| With the gradual improvement of China’s attention to the ecological environment,rapid development has been made in the field of sewage treatment.At the same time,the sewage discharge standards have been raised year by year.Compared with the existing activated sludge process,aerobic granular sludge technology has the advantages of fast separation of mud and water,high efficiency of pollutant removal and few post-treatment links.However,the engineering application of this technology has not been realized in China.Restricted by the special flow field conditions of sludge granulation,aerobic granular sludge reactor’s structure is usually cylindrical with large aspect ratio,this type of reactor is difficult to manufacture and has high manufacturing cost in the application process.Therefore,a new type of reactor was developed,which will greatly promote the engineering application of this technology.In this paper,three dimensional gas-liquid two-phase numerical simulation was carried out for cylindrical reactor and regular prism reactor by numerical simulation method.The state of gas-liquid two-phase flow field and the distribution of turbulent kinetic energy in the reactor with different section types were investigated.Studies have shown that the two reactors have similar gas-liquid two-phase flow fields,and the distribution of liquid velocity is also similar.In terms of flow field state uniformity,the cylindrical reactor is better than the regular prism reactor.However,the turbulent kinetic energy in the liquid phase is higher in the regular four-prism reactor.The numerical simulation results show that the regular prism reactor also has the special flow field state of aerobic granular sludge granulation.It lays a foundation for the subsequent miniaturization experiment of aerobic granular sludge culture.Taking actual domestic sewage as the raw water,a miniaturization experiment of aerobic granular sludge culture was carried out in a regular four-prism reactor.The culture results showed that the sludge granulation takes about 34 days to form,The reactor was operated for 74 days,aerobic granular sludge with particle size ranging from 0.8mm to 2.0mm was obtained.The settling performance and pollutant treatment effect of granular sludge are good.Sludge settling speed is stable at 42m/h,Sludge volume index reached 47mL/g,The removal rates of COD,total nitrogen and ammonia nitrogen in the reactor effluent water were 96%,93%and 97%.It is proved that the flow field environment in the normal prism aerobic granular sludge reactor is suitable for the formation and growth of aerobic granular sludge.A pilot test platform for aerobic granular sludge culture was designed and built.The pilot experiment of aerobic granular sludge culture was carried out.Apparent granular sludge was found on the 40th day of culture in the experiment.After 60 days of cultivation,the sludge volume index and sludge concentration in the reactor were 62mL/g and 2510mg/L.The removal rates of COD,total nitrogen and ammonia nitrogen in the effluent water were 90%,85%and 93%.The mature aerobic granular sludge has been successfully cultivated in the pilot scale reactor.The feasibility of using the regular prism reactor in this technology is proved.A complete design scheme of the integrated aerobic granular sludge reactor system was proposed in this paper.It includes the process system of aerobic granular sludge technology,reactor main structure,aeration system,integration scheme between groups,etc.It can realize the approximate continuous operation of sewage treatment system by adopting the operation mode unique to the integrated reactor,and solve many problems caused by intermittent operation of equipment.It provides reference for promoting the engineering application of aerobic granular sludge technology. |
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