| With the acceleration of urbanization and industrialization in the world,nitrogen pollution in water has become an increasingly serious problem.Since the 13 th Five-Year Plan,China has set higher discharge requirements for sewage treatment,and for the first time,total nitrogen has been included in the total quantity control index.All these have put forward higher standards for wastewater nitrogen removal technology.Therefore,research on high-efficiency biological nitrogen removal technology has become a popular direction in water treatment.This study is based on an isolated and identified aerobic denitrification strain DN-7 with high denitrification ability,and explored its adsorption and filming effect on the surface of 4 common biological carrier fillers.The three key factors affecting the nitrogen removal ability of DN-7 strain were studied,and the optimal condition of single factor was determined.By means of response surface analysis,the key influencing factors were comprehensively optimized,and the optimal nitrogen removal conditions were obtained,which were verified by experiments.Based on this,the SBBR(Sequence Batch Biofilm Reactor)reactor was constructed to denitrogenate the actual landfill leachate,and the changes of ammonia nitrogen and total nitrogen were monitored during the operation.At the same time,the abundance of the strain DN-7 after the stable operation of the SBBR reactor was investigated by means of dilution coating plate method and high-throughput sequencing technology,which provided the basis and technical support for the actual engineering construction.The main conclusions of this study are as follows:In the study of carrier packing,four kinds of commonly used water treatment fillers,such as three-dimensional elastic packing,braid biological packing,polypropylene composite packing and square block polyurethane pore packing,were carried out the experimental study on the surface of biological carrier packing.The experimental results showed that braided biological filler was the most suitable for the growth of DN-7 strain,and the net weight gain was the largest under the same culture conditions.In the experiment on the effect of single factor on the nitrogen removal ability of DN-7,the type,pH and ratio of carbon and nitrogen were respectively studied.The results showed that among the four kinds of small molecular carbon sources,the nitrogen removal effect of fumaric acid and trisodium citrate culture was good,and fumaric acid was the best.For pH factor,DN-7 has the strongest nitrogen removal ability when pH=9.When C/N=9,the removal effect is the best.In the comprehensive nitrogen removal optimization experiment,the comprehensive effect of three key influencing factors was studied.The experiment showed that DN-7strain had the best nitrogen removal efficiency under the conditions of C/N=7.69,pH=9.9,trisodium citrate/fumarate =3.The results show that when the influent ammonia nitrogen and total nitrogen are 2380.26 mg/L and 2432.35 mg/L,respectively,and the hydraulic retention time HRT is 192 h,the removal rates of ammonia nitrogen and total nitrogen are97.27% and 95.47%,respectively.In the study of the pH change of the reactor,the pH of the reactor was measured regularly.The results showed that the pH value in the SBBR reactor system constructed by DN-7 strain was stable,and its value between 9.8 and 9.9.It is less affected by temperature and has good denitrification effect when the temperature is above 20?.When the temperature drops to 12-15?,the removal rates of ammonia nitrogen and total nitrogen can still reach 93.91% and 92.18% in the stable operation reactor.In the microbial community structure experiment,the abundance of the strain DN-7 after the stable operation of the reactor was explored by means of dilution coating plate method and high-throughput sequencing technology.The results showed that the strain DN-7 was the dominant strain in the reactor,accounting for 83.9%,and the top four bacterial genus accounted for 97.7% of the whole microbial population. |
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