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Recently development in Aguaclara technology have shown that the Gtheta model may be inappropriate to describe flocculation. A main goal of the pilot plant flocculation team was to determine the optimal flocculation configuration: Tapered or Uniform Baffle Spacing. Using the Gtheta model a tapered configuration would expose flocs to high shear initially and as flocs grew they would be exposed to less shear. Using an energy dissipation model, the uniform configuration would be optimal. The tapered flocculator
The Pilot Plant flocculation team approached this problem by first determining the optimal spacing for the tapered flocculation configuration. It was then determined that the two configurations would only be comparable if the uniform spacing was equal to the last section of the tapered spacing. The tapered and uniform spacings were compared consecutively. The tests were then run in the same day to ensure similar environmental conditions and comparable data.
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Figure 2: Uniform vs. Tapered Configuration. (12/14/08)
Conclusions
Conclusions
The alum dose set based on plant PAC dosage gave the best results for an incoming turbidity of 2.3 NTU. If this relationship is confirmed to work at a broad range of incoming turbidities, it can hopefully be used by future semesters. The plant operators obviously have much more experience determining alum dosing and this relationship can help us take advantage of their expertise.
The turbidity profiles along the flocculator show little difference between the uniform and tapered configuration. Neither configuration shows a better effluent turbidty than the raw water turbidity. The tapered flocculator performed slightly better than the uniform flocculator, this is to be expected as more reasonable energy gradients were occuring in the tapered flocculator. Although the energy gradients are extremely low, clearly flocculation is occuring as seen by the initial increase in turbidity. This increase shows that flocs too small to settle out but large enough to increase the turbidity of the flocculator were forming. In addition, these flocs began to increase in size and number and proceeded to settle out.