A Study On Inverted A～2/O Integrated Oxidation Ditches Technique In Municipal Wastewater Treatment

This thesis is based on nearly one year's experiment on Inverted A²/O Integrated Oxidation Ditch Technique using 120m³/d middle full-scale test unit for municipal wastewater treatment.The experiment results shew that the Inverted A²/O Integrated Oxidation Ditch Technique is highly effective in removing organic substance,nitrogen and phosphorus.When BOD₅,COD, SS,NH₃-N,TN,TP contained in the influent are respectively 182.12mg/L, 343.23 mg/L,143.37 mg/L,57.66mg/L,76.86mg/L,5.45mg/L,the removal efficiency reached 94.66%,91.88%,95.91%,89.77%,81.73%,90.27% respectively.The NH₃-N,TN,and TP removal efficiency are respectively 8.68%,9.94%,8.29%higher compared with what can be achieved by traditional A²/O process.The effluent quality complies with Level 1B standard stipulated in the Discharge Standard of Pollutants for Municipal Wastewater(GB18918-2002).The Inverted A²/O Integrated Oxidation Ditch Technique has rather good capability of resisting organic shock load and hydraulic load.When used in low concentration municipal wastewater treatment,the removal efficiency of NH₃-N,TN and TP could increase by 22.68%,13.90%,and 12.06%as compared with the traditional A²/O process.The orthogonal test shew that such factors as HRT,DO in the aerobic zone,sludge return ratio(r),and water allocation ratio between the anoxic zone and the anaerobic zone(R)all exert influence on the removal efficiency of A²/O integrated Oxidation Ditch Technique with the degree of influence being HRT＞R＞DO＞r.The ideal parameters are as follows:HRT:7hr,DO: 3mg/L,sludge return ratio:100%,water allocation ratio between the anoxic zone and the anaerobic zone:4:1.Through fitting and verification of the degradation kinetic model of organic substance in the aerobic zone,parameters in degradation kinetic model of organic substance contained in municipal wastewater of Xin Tianzhai,Guiyang(the Meat Processing Factory section)were obtained as follows:Y=0.733mgvSS/mgBOD5;q_max=2.27mgBOD₅/mgvss.d,Ks= 101.54mgBOD₅/L,K_d=0.045/d.The Inverted A²/O Integrated Oxidation Ditch Technique enjoys such advantages as high removal efficiency,short process,stable operation, convenient management,and low investment and operation cost,and therefore,has a good prospect for popularization in small and medium -sized cities.