Study On Municipal Sewage Treatment By Alternating Aerobic/Anoxic/Idle Operation In SBR

Recently, with the development of economy and explosion of population, moreand more nitrogen and phosphorous was discharged into river. Excess nitrogen andphosphorous (Pi) have long been viewed as major factors causing eutrop hicationwhich could lead to a series of other environmental problems. Therefore, thetreatment of the wastewater not only require COD removal, but also need to take offnitrogen and phosphorous from sewage. As the increasingly strict sewage dischargingstandard,the wastewater treatment techniques of nitrogen and phosphorous require todevelop.In order to achieve simultaneous removal of nitrogen and phosphorous, thebiological treatment process consisting of idle, aerobic and anoxic periods wasapplied for the treatment of synthetic wastewater in a sequencing batch reactor. Threesets of trial tests were conducted to determine an appropriate aeration time and theyshowed that2.5hours aeration was applicable for this process. Due to insufficientaeration time, trial test A, although it could keep stable denitrification via nitrite, itleads to undesirable TN and TP removal efficiency. Due to overlong aeration time,although TN and TP could been largely removed, this process could not keep stabledenitrification via nitrite. After3weeks’ acclimation, trial test B (2.5hours aeration)achieved a desirable and stable total nitrogen and phosphorous removal e fficiency,averaging85.0%and83.3%, respectively. The results demonstrated that stable partialnitrifcation could be achieved by controlling duration of aeration (2.5hours) andinternal storage compound (PHB) can be used as a proper carbon source fordenitrifcation via nitrite. Additionally, single stage oxic phosphorous removal couldalso be achieved during aeration period. Interestingly, during the process, it wasobserved that nitrogen could be excessively accumulated by microorganisms, whichwas completely different from the conventional nitrogen removal theories. Almost26.0%of TN was removed through this unconventional pathway.After it applied to synthetic wastewater, it was applied to treat real sewage to test feasibility of this treatment in practical operation. The results showed that single stageaerobic phosphorous removal and storage compounds driving denitrificaition vianitrite was successfully achieved. The key to achieve stable single stage aerobicphosphorous removal and storage compounds driving denitrificaition via nitrite wascontrolling aeration time. On one hand, enough aeration time could ensure ammoniumand TP that could be largely removed. On the other hand, an appropriate aeration timecould make sure that PHB concentration keep adequate level which could satisfy thecarbon requirement for denitrification. Besides, In long-term treatment of municipalsewage by applying this operational method, average removal efficiency of COD,total nitrogen,total phosphorous was85.29%,74.09%and87.97%,respectively. Thestudy demonstrates that aerobic-anoxic-idle operational method could successfullyachieve a combination of single stage aerobic phosphorous removal and storagecompounds driving denitrificaition via nitrite. Additionally,it could achieve adesirably and steady nitrogen and phosphorous removal efficiency in long-termoperation.