Study On The Removal Of Nitrogen And Phosphorus By A~2/O-SBR Process In Treating Aquaculture Wastewater

One of the key problems restricting the sustainable development of aquaculture is the standard discharge of aquaculture tail drainage.Phosphorus Phosphorus is the limiting nutrient element in freshwater ecosystems and is the key cause of eutrophic algal blooms in many freshwater ecosystems.Therefore,phosphorus in aquaculture tail water has been widely concerned.In this study,the anaerobic/anoxic/aerobic（A2/O）process was used to treat aquaculture wastewater and explore its treatment effect,hoping to provide theoretical support for the discharge of aquaculture water.This research is divided into three parts:1.Preliminary research on the working conditions of the reactor in the A²/O process test deviceThis part is to explore the effect of treating simulated domestic wastewater.During the system startup phase,biological flocs are added to the system,and the mixed liquid suspended solids（MLSS）of the system has been rising steadily,and the SV30 is also behind the starter.Gradually stable,the sludge settling performance is good.In the process of treating simulated domestic sewage by A²/O process,the removal rate of chemical oxygen demand（COD）was stable at more than 80%,and the effluent concentration was 50～100mg/L,which reached the"Urban Sewage Discharge Standard"（GB18918-2002）secondary standard.The total ammonia nitrogen（TAN）concentration in the effluent was stable between 6 and 12 mg/L,and the removal rate gradually increased from 40%in the previous stage to 99%.The concentration of total nitrogen（TN）in the effluent is slightly higher in the early stage,but the influent concentration of TN in the late operation can be stabilized at about 40mg/L,the TN concentration in the effluent is about 5mg/L,and the removal rate can be stabilized at 70%～80%%.The influent of total phosphorus（TP）fluctuated but was basically stable at around 10 mg/L,the TP concentration in the effluent decreased,fluctuating between 2 and 8 mg/L,and the removal rate was around 40%.In the later period,the phosphorus removal rate gradually increased to about 55%.The influent phosphate(phosphorous salts,PO₄^3-)concentration is basically stable at 8mg/L,the effluent concentration also decreases to about 3mg/L over time,and the phosphate removal rate also gradually increases and stabilizes from the initial 30%.above 60%.It shows that the A²/O test device constructed in this study can effectively remove nitrogen and phosphorus in water.2.Study on the effect of A²/O process test device on the treatment of simulated aquaculture wastewaterIn the enrichment stage of denitrifying phosphorus accumulating bacteria,after three stages of enrichment culture,the phosphorus removal rate of the system reaches more than80%.During the treatment of simulated aquaculture wastewater with denitrifying phosphorus removal bacteria,the removal effect of COD_Cr was remarkable.After the system was stabilized,the removal rate could reach 90%.1996)Tier 1 emission standard.The concentration of nitrate（Nitrate,NO₃^--N）in the effluent of the system is basically stable between 0 and 3 mg/L,and the removal rate of NO^3--N reaches more than 95%,or even100%.The PO₄^3-concentration of the effluent is basically stable at 5～6mg/L,and the phosphorus removal rate of the system is between 40%and 50%.The average TN concentration in the effluent is 5mg/L,and the removal rate is stable at about 88%.The TP concentration of the effluent is between 5 and 7 mg/L,and the effluent concentration tends to be stable at 5.92 mg/L in the later stage of the reaction.The removal rate fluctuates greatly,ranging from 30%to 50%.3.To explore the treatment effect of A²/O process test device in the treatment of biological flocculation wastewater and circulating aquaculture wastewater.In the case of treating circulating aquaculture wastewater except adding carbon source to maintain the carbon-nitrogen ratio at 3.4:1,the overall effect of the A²/O process applied to denitrification,nitrogen and phosphorus removal is not significant.The NH₄⁺-N concentration of the effluent increases.The concentration of NO₂^--N in the influent and effluent is not very different,the concentration of the effluent reaches the first-class standard for comprehensive sewage discharge（GB 8978-1996）,the removal rate of NO₃^--N reaches50±0%,and the removal rate of TN reaches 33.82±0.03%.TP increased,the removal rate of PO43--P was 6.13±0.01%,and the removal rate of PO₄^3--P was not significant.Adding sodium acetate externally to maintain the carbon-nitrogen ratio at 3.4:1,the A²/O process applied by denitrification,nitrogen and phosphorus removal has a significant operating effect on circulating aquaculture wastewater.The concentration of NH₄⁺-N in the effluent rises and reaches the sewage discharge standard.The concentration of NO₂^--N in the influent and effluent is 0±0mg/L,which reaches the first-class standard for comprehensive sewage discharge（GB 8978-1996）,and the removal rate of NO₃^--N reaches 100±0%.The removal rate of TN reached 70.33±0.01%.The removal rate of TP reached 33.26±0.04%,the removal rate of PO₄^3--P was 32.26±0.03%,and the removal rate of PO₄^3--P and TP was not significant.Adding sodium acetate externally to maintain the carbon-nitrogen ratio at 3.4:1 to treat biological floc wastewater,the A²/O process of denitrification,nitrogen and phosphorus removal has a significant operating effect on biological floc wastewater.The concentration of NH4+-N in the effluent drops from 2.1±0.1mg/L in the influent to 0±0mg/L in the effluent,reaching the first-class standard for comprehensive sewage discharge（GB 8978-1996）.The concentration of NO₂^--N increased to 4.05±0.08mg/L,and the removal rate of NO₃^--N concentration reached 95.89±0.01%.The removal rate of TN reached 80.06±0.01%.The TP concentration increased to 7.8±0.50mg/L,and the removal rate of PO₄^3--P was 22.22±0.24%.This study has guiding significance for the use of A²/O process to treat aquaculture wastewater,and provides data support for future research on the treatment effect of aquaculture wastewater.