Research On Enhanced Electrochemical Precipitation Method For Treatment Of High Nitrogen And Phosphorus Wastewater

In the process of accelerated development of industrialization,a large number of water pollution has been aggravated,and excessive nitrogen and phosphorus are the main pollutants.In order to improve the ecological environment,the nitrogen and phosphorus emission standards have been raised in recent years,so the treatment of high nitrogen and phosphorus wastewater is facing new challenges.Based on electrochemical precipitation,this paper proposes two strengthening methods:Electrolytic MAP circulation method and Electrochemical deposition/Electrochemical oxidation method.Based on the investigation of removal effect and the analysis of the reaction mechanism,a more efficient and energy-saving nitrogen and phosphorus removal method is obtained through the comparative analysis of the results,which provides a theoretical basis for its application in practical engineering.The electrolytic MAP circulation method is to collect part of the nitrogen and phosphorus in the sewage in the form of MAP,and then recycle the remaining ammonia nitrogen in the sewage after electrolysis.During the electrochemical precipitation process,AZ31 magnesium was used for the anode and 304 stainless steel plate for the cathode.Under the optimal conditions,the removal rates of ammonia nitrogen and phosphate were 67.87%and 98.01%when the current density was 400A/m²,the initial p H was 7,the initial concentration of Cl^-was3000 mg/L,and plate gap was 1cm.In order to improve the ammonia nitrogen removal rate,MAP precipitation was electrolyzed in Na Cl solution.Both anode and cathode were inert electrode graphite,and the MAP decomposition was the best under the conditions of reaction time of 2h,voltage of 5V,initial Cl^-concentration of 600mg/L,and initial ammonium phosphate amount of 1.5g.Under this condition,the removal rate of residual ammonia nitrogen was increased to 92.76%.It can be seen that the electrolytic MAP circulation not only significantly improves the removal effect of ammonia nitrogen,but also can recycle the MAP to reduce emission.The EP/EO method was used for denitrification and dephosphorization.The electrodes were connected by repolarization test,DSA electrode（Ti/Sn O₂-Sb₂O₃/Pb O₂）,AZ31magnesium,and Ti electrode were placed in parallel.Though single-factor experiments,when the current density is 300A/m²,the initial p H of is 7,the initial Cl^-concentration is 3000mg/L,and the plate gap is 1cm,the removal rate of ammonia nitrogen is over 99%at the end of the reaction.At the same time,the removal effect of phosphate reached 98%.Compared with the separate electrochemical precipitation process,the removal effect of ammonia nitrogen was increased by 1.46 times,and the reaction time was shortened.Under the condition of continuous operation for slaughterhouse wastewater treatment with two methods,the tests show that the removal rate of nitrogen and phosphorus in the actual wastewater by the electrolytic MAP cycle method is more than 90%,can meet the"Emission Standard of Pollutants for Livestock and Poultry Industry"（GB18596-2001）.The concentration of ammonia nitrogen and phosphate in the effluent of the farm wastewater treated by the EP/EO method can also meet the discharge requirements in the above standards,and the removal effect of COD is also more than 60%,indicating that this method is better than the former.