Study On The UAFB-EGSB Treating Domestic Wastewater

Faced with water and land resource shortages and energy crisis issues, it is futuretrend to develop and research new sewage treatment process. To minimize the floorspace and turn the organics in sewage into resources for sewage recycling use, thisresearch made use of an integrated process combined UAFB (Up-flow AnaerobicFixed Bed) and expanded-granular sludge bed (EGSB) for the municipal sewagetreatment.With combination of integrated process and culturing the AOB-ANAMMOXgranular sludge in EGSB, the research mainly studied the steady running of UAFB andinvestigated distribution of the granular sludge particle size, surface morphology andinternal microorganism. It also studied organics and nitrogen removal efficiency,economic benefit evaluation of the integrated process and organics transformation ofUAFB at different temperature and different HRT conditions.The results showed that UAFB had a strong potential to resist hydraulic impact,and completed start-up in34d with the COD removal rate more than95%. Adjustingthe influent substrate concentration and up-flow velocity of EGSB could speed up thesludge granulation. After running for80days, reactor cultivated anammox granularsludge successfully with average particle diameter0.556mm. Total nitrogen removalvolume load could reach4.758Kg-N/m~3d. By effective control of dissolved oxygenconcentration, AOB-ANAMMOX granular sludge appeared in the reactor at180d. Itsaverage diameter was0.817mm, mainly AOB in the sludge surface and closely spacedANAMMOX bacteria inside. When integrating different process, rising actual sewageinfluent ratio gradually helped microbes adapt to the new condition in reactor. After23days’ running, the integrated process removed organics and total nitrogensimultaneously, with the removal rate more than85%.Different temperature and HRT had different effect on the integrated process. Asdecreasing running temperature, nitrogen removal rate decreased obviously whiledidn’t change so much. The COD and nitrogen removal rate were91.9%,91.1%and84.4%,65.1%at temperature of30℃and10℃. The UAFB’s methane productionchanged from50.23mL/d to17.58mL/d with decreasing running temperature, but themethane gas proportion of all the digestion gas was increasing gradually. Shorting HRTreduced the COD removal rate and effluent COD was less than50mg/L. When decreasing HRT from4h to2h, ammonia removal rate changed from88.7%to66.2%.Reactor recovered and run stably with increasing HRT to4h.Compared with A~2/O wastewater treatment process, the integrated sewagetreatment process could decrease the construction investment cost by52.1%, cut downthe floor space by more than90%and save the running expense by14.9%annually. Atthe same time, the value created by using methane into electric power generation andsewage recycling was running cost’s20.5%. There was a big potential for theintegrated process in the future of urban wastewater treatment process.