| Water pollution is one of the main problems in current water environment,and nitrogen pollution is particularly harmful to it.Aiming at wastewater containing ammonia nitrogen,experts and scholars proposed a number of treatment processes-traditional nitrogen removal processes and new biological nitrogen removal processes.Based on the two shortcomings of above technologys:?weak adaptability;?the effect of ammonia nitrogen removal is not ideal,the preparation of modified calcium alginate(Calcium alginate,CA)double-responsive nitrifying microspheres and ammonia diffusion properties were carried on,which was in order to provide a new effective way for the treatment of wastewater containing ammonia nitrogen under low temperature and provide data reference for realizing its practical application.In the experiment,the nitrifying bacteria were enriched by sequential batch activated sludge method(SBR).The immobilized nitrifying bacteria microspheres with uniform particle size were prepared by embedding method,modifying it by NaCl solution and studying its diffusion performance.Determining the optimal mixture ratio after investigating the effect of the preparation ratio of modified CA double-responsive nitrifying microspheres on ammonia diffusion performance.The processing effect in actual wastewater by using modified CA double-responsive nitrifying bacteria microspheres were also investigated.The conclusions were as follows:After 15-days enriched and cultivated,the SBR reactor was successfully started.The ammonia removal rate of simulated wastewater has been over 90%.The nitration reaction proceeded thoroughly,and there is almost no accumulation of nitrite nitrogen.The color of activated sludge in the reactor changed from grayish black when first salvaged to khaki,and the sedimentation performance did well.Simultaneously,the microbial population structure showed that the enrichment effect of nitrifying bacteria was better.The experiment treated calcium alginate(CA)nitrifying bacteria microspheres with different concentrations of NaCl solution to improve its ammonia diffusion performance,and the optimum concentration was 0.3%.FTIR(Fourier Transform infrared spectroscopy)result verified that the improvement of microsphere diffusion performance was due to the structural substitution of Na+ and Ca2+.The modified CA double-responsive nitrifying bacteria microspheres were prepared by using N-isopropylacrylamide(NIPAAm)and acrylic acid(AA)as monomer materials and N,N-methylenebisacrylamide(MBA)as crosslinker,and the experiment investigated for ammonia diffusion performance under different preparation conditions by measuring its ammonia nitrogen removal rate.The optimal response conditions were determined by single factor experiments:NIPAAm = AA = 200 mg,MBA = 4 mg.The effects of temperature and pH on the ammonia diffusion properties of modified CA double-responsive nitrifying microspheres are as follows:when the temperature is lower than 30 ?,the ammonia nitrogen increased with the temperature added,the maximum removal rate of which is 36.99%.When the temperature is higher than 30 ?,the ammonia nitrogen removal rate decreases with the temperature adding,and the ammonia nitrogen removal rate at 40 ? was only 23.23%.At pH interregion from 6.0 to 9.0,the ammonia nitrogen removal rate increased while pH increased.At pH=6.0,the ammonia nitrogen removal rate was 26.35%.It was 35.48%when at pH=9.0.It macroscopically improved that the immobilized nitrification bacteria microspheres were one kind of embedded microspheres with double sensitivity to temperature and pH.In addition,the SEM(Scanning Electron Microscope)pictures of modified CA double-responsive nitrifying bacteria microspheres were further were verified its responsive characteristic from the microstructure,while there were more micropore structure on the surface of the microspheres under low temperature(alkaline)conditions and less under high temperature(acidic)conditions.The modified CA double-reacting nitrifying bacteria microspheres were applied to treat the actual wastewater.Under the condition of HRT=6 h and initial ammonia nitrogen being 7 mg·L-2,microspheres showed about 50%removal effect on the low-temperature micro-polluted wastewater of ammonia,as well as a certain ability to remove COD.There was a phenomenon that microorganisms flowed out of the carrier late in the running phase.And then,the microbial population structure showed that the microbial community structure in the modified CA double-responsive nitrifying microspheres changed after 40 days operated in actual domestic sewage.We preliminarily concluded that the service life of the microspheres was 30 days.In summary,the modified CA double-responsive nitrifying bacteria microspheres can effectively remove ammonia nitrogen in low-temperature micro-polluted wastewater,which was economical,simple and operated easily.However,in order to promote the widely practical application of immobilization nitrifying bacteria technology,more research should be focused on carrier materials with complete performance,exploring particle preparation reactor with high efficiency and improved mass transfer performance of immobilized nitrifying bacteria. |
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