Floating Flocs

Overview

Floating flocs in the sedimentation tanks of AguaClara plants in Tamara, Ojojona, and Marcala result in polluted effluent water. While some treatment plants use floating floc to treat water, AguaClara plants rely on flocs settling out at the bottom. The cause of the problem is thought to be bubbles forming on floc particles due to supersaturation of influent water, which occurs when the total dissolved gas pressure is greater than the local solution pressure. The goal of the Floating Floc team is to find an efficient and cost-effective approach to remove excess gas from water and to implement that method in current and future AguaClara plants to improve the sedimentation process.

Currently, the Floating Floc team is conducting research with a back-washed sand filter to remove excess gas from the water in the grit chamber before it reaches the sedimentation tank. Placing sand in the water would provide a surface area other than the floc particles on which bubbles can form to leave the water. The aim is to remove enough gas from the water in the grit chamber, so that the water entering the sedimentation tank has a lower bubble forming potential. The research being performed specifically focuses on observing and quantifying the effectiveness of different sand grain sizes at different depth of the sand bed. We postulate that smaller grain sizes would increase the effectiveness of gas removal from the water, because their surface area to volume ratio are larger and also that a greater sand bed depth would be more effective since more surface area would be provided for bubble formation. However, with smaller sand grain sizes a floating sand problem occurs. Similar to the floc situation, smaller sands are more likely to be carried away by the bubbles, which may result in significant sand loss over time. Our main objective is to find the optimal parameters to maximize gas removal and minimize the amount of sand carried away by bubbles. Our conclusions may result in adjustments to the grit chamber dimensions of AguaClara plants.

Floating Floc Team Semester Goals
Floating Floc Team [Research Proposal]
Floating Floc Team Meeting Minutes
Floating Floc Team [Future Challenges]

Current Research

[Floating Floc Sand Filter Method]

• The sand filter approach involves forcing water upward through a layer of sand, as if backwashing a sand filter. The sand filter method provides a substance besides the sediment in the water on which the bubbles can form. When the bubbles grow large enough, they will rapidly rise to the surface.

Additional Information

Floating Floc Aeration Method

• This page discusses past research on the aeration approach to dissolved oxygen removal. The aeration approach attempted to use bubbles as a catalyst to increase the rate of dissolved oxygen transfer out of solution by allowing dissolved oxygen to diffuse into the bubbles. This would increase the bubble size and cause the bubble to rise faster.

Theoretical Modeling of Aeration Method

• This page discusses the theory behind the Aeration method and contains mathematical models predicting air flow through orifices of different sizes and variable length pipes.

Floating Floc Team Annotated Bibliography

Aeration Method Quiz
This quiz checks that you have a basic understanding of the principles behind this research.