| In recent years,with people’s deeper understanding of water resources,the idea of water treatment has also undergone a transformation,from the original use of raw water to remove pollutants through specific procedures to achieve the purpose of water purification to the recycling of water resources.The tail water of urban sewage treatment plants is a rich,stable,and concentrated water resource.The reasonable utilization of the tail water of sewage treatment plants will provide powerful water resource supplementation for water scarce areas.For the recycling and utilization of tail water from urban sewage treatment plants,emphasis should be placed on green,economic,safe,and sustainable considerations.The biofilm activated carbon technology uses activated carbon as the carrier,and microorganisms grow on the surface of activated carbon to form an active biofilm.This produces biofilm activated carbon,which not only plays a physical adsorption role of activated carbon,but also fully utilizes the biodegradation effect of the surface biofilm to remove pollutants.It has the characteristics of good removal effect,convenient operation and management,and low price,and is an optional method for advanced sewage treatment.This study explores the residence time of fluids in the biofilm activated carbon reactor by designing and constructing a laboratory scale biofilm activated carbon reactor based on its hydraulic characteristics;Starting from different ways of increasing ammonia nitrogen load,by comparing the fixed inlet ammonia nitrogen concentration,increasing inlet flow rate,fixed inlet flow rate,and increasing inlet ammonia nitrogen concentration,this study explores the more suitable operating mode and optimal operating conditions for biofilm activated carbon reactors;Starting from the process of combining micro current with biofilm activated carbon,this study explores the influence of different micro current sizes on biofilm activated carbon,and analyzes the mechanism of the influence of micro current on biofilm activated carbon.Based on batch experiments and microbial community analysis,the effect of micro current on the concentration parameters of ammonia oxidizing bacteria was analyzed.The research results indicate that:(1)By conducting 9 identical tracer simulation experiments on the biofilm activated carbon reactor,combined with a multi reactor series model.The tracer simulation experiment shows that when the designed inlet flow rate is16m/h,the number of series reactors in the biofilm activated carbon reactor is 16-30(an average of 22),and the hydraulic average residence time is 159 s.(2)When the influent load is small,different influent methods have no significant impact on the biofilm activated carbon reactor.Under a load of 8.0mg-N/L/h,the biofilm activated carbon reactor has an ammonia nitrogen removal rate of over 98% for both different load increasing methods,with an average ammonia oxidation rate of 35.01 mg-N/L/h and 36.36 mg-N/L/h,respectively.The average ammonia nitrogen consumption per hour is 25.46 mg-N/h and 26.93 mg-N/h,respectively.(3)The biofilm activated carbon reactor has better adaptability to increasing the ammonia nitrogen load by increasing the flow rate.During the process of increasing the load,the biofilm activated carbon reactor maintains good stability in removing ammonia nitrogen.However,increasing the ammonia nitrogen load by increasing the concentration will have an impact on the biofilm activated carbon device,leading to unstable effluent of the biofilm activated carbon reactor.(4)Under high load conditions,the biofilm activated carbon reactor has a good treatment effect on increasing the ammonia nitrogen load by increasing the flow rate.When the ammonia nitrogen load of the two different methods is stable at 15 ± 1mg-N/L/h and 11 ± 1 mg-N/L/h,the ammonia nitrogen concentration in the effluent of the biofilm activated carbon reactor is maintained at 2.5 ± 0.5 mg-N/L and 10 ± 1 mg-N/L,and the NOR is maintained at 85 ± 10 mg-N/L/h and 55 ± 5 mg-N/L/h,respectively.The average hourly ammonia nitrogen consumption is 84.5 mg-N/h 56.24 mg-N/h.(5)The impact of different current intensities on the biofilm activated carbon reactor is different.When the micro current is high,it will have a negative effect on the efficiency of removing ammonia nitrogen by biofilm activated carbon.When the micro current intensity is suitable,it will have a positive effect on the efficiency of removing ammonia nitrogen by micro current.When a current of 5m A is applied to the biofilm activated carbon reactor,the reactor performance significantly improves the removal rate of ammonia nitrogen The ammonia oxidation rate and the mass consumption of ammonia nitrogen per hour reached 84.88%,18.51 mg-N/L/h,and52.41 mg-N/h,respectively;After removing the microcurrent,the reactor after microcurrent domestication showed better performance,further improving the ammonia nitrogen removal rate,ammonia oxidation rate,and the quality of ammonia nitrogen consumed per hour to93.59%,22.29 mg/N/L/h,and 64.27 mg-N/h.(6)External current can increase the sensitivity and tolerance of heterotrophic bacteria to the substrate,and increase the tolerance of ammonia oxidizing bacteria to the substrate.After micro current cultivation,the maximum activity of ammonia oxidizing bacteria and heterotrophic bacteria was improved,with the maximum activity of ammonia oxidizing bacteria being 1.93 times that of the blank group and heterotrophic bacteria being 4.62 times that of the blank group.The applied current can significantly change the microbial community structure of the biofilm activated carbon reactor.Under the 5 m A micro current,Proteobacteria(27.13%)and Acidobacteria(48.88%)are the dominant bacteria in the biofilm,while Proteobacteria(54.01%)and Bacteroidetes(20.91%)are the dominant bacteria in the blank biofilm;After removing the microcurrent and continuing to cultivate for a period of time,the relative abundance of nitrifying spirochetes in the biofilm after microcurrent domestication significantly increased,2.73 times that of the blank group. |
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