| Nitrifiers are the key organisms in biological nutrient removal?BNR?system,and influences the biological nitrification efficiency directly.Nitrifiers are sensitive to environment,therefore the operating conditions?temperature,DO,sludge retention time and hydraulic retention time?of the BNR influence the nitrifier community structure and nitfication kinetics.In this study,one sequencing batch reactor?SBR?was operated at?25? and 30??to treat simulated wastewater with high ammonia.The nitrification kinetics were determined by oxygen uptake rate?OUR?,and the nitrifier community was determined by fluorescence in situ hybridization?FISH?,in order to investigate the effect of temperature on the nitrifier community and kinetics under high ammonia loading.The main results are as follows.?1?The maximum specific ammonia utilizated rate?SAUR?was?21.55 ± 2.87?mgN /?gVSS·h?,and the maximum specific nitrite utilized rate?SNUR?was?32.57 ± 3.02?mgN /?gVSS·h?at 25?,and the maximum SAUR was?39.26 ± 3.36?mgN /?gVSS·h?,and the maximum SNUR was?22.53 ± 3.82?mgN /?gVSS·h?at 30?.The maximum SAUR at 30? is 1.79 times of that at 25?,while the maximum SNUR at 30 ? is 0.69 times of that at 25 ?.High temperature increases the SAUR due to the nitrifiers activity increases with temperature,while it decreases the SNUR due to the free ammonia and free nitrous acid inhibition in this study.?2?The half saturation constants?KN?of ammonia oxidizing bacteria?AOB?and nitrite oxidizing bacteria?NOB?at 25?were?0.96 ± 0.21?mg/L and?8.38 ± 0.58?mg/L,respectively.At 30?,the KN of AOB and NOB were?26.33 ± 1.32?mg/L and?5.43 ± 0.44?mg/L,respectively.Under the experiment conditions,high temperature decreases the AOB substrate affinity,but increase the NOB substrate affinity due to the free ammonia and free nitrous acid inhibition.?3?The oxygenhalf saturation constants?KO?of AOB and NOB at 25?were?1.16 ± 0.45?mg/L and?1.12 ± 0.38?mg/L,respectively.At 30?,the KO of AOB and NOB were?0.71 ± 0.14?mg/L and?1.44 ± 0.10?mg/L,respectively.Under the experiment conditions,the temperature has no significant effect on the dissolved oxygen affinity of AOB and NOB.?4?At 25?,the fraction of AOB(AOB/EUBmix)in the activated sludge was?28.02 ± 8.46?%,Nitrosomonas europaea and Nitrosospira were?26.24 ± 7.82?% and?1.78 ± 0.64?%,respectively,the dominant AOB was Nitrosomonas europaea,the fraction of NOB(NOB/EUBmix)was?13.64 ± 3.96?%,Nitrobacter and Nitrospira were?6.89 ± 1.13?% and?6.75 ± 2.83?%,respectively,Nitrobacter and Nitrospira coextisted at similar level.At 30?,the fraction of AOB was?46.19 ± 17.55?%,Nitrosomonas europaea and Nitrosospira was?44.19 ± 16.36?% and?2.00 ± 1.19?%,respectively,the dominant AOB was Nitrosomonas europaea,the fraction of NOB was?12.41±2.44?%,Nitrobacter and Nitrospira were?9.74 ± 1.53?%,?2.67±0.91?%,respectively,the dominant NOB was Nitrobacter.These results indicated that high temperature will increase quantity of the nitrifiers,especially the r-strategists?Nitrosomonas europaea and Nitrobacter?. |
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