Simulation And Analysis Of Johannesburg Process For Municipal Wastewater Treatment In Dengjiacun, Xi'an

On the basis of the activated sludge NO.2 and the Takàcs settling model, a simulation program for the wastewater treatment process with Visual Basic 6.0 under Windows XP operation system was constructed. The simulation program was adjusted by the COST simulation benchmark and then was used to simulate and analyse municipal wastewater treatment process in Dengjiacun, Xi'an.The user's interface, access database, data input and output, calculation method and integral steps were discussed for the program development. The results showed that the calculation precision, run velocity and data management in the program can fit the requirement of application.The software was used to simulate the Johannesburg process and analyse the biomass, nitrogen and phosphorus in effluent during the sludge-cultivating. Furthermore, the thesis had predicted the effluent quality under different operation and control conditions such as influent distribution ratio, mixed liquor recycling ratio, activated sludge circulation ratio, SRT and volume ratio between anoxic and oxic zone in the model. The main conclusions are summarized as follows:(1) The change of the influent distribution ratio affected the concentration of NO₃-N and COD in the anaerobic zone which had a great impact on the efficiency of the biological phosphorus removal in the system. But the change of the influent distribution ratio was of no effect on the efficiency of the biological nitrogen removal;(2) Nitrogen removal can be enhanced by increasing the mixed liquor recycling ratio. When the mixed liquor recycling ratio was higher than 150%, the NO₃-N in effluent was hardly changed. The efficiency of the biological total nitrogen removal increased by 3.5% when the mixed liquor recycling ratio increased from 125% to 150%;(3) With the increasement of the activated sludge circulation ratio (ranging from 30% to 100%), the effluent quality changed as follows: the concentration of TN, NH₃-N, NO₃-N induced while the concentration of TP, PO₄^2-, TCOD and SS increased. And the activated sludge circulation ratio can not enhance the efficiency of the biological nitrogen removal effectively;(4) The concentration of COD, TP, TN and ammonia-nirtogen in effluent satisfied all requirements when the SRT is controlled in 12d. The SRT in the actual process is 15d and the efficiency of the biological total nitrogen removal remained steady when it was more than 15 days;(5) When the volume ratio between anoxic and oxic zone changes from 1:14.7 to 1:2.3, NO₃-N in the anoxic zone decreases from 3.1 mg/l to 0.04mg/l and the efficiency of the total nitrogen removal increased by 25.7%. It showed that the volume ration between anoxic and oxic zone has a tremendous effect on the nitrogen removal process.