Research On Partial Nitrification Of Zeolite Biological Aerated Filter-ANAMMOX Process For Ammonium Wastewater Treatment

Compared to the traditional nitrification and denitrification process,autotrophic nitrogen removal process via partial nitritation?PN?and anaerobic ammonium oxidation?ANAMMOX?had been proven to be low-carbon and economically promising as consuming less oxygen and no external organic carbon is needed.Autotrophic nitrogen removal process has been successfully implemented on full-scale wastewater treatment,such as sludge digestion,and landfill leachate.The AOB and ANAMMOX bacteria can maintain highest metabolic and proliferation rate in the two-reactor configurations knowed as two-stage PN-ANAMMOX process with fast start-up rate,high processing capacity and strong recovery ability after shocking.Nevertheless,the two-stage PN-ANAMMOX has not yet been fully understood and there are some problems remained to be solved.Low ammonium removal rate,frequent instability and sludge bulking are common in the PN process.The whole nitrogen removal efficency is unstable as the high concentrations of ammonium and nitrite in the two-reactor configurations.In this study,zeolite biological aerated filter?ZBAF?reactor was used for ammonium wastewater treatment,and the operational performance and working mechanisms of PN in this reactor were investaged.The Up-Flow Blanket Filter?UBF?reactor was established to investigate the fast start-up of ANAMMOX unit.The operational performance and resistance with ammonium loading fluctuation were tested on the combinning PN-ANAMMOX process via PN-ZBAF and ANAMMOX-UBF.Specific conclusions are listed as follows:?1?Partial nitrification can be achieved by controling the Free Amonina?FA?in the ZBAF reactor,and the inhibition of FA on the NOB was proved to be the key point to realize partial nitrification.During the stable stage,the nitrite accumulation rate?NAR?can be higher than 98%.The analysis of microbial community structure showed that the Nitrosomoadaceae is the only functional bacteria related to nitrogen removal.The enrichment of AOB was occurred in ZBAF with more than 61%of all bacteria.?2?The performce of ZBAF was influented obviously by the influent ammonia loading rate?NLR?.The nitrite production rate?NPR?decreased from 0.760kg/m³/d to 0.680 kg/m³/d with the NLR increasing from 1.195 kg/m³/d to1.400 kg/m³/d.Furthermore,after the NLR increasing to 1.680kg/m³/d,the NPR dropped rapidly and the ZBAF almost crash.When maintaining the constant NLR of 1.020 kg/m³/d,ZBAF showed stable nitrification capcacity with NPR of 0.76 kg/m³/d even though influent ammonium concentration increate from 350to 550mg/L.The NH₄⁺-N was fully mixed in ZBAF due to the strong absorption characteristic of zeolite for NH₄⁺-N.During the partial nitrification stage,the nitrite and TN concentrations were increase with the height of ZBAF.The analysis results of element content of zeolite in ZBAF further proved the fully mixed state of ion exchange process in zeolite.Kinetic analysis results revealed that the production of nitrite followed the zero-order kinetics model,and the activity of AOB was not affected by the concentrations of NH₄⁺-N and FA.?3?By using denitrify sludge as seed for ANAMMOX-UBF,and increasing the influent substance concentration gradually,start-up of ANAMMOX-UBF was achieved after 53d.The nitrogen removal rate and total nitrogen removal rate reached 1.0kg/m³/d and 83%,respectively.Compared to the seed sludge,the relative abundance of Brocadia-ANAMMOX increased obviously to 7.2%.?4?The two-stage PN?ZBAF?-ANAMMOX process was affected by the influent NH₄⁺-N concentration.The NLR of PN process can keep high level with influent NH₄⁺-N concentration between 250⁴50 mg/L,among which NLR reached highest level of 1.333kg/m³/d with the influent NH₄⁺-N concentration of 250 mg/L.When the influent NH₄⁺-N concentration increased to 550 mg/L,the NLR of PN dropped rapidly to 0.76 kg/m³/d.The periodic NLR fluctuation caused no obvious influence on nitrogen removal in the two-stage PN?ZBAF?-ANAMMOX process,showing excellent shock resistance with average TN removal rate of 85%.