| Nowadays, the situation of environmental protection in our country is still severe. Traditional technology can not deal with the serious contamination and fit for the increasing standard. For enhancing the efficiency of wastewater treatment system, bioaugmentation should be introduced. However, the variation of bacterial community may be unpredictable, which restricts bioaugmentation to be widely used.This research finished the bioaugmentation strategy treating with high ammonia nitrogen and high-salinity chemical wastewater. The molecular ecological methods were used to detect the variation of functional bacterial community during bioaugmentation. The abundance, diversity and metabolic activity of bacterial community were analyzed to confirm the key factors, which could provide a theoretical basis for the practical engineering applications.The bioaugmentation for high ammonia nitrogen wastewater was carried out with the bacteria community of short-cut nitrification (SCN), the principal part of which was ammonia-oxidizing bacteria (AOB).Autotrophic domestication lasted120days was carried out in a lab-scale SBR. The impact on SCN was discussed for different factors such as high ammonia nitrogen, low dissolve oxygen and high temperature. The changes of substrate and product were measured to calculate ammonia removal efficiency and nitrite accumulation rate. Analyzed along with growth kinetics, high temperature could make SCN incomplete and low dissolve oxygen could weaken ammonia removal efficiency. So free ammonia (FA) caused by high substrate and alkalinity should be the reasonable operated factor, which could be also proved by monitoring one cycle. DGGE, as well as cluster, PCA and diversity index analysis were used to confirm that FA should also be the key factor of AOB diversity. Quantitative PCR tests showed that the abundance of AOB increased about20times and comprised75.6percent of the total bacteria, and nitrite-oxidizing bacteria (NOB) was washed out from the system, leading to SCN. Meanwhile, the abundance of ammonia-oxidizing archaea (AOA) was decreased during domestication though AOA could also use ammonia nitrogen as substrate, which suggested that SCN was drove by AOB instead of AOA.Autotrophic domestication lasted30days was carried out through the inhibition of FA. The bacterial community of SCN showed the same level of abundance and activity with the domestication lasted120days, and the efficiency was promoted. The real and SEM photo were taken. Clone library and T-RFLP analysis with amoA and DGGE analysis with16SrDNA showed that Nitrosomonas-like group kept dominant and Nitrosospira-like group changed obviously. Biolog ECO-plate assay proved that the abundance and metabolic diversity of heterotrophic bacteria decreased during autotrophic domestication.The bioaugmentation for biological aerated filter (BAF) with low carbon and high ammonia wastewater from soda plant was carried out with the biofilm formed from the bacteria community of short-cut nitrification.Zeolites which could absort ammonia were chosen as fillings and the AOB-zeolite-bioregeneration model was summed. Natural zeolites were modified and characterized. X-ray diffraction analysis showed that modification could not change the basic crystal structure of zeolites. SEM observation showed that modification could open the holes in zeolites and enlarge the specific surface area. X-ray fluorescence spectrometric analysis showed that the major elements did not change after modification, but heavy metals were removed. Therefore, modified zeolites were proved to be suitable immobilized matrix. Freundlich and Langmuir adsorption isotherms were fitted according to the saturated adsorption capacity under different concentration of ammonia. Compared with natural zeolites, the ammonia adsorption capacity of modified zeolites increased largely, which was beneficial to create a low-carbon and high-ammonium microenvironment for nitrifiers.Immobilization of nitrifiers on zeolites was realized by the system of autotrophic domestication. SEM images proved that AOB was distributed on zeolites and more in the holes. The ammonia removal capacity of bio-zeolite was measured by sequencing batch experiment, according to which the amount of fillings and HRT was calculated. BAF got steady after10days. The removal of ammonia was92.1%and nitrite accumulation rate was91.3%, but both of them decreased when COD load was rised.The results of DGGE proved that zeolites did not change the community structure of AOB on fillings. The results of qPCR showed that the abundance of AOB and total bacteria on modified zeolites were higher than those on natural zeolites and in sludge, which revealed that zeolite should be the specific immobilized matrix for AOB and modification was also beneficial for the immobilization of AOB.The bioaugmentation for high-salinity chemical wastewater was carried out with indigenous salt-tolerant bacteria.These three strains were screened from contaminative soil in situ, using sodium methanesulfonate, methylene dichloride, and isopropanol as single carbon source correspondingly. The three strains were identified by16SrDNA and named Arthrobacter sp. NKAT3-1, Pseudomonas sp. NKAT3-2and Pseudomonas sp. NKAT3-3. Their activity of growth and degradation was investigated with lab-scale experiments. Through measuring cellular content after extraction, their salt-tolerant mechanism was confirmed to be compatible-solutes strategy for moderately halophilic bacteria, with amino acid and betaine playing important roles. To offer a certain amount of amino acid and betaine could hardly change the growth activity of three strains.1.5L culture of three salt-tolerant degrading strains were fermented and then inoculated into300L biological contact oxidation reactor filled with wastewater. The removal of COD, NH4+-N and TP was measured and the effluent conformed to the Chinese national standard. It was also compliance about bioaugmentation for300m3reactor. T-RFLP analysis revealed that bioaugmented strains dominated over others in the biofilm. It was introduced that biofilm fragments in sedimentation tank were inversely flowed to each reaction tank, and the results of qPCR demonstrated that this process could successfully maintain the bacterial abundance in the reaction tanks. |
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