Research On Advance Removal Of Phosphorus From Secondary Effluent Of Slaughterhouse Wastewater By Combined Denitrification-adsorption Process

Slaughterhouse wastewater was an important industrial wastewater in China and had the characteristics of large discharge and high pollution load.In order to further reduce the impact of slaughterhouse wastewater discharge on the water environment,the ministry of ecological environment organized the revision of the discharge standard of water pollutants for slaughtering and meat processing industry,and the requirements for TP discharge were added to the published second draft.Therefore,in order to effectively control the phosphorus emission from slaughterhouse wastewater,this study carried out the research on the combined denitrification-adsorption process for the secondary effluent of slaughterhouse wastewater after the traditional anaerobic/aerobic treatment process.In this study,a SBR reactor based on heterotrophic denitrifying phosphorus removal and sulfur autotrophic denitrifying phosphorus removal was constructed firstly.The denitrifying phosphorus accumulating bacteria were acclimated and enriched in the alternating anaerobic/anoxic operation mode,and the phosphorus removal performance was studied.The results showed that the highest removal rates of NO₃^--N and PO₄^3--P were 100%and 50%respectively,and the sludge concentration was stable at about 5000 mg/L.In the heterotrophic denitrifying phosphorus removal reactor,the highest removal rates of NO₃^--N and PO₄^3--P were88%and 23%respectively due to sludge loss.Sulfur autotrophic denitrifying phosphorus removal process was superior to heterotrophic denitrifying phosphorus removal process in nitrogen and phosphorus removal.Besides,adsorbent DSGA1(desulfurized gypsum,montmorillonite,clay)and adsorbent DSGA2(desulfurized gypsum,steel slag,fly ash)based on desulfurized gypsum were developed.The phosphorus removal performance and mechanism were also studied.The results showed that the adsorption capacity of DSGA1 and DSGA2 were 0.82 and 15.58 mg/g,respectively.There were surface adsorption,internal diffusion and chemical precipitation in the process of phosphorus removal by DSGA1 and DSGA2.The adsorption capacity of DSGA2 was obviously larger than that of DSGA1.Therefore,DSGA2 was selected for the continuous flow experiment treating the secondary effluent of actual slaughterhouse wastewater.The results showed that the adsorption capacity was affected by NO₃^-and the calculated Q_P was 2.50 mg/g.Based on the sulfur autotrophic denitrifying phosphorus removal process and adsorbent DSGA2,the combined process of sulfur autotrophic denitrification-adsorption was established,and its phosphorus removal performance and operation cost were evaluated.The results showed that when the concentration of TN and TP was 25 mg/L and 2 mg/L respectively after treated by coupling process of adsorption-denitrification,and the treatment cost was significantly reduced.The combined sulfur autotrophic denitrification-adsorption process developed in this study could realize the phosphorus removal of the secondary effluent of slaughterhouse wastewater,which effectively reduced the process operation cost and realized the comprehensive utilization of waste.It also provided theoretical and technical support for the deep phosphorus removal of slaughterhouse wastewater in China.