| China’s remote mountainous areas in the northwest have long been plagued by the deterioration of drinking water quality,affected by the climatic conditions in the northwest and other factors,in the snowmelt season and heavy rainfall season,the turbidity of its drinking water sources will occur for a short period of time surge.The topography and water pollution in Northwest China restrict its large-scale development of conventional water plant process,so circulating granulation fluidized bed as a highefficiency water treatment equipment is widely used.Through experiments,it is found that circulating granulation fluidized bed can not only effectively treat sudden high turbidity water,but also cope with low temperature and low turbidity water,and the removal of organic matter is also higher than conventional process.It proves that circulating granulation fluidized bed is an effective means to deal with water pollution.Taking a reservoir water in Xi’an and a reservoir water in Xining as the treatment objects,the results of circulating granulation fluidized bed parameters preferences show that 100 mesh magnetic powder as loading medium is the best choice for turbidity removal,200 mesh activated carbon is the best choice for organic removal;PACl and loading medium are added at the same time to be the most beneficial for water purification.The experimental results show that 100 mesh magnetic powder is the best choice,the maximum upward flow rate is 120 m/h,the minimum dosage of PACl and PAM is 20mg/L and 0.6 mg/L respectively,and the best stirring speed is 6～9 r/min.When the dosage of loading medium is 100 g/L,the best effect on turbidity removal is achieved.The maximum upward flow rate of circulating granulation fluidized bed was 120 m/h.PACl dominated the removal of turbidity.The particle size distribution of agglomerate particles in the circulating granulation fluidized bed was gradually increasing from top to bottom,and the free sink speed of agglomerate particles increased with the increase of particle size,and the agglomerate particles grew rapidly to stability within 3 h of start-up and slowed down in the subsequent operation process.After a certain period of time,it decreases.The setting of circulating system has a great influence on the maximum rise load of circulating granulation fluidized bed and the efficiency of purified water,and the fluidized bed with circulating system can increase the rise load by 10～30 m/h compared with that without circulating system.The design scale of the water plant is 14000 m~3/d,and the water supply should reach600m~3/h.Therefore,four 150m~3/h circulating granulation fluidized beds are activated to cope with the water quality emergencies under different circumstances.In this experiment,the dosage of PACl is 25～30mg/L,the dosage of PAM is 1.5～2.0 mg/L,the stirring speed is 3 r/min,the rising flow rate is 47.78 m/h,and the turbidity of feed water is 10 NTU,1000 NTU and 5000 NTU as the feed water condition.It is proved that the circulating granulation fluidized bed has excellent treatment effect on both low turbidity water and high turbidity water,and the treatment load is increased to 3 times of the first generation fluidized bed and 4～5 times of the common wastewater plant treatment process.In this experiment the operation cost is mainly divided into electricity cost and drug cost,where PACl is 1000 yuan/ton and PAM is 15000 yuan/ton,while the average dosing amount of PACl is 25mg/L and the average dosing amount of PAM is 1.2mg/L,then the cost of PACl is 0.025 yuan/m~3 and the cost of PAM is 0.017 yuan/m~3,and the total cost of dosing is 0.042 yuan/m m~3;electricity cost is 0.7 yuan/k Wh,running cost includes lifting pump,dosing pump(metering pump,screw pump),fluidized bed mixing motor electricity,electricity consumption is 0.082 KWh/m~3,daily water supply is 600 m~3/h×24h,so the total running cost is 0.124 yuan/m~3,according to the daily running 24 h,the running cost is 1785.6 yuan/day. |
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