Optimization Of Rapid Treatment Of Aquaculture Wastes By Response Surface Methodology

For a long time,excessive amounts of antibiotics and heavy metals were used as feed additives in ivestock and poultry farming,what can promote the growth of livestock and poultry,but also leads to a huge hidden danger.Excessive amounts of antibiotics and heavy metals cannot be completely absorbed and transformed by livestock.most of antibiotics and heavy metals are excreted in the feces,which eventually leads to problems of environmental pollution.Antibiotics can induce the production of resistant microorganisms,and heavy metals accumulate through the food chain and ultimately endanger human health.After anaerobic fermentation of livestock and poultry manure,antibiotics and heavy metals still partially remain in the biogas slurry and biogas residue,which can still cause secondary pollution to the environment.How to deal with livestock and poultry farming waste has become an urgent problem to be solved in environmental protection.This study investigated and researched 29 biogas projects and nearby farms in the suburbs of Beijing.After the detection of antibiotics and heavy metals in livestock manure,biogas residue and biogas slurry samples,the livestock manure and biogas slurry and biogas residue were combined with the governmental relevant standard values or abroad,in order to judged whether them are suitable to use as a fertilizer or not.Excessive harmful substances are degraded or converted by composting.The contents of study are as follows:1.Biogas project and nearby farm were researched.We separately collect the anaerobic fermentation raw materials,which provided by the farm to the biogas project,and biogas residue and biogas slurry,which separate the anaerobic fermentation residual liquid to solid and liquid by low-speed centrifugation.The content of antibiotics and heavy metals in all samples of manure,biogas residue and biogas slurry was detect.Antibiotics include:Tylosin,Chlortetracycline,Oxytetracycline,Enrofloxacin,Ciprofloxacin,Chloramphenicol,Ofloxacin,Sulfamonomethoxine,Sulfamethazine,Sulfathiazole,Sulfamethoxazole,heavy metals include:Cu,Zn,As,Pb,Cd.The survey results show that the main antibiotics in samples are chlortetracycline and oxytetracycline.The sum of chlortetracycline and oxytetracycline in all samples accounted for more than 79.06%of total antibiotics.The average content of chlortetracycline in livestock and poultry samples was 17.516 mg/kg,and oxytetracycline was 57.450 mg/kg;the average content of chlortetracycline in biogas residue samples was 6.723 mg/kg,and oxytetracycline was 19.046 mg/kg;The average content of chlortetracycline in the liquid sample was 3.479 mg/kg,and the oxytetracycline was 10.580 mg/kg.The main residual heavy metals are Cu and Zn,accounting for more than 89.96%of total content.The average content of Cu in livestock and poultry samples was 214.371 mg/kg,the average content of Zn was 686.706 mg/kg;the average content of Cu in biogas residue samples was 471.022 mg/kg,and the average content of Zn was 1668.017 mg/kg.2.The response surface method is used to optimize the composting process,and the livestock manure and biogas residue are treated by aerobic composting method.17 sets of orthogonal experiments are designed by Box-Behnken method.Ratio of raw material,ventilation volume and initial moisture content,three kinds of influences factor of aerobic composting are considered as dependent variable.antibiotic degradation amount,total amount of nitrogen,phosphorus and potassium were considered as the response value,and 17 groups of aerobic composting experiments were completed for 15 days.The initial sample and the final sample were taken to detect content of antibiotics and NPK,and the optimal process of aerobic composting was predicted by regression model to ensure the efficient degradation of antibiotic and minimize the loss of NPK.According to the data analysis,it can be seen from the regression equation that when the ratio of carbon to nitrogen is 30,the ventilation is 1.13 L/min kg,the initial water content is 69.61%,and the antibiotic degradation rate is the highest,which is 86.48%.When the carbon to nitrogen ratio is 30,the optimum ventilation is 1.29 L/min kg,and the initial moisture content is 65.54%,the nitriding phosphorus content of the compost finished product is the highest as 5.20%.The significant order of influence on the degradation rate of antibiotics due to the ratio of raw materials,ventilation and initial moisture content is:ventilation volume>raw material ratio>initial water content,the order of influence on the total content of NPK is:ventilation>initial Moisture content>raw material ratio,it can be considered that the change of initial water content has the least obvious effect on antibiotic degradation,but it has obvious influence on the total content of NPK.Therefore,the optimal initial moisture content can be adjusted from 69.61% to 65.54%.At this time,the degradation rate of antibiotics is 85.99% and the total content of NPK is 5.15%,which is compared with the optimal results.There is a slight dropWith the carbon-nitrogen ratio of 30,the ventilation volume was 1.13 L/min kg,and the initial water content of 65.54%,the optimal process parameters were verified.The final product of the compost was obtained.The degradation rate of the antibiotic was 87.43%,and the total nutrient content was 4.98%,the deviation from the predicted value is less than 5% of the predicted value,then the experimental results are valid,and the regression model is valid.