| According to the reactor theory, concentric-circles reactor with movable partition-wall (called OGO reactor for short) was developed based on the OCO reactor. The dissertation studied OGO technology for domestic wastewater treatment systematically, and related in the main to the following areas. Firstly, by comparison experiments, removal effects and stability of nitrogen and phosphorus, and flow pattern characteristics were investigated. Secondly, by orthogonal experiments, the optimized controlling conditions of OGO system were obtained. Thirdly based on the long time experimental data for operation of OGO process, the removal effects of nitrogen and phosphorus, activated sludge characteristics and oxygen demand in process, removal effects and parameter optimization under low temperature etc were analyzed. And by tracing to the nitrogen concentration and calculation of nitrogen balance in OGO reactor, the mechanism and effecting factors of simultaneous nitrification and denitrification (SND for short) were also studied.This research was mainly carried out in the following several aspects:①Because of the extending of the partition-wall in reactor, the effective volume and retention time of anoxic zone have been increased. The macro-zoning of aerobic/anoxic zone and dynamic allocation of substance are optimized, and the stability of anoxic environment aslo increases greatly. So the OGO reactor can exploit removal potential of nitrogen and phosphorus fully. For domestic wastewater treatment, when the concentration of NH3-N and TN in influent are 15.67～35.42mg/L and 19.6840.08mg/L respectively, and the concentraton in effluent are 3.97～9.48mg/L and 7.86～13.85mg/L respectively. Compared to OCO reactor, removal efficiencies of NH3-N and TN had increase from 56.5% to 70.8% and from 68.2% to 80.4% respectively. Removal effect of nitrogen has increased obviously.②The two speed-adjustable stirrers in OCO reactor are taken the place of a movable guide-wall, which is at the beginning terminal of the entrance in the aerobic area and the anaerobic area in OGO reactor. Return of mixing liquid can be realized automatically and the circulatory flow also can be adjusted effectively by the opening angle of the movable wall. The calculation model of the relationship between the size of the opening angle of the movable wall and the flow distribution shows that, when the opening angle ofαvaries from 0°to 25°, the ratio of Qanoxic/Qaerobic varies from 1.19 to 2.85。For the treatment of domestic sewage, when b/a=1/2～1/4 , namely the opening angle ofαis 0～15o, the total effluent quality is good. Compared to the OCO reactor, the average removal rates of TN and TP in the OGO reactor vary from 56.5% to 70.8% and from 68.2% to 80.4% respectively. And the reliability and stability of the biological phosphorous and nitrogen removal effects for domestic sewage treatment in OGO reactor improve obviously.③The experimental results of the residence time distribution function (RTD for short) show that, under the experimental conditions, Pe values in OCO reactor and the OGO reactor are 2.1(1/Pe=0.476)and 2.6(1/Pe=0.385)respectively. Compared to OCO reactor, the translation effects for OGO reactor in the mass transfer process increase nearly 19%, and the volume utilization ratio of plug flow patterns also increase greatly. So it is more in favor of distribution of substrate, DO concentration, strengthening of the pushing flow pattern characteristics and improving of the reacting efficiency in reactor. Meanwhile, OGO process can improve the hydraulic behavior of mixing zone remarkably, and avoid the problem of sludge-settlement in mixing zone effectively.④By orthogonal experiments, the optimal parameters for OGO process for domestic wastewater treatment are obtained. When the volumetric ratio of the anaerobic, anoxic and aerobic zone (calculated as G-Partition Wall into an close circle) is 1:3.2:4.6 and the return ratio of sedimentation sludge is about 60%, 1) the total HRT is about 9.5h (1.2h in anaerobic zone) ; 2) Sludge retention time(SRT) is 18 days; 3) the DO concentration in the middle aeration zone is about 1.5 mg/L,④the sludge load is about 0.30.4 kgCOD/(kgMLSS·d). Under optimization operating conditions for OGO process, for sewage treatment, average removal rates of CODcr,NH3-N,TN,TP are 92%,81%,73%,83% respectively ,and the water quality in effluent of the system can meet the primary standard (B level) requirements of Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant(GB18918-2002) .The system has a great capability of tolerated shocking load, and strong abilities of recovering and adjusting for activated sludge in OGO reactor.⑤In anaerobic, aerobic, anoxic zone and mixing zone ,the average particle size of the activated sludge flocculation in OGO reactor is about 42670μm ,and with a wide grain diameter distribution. There are a great number of diversities of the activated sludge microorganisms with favorable activity in OGO system. Under normal operating conditions, the MLSS, SVI in the system are basically stabilized in the range of 2.33.1 g/L and 96128 mL/g respectively. The apparent yield coefficient of activated sludge in OGO system is about 0.1996 kgMLSS/kgCOD. The total oxygen demanded is about 1.13kgO2/kgBOD5(0.59kgO2/kgCOD), slightly lower than 1.41.9 kgO2/kgBOD5 in the conventional A2/O process.⑥Under the condition of low temperature, for domestic sewage treatment, the average removal efficiencies of CODcr,NH3-N,TN,TP are 90.1%, 77.7%, 69.7% and 81.8% respectively. The apparent temperature-influence coefficientθa in the system is about 1.023, which is lower than the classic value in the traditional activated sludge system for biological nitrogen removal. It is sufficiently suggested that the OGO process has a great adjusting and controlling capability at a low temperature. Measures such as appropriate increaseof the HRT in the anaerobic zone or decrease of the opening angle of moveral guide-wall etc can promote pollutant removal efficiencies at low temperature in winter, especially for biological nitrogen removal effect.⑦Because of the influence of DO concentration gradient, the nitrification and denitrification effects in OGO process are distributed in loop zone non-homogeneously to a certain extent. The contribution of biological nitrogen removal in OGO process is mainly by the way of SND. Average TN removal amount in loop area is about 69% of total nitrogen removal amount in the whole system. Macro-partitioning theory is the same with the phenomenon of SND in the loop zone, the micro-environment theory in the activated sludge has relatively minor effects on SND. Six strains with denitrification ability under aerobic conditions are purified and separated in the study. Strain B and strain E have good degradation efficiency to nitrate nitrogen and the conversion of nitrate is about 26%～30% and the accumulation of nitrite is less than the other strains. SND in OGO system could be explained from the angle of microorganisms'theory.⑧The concentration of DO in the aeration zone, the ratio of C/N in influent and the SRT of the system have significant influence on the denitrification efficiencies of SND in the process, and the concentration of DO in the aeration area, the ratio of C/N in influent have strong related effects on the nitrogen removal. In OGO system , when the loading of N of activated sludge is kept the same relatively, the optimum C/N in influent is 7～18. And in this scope, OGO system have best effects on nitrogen removal and SND, and the average removal efficiencies of TN in OGO process reached to 74.15%, the ratio of SND/TN is 59.94%. According to results on dynamics parameters study for optimum DO model, that the calculation values of optimum concentration of DO based on the model are basically in consistence with the value from the optimizing experiments in OGO system.To sum up, the development of OGO technology has innovative property, and experimental results can provide technical supports for the practical applications of OGO process.
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