Study On The Kinetics Of Anammox And The Effect Of Ni²⁺

Nitrogen pollution is one of the main source of water pollution.Anammox,as a new microbial denitrification technic,has been widely used,since it brings high efficiency and almost no pollution.Anaerobic ammonium oxidation kinetics and the effects of Ni²⁺on Anammox bacteria were studied in this research,which includes the following two parts:The batch test of Anammox substrate concentration was conducted for the kinetic fitting of substrate concentration.The optimal substrate concentration for Anammox bacteria growing was derived from Monod model and Haldne model.A batch experiment to test the influence of heavy metal was conducted in the obtained optimal substrate concentration.The short-term influence curve of Ni²⁺on Anammox bacteria was obtained according to the dose effect formula.A long-term test was conducted.The nitrogen removal performance of Anammox reactor and growth performance of Anammox bacteria?e.g.,EPS,SEM,DHA,particle diameter,community structure?were measured and analyzed.The main results and conclusions are as follows:?1?As the result of kinetic test,Monod is more suitable for estimating the ammonia nitrogen kinetic parameters.By using Monod for estimation,Vmax,the maximum ammonia nitrogen reaction rate,was 739.476 mg N/?gVSS.d?,and K_S,the half saturation constant,was 160.803 mg/L;Haldane is more suitable for estimating nitrite nitrogen concentration,By using Monod for estimation,Vmax was2185.034mgN/?gVSS.d?,K_S was 371.242mg/L while K_I,the inhibition constant,was147.460mgN/L.The optimal growth concentration of Anammox bacteria was determined to be 130mg/L for ammonia nitrogen and 156mg/L for nitrite nitrogen.?2?The dose-effect fitting curve shows that the semi-inhibitory concentration of Ni²⁺was 19.44mg/L,and when the SAA is reduced by 10%,the Ni²⁺concentration is 8.57mg/L.The activity of Anammox bacteria can be divided into two stages.During the stimulation stage?0-6mg/L?,the anaerobic ammonium oxidation SAA reaches the highest level of 125.92%when Ni²⁺concentration is 2mg/L;during the inhibition stage?6-50mg/L?,the inhibitory effect was obvious,and the anaerobic ammonium oxidation SAA was 2.51%when the Ni²⁺concentration was 50mg/L.?3?The long-term influence test of Ni²⁺showed that the system without Ni²⁺ could be operated stably.When the concentration of Ni²⁺was 0.5mg/L,the denitrification performance was improved.When the concentration of Ni²⁺reached2mg/L,the ammonia-nitrogen removal started to be suppressed.When the Ni²⁺concentration reaced 4mg/L,the nitrite-nitrogen removal started to be suppressed.In the long-term test,Ni²⁺had a toxic accumulation effect in the granular sludge and the Ni²⁺concentration was lower.At the end of the experiment,the mud structure was destroyed,the granular sludge was more flocculated,and the sedimentation performance was poor.Granular sludge is more advantageous than flocculent sludge against heavy metal intrusion,and the effect of removing Ni²⁺is also reduced.On the outside of the sludge,the Ni²⁺content of the effluent increases with the increase of the influent Ni²⁺concentration.The Ni²⁺removal load of the reactor is always reduced in each stage,but the removal rate is higher than that of the previous stage.Each time of increase in concentration causes a brief increase of the removal rate,which is because of the buffering effect of the sludge on external unfavorable factors.?4?Scanning electron microscopy of the inoculated sludge showed that the sludge grew well as particles,mostly spherically aggregated and closely arranged.It was the typical anaerobic ammonium oxidizing bacteria morphology.After that,it changed into various forms,the surface was irregular,and the bacterial cells were distributed in chaos.The growth state was obviously deteriorated.The average particle size of the sludge particles was reduced from 759.173um to 441.095um,and the granular sludge changed from granular red to flocculent brown.?5?The long-term Ni²⁺accumulation will bring a great influence on species richness,community diversity and the share of dominant species.In this experiment,the content of Anammox bacteria decreased from 59.89%to 36.72%.Under long-term operation of the reactor,Anammox bacteria was not the dominant species.