IMPROVEMENT OF DRINKING WATER QUALITY THROUGH THE OPTIMIZATION OF RAPID-MIX CONDITIONS IN COLD REGIONS

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(1) From the dynamic coagulation experiment, it was made clear that an agglomeration process after a coagulant injection comprises the following three stages, that is, the preparation, the progression and the stabilization, and the number of un-agglomeration particles in the stabilization stage was greatly influenced by coagulant injection rate, and both rapid agitation and slow speed agitation.(2) Strengthening of both the rapid agitation and the slow speed agitation, even if either case is done, are effective for the improvement of treated water quality. In addition, total G.T value which minimizes treated water turbidity and STR differs from one coagulant to another, and in case of the PAC use, total G.T values necessary for achieving treated water turbidity lower than 0.5 mg/L and STR smaller than 2, are 160000〜300000.(3) With the water temperature lowering, the time until the stabilization stage appeared was lengthened, and the number of remaining un-agglomeration particles in the … More stage increased. The reason of retarding the appearance of stabilization stage is because the preparation stage was prolonged. However, there is no significant change in the length of the progression stage. The reason of the residual particle number increasing in the stabilization stage is therefore because the agglomeration speed lowers in the progression stage. Adoption of high total G.T value was considerably effective in reducing the number of residual particles.(4) How to utilize the non-ionic polymer for enhancing the treatability of turbidity and STR when water temperature was reduced was examined. As a result, the effectiveness of the rapid agitation method of serial two steps (the first step : PAC injection, and the second step: non-ionic polymer injection) was verified.(5) From experiments on the removal of humic substances which are of special concern in cold regions, the following were clarified : that the sufficient rapid agitation until it comes in the agglomeration stabilization stage is the most important and that the combined use of optimization of GR value and PAC injection rate is effective for lowering both STR and color degree. Less