Study On Advanced Treatment Of Dairy Farming Wastewater By Heterogeneous Ozone Catalytic Oxidation

The dairy farming wastewater produced by a dairy farming center in Guangzhou has been treated by conventional anaerobic and aerobic processes.The effluent has poor biodegradability and poor water quality conditions,which can not meet the requirements of reuse and irrigation,and can not meet the discharge requirements.Moreover,it has certain regional characteristics,so it is difficult to solve the problem of wastewater treatment.This paper analyzes the organic pollutants in the wastewater and the daily feeding of dairy cows,and speculates that the main components of the wastewater contain animal hormones,antibiotics,and flavonoids and anthraquinones.There are a lot of polybenzene ring structure in these substances,with stable chemical properties,it is difficult to be removed by the traditional biochemical method.After aerobic aeration,the effluent often appears reddish brown,and the COD_Crand chroma indexes can not meet the discharge standards.Therefore,this paper will focus on solving the problem of COD_Crand chromaticity.Taking heterogeneous ozone catalytic technology as the main line,the combined process of heterogeneous ozone catalytic oxidation and contact oxidation is proposed to treat the effluent from the tertiary oxidation pond for advanced terminal treatment.Through the early laboratory test and the late pilot test,the treatment of dairy farming wastewater was studied from multiple angles,which could be divided into the following three parts:（1）Sulfamethoxazole（SMX）antibiotics are used to treat dairy cows in dairy farming centers,which leads to the problem of residual antibiotics in wastewater,laboratory test was conducted to treat SMX by heterogeneous ozone catalytic oxidation.The trend and kinetic parameters of the degradation of SMX by this reaction system were investigated from the initial concentration of SMX,the acceleration rate of ozone,the amount of heterogeneous catalyst and the p H value.Under the same conditions,the degradation efficiency of SMX will increase with the decrease of the initial concentration of SMX.Within a certain range,increasing the ozone dosing rate and the amount of heterogeneous catalyst can also effectively improve the degradation efficiency of SMX,but too much dosage will also cause waste.Therefore,the dosage of these two factors needs to be set according to the specific conditions in the actual project.Under the same conditions,the rate of SMX degradation in alkaline environment is higher than that in acidic environment.This is because alkaline environment is more conducive to ozone decomposition to produce highly oxidized HO·.In practical engineering,ozone catalytic process is more suitable to be used with p H of 9.In this reaction system,SMX degradation rate is higher,and its degradation completion time is much lower than the ozone catalytic reaction time for treating dairy wastewater.Therefore,it is determined that the wastewater after the ozone catalytic reaction has little influence on the subsequent biochemical reactions.In addition,the biodegradability（B/C value）of wastewater after ozone catalysis was increased from 0.21 to 0.54,and the COD_Crof wastewater after ozone catalysis and biochemical treatment could be greatly reduced by 50%,providing feasibility theoretical support for later pilot tests.（2）The pilot test determined the optimal working conditions by exploring the influence of ozone dosage,ozone catalytic reaction time and catalyst dosage on the effluent COD_Crand chromaticity removal rate:the ozone dosage was 120 mg·L^-1,ozone The catalytic reaction time is 30 min and the amount of catalyst in the device is30 g·L^-1.And the 3E evaluation model proves that the optimal working condition is the most economical and beneficial condition.（3）Under optimal conditions,the effluent chromaticity of the pilot system was stable at 8 times,meeting the emission requirements;the removal rate of COD_Crunder continuous operation was 58.82%.Under 50%reflux conditions,the COD_Crremoval rate during continuous operation is 63.27%,and the COD_Crvalue of the effluent is stable at 180 mg·L^-1,and it does not increase the salinity of the effluent,meeting the reuse irrigation standard,and can be reused for orchard irrigation or cow house cleaning in the breeding farm.The whole process reduces the treatment cost of about4.59 yuan·（m³）^-1and has strong practical value and good economic benefits,and provides practical engineering experience and guidance for the treatment of dairy farming wastewater in South China.