Numerical Simulation And Experimental Research Of Two New Clarifiers

As a significant structure in water treatment, the application of clarifier combined with flocculation and sedimentation is widespread. The exploiture and test of efficient pump-sucked external reflux clarifier and cylinder internal reflux efficient segregation apparatus are discussed in this paper. Both of them are approved to be economical and efficient through investigation, and the defects of traditional clarifier such as large occupation of land, high quantity of sludge reflux, great consumption of flocculants and low utilization ratio are avoided.The investigation is separated to two segments: computer simulation and pilot test. Computer simulation provides academic guidance for empolder of installation. The flow characteristics of fluid are represented by turbulence model and two-phase flow matrix which are both utilized in Computational Fluid Dynamics (CFD). Modeling and meshing are accomplished by Gambit. Numerical simulation of the devices is achieved by FLUENT. Analysis of flow characteristics and influence of microvortex on flocculation in flocculating zone are the critical content. In settling zone, granule volume fraction and distribution of turbulent kinetic energy are analyzed to portray flux vectorgraph and curve of turbulent kinetic energy. Results of Numerical simulation gave proofs to that flocculation and sedimentation of devices mentioned before could work well in water treatment.Pilot test was implemented in one of water treatment facilities in Chongqing region in summer. Raw water in investigation is pumped from the Yangtze River. During the pilot test, temperature, pH, turbidity, permanganate index, UV₂₅₄ range of raw water is 24.2-26.6℃, 7.6-8.0, 164-4500NTU, 1.04-6.5mg/L, 0.021-0.119 abs/cm, respectively. Complex flocculants utilized are aluminium polychlorid compounded with poly dimethyl diallyl ammonium chloride (w/v of 5‰). Investigation of efficient pump-sucked external reflux clarifier indicated optimum removal of pollutants in raw water under the conditions of influent surface load, sludge reflux ratio and dosage of complex flocculants is 10stere per hour, 10%, 18-20mg/L, respectively. Turbidity, permanganate index, UV₂₅₄ of effluent is 2.54NTU, 1.01mg/L, 0.049abs/cm, respectively. The maximum removal ratio of turbidity is 99.93% while COD_Mn and UV₂₅₄ is 83.74%, 51%, respectively. The result of research on cylinder internal reflux efficient segregation apparatus is similar with efficient pump-sucked external reflux clarifier. Whereas the operational condition is that influent surface load, rotation rate and dosage of complex flocculants is 10stere per hour, 60r/h, 20-22mg/L, respectively. The maximum removal ratio of turbidity is up to 99.9%, while COD_Mn and UV₂₅₄ is 83.98%, 53.47%, respectively. Turbidity, COD_Mn and UV₂₅₄ of effluent is 3.98NTU, 1.03mg/L, 0.047abs/cm.Both efficient pump-sucked external reflux clarifier and cylinder internal reflux efficient segregation apparatus performed well. The resistant capacity of impact load is higher, continuous operation is more stable and dosage of flocculants decreases.