Design And Research Of The New Continuous Sand Filter

Human can not survive without water. By reusing the treated sewage andeffluent, their harmful effects on the environment can be avoided andmeanwhile the shortage of water resource can be solved in some extent.Continuous sand filter plays an important role in the filtration area and widelyused in water treatment fields.In this thesis, the present state and future trend of the sand filter wereanalyzed and the working principles, characteristics and structures of thecontinuous sand filters were introduced. To solve some problems existed in thepresent sand filters，traditional sand lifting system and sand washing systemwere improved by adopting new structures namely corrugated sand-liftingpipe and spiral sand washer. CFD software FLUENT was used to simulate thefunctions of the corrugated sand-lifting pipe and the spiral sand washer. Byperforming parametric analysis, their structures were optimized. Comparingthe corrugated sand-lifting pipe with the traditional sand-lifting pipe indicatesthat if the amount of sand-lifting is the same，the turbulence of fluid and thesand washing effect were greatly enhanced in the corrugated sand-lifting pipe.Similarly, comparing the spiral sand washer with the traditional sand washer, it is found that the sand washing path of the spiral sand washer is longer and theseparation of the sludge and sand is better, or in other words, the spiral sandwasher is superior to the traditional sand washer in many respects. In addition,on the basis of the numerical simulation, experiments for the performance ofthe spiral sand washer were also conducted. Finally in this thesis, the entireNCSF continuous sand filter is designed and the size of the series of NCSFcontinuous outer loop sand filters was given.