Denitrfying Phosphorous Removal By Granular Sludge In SBR Process

Denitrifying phosphorus removal combines denitrification and phosphorus removal to one process avoiding competition for the organic substance in conventional biological phosphorus and nitrogen removal system.It has the great significance on development of cost-effective and efficient N and P removal process because of saving carbon source and reducing energy consumption,In this paper,based on mature denitrifying phosphorus removal granular sludge in SBR reactor,characteristics of granular sludge,effect of denitrification phosphorus removal and transformation of relations in anaerobic substrates were investigated.The results showed as follows:(1) The mature granules is of a spherical form with 1.0to2.0mm in diameter,28to45m/h in settling velocity,94%in water contect and 30to50mL/g in SVI.SEM test showed that bacterial in granules are diversified.The dominant bacterials on the surface of granules are filamentous and cocci,and that with the internal is bacillus.(2) The concentration of nitrate-nitrogen had some effects on phosphorus absorption in anoxic stage.The ratio of uptaking P amount in anoxic stage to total process increased from 47%to78%when the concentration of nitrate-nitrogen increased from 12%to20%.The initial max.specific uptake phosphorus rate and max. specific denitrifying rate increased as the concentration of nitrate-nitrogen rose.They were 16.2mg/gVSS·h and 14mg/gVSS·h when the concentration of nitrate-nitrogen was 12mg/L.They were 29.1mg/gVSS·h and 17.9mg/gVSS·h when the concentration of nitrate-nitrogen was 15mg/L,but they were no longer effected when the concentration of nitrate-nitrogen was 20mg/L.1.65mg phosphate was taken up when 1mg NO₃-N was utilized.(3) The impact of SRT was an important factor in biological phosphorus removal. Long SRT was not good for the removal of phosphorus.Under the condition of concentration of influent PO₄^3--P l0mg/L,when the SRT were 16d,20d and 26d the effluent phosphorous concentration was below 1mg/L.Along with SRT increasing to 40d,the effluent phosphorous concentration rose,which fluctuated between 1 and 3mg/L.(4) Static test results showed that DNPAOs stored to 0.9mgPHB,decomposed 0.94mgPoly-P and released 0.29mgPO₄^3--P when it absorbed lmgCOD in anaerobic stage.