Study On The Technique Of Sorbic Acid Wastewater Treatment

Sorbic acid is a kind of lowest toxicity antiseptic which is brought about industrialization currently. It participates metabolism process of human body and is oxidized into carbon dioxide and water as well as the other natural unsaturated acid. As a kind of antiseptic, in most cases the sorbic acid is replaced by its potassium salt—sorbic acid potassium because itself is water-soluble worse and both of them have the same antisepsis effect. The sorbic acid and its salts are the good antiseptic of food, medicine and cosmetics and generally accepted internationally as efficient and low poisonous conservancy, which are the best renewal products to substitute the older generation antiseptics, such as sodium nitrite and sodium benzoate. Along with the development of economy and exaltation of the people living level, the request of the additive of food, drugs and cosmetic is strict gradually. The requirement of deluxe antiseptic such as sorbic acid and its salts increases day by day. What's more, some nations have already forbidden using the sodium benzoate. Sodium benzoate has been replaced by sodium sorbic acid in child's food in our country. The sobic acid can be also used for prepare of compound antiseptic, insecticide and synthesizing rubber industry etc. With the antiseptic renewing, the sorbic acid and its salts will be used further and the capacity of its market will also increase day by day.The project of "Study on the Technique of Sorbic Acid Wastewater Treatment" is an applied foundation research surpported by science and technology office, Jilin province. The sorbic acid has some characteristics of high COD concentration (higher than 10000 mg/L), low pH and can hardly be bio-degraded. We are trying to treat this kind of wastewater by the methods of three-dimensional-electrode, Micro-Electrolysis and Fenton Reagent, White-rot Fungus, Pressurized Bio-oxidation Process, Hydrolyzation and Acidification and Bio-contact Oxidation. It aims at operating parameters of every pretreating methods and the direct influence factor of increasing B/C value. Therefore the wastewater can be biodegraded easily. A set of design reasonable, viable economic technique will be proposed.Aiming at high COD concentration waste water produced in one sorbic acid plant setted up lately in Jilin City, this paper adopt the processing technique of physical chemistry and biochemical to start experiment research. That sorbic acid wastewater has the characteristics of high COD value (higher than 10000 mg/L), low pH value and bio-chemical degraded hardly decides its treatment technique particularity differing from the treatment process of other sewage. If directly getting into original wastewater processing device, it will bring tremendous impact and the effluent can't attain sewage discharge standard. Therefore it is necessary to carry on a deeper research to the treatment processing of the sorbic acid wastewater of high COD value and hard biodegradable. The study includes main factor effecting treatment efficiency and bio-chemical characteristic of exponent biodegraded hardly, put forward in the sorbic acid wastewater treating process adapting the state of our country. At last the wastewater treated can reach the national discharge standard. The main research contents include:1. The iron and carbon micro-electrolysis, Fenton reagent oxidation pretreatment experimentAiming at waste water from some sorbic acid factory in Jilin, we adopt the method of iron and carbon micro- electrolysis to treat the wastewater and then make the Fenton reagent by adding hydrogen peroxide to oxidize and decompose the organic matters in the meantime; It emphasizes influence of the treatment efficiency by the facts of F/C value, reaction time, pH condition and dosage of H₂O₂. At the end we treat the wastewater further by pressurized bio-oxidation process reactor to reach the discharge standard.2. The 3D electrode pretreating experimentThe toxicity of the wastewater to aerobes can be lowered after pretreated by the 3D electrode method and then treated with bio-chemical method at the end. According to the articles, it is stressed to study the wastewater degradation efficiency influence by the electrode material, the polarity style, electrolyzing time, added voltage and pH condition. At the same time the electric current efficiency and energy consumed will be tested to demonstrate whether the 3D electrode method is economic or not.3. Pretreating experiment with the white-rot fungusSorbic acid is a kind of food antiseptic, and the wastewater from its producing process can not be biodegraded because the microorganism is restrained by the sorbic acid. In the meantime white-rot fungus has the characteristic of oxidizing pollutant outside the body (influenced lightly by organic matter toxicity). Thus we consider making use of white-rot fungus (cultivated in the laboratory) to pretreat the wastewater in order to lower organic matter toxicity, and then make it easily to be biodegraded with aerobes.4. Bio-contact oxidation and pressurized bio-oxidation experiment researchMaking use of an ABR reactor to carry on pretreating wastewater, we can control experiment to keep fore two stages of the three bio-anaerobic reaction stages, and avoid producing methane stage which is difficult to control. Basing on above we investigate the variety of the water COD concentration and the water value of B/C. Assisted with Bio-contact Oxidation, the water being treated may be discharged according to the national standards.In this research the sorbic acid wastewater will be treated mainly by pressurized bio-oxidation method comparing with the hydrolyzation and acidification, bio-contact oxidation method. The water pretreating methods mentioned above are all to make convenience of the activated sludge treatment for it is the cheapest relatively. According to the advantage of pressurized method this section mainly explains the gas transferring theories, dynamics parameter and model of the sorbic acid wastewater treatment processing by pressurized bio-oxidation method. With continuous and intermittent experiment, we will obtain various dynamics parameters of the reaction processes, analyze the relation between volume burden Fv, sludge burden Fw and removing percentage of COD. At the end we will make the COD burden impacting experiment and discuss the sludge inflation problem, also give a definite counterplan.Combining the pretreatment experiment effect and making use of bio-contact oxidation, pressurized bio-oxidation, we can get a suit of integrated process to treat the sorbic acid wastewater and then make it to touch the discharge standard. At the same time the best processing conditions should be examined, in order to lay technique foundation for carrying out the wastewater treatment processing industrialization.5. The mechanism research of experiment reactionIn each experiment step mentioned above, we will test and analyze the influent and effluent with GC-MS analysis instruments (from environmental protection monitoring station, Jilin City) and then understands degradation mechanism of the pollutants in the wastewater treatment. Therefore we use it to guide and control the experiment conditions and explore the other study method further in the meantime.Basing on long time experiment research and considering the all kinds of experiment effect, treatment expenses and production fact, we define a whole set of sorbic acid wastewater treatment united technique which is technique reasonable, economic feasible. This research conquered the sorbic acid characteristics of low pH value and bio-degradation worse. Hydrolyzation and acidification, three-dimensional-electrode, micro-eletrolysis and Fenton reagent oxidation, white-rot fungus were adopted to pretreating the wastewater in order to remove COD, adjust the pH value, enhance the B/C value, lower its bio-toxicity and then make it possible to be bio-degraded. The main research conclusions include a few aspects as follows:1. In the process of the micro-electrolysis and Fenton reagent oxidation, a good expectation effect was abtained. First, the micro-electrolysis adapted the low pH value of sorbic acid wastewater and the electrolysis effect came to an extreme limit in this conditions. It mainly saved the fore processing to neutralize the water with alkali applied in the other treatments, saved manpower, material resources and the devotion in time, shortened the treatment processes; Secondly, it was united Fenton reagent oxidation processes after the micro-electrolysis. This is to make use of a great deal of ferrous which were formed in the micro-electrolysis(iron and carbon) and were one component of the Fenton reagent(ferrous were a necessity part of Fenton reagent); The third, flocculation processing can take advantage of the ferric which were made from the oxidation process of the Fenton reagent; At the end, passed by the all processing the COD of the wastewater were removed in a great measure, the value of pH is about close to neutral, and the B/C of waste water gets an obvious exaltation. It lays foundation for the follow-up aerobic bio-chemical processes.The best parameters of threating the sobic acid wastewater with the micro-electrolysis include: HRT is 4 hours, Fe/C value is 3:2 and the influent pH value is 1.5. hi the fenton reagent oxidation process, dosage of H₂O₂ should be controlled to 0.5 Q_th; reaction time is 2 hours and the pH value is 3. The whole percentage of COD removed can be up to 75% under these conditions.2. The three-dimensional electrode was composed of stainless steel anode, activated carbon cathode, with the fillings of the activated carbons and beading. The device obtained certain effect to treat the sorbic acid wastewater and united with bio-degradation method can make the wastewater to reach the discharge standard. According to various economic indexes, although the processing is a very good method which can remove COD efficiently, it consumes more and greatly electricity compared with other treatment. Its application foreground is limited to a certain extent. Therefore we expelled this treatment method in the processing route for the further experiment.We decided the best reaction conditions by the single factor. The first, reaction time should be controlled to 20-30 minites;The second, added voltage is 20V; And the third, pH value should be controlled to 4.0±0.2.3. We make use of white-rot fungus to pretreat the sorbic acid wastewater. Through experiment proved, when the wastewater pH value approaches 6 or so, the wastewater treated by white-rot fungus are apt to be bio-chemical treated and create a beneficial condition for the following bio-chemical processes, where we can see the main effect of white-rot fungus is to promote BOD/COD value greatly, besides removing COD from the wastewater. It can provide a convenient condition for the following bio-chemical treatment processes, and not degrade the organic matter directly in the wastewater in a short time.Treated with white-rot fungus the sorbic acid wastewater's B/C value can reach 0.41 from 0.17 and the B/C value of the sorbic acid wastewater (pretreated by the micro-electrolysis and Fenton reagent oxidation) can be up to 0.65 from 0.39 in 180 minites.4. The comparison researches between hydrolysis and acidification, bio-contact oxidation and pressurized bio-oxidation in the bio-degradation processes. With the sorbic acid wastewater after pretreated as the research object, the study analyzed the gas transfer theories, oxygen consuming velocity and oxygen providing ability of the pressurized bio-reactor. It clued on the relationship among the organic matter degradation, sludge growth, oxygen consuming action, designing parameters, running parameter and the surroundings factors inside the system.The study results showed that the two kinds of these methods can get a better water treatment effect and the sorbic acid wastewater after treatment can reach the discharge request. But comparing the two methods of treatment processes, hydrolysis and acidification, bio-contact oxidation process is a time consumed process and difficult to control and that the HRT is longer which results in high expense of equipment and construction, and much higher the first investment; On the other hand, the pressurized bio-oxidation processes have the advantages of the small area covered, the bigger sludge burden and volume burden, and the treatment time shortened. At the same time it put forward the practical solution for the sludge inflation question occurred in the treating system. For the sorbic acid wastewater, the pressurized bio-oxidation method as an aerobic treatment processes is put forward as a prior choice.5. It can be conclude by analyzing the GC-MS spectrums of the raw wastewater and the all phases effluent that the organic pollutant's species and quantities descend obviously after the pretreatment. The long chain, unsaturated, and lower volatility organic compounds transform to short chain, easy biodegraded, and high volatility organic compounds. This transformation makes the wastewater biodegraded easily.Basing on the pretreatment experiment researches, we make sure a best processing route, namely the micro-electrolysis and Fenton reagent oxidation, the white-rot fungus pretreatment united with the pressurized bio- oxidation treatment processes, which can make the waste water effect stable and to reach the discharge standard. At the same time the treating expenses of the set of treatment processes is reasonable and cost-effective which make the business enterprise to accept it easily. This project has already provided a thorough and dependable experiment data for the sorbic acid wastewater treatment processing design of one of the sorbic acid factory in Jilin province. It lays foundation for the stable treating and reaching the discharge standard ofwastewater.