Fundamental Research Of Partial Nitrification And Anammox Two-stage Process For The Treatment Of Low Ammonia Nitrogen Wastewater

In order to develop an economic and efficient treatment technology of low concentration ammonia nitrogen wastewater,this paper first studied the the start-up and operation parameters of partial nitrification（PN）process in the activated sludge sequencing batch reactor（SBR）and the continuous biofilter reactor,respectively.Then,the start-up strategy and nitrogen removal performance of the low concentration nitrogen wastewater treated by partial nitrification process were further investigated in the continuous anammox biofilter reactor（CABR）,in order to provide the technical support for the treatment of low concentration ammonia nitrogen wastewater by partial nitrification and anammox two-stage process.The main results and conclusions were as follows:（1）Under the condition of maintaining influent NH₄⁺-N concentration of 150±5mg/L in SBR,PN process could be successfully started after only 19 days through intermittent aeration and gradually increasing aeration rate.The average concentrations of NH₄⁺-N and NO₂^--N in the effluent were 66.49 and 63.17 mg/L,respectively,in the stable stage.The ratio of the effluent NO₂^--N to NH₄⁺-N maintained at 0.84～1.05,and the average nitrite accumulation rate（NAR）in the effluent reached 93.25%.When the influent NH₄⁺-N concentration was further reduced to 75±5 mg/L,the average NAR of the effluent was 95.40%and 95.04%,respectively,under intermittent and continuous aeration modes,and PN reaction could be still achieved stably.（2）For PN process in SBR,when the influent NH₄⁺-N was finally reduced to 60±5mg/L,the average NAR were decreased from 85.80%to 61.01%and 30.45%with the decrease of water temperature from 32℃to 27℃and 22℃,which indicated that PN process was more unfavorable with the decrease of temperature.（3）When the influent NH₄⁺-N concentration was maintained at 105±5 mg/L and HRT was kept at 4 h in the partial nitrification biofilter reactor（PNBR）,PN process could be successfully started after only 12 days through continuous aeration and gradually increasing aeration rate.The average concentrations of NH₄⁺-N and NO₂^--N were 44.24and 54.78 mg/L,respectively,in the stable stage.Meanwhile,the ratio of NO₂^--N to NH₄⁺-N in the effluent was 0.98～1.37,and the average NAR was 99.14%.However,when the influent NH₄⁺-N was 60±5 mg/L and HRT was further shortened to 2 h and 1 h,the average NAR was 99.26%and 10.08%,respectively.（4）When the influent NH₄⁺-N concentration was kept at 60±5 mg/L and 1 mmol/L potassium chlorate was continuously added in the PNBR under HRT of 1 h,the average NAR was increased from 75.57%to 82.89%and 85.23%as the temperature was decreased from 30℃to 25℃and 20℃,respectively.The result indicated that the PN performance of the PNBR was not affected by gradient cooling（30℃→25℃→20℃）,when 1 mmo L/L potassium chlorate was added into the influent.（5）During the restart stage of CABR,the influent NH₄⁺-N and NO₂^--N were controlled to 50±3 and 50±3 mg/L,respectively.By gradually shortening HRT,the influent NLR were increased from 0.29 to 2.43 kg-N/（m³·d）in just 21 days,and the effluent TN concentration was less than 15 mg/L.During the operation stage,the influent NH₄⁺-N and NO₂^--N were reduced to 28±2 and 28±2 mg/L,respectively,and the HRT of CABR was gradually shortened to 20 min.At this time,the NLR was 4.20±0.10 kg-N/（m³·d）,and the average removal rate of TN was stabilized at 86.33 in the stable stage.Even more,the average TN removal rate in CABR could be stabilized at 86.42%in the stable stage when the HRT was 20 min and the water temperature was lowered to 25℃.（6）The water quality along the CABR showed that anammox process mainly occurred in the 0～20 cm section of the reactor,and the biomass concentrations of the granular sludge and biofilm were 17.41 and 8.61 g/L,respectively.Meanwhile,and the corresponding specific anammox activities（SAA）of the granular sludge and biofilm in the 0～20 cm zone were 0.43 and 0.28 g/（g-VSS·d）,respectively.The high throughput sequencing analysis results further demonstrated that Candidatus Brocadia was the dominant anammox bacteria in different zones of CABR.To be specific,the proportion of Candidatus Brocadia was 31.34%and 34.05%,respectively.in the granular sludge and biofilm of 0～20 cm zone.In addition,Candidatus Brocadia accounted for 25.43%and29.67%in granular sludge and biofilm of 20～47 cm zone,respectively.