Treatment Of High Ammonia Wastewater By Partial Nitrification And Anaerobic Ammonia Oxidation

As new biological nitrogen removal technologies,partial nitrification?PN?and anaerobic ammonium oxidation?Anammox?have the advantages of low energy consumption,no additional organic carbon,low sludge production and low operating costs,which are suitable for treatment of wastewater with low C:N ratio and high ammonium concentration.However,since both ammonia oxidation bacteria?AOB?and anaerobic ammonium oxidation bacteria?An AOB?are autotrophic bacteria,they have some disadvantages,including slow growth,long double time and sensitive to the environment condition.It is difficult for two processes to quick start-up,stable operation,and system recovery in practical application.Therefore,it is essential to investigate the strategies of quick start-up of PN or Anammox and controlling the stability of the systems for their engineering applications.This research focuses on PN and Anammox for treatment of high ammonia wastewater.Firstly,fast start-up of Anammox with activated sludge as inoculum in a sequencing batch reactor?SBR?was studied,as well as that the change of microbial community was discussed.Then,the role of extracellular polymeric substances?EPS?in Anammox granulation was studied.The distribution of EPS and Anammox bacteria in Anammox granules were explored by multi-fold fluorescent staining and fluorescence in situ hybridization?FISH?.Secondly,the feasibilities,advantages and disadvantages of PN system under the dual control of dissolved oxygen?DO?and free ammonia?FA?or DO and free nitrous acid?FNA?were investigated.The evolutions of microbial community under the two dual controls were detected by use of FISH and high-throughput sequencing.Finally,the PN-Anammox process was used for treatment of reject water,and the transformation of nitrogen,nitrogen removal efficiency,influencing factors,the effects of reject water on EPS and the microbial communities were investigated.The main results and conclusions are as follows:1. The feed-batch feeding pattern could wellcontrol the concentrations of ammonia and nitrite in the SBR,created the best condition for the proliferation of An AOB,shorten the start time of Anammox,and successfully cultivate Anammox granular sludge.In addition,high-throughput analysis showed that the cultured Anammox bacteria were Brocadia.When the reactor was stable,the removal efficiency of ammonia and nitrite was more than 99%,the removal efficiency of total nitrogen was89.87%±0.43%,and the total nitrogen loading was 2.49 kg/?m³·d?.The stoichiometry molar ratios of nitrite consumption and nitrate production to ammonium consumption were calculated to be 1.32±0.08 and 0.24±0.03,respectively.The maximum activity and specific growth rate of Anammox bacteria were 357.59 mg NH₄⁺-N/?g MLVSS·d?and0.043 g MLVSS/g NH₄⁺-N,respectively.A modified Stover-Kincannon was more suitable for modeling the removal efficiency of ammonia and nitrite than for modeling ammonia and nitrite concentration of effluent.The maximal total nitrogen removal loading of the reactor was predicted to be 9.18 kg/?m³·d?.2.EPS played an important role in the granulation of Anammox sludge.Protein was the main component of EPS.The content of protein and the ratio of protein to polysaccharide in EPS increased during sludge granulation.EPS were distributed along the radial direction of the Anammox granular sludge,and the content of EPS was higher in the outer layer of granules than those in the center of granule.Protein constituted the framework of Anammox granule.In addition,polysaccharide mainly concentrated in the outer layer of granular sludge and maintained the stability of granular sludge.Affected by the substrate transfer resistance,An AOB were close-grained and more in the outer layer of granule,but were relatively loose and less in the center of granule.The distribution of EPS in granular sludge was consistent with the distribution of Anammox bacteria in granular sludge.3.Both dual control strategies of FA+DO and FNA+DO could achieve PN.The effluent of both controlled PN processes was suitable as the influent for Anammox.However,there were big differences in microbial activity and system stability between two PN processes.In terms of the performances,the dual control of FNA and DO can shorten cultivation period and achieved the high biological activity,which was more suitable for achievement and stable operation of the PN process.The activity of AOB and nitrite oxidation bacteria?NOB?was inhibited by low DO?0.5¹ mg/L?and high FA?p H 8.0,FA>40 mg/L?,and the activity of AOB was decreased by 45.33%of the maximum activity.Low DO?0.5¹ mg/L?and high FNA?p H 7.0,FNA>0.023 mg/L?only inhibited the activity of NOB,and had no effect on the activity of AOB.With PN process,the dominant species of NOB were changed from Nitrospira to Nitrobacter and NOB eventually were eliminated,while the dominant species of AOB was Nitrosomonas and remained.But the morphology of Nitrosomonas under the two controls was different.In the reactor of controlled DO and FA,AOB was mainly cocci while in the reactor of controlled DO and FNA,AOB was mainly bacilli.Control strategy mainly affected the amount of microorganisms in the sludge and the relative abundance of the AOB.DO and FNA dual control strategy was conducive to improvement of AOB in PN reactor.4.The average ammonia removal rate was 83.37%when the two-stage process?PN-Anammox?was used to treat reject water.In this case,the ammonia concentration in influent of the two-stage was 1000 mg/L and the hydraulic retention time?HRT?of PN and Anammox was one day.The effect of organic matter in reject water on Anammox was greater than that in PN process.In the case of not adjusting the basicity of the water,the NO₂^--N/NH₄⁺-N ratio in the effluent of PN reactor was more than 1 and the effluent satisfied the substrate concentration requirement of Anammox,which created favorable conditions for the subsequent operation of Anammox.The stoichiometry molar ratios of nitrite consumption and nitrate production to ammonium consumption were 1:1.14±0.10:0.18±0.02 which were lower than the theoretical value.The EPS content of the sludge in both the PN and Anammox reactors were increased when the reject water was treated.In addition,the organic matter present in the actual reject water resulted in the proliferation of a large number of other heterotrophic microorganisms in the sludge of the two reactors,reducing the relative abundance of AOB and An AOB,but had no significant effect on their species.