Experimental Study On Turbidity Removal Effect Of Vortex Clarifier And Grid Clarifier

To solve bottleneck problem of low coagulation efficiency and poor ability to against theload impact in traditional clarifier running, in this paper a parallel test with turbidity removingeffect, water-yielding capacity and ability to against the load impact of vortex clarifier andgrid clarifier was carried out. From research of actual running results, best operation conditionand design parameter was established. The findings olso offer design parameter and practicalreference for using of vortex clarification technique in clarifier modifying, centralized watersupply of village and other projects.In this paper, firstly, a suitable coagulant and its best dosage was confirmed by a statictest of turbidity removing effect with different coagulants and dosage. The test is under theworking condition of lake water from Kongmu Lake and mimic muddy water. Then, adynamic test with starting of vortex clarifier and grid clarifier, affecting of treatmentefficiency by coagulant dosage and flocculation time and ability to against the load impactwas carried out. With the analysis and contrast of running results, best operation condition anddesign parameter of vortex clarifier and grid clarifier was established.The main conclusion were obtained as follows:(1) In the static test,with the condition of lake water from Kongmu Lake, the flocculationeffect of PAC, Al2(SO4)3and FeCl3was studied. And the suitable coagulant was PAC, its bestdosage was20~25mg/L. With the condition of200NTU mimic muddy water, the flocculationeffect of PAC, Al2(SO4)3and FeCl3was also studied. And the suitable coagulant was PAC, itsbest dosage was25~30mg/L.(2) While the raw water was lake water from Kongmu Lake, rate of flow was10m3/h and thedosage of PAC was15mg/L,25mg/L and35mg/L, time from water entering to having a stableoutlet water of vortex clarifier was shorter than grid clarifier.Start of vortex clarifier is morequickly than grid clarifier.(3) While the raw water was lake water from Kongmu Lake, rate of flow was10m3/h and thedosage of PAC was increased from10mg/L to40mg/L, effluent turbidity of vortex clarifierwas low than grid clarifier. The lowest effluent turbidity of vortex clarifier was0.73NTU, andthe best coagulant dosage was25mg/L. The lowest effluent turbidity of grid clarifier was0.89NTU, and the best coagulant dosage was30mg/L. Floc size of vortex clarifier and gridclarifier was both increased first and then reduced. In the same coagulant dosage, floc size ofvortex clarifier was bigger than grid clarifier. Their floc size reach the maximum, whendosage was their best coagulant dosage. The zeta potential of the two clarifier was bothincreased first and then reduced with the increasing of PAC dosage, but at the same dosage, there didn’t have great difference between the zeta potential of two clarifier.(4) While the raw water was lake water from Kongmu Lake, coagulant dosage of PAC was25mg/L, rate of flow was increased from7m3/h to13m3/h, time of flocculation was reducedfrom9.7min to5.2min, the effluent turbidity of two clarifier was both reduced first and thenincreased. And in the same rate of flow, the effluent turbidity of vortex clarifier was lowerthan grid clarifier. Vortex clarifier get its best running effect when rate of flow was10m3/h,time of flocculation was6.8min and surface loading is5.1m3/(m2·h). Grid clarifier get its bestrunning effect when rate of flow was9m3/h, time of flocculation was7.6min and surfaceloading is4.6m3/(m2·h).(5) The effluent turbidity of two clarifier was both increased when the rate of flow increasedfrom7m3/h to10m3/h and10m3/h to13m3/h suddenly, and rangeability with effluent turbidityof10m3/h to13m3/h was greater than7mm3/h to10m3/h. Rangeability with effluent turbidityand time from water entering to having a stable outlet water of vortex clarifier were lowerthan grid clarifier. Ability to against the water quantity load impact of vortex clarifier wasbetter than grid clarifier.The effluent turbidity of two clarifier was both increased firstly and then stable when theturbidity of flooding water increased from18NTU to200NTU suddenly and then stable.Changing of effluent turbidity lags behind the flooding water. Rangeability with effluentturbidity and time from water entering to having a stable outlet water of vortex clarifier werelower than grid clarifier. Ability to against the water quality load impact of vortex clarifierwas better than grid clarifier.