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• Continue the effort to create an AutoCAD video that will show the assembly of the plant with descriptions of each part. This video could serve as the documentation that gets sent to a user who designs a plant with the Design Tool that explains the technology behind each piece.
  

Tube Floc

The development of FReTA and the data processing methods used to analyze its measurements has given AguaClara a powerful research tool. This investigation into fluid shear influences on hydraulic flocculation was the first of many studies that could be performed with this apparatus.

Results of this study suggest several directions for future research into fluid shear influences on hydraulic flocculator performance. Present results clearly show that shear induced breakup significantly affects both the mean floc size and residual turbidity. Steady state floc sizes were observed at high velocity gradients, but not at low velocity gradients. Perhaps extending the length of the tube flocculator to twice or even three times the current length will provide new insights on how floc sizes and residual turbidities are affected at low velocity gradients.

Additionally, an investigation into the utility of tapered flocculation designs should be performed. Hydraulic flocculators in AguaClara plants are currently designed such that the energy dissipation rates incrementally decrease over the length of the flocculator. The present study showed that while the influences of shear induced breakup was evident early on in the flocculator, floc sizes were not nearly as limited by shear as they were later on in the flocculator.

Different influent synthetic water compositions (particle type, particle concentration, introduction of organic acids, pH, alkalinity, etc.) should also be tested to see how they affect hydraulic flocculation. For example, performing experiments with different initial turbidities can provide insight into how particle concentration affects floc strength and turbidity removal efficiencies. Likewise, varying the pH of the influent may help elucidate changes in floc strength as a function of pH. It is possible that floc strength is well correlated with optimal alum dose and pH.

There are also questions regarding the role of rapid mix and how it affects flocculation. Do changes in the energy dissipation rate in the rapid mix or in the first

stage of flocculation affect the final floc sedimentation velocity and residual turbidity?

A laboratory scale hydraulic flocculator that operates under turbulent conditions that are relatively homogeneous and easy to characterize could go a long way into understanding turbulent flocculation. Comparison of residual turbidity and floc sedimentation velocity from turbulent and laminar flow flocculators could be used to validate flocculation models.

Plate Settler Spacing

Challenges for Fall 2009 and Beyond

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