The purposes of this study are to minimize the area of the sedimentation basin, to reduce coagulant dosage(Alum) and to produce much more drinking water than it of the conventional water treatment plant by surface loading rate. In the conventional water treatment plant, because the trace of flocs is very wide parabola, the time to settle flocs needs a lot. The settling time is very long because of slow sedimentation. The micro flocs and pin flocs can also cause the loading rate increase of the filter basin. To solve these problems, the flocs must be made compact flocs by considering its diameter, density and so on. The flocculation and the settling time depend on these factors according to the Stoke's law, too. Therefore, the Pelletization is the best method to produce compact flocs for the rapid flocculation and sedimentatin. There are two ways to pelletize the flocs with polymer. The secondary method is the Indirect Way(Mechanical Syneresis) which is made the compact aggregate, and the primary method is proceeded the Direct Way(one by one attachment) which the grown pellets are made.〔N. Tambo et al.〕
According to tht theory above, in this study without polymer, after being made the small and weak pellet seeds(secondary particles) in the isoelectric point by attaching the primary particles to itselves by the cohesive attraction(Van der Waals force and gravity force) like the compact aggregates, and then the grown pellets is made in the low zeta potential with long hydraulic retention(HRT) and solid retention time(SRT) by attaching the primary particles to the pellet seeds by the up-flow rate and mixing intensity.
Manufacturing the pelletization pilot plant, the pelletization was tested with the raw water. This study shows it possible that the Pelletization without polymer can be made compact flocs(pellets). The important characteristics of the pelletization may be rapid flocculation and sedimentation.
Results obtained from this study were as follows;
1. As a result of observation by using the Radio Isotope Tracer and photo analysis, the flocculation and sedimentation by the pelletization was proceeded in the high HRT and SRT by the low up-flow rate(0.25cm/sec) and the low mixing intensity(6rpm) without polymer.
2. The rate of the TOC removal was relatively high because the primary particles absolutely were attached to pellet seeds by the low up-flow rate.
3. The pelletization was well proseeded with the low turbid raw water, and the pellet diameter of the high turbid raw water was larger than it of the low one. The water content of the waste sludge(less than 95%) was very low regardless of the turbidity of the raw water.
4. The amount of the coagulant(Alum) dosage could be reduced without regard to the turbidity of the raw water(about 50%). The pellet diameter was much larger in the lower coagulant dosage and the higher turbid raw water. It was 1.0 ~ 5.5mm in low and high turbidity raw water.
5. The effect rate of the Pelletization Process without polymer was improved throughly and the surface loading rate(100∼150㎤/㎠·hr) was very high in comparison with the conventional water treatment(the surface loading rate:57 ∼ 74 ㎤/㎠·hr). Also, the pellets was rapidly settled down because the it had high density.
