| With increasing the ammonia concentration in municipal domesticsewage, the capacity of original biological denitrification process hasbeen difficult to meet the ammonia emissions limits specified in theGB18918-2002, such as the activated sludge process and biofilmprocess. And making the water eutrophication more and more serious.Therefore, the domestic and international experts and scholars areimproving the existing biological denitrification process or developingthe economical and efficient biological denitrification technology,which has been a hotspot research in the current control of waterpollution.The A/O biological denitrification technology is one of the maturetechnologies and widely used in current urban sewage treatment plants,and the nitrifying bacteria in aerobic stage is the main microorganism ofnitrification. The nitrifying bacteria is a kind of aerobic and autotrophicmicrobiology with long growth cycle, and vulnerable to the influence ofexternal environment. So the main purpose of this subject is enrichingthe nitrifying bacteria from the activated sludge, and immo bilizes it,then applies the immobilized nitrobacteria to the aerobic section of A/Oprocess to strengthen the denitrification capability of A/O process. Atthe same time, optimizing the operation parameters of strengthensystem and analyzing the comprehensive decontamination ability of it.Under the experimental conditions of T is20~30℃, pH is7.0~8.0, DO is2.0~3.0mg·L-1, through improving the ammonia loading ofnutrient solution gradually is better to enrich the nitrobacteria fromactivated sludge. When the ammonia loading is0.3g·g-1·d-1, the degradation rate of ammonia nitrogen can reach3.48mg·g-1·h-1; the C/Nratio is1.8which is conducive to the growth of activated sludge flocs.After eight weeks of enrichment culture, the number of nitrosobacteriaand nitrobacteria are increased to1.1×108and1.4×108per milliliter ofsludge respectively, they are5.5×103times and3.1×104times that theno enrichment of sludge. And comparing the removal efficiency ofammonia nitrogen pre and post, the results show that the concentrationsludge can degrade the85.1%of the ammonia nitrogen in water within10h, the nitrification rate is three times than that of the no enrichmentof sludge.Using polyhedral hollow ball as the carrier for adsorpting andfixing the nitrifying bacteria has much advantage, such as the simplemethod, the long using period, the low cost and the better effect ofwastewater treatment. The fixed nitrobacteria under the optimum dosingquantity is11per litre mixture. With an increasing time, the fixednitrifying bacteria can still keep a higher removal of ammonia nitrogen;Under low temperature, through the fixed state of nitrogen removal ratebecomes a little lower, it can keep high ammonia nitrogen removal ratein general. The efficiency of nitrogen removal is better than the state ofsuspension nitrobacteria.When optimizing the operation parameters of process, the resultshows that the oxygen concentration of A/O aerobic period is2.5mg·L-1,the reflux ration of nitrate solution R is2.0, the sludge return ratio r is60~80%, SRT is10~15d, HRT is7h (denitrification system is3h,nitrification system is4h). The strengthen system not only has enoughamount of microbes, but also the activated sludge and fixednitrobacteria could keep higher activity. The effect of ammonia nitrogenand total nitrogen removal is good, all the indexes could meet the therequirement of emission standard.Under the operating parameters of optimum, comprehensiveanalyzing removal efficiency of the strengthening system forconventional pollutant indexes. The experimental result sh ows that theremoval rate of the system to COD reached more than94.5%, the removal rate of ammonia nitrogen is more than96.0%, and the removalrate of total nitrogen is more than85.0%. At the same time, the systemcan still keep high removal efficiency to ammonia nitrogen and totalnitrogen under low temperature, the treatment effect is better than thesingle A/O denitrification process. |
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