Study On The Optimization Of Variable Flow Rate And Double Layer Inclined Plate Coagulation-sedemengtation Technology

The optimization of conventional drinking water treatment process is still one of the important means to meet the requirements of the strict water quality.For conventional process,what's remarkable is that a large quantity of small particles remains after settling.Such kind of problem will not only increase the burden of the subsequent treatment process,but also pose a safety hazard.Variable speed and double layer inclined plate cogulation sedimentation tank,in which dynamic particle suspension area of a certain thickness forms inside,can enhance the removal ability of small particles.Therefore,it is of great significance to carry out process intensification based on this process and to further highlight the technological advantages of dynamic particle suspension area.Several aluminum-based coagulants were prepared,which comprise polyaluminum chloride(PACl),alchlor(AlCl3)and PACl20(mostly composed of Al13).These were used in studies of running results of reforcing measures applied to the process.Sludge reuse,breakage and regrowth with additional coagulants or coagulant-aids were considered in the study.And turbidity,UV254,residual Al,particle number and size distribution were regarded as testing index and analyse indicators.Besides,the law of the characteristics of the flocculation particles and the dynamic particle suspension area changing with the reforcing measures,was analyzed.Results showed that the effluent water quality under certain reforcing measures can be improved.For PACl,turbidity and particle number of effluent water could be obviously reduced in the process of first-time-sludge or second-time-sludge reuse,a faster mixing speed in the latter growth stage,breakage and regrowth with additional coagulant less than 4mg/L,diatomite or polyacrylamide less than 3mg/L,meanwhile,the removal efficiency of humic acid could be slightly improved either.The minimum turbidity of each working condition can be 1.7NTU,5.0NTU,4.1NTU,2.7NTU and 2.2NTU.For AlCl3,the applicable reforcing measures included first-time-sludge reuse,a faster mixing speed in the latter growth stage,breakage and regrowth with additional coagulant less than 10mg/L or polyacrylamide less than 2mg/L.The minimum turbidity of each working condition can be 5.5NTU,7.0NTU,6.8NTU and 4.9NTU.For PACl20,the process of first-time-sludge,breakage and regrowth with diatomite or polyacrylamide less than 3mg/L,was effective.The minimum turbidity of each working condition can be 5.4NTU,6.7NTU and 4.5NTU.However,some reforcing measures,such as sludge reuse or breakage and regrowth with coagulant aids,could lead to the problem of relatively high residual Al in effluent water.Particles with larger diameters could be accumulated or renewed in the dynamic particle suspension area to improve the removal efficiency of suspended micro-particles.The proportion,the distribution range and the compactness of particles with larger diameters contribute a lot to the processing capacity of the dynamic particle suspension area.Meanwhile,its capacity is influenced by the characteristics of coagulated effluent,such as the particles' size distribution and morphological characteristics.