Discussion Of MAP Method Using Sodium-filtered Sea Water As Source Of Magnesium And Its Practical Engineering Application Methods Regarding The Handling Of Pig Manure Liquid Wastes

Breeding farms in China generally deal with liquid wastes using technologies based on anaerobic digestion.However,the high concentration of nitrogen and phosphorous resulting from the anaerobic digestion of livestock manure liquid waste serves as a potential source of water body pollution.Under the current circumstances where the proportions of ammonia,nitrogen and phosphorous are higher in livestock manure liquid waste than in both industrial and civil liquid wastes,more attention ought to be attached to this issue.This paper discusses the feasibility of a method to reutilize the nitrogen and phosphorus in liquid wastes by recovering struvite in pig breeding farms from anaerobic digested liquid waste,neutralizing their potential pollutive threat.A series of experiments were conducted to confirm the validity of using sodium-filtered sea water as a source of magnesium when recovering struvite,the removal rate of ammonia and nitrogen reaches 50%,while the purity of the struvite sediment is greater than 70%Sodium-filtered sea water acquired near Hamburg is used as magnesium source to add to anaerobic digested pig manure liquid waste.When PH = 9,the sediment formed are tested to be struvite sediment with a purity of 70%.With the PH unchanged,the nitrogen removal rate and struvite purity are inspected when the molar ratio of magnesium and ammonium in the anaerobic digested pig manure liquid waste are 1:1,1.1:1,1.2:1,1.3:1,1.4:1,1.6:1,1.8:1 and 2:1 respectively.Results show that the removal rate of nitrogen reaches its peak at 63%when the molar ratio of magnesium and phosphorous is 1.3:1,and the purity of struvite reaches its maximum at 75%when the molar ratio is 1.4:1.When magnesium is excessively added,the recovery rate of nitrogen and purity of struvite both increases as the magnesium and phosphorous molar ratio changes in a certain range.This indeed shows the advantageous potential to apply the method.Through testing on samples acquired from Hamburg,the aim of this paper is to provide practical digested waste handling methods for the real-world engineering case set in Zhuhai's Doumen Pig Breeding Farm.Sedimentation of struvite is not only economical but also practical as the struvite sediment is itself an excellent controlled release fertilizer.This method also simultaneously removes the nitrogen and phosphorous in the digest manure liquid waste.Using sodium-filtered sea water as added source of magnesium also saves the cost for purchasing extra chemicals.Using different combinations of chemicals,the costs are different for handling one cubic meter of fermented pig manure liquid with the same conditions.Considering the cost of purchasing sodium-filtering machineries,it is not the most cost-effective option to use sodium-filtered sea water as source of magnesium in the short term.However,in the long term this method is as environmental friendly as highly efficient,which is well worth the investment.This paper also proposes some ideas to improve the utilization of sodium-filtering reactors and sediment recovery equipment,as well as ideas to reutilize the liquid wastes after recovering the struvite sediments by adding microorganisms to produce liquid fertilizers.