Upgrading And Improvement Of A~2o Municipal Wastewater Treatment Process With High-standard Effluent

In recent years, China has increased the intensity of urban sewage treatment, thenumber of sewage plant increases. However, many plants have less efficient withdealing with N, P and the effluent quality can not reach the standard of"Pollutantdischarge standards of urban sewage treatment plant"（GB18918-2002）. The mainreason is that traditional process has the problem that carbon source competition andsludge ages contradiction when it deals with low carbon and nitrogenratiowastewater.These problems make it can not reach the standard and it needs to bechanged.The A2O process is a typical traditional process, there are many variation in recentyears. They can deal with the problems which the conventional process had, however,they are complex, unstable and expensive. This research, according to the theory ofdenitrifying phosphorus removal, have a good treatment effect when it deal with lowcarbon and nitrogen ratio wastewater, and it is a new variation of A2O process. We callit ANAO process.This research mainly includes small test and pilot with ANAO process, the start、operation of the ANAO process, and the contrast with A2O process. The small testshows: nitrification tank of the ANAO process has a stable treatment effect because ituses the fiberfill and the membrane can grow quickly. Results showed that COD andammonia of the A2O process, could be removed effectively, while, TN and TP removalswere poor. It was due to the deficiency of carbon source. As for the ANAO process, theremovals of COD, ammonia, TN and TP were82%,97%,70%and98%, respectively,and the first-A standard could be achieved. The uptakes of phosphorus in the anoxic andaerobic tank were significant. The average amounts of phosphorus uptake were9.5mg/Land6.04mg/L each. Moreover, the secondary phosphorus uptake could ensure thequality of effluent. On another aspect, nitrification was efficient, indicated by7.15mg/Lammonia removal in the aerobic tank.Pilot add nitrification reflux to the small test, and it solves the problem that effluentTN can not reach the standard when influent ammonia is too high, and TN of effluent isunder10mg/L. According to controlling the sludge volume of two pilot, comparing theremoval effect of the two pilot, A2O process has a bad removal effect for TP, when weincrease sludge volume, the A2O process may appear the problem that superscalar of TN,and the effluent quality of ANAO is better than the other. Also, we discuss the balanceproblem of C, N, P that in the ANAO system, and we find that ANAO process has manyadvantages than A2O process like that carbon saving, simple transformation, low sludge production, different bacteria culturing separately. These advantages solve the problemsin conventional process, and make the effluent reach the level A standard. The ANAOprocess suitsto use in a new wastewater treatment plant or upgrading of the existingwastewater treatment plant processes.