Application Research Of Improved Bio-slow Sand Filtration Technology In Cellar Drinking Water In Northwestern China

In the region of northwesten China,with dry climate and extremely scance water resources.rainfall is an important supplement to water resources.People collect rainwater from roofs,courtyards,natural slopes,etc.to provide drinking water for human and livestock in the season of water shortage,but the rainfall runoff may bring organic and inorganic pollutants such as dust,animal manure,domestic waste,agricultural waste and agricultural machinery waste into the cellar water,causing water pollution.Due to the widespread and high health risks to local people,it is urgent to develop and adapt to the household water dispersal treatment technology.Bio-slow sand filtration has simple process principle,and has good water purification effect.It can reduce the content of various pollutants in the raw water.Generally,the drinking water quality standard can be achieved without the need of a disinfection unit;the construction can be locally prepared according to local conditions,and the initial construction cost is low.Since there is no need to add water treatment chemicals,the operation cost is low,the economy is superior,and it is suitable for rural decentralized water purification demand.In this paper,4 sets of filter columns filled with different effective sizes of filter materials were used to study the removal effect of various pollutants,optimize the particle size of filter materials,the recovery period and operation period of intermittent operation,as well as the film hanging period and operation period of sand filling mixed operation.This process is operated by natural membrane method,and the water quality of the effluent during operation is lower than the national drinking water standard.It is concluded that the removal effect of the three different grades of filter materials on the pollutants is 0.28mm>0.39mm>0.50 mm,but the effect is not obvious.The larger the effective size of the filter material,the more the filming period is.The effective membrane diameter of 0.28 mm and 0.39 mm is 20 days,and the effective membrane diameter of 0.50 mm is 25 days.The influence order of three different graded filter materials on operation cycle is 0.39 mm > 0.50 mm > 0.28 mm.The intermittent operation of Bio-slow sand filtration process has a good effect on the removal of contaminants.The recovery period of the biolayer of the process is short and the operation period of the filter column is increased.The bio-layer recovery period of the 1,2,3,4,7,and 10 days intermittent process is 1 day,3 days,4 days,4 days,5 days,and 5 days,respectively.The extended operation period is 6 days and 9 days respectively.,15 days,21 days,15 days,15 days.The recovery period of the bio-layer of the filter medium in the 4-day intermittent period of the 6 batch period processes is short,the filter column has the longest extension period and the removal efficiency is high.The filling-mixing Bio-slow sand filtration process has a good effect on pollutant removal.The effluent quality during the operation period is lower than the national drinking water quality standard.The process shortens the filming period of the biological layer and improves the effluent water quality,but at the same time shortens the running period.Sand filling 0mm mixing 30 mm process hanging period is 3 days and the running period is 11 days;sand filling 10 mm mixing 40 mm process hanging film period is 3 days and the running period is 27 days;sand filling 20 mm mixing 50 mm process hanging film period is 4 days and the running period is 39 days;the sand-filling 30 mm mixing 60 mm process is 5 days and the running period is 42 days.In the 4 kinds of sand-mixing process,the 20 mm mixing 50 mm process has the best effluent quality,the membrane efficiency and operation period are relatively best.The effect of filter column shading on the operation effect of the filter column is different: For the traditional Bio-slow sand filtration process,the filter column shading is beneficial to the pollutant removal effect.For the intermittent Bio-slow sand filtration and the sand-mixing hybrid slow filter process,the filter column shading effect is not obvious.