| Anaerobic Ammonia Oxidation(Anammox)is a promising new biological nitrogen removal process.It has the advantages of strong denitrification capacity,low operating costs,and low residual sludge volume.However,the low proliferation rate of Anammox bacteria leads to the slow start-up of process.To a certain extent,it limits the development and application.Mature Anammox bacteria used as inoculation sludge which will significantly shorten the process start-up time.Therefore,there are the establishment of an Anammox bacteria seed base and the exploration of the methods for the preservation and rejuvenation of mature Anammox bacteria.They can solve the problem of the application of anammox bacteria.This paper mainly studies the preservation and rejuvenation methods of mature anammox bacteria.The Anammox sludge was prepared into powdery bacterial agent by vacuum lyophilization technology.After long-term preservation,it was rejuvenated.The suitable cryoprotectant selection and preservation conditions during the preservation process were explored.Meanwhile,the suitable condition control during the rejuvenation of the powdery bacterial was studied.The conclusions are as follows:(1)The bacterium powder prepared with glycerin,sodium alginate gel and dimethyl sulfoxide(DMSO)as the cryoprotectant and the bacterium powder prepared without cryoprotectant were preserved for 60 days.The influence of the existence of the preservation matrix at the same time was studied.After adding 1%(v/v)Anammox biomass during rejuvenation,each bacterium powder can express Anammox activity in a short time.After 54 days of rejuvenation experiment,the rejuvenation effect of Anammox bacteria powder with 3%(w/w)DMSO as cryoprotectant and without preservation matrix was best.At the end of the experiment,its average Specific Anammox Activity(SAA)was 115.84 mg-N/g VSS/d,and the activity recovery rate was 89%.The Anammox stoichiometry ratio was very similar to the theoretical value.At the same time,the activity recovery rate of bacteria powder with 3%(w/w)sodium alginate gel which worked as the cryoprotectant and non-cryoprotectant were above 70%.Otherwise,the rejuvenation process of different bacterial powders showed obvious differences.In this experiment,under the same conditions,the preservation and rejuvenation effect of Anammox bacteria by vacuum lyophilization method was better than the 4 ? refrigeration method.(2)The bacterium powder which contained sodium alginate gel and DMSO and the bacterium powder without cryoprotectant were preserved for 150 days.The addition of fresh Anammox sludge at the end of the autolysis period significantly accelerated the Anammox activity.Experimental results showed,after 33 days of rejuvenation,the average SAA at the end of the rejuvenation period of bacterial powder containing 3%(w/w)sodium alginate gel or 3%(w/w)DMSO was 120 and 130 mg-N/g VSS/d,respectively,and the stoichiometric ratio were very close to the theoretical value,the activity recovery rate were above 89%.The unprotected bacterial powder had the highest SAA.However,the stoichiometric ratio was different from the theoretical value.(3)The bacterium powder prepared by mixing sodium alginate gel and DMSO in different proportions as mixed cryoprotectants was preserved for 150 days.Thereafter,it was rejuvenated by the improved method.Experimental results showed,after 33 days of rejuvenation,the total nitrogen removal growth rate,SAA,and stoichiometric ratio of the powder of the mixed cryoprotectant were significantly inferior to the single cryoprotectant.This result illustrated that,under the same conditions,the mixed cryoprotectant is not superior to single cryoprotectant.Also found that the rejuvenation effect of the reactor is positively correlated with the proportion of DMSO in the mixed cryoprotectant.When 2%(w/w)DMSO+1%(w/w)sodium alginate gel was using as cryoprotectant,the SAA of the powder was 103 mg-N/g VSS/d,the stoichiometric ratio of the theoretical value.The rest of the bacteria powder had poor rejuvenation. |
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