Simulation And Optimization Of Water Distribution System Of UBF (Upflow Blanket Filter) Reactor In Livestock Farm

With the development of intensive mode in agricultural production, large-scale farm gradually turns into an important mode of livestock breeding in China. But the result is serious environmental pollution around caused by a large number of livestock wastes. In response to this event, scholars at home and abroad have taken in-depth researches in wastewater treatment technology of livestock and poultry breeding industry. With the benefits of low investment costs, fast operation, small working place, less sludge discharge and great treatment effect, UBF process is being used for wastewater treatment of large-scale farm more and more.UBF reactor is an important unit for wastewater anaerobic digestion in UBF process, and the operation of UBF reactor will have a direct impact on the effect of wastewater treatment. The distributing uniformity of water distribution system is one of key factors affecting UBF reactor treatment. At present, the problem that poor effect of treatment caused by the design flaws of UBF reactor water distribution system is common. According to this situation, this paper uses CFD method to study the uniformity of water distribution system in UBF reactor, based on FLUENT.Considering the wastewater treatment needs of a large-scale pig farm in Chongqing Hechuan, this paper designed a set of UBF reactor water distribution system for a middle temperature UBF-SBR wastewater treatment process. According to the operating condition, it is discovered that this wastewater treatment process works quite well except for appearance of some immovable region in UBF reactor. This paper builds the modeling of UBF reactor water distribution pipelines through GAMBIT, summarizes the principles and methods of determining the calculation parameters in the numerical simulation of water distribution system, uses FLUENT to analyze the water distribution pipes, and then finds that the difference among velocities of wastewater outlets of water distribution pipes in UBF reactor is distinct. The difference between the maximum speed and minimum speed is 80%, which means the flow out of pipes has big different agitating effects on sludge at the bottom of reactor. The "dead zone" will probably arises at the outlets of pipes with low flow velocity, and the "short cut in flow" also will probably arises at the outlets of pipes with high flow velocity as well. These results are similar to the real situation during the UBF reactor's operation, it proves that numerical simulation is practicable. However, using the same way above to analyze the whole internal flow field in UBF reactor, it is shown that the internal flow field in this given UBF reactor (i.e. the layout of outlets is determined and the influent velocity of wastewater is below a certain value) wholly tends to uniformity after it is higher than the outlets of pipelines, which means that outlets have different velocities of flow fields and different agitating effects, but the velocity of whole internal flow field tends to uniformity gradually after they are reflected by the bottom of reactor. Taking simple configuration, obvious effect and convenient manufacturing as the principle of optimization, this paper optimizes the water distribution system of UBF reactor in the layout of bottom reflector cone and optimization of water distribution pipelines. After the numerical simulation through FLUENT, this paper finally gets the optimal combination from all schemes, not only the internal flow field of UBF reactor has good uniformity, but also the flow out of pipelines has more uniformal agitating effects, and the chance of short cut in flow and dead zone's appearance decreases sharply. It also creates the conditions for the entire wastewater treatment process in the best operating condition. At the same time, such optimal choice will provide some valuable reference for the design of UBF reactor water distribution system in the future.