Research On Wastewater Treatment Technology Of Large-Scale Dairy Farm

Large-scale dairy farm wastewater is one of the main sources of livestock and poultry pollution.At present,anaerobic fermentation combined with deep treatment and stable storage combined with subsequent utilization are the main methods of large-scale dairy farm wastewater treatment and disposal at home and abroad,Dairy-hall wastewater treatment technology is a difficult problem of dairy farm wastewater treatment and utilization technology,development the economical and efficient technology of large-scale aquaculture wastewater,especially development the treatment and utilization technology of dairy-hall wastewater,is a hot research topic at present.In order to explore the large-scale dairy farm wastewater treatment technology,carried out the following three parts:?1?According to the water quality and quantity characteristics of the milking hall,the process parameters of the integrated equipment were designed by combining A/O and membrane bioreactor?MBR?.By monitoring the water quality of inlet and outlet of the equipment,and calculating the economic benefit of equipment operation,the effect of A/O and MBR processes on dairying wastewater treatment was evaluated.?2?Using milk hall wastewater as the main raw material,nitrogen and phosphorus were removed by struvite crystallization precipitation method.In order to achieve the best removal effect,five factors?pH,phosphorus-nitrogen ratio,magnesium-nitrogen ratio,stirring time and stirring speed?affecting struvite crystallization were screened and optimized using single factor test,PB test and response surface test.?3?According to the water quality and quantity characteristics of dairy farm mixed wastewater,using purification effect of iris with different concentration gradients the relationship between the contents of COD,NH₄⁺-N,TP and TN in waste water and the growth rate and biomass change rate of the yellow-flower-iris was studied,for determining the tolerance value of yellow flower-iris to cattle wastewater.The results showed that:?1?A/O and MBR combined process was used to treat the milk hall wastewater,COD?90 mg·L^-1,TN<20 mg·L^-1,TP<5 mg·L^-1 in effluent,which meeting the emission standards for livestock and poultry?GB18596-2001?.The cost of treating each ton of water is less than 1.7 yuan.This method provides a more efficient and energy-saving process for the treatment and utilization of milk wastewater.?2?Nitrogen and phosphorus in milk hall wastewater were removed by struvite crystallization precipitation method.According to the response surface test results:pH,P/N and Mg/N were the main factors affecting the N and P removal rate.The optimal condition is:pH=10,P:N=0.876 and Mg:N=1.1,in these conditions,The recovery of ammonia nitrogen and phosphate was 96.00%,89.00%,respectively.Test results showed that:the recovery of ammonia nitrogen and phosphate was 88.73%,91.34%,respectively.?3?As a common plant in water purification system,iris can effectively reduce nitrogen and phosphorus in cattle farm wastewater and purify water quality.When the COD,TN,TP and NH₄⁺-N concentrations of cattle farm wastewater were higher than 1250.7,150.4,36.5 and100.2 mg·L^-1,respectively,the growth of yellow iris was inhibited.One week after the experiment,the removal rates of COD,NH₄⁺-N,TN and TP were 57.1%,59.49%,82.59%and72.39%,respectively,among which the removal rates of TN and TP were the most obvious.When the dilution ratio was appropriate controlled,the growth of yellow iris would not be inhibited.The iris irides showed good absorption and removal effects on the pollutants in cattle manure wastewater.According to the source and water characteristics of the wastewater from the milking hall of large-scale dairy farms,a treatment technology based on the A2O+MBR combined process was established,which can treat the wastewater of the milking hall separately and reuse it,the inorganic salts in the rinsing water of the milk hall are prevented from entering into the fecal wastewater area to reduce the impact on the fecal wastewater treatment.There are a lot of available nitrogen and phosphorus nutrient elements in the milking hall wastewater.A large-scale milking hall wastewater treatment method combining aerobic pretreatment and struvite crystallization was established to recover nitrogen and phosphorus elements in the wastewater.