Study On The Removal Of Pollutants In Aquaculture Wastewater By Electrochemical Method

Since1988, the Ministry of agriculture proposed "shopping basket program", China’s livestock husbandry developed rapidly. The phenomenons of heavy metals, hormones and antibiotics’illegal using became more and more common in livestock husbandry. The majority of these substances couldn’t be absorbed by animals and discharged out of the bodies in the form of prototype or metabolites by excrement and urine, which posed a great threat to the environment and human health. The common medicine of livestock husbandry contains heavy metals copper(Cu), zinc(Zn), hormone olaquindox and antibiotics such as oxytetracycline (OTC), tetracycline (TC) and chlortracycline (CTC). At the present stage main trend technologies for wastewater treatment of husbandry is "Solid-liquid Separation-Anaerobi-Aerobic" Biological treatment process. The focus was on the three characteristics of aquaculture wastewater "high CODcr, high nitrogen, high phosphorus". The potential harm of heavy metals, antibiotics and hormones always be ignored in effluent index. A relatively high level of this material residues could be detected in breeding waste water, it also had a high pollution level in the waters around the animal farm and the sewage returning land. As a new wastewater treatment technology, Electroytic-Oxidation technology, which includes strong electro-oxidation and electro-deoxidation, can degrade of organic matters and heavy metals effectively. Therefore, in this thesis,we take Cu, Zn, OTC, TC, CTC and olaquindox as target pollutants, through the simulation test, searching the suitable processing conditions, provides scientific basis for practical application to the treatment of antibiotics, hormone and heavy metals in animal farm wastewater. The decision as fellow:(1) The Electrochemical Method could efficiently remove the antibiotics and hormone in aquaculture wastewater. Single factor text derived the optimized electrolytic voltage is5V, electrolysis time is16min, initial pH value is8, aeration time is1.5h. The preliminary dynamics research shows olaquindox, OTC, TC, CTC of electrolytic degradation process are in line with the first-order kinetics. The rearch of electrode passivation phenomena shows changing the electrode polarity regularly could improve treatment efficiency. The test of three kinds of common coexisting substances citric acid, acetic acid and sodium dodecyl sulfate (SDS)’influence on the removal of antibiotics and hormones indicated:Citric acid of low concentration can improve the removal efficiency of antibiotics and hormones, the optimized citric acid concentration is0.02mol/L, effect of acetic acid on antibiotics and hormones removal efficiency was similar to removal of citric acid, when adding0.175mol/L acetic acid, the removal rate of olaquindox, OTC, TC and CTC could achieved the best respectively70.8%,68.1%,59.7%and73.5%. Each dosage of SDS could promote the removal rate of olaquindox, but it could restrain the removal rate of tetracycline.(2) The Electrochemical Method could remove heavy metals Cu, Zn in aquaculture wastewater to a certain degree. The single factor experiment of electrolytic voltage, electrolytic time, initial pH value, initial concentration of wastewater indicated that optimized conditions were electrolytic voltage5V, electrolytic time45min, initial pH value8, initial concentration of wastewater CODcr3000mg/L. The effects of different concentrations of Citric acid, acetic acid and SDS on heavy metals Cu, Zn were different Significantly, but on the whole, they have Some inhibitory effect to the removal of heavy metals Cu, Zn.The citric acid had significant restriction on the removal of Cu、Zn, the removal rate of each test group add citric acid had a big fall contrast to control group.The effect of acetic acid on the Cu removal rate was insignificant, but it had a strong restriction on the Zn removal. Each concentration of SDS had significantly restriction on the Cu removal, and it also had a strong restrictionon the Zn removal rate.At last, through the interation of the test of removal of antibiotics, hormones and heavy metals Cu, Zn, elicited the integrated optimal removal condition:electrolysis voltage15V, electrolysis time45min, aeration time lh, initial wastewater concentration CODcr3000mg/L, initial pH value8. The wastewater would be acidized in the process of electrolysis.In order to improve the effect of treatment adjusting the pH value continuously, the removal rates of Olaquindox, OTC, TC, CTC were98.7%,97.7%,96.2%,96.8%severally, the removal rates of CODcr、Cu、Zn reached72.1%,53.6%,56.8%, increased9.9%,19.1%,21.2%. The optimal HRT was90min at continuous operation, on this condition the removal rate of olaquindox, OTC, TC, CTC, Cu, Zn, CODcr were83%,88%,83%,87%,51%,57%,32%, achieved a good removal effect.