Effect Of Alkalinity And Agitation On Partial Nntrification In SBR And Experimental Study Of PN-A System For Waste Leachate Treatment

Currently,the main method of treating waste leachate in China is sanitary landfill,which is economical and efficient and has a large treatment capacity.The process of landfilling generates waste leachate which is harmful to the environment and human beings.It has a high ammonia and nitrogen content,high organic matter concentration and low biochemical properties,so the treatment of leachate has been a major challenge.Partial Nitrification(PN)and Anaerobic Ammonia Oxidation(Anammox)are new biological denitrification processes which,compared to traditional nitrification and denitrification,have the advantages of no additional carbon source,low sludge production,low economic costs and small footprint.To achieve good biological denitrification,a strict control of the ratio of nitrite nitrogen to ammonia nitrogen in the feed water of the anaerobic ammonia oxidation reaction of 1.32 is required,so the stable operation of the partial nitrification reaction in the front reactor is the key to the success of the combined process.The DO concentration,aeration duration and feed water ammonia nitrogen load were adjusted at medium temperature to achieve the start-up and stable operation of partial nitrification.Once the system was stabilised,the alkalinity and agitation were varied to analyse the effectiveness of partial nitrification.A combined process of partial nitrification and anaerobic ammonia oxidation was then tested for denitrification using simulated wastewater and waste leachate,and the results of the study were as follows:(1)When the DO concentration was 0.5mg/L,the activity of both NOB and AOB was inhibited in a near-anoxic state in the reactor.When the DO concentration was 1.0mg/L,the rate of increase of AOB was higher than the value-added rate of NOB,which made AOB become the dominant strain ice to maintain a higher activity.(2)Control the DO concentration to 1.Omg/L,adjust the aeration time,use the "end pH method" and "ammonia valley point" to achieve partial nitrification.The pH value was lowest when the aeration duration was 228min,and the reactor operation was changed to 15min inlet,60min anoxic stirring,228min aeration,l0min sedimentation,15min drainage and 32min resting.the NO2--N/NH4+-N ratio in the effluent was 1.2,and partial nitrification was successfully started.Raising the influent ammonia nitrogen load to 300mg/L,the effluent NO2--N/NH4+-N ratio reached 1.26,achieving stable operation of partial nitrification.(3)In the case of excess alkalinity and sufficient alkalinity,the complete reaction of nitrification can be achieved,and the ammonia nitrogen is almost completely converted into nitroso-nitrogen.When the alkalinity is insufficient,the lack of total inorganic carbon inhibits the activity of AOB from completely converting ammonia nitrogen,so partial nitrification can be achieved,and the NO2--N/NH4+-N ratio of the effluent is 1.26,which meets the requirements of partial nitrification effluent.At the same time the combined inhibition of NOB by FA and FNA prevents it from converting nitritic nitrogen to nitrate nitrogen.In the case of insufficient alkalinity,the removal rate of ammonia nitrogen can be controlled by the feed water ratio of alkalinity to ammonia nitrogen.(4)Change the operation of the SBR reactor,when using static instead of anoxic stirring,as the anoxic stirring process is an anaerobic release process of polyphosphorus bacteria,the effect on ammonia nitrogen is smaller and the effluent NO2--N/NH4+-N ratio is similar to the ratio when anoxic stirring is used.When operated with aeration followed by anoxic mixing,mainly denitrification reaction nitrification generated nitroso-nitrogen and nitrate nitrogen,the effluent NO2--N/NH4+-N ratio is relatively low can not meet the requirements of part of the nitrification effluent.(5)To investigate the effect of the combined process on the simulated effluents,a combination of a well-functioning SBR reactor and a UASB reactor was used.After 30 days of operation of the combined process,83%of ammonium nitrogen and 90,10%of TN were removed.The nitrogen removal effect of the combined process was then investigated using actual leaking oil and after 30 days of reactor operation,the nitrogen removal rate was 82.8%,the TN removal rate was 83.9%and the COD removal rate was 81.7%.