of the wastewater treatment were discussed, including electrode material, applied voltage, pH value, electrolysis time, and so on. The experimental result showed that the removal ratio of COD was reached to 48% and the BOD/COD was increased to 0.40, when the voltage was 20V, the working electrodes distance was 11 cm, the electrolysis time was 20～30min,the pH value of wastewater was 4.0, under the condition of stainless steel as an anode, graphite as cathode and cylindrical activated carbon as particle.(2)In the experiment, wastewater was treated by Fe-C micro-electrolysis by changing the iron dosage, the ratio of iron to carbon (Fe/C) and initial pH of wastewater. The optimal pretreatment process conditions of polyester resin wastewater by Fe-C micro-electrolysis were room temperature, initial pH=1.5, Fe/C=3/2, reaction time=4h. Under the optimal conditions, through Fe-C micro-electrolysis treatment, wastewater COD removal efficiency could approach 45%. After Fe-C micro-electrolysis treatment, so the organic loading of subsequent biological treatment unit could be decreased sharply.(3)As sorbic acid wastewater was pretreated by Fenton reagent. In the experiment, polyester resin wastewater was oxidized by Fenton reagent by changing the dosage of H2O2, reaction time and the original pH of wastewater. The optimal pretreatment process conditions of wastewater by Fenton reagent were room temperature, initial pH=3, the dosage of H2O2 is 0.5Qth, reaction time=2h. Under the optimal process conditions, the total COD removal rate of wastewater was above 75%. The biodegradability of wastewater was improved remarkably after micro-electrolysis Fenton reagent treatment, its BOD/COD level increased from 0.19 to 0.44.(4)On the base of general analysis of the technology and the cost, the pretreatment of Fe-C micro-electrolysis Fenton reagent is more practical in application. It have the advantages of good effect and lower cost, so it could be considered as pretreatment process of sorbic acid wastewater.