The Effect Of Cascade Mixing On Flocculation

In the article, the control index was studied by the flocculation kinetics mechanism. The cascade flocculation test was designed, and the turbidity removal law was studied. The optimal value of each control index could be got by the test, and ccompared the pros and cons with control indexes. It figured out the value of control indexes and then analyzed the relation in control indexes of the first step flocculation, the second step flocculation and the third flocculation.(1) In the first step flocculation test, the water samples’turbidity was 100 NTU and 200 NTU, the test was presented:The relative deviation of the value GT/Re1/2、Eu、E1/3T was close and small, so they were better suited as a flocculation control parameters than GT. The best values of control parameters of the 100NTU was presented, The GT/Re1/2 was in the range of 1020-1247, the average was 1106; The Eu was in the range of 641～784, the average was 689; The E1/3T was in the range of 12150～14850,the average was 13244. The relative deviation of GT/Re1/2、Eu、E1/3T were 5.0%.(2) In the two steps flocculation test, whose water samples’ turbidity was 100 NTU, the test was presented:The relative deviation of the value GT/Re1/2、Eu、E1/3T and nT was close and small, so they were better suited as a flocculation control parameters than GT. The best values of control parameters o was presented, The GT/Re1/2 was in the range of 294～319, the average was 308; The Eu was in the range of 201～185, the average was 193; The E1/3T was in the range of 3812～3512, the average was 3621. The ratio between the first step flocculation and the second step flocculation test was 3.2-3.8 times in GT/Re1/2、Eu、E1/3T, but the regularity of GT was not clearly. The relative deviation of GT/Re1/2、Eu、E1/3T were 3.0%-3.4%.(3) In the three steps flocculation test, whose water samples’turbidity was 100 NTU, the test was presented:The relative deviation of the value GT/Re1/2、Eu、E1/3T was close and small, so they were better suited as a flocculation control parameters than GT. The best values of control parameters o was presented, The GT/Re1/2 was in the range of 182.5～213.5, the average was 201; The Eu was in the range of 114～134, the average was 126; The E1/3T was in the range of 2175～2550, the average was 2406; The nT was in the range of 490～325, the average was 320. The ratio between the first step flocculation and the second、the second and third step flocculation test was3.5:1、1.5:1 times in GT/Re1/2、Eu、E1/3T, but the regularity of GT was not clearly. The relative deviation of GT/Re1/2、Eu、E1/3T were 4.7%～4.8%.In the process of flocculation:The G is Gradually reduce with flocculation series increased, residual turbidity was rapidly reduce with flocculation precipitation series increased, the flocs formed larger and settling velocity faster with flocculation precipitation series increased. The test results shows that,among the GT、GT/Re1/2、Eu、E1/3T four indicators GT’s value relative deviation was the largest, the relative deviation of GT/Re1/2、Eu、E1/3T were small and close, so GT/Re1/2、Eu、E1/3T in this experiment was suitable for the conditions. The treatment effect was more better by the the more series of Cascade flocculation.