Study On Removal Of Phosphorus From Pig Manure By Chemical Method

The current mainstream treatment process for pig farm wastewater has a major problem:the removal of phosphorus depends on a single chemical phosphorus removal process and lacks the protection of multiple links in the treatment route.The phosphorus content of pig farm manure in dry and liquid bubble manure removal methods is too high,resulting in excessive phosphorus treatment pressure in the subsequent wastewater treatment process;at the same time,the lack of biological phosphorus removal in the anaerobic biogas slurry treatment process results in the chemical phosphorus removal pressure at the end is relatively high.If the high concentration of phosphorus can be fixed at the source of wastewater treatment in pig farms,and the crystallization method can be used to further remove the phosphorus in the anaerobic fermentation biogas slurry,the phosphorus treatment pressure at the end of the wastewater treatment process can be greatly reduced.The effects of the types and dosages of phosphorus-fixing agents on the mixed manure and the wastewater after solid-liquid separation are studied.The mechanism of phosphorus fixing and the reason for the removal of ammonia nitrogen are analyzed respectively.The reasons for ammonia nitrogen removal and the phosphorus forms of two pig farm manures were analyzed respectively.The experiment showed that:dry cleaning The effect of adding medicines to fix phosphorus is not obvious,mainly because the proportion of Ortho-P and Na OH-P involved in the crystallization reaction in dry cleansing manure is slightly lower;the effect of adding medicines to fixing phosphorus is more significant,mainly because Because the proportion of these two kinds of phosphorus in the vacuole manure is relatively high.Considering economic costs,the appropriate dosage of vacuolar fecal phosphorus fixing agent is 250 mg/L,and the effect of magnesium source is the best,followed by calcium source,and finally iron source.Exploring the application of crystallization method to remove phosphorus in anaerobic fermentation biogas slurry,including the types and dosage of magnesium source,the dosage of calcium source and the reaction time,etc.Experiments show that three types of magnesium sources are added to the biogas slurry.Phosphorus removal,Mg（OH）₂ has the most significant effect on phosphorus removal,the suitable dosage is500 mg/L,and the nitrogen removal effect is also the best at this time;Mg Cl₂ and Mg SO₄ have certain phosphorus removal effects but are far inferior to Mg（OH）₂;The appropriate dosage of Ca（OH）₂ is 250 mg/L.In addition,prolonging the reaction time has a significant effect on the removal of nitrogen and phosphorus,and the optimal reaction time is 30-40 min.The two methods of adding biochar during the crystallization process of anaerobic fermentation of biogas slurry in pig farms and setting up a biochar filter column after crystallization is completed on the adsorption and removal effect of nitrogen,phosphorus,calcium and magnesium,and at the end,a chemical precipitation method is used to remove the remaining calcium and magnesium ions in the crystallized water.Experiments show that:anaerobic fermentation in pig farms When biochar was added in the crystallization process of biogas slurry,the removal rate of TP,Ca²⁺and Mg²⁺gradually increased with the increase of the dosage,and the removal rate of ammonia nitrogen showed a fluctuating trend.Corn stalk biochar and rice husk biochar have good adsorption effects on nitrogen and phosphorus,with removal rates of 20%and 60%,respectively,and their adsorption effects on calcium and magnesium ions are not significant.By setting up a biochar filter column when the water is discharged after the crystallization of the biogas slurry is completed,the removal rate of TP by straw charcoal and rice husk charcoal is about 30%,the removal rate of ammonia nitrogen is about 17%,and the removal rate of calcium and magnesium ions is less than 8%.The adsorption and removal effect of rice husk charcoal on nitrogen,phosphorus,calcium and magnesium is generally better than that of straw charcoal.The optimum dosage of sodium carbonate in the effluent after crystallization is 400 mg/L,and the concentration of remaining calcium and magnesium ions is at a relatively low level.