h1. Floating Flocs
h2. Abstract
{float:right|border=2px solid black|width=200px}
[!floating floc.jpg|width=200px!|Dissolved Air Flotation of Flocs]
{float}
Rising flocs in the sedimentation tanks have been polluting the effluent water at the plants in Tamara, Ojojona, and Marcala. While some treatment plants rely on floating floc to remove particles from water, AguaClara plants are designed to have flocs settle out at the bottom of the tanks. Initially the floating floc was thought to be caused by alum overdosing but the problem persisted even after the dosage was changed. The speed at which the flocs rise in the tank suggests that air bubbles are lifting them to the surface.
\\
{float:left|border=2px solid black|width=250px}
[!sludgeTop.jpg|width=250px!|Dissolved Air Flotation of Flocs]
{float}
Gas bubbles form in water when the total dissolved gas pressure is greater than the local solution pressure or when the water is supersaturated with gas. Supersaturation of the water flowing into the plants may be caused by a pressure drop to below atmospheric pressure due to very high rates of mixing caused by turbulence at the plant entrance and churning in the grit chamber. Cracks in the transmission lines combined with high pressure regions would also result in gas being infused into the influent water.
A procedure is needed to either prevent supersaturation of influent water or remove excess gas prior to sedimentation to increase the effectiveness of the water treatment plant. Currently, research is being performed using a back-washed sand filter to remove excess gas from the water. The hope is that decreasing the amount of gas in the water at the beginning of the water treatment process will solve the problem of rising floc in the sedimentation tanks.
h2. Introduction and Objectives
The goal of the Floating Floc Team is to find a solution to the floating floc problem at AguaClara plants. We are currently looking into a back-washed sand filter approach, which involves decreasing the gas content of the water in the grit chamber before it enters the flocculation tank. Supersaturation in the influent water causes gas bubbles to form on dirt particles in the water. This results in flocs floating to the surface and contaminating the effluent water instead of settling out.
Our aim is to find the most efficient and cost-effective remedy to the problem and to implement that method in current and future AguaClara plants.
Floating Floc Team [Semester Goals|Floating Floc Goals]
Floating Floc Team [Meeting Minutes|Floating Floc Meeting Minutes]
h2. Current Research
[Floating Floc Sand Filter Method|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.
h2. Additional Information
[Theoretical Modeling of Aeration Method|Floating Floc Research]
* This page discusses the research into the floating floc phenomenon that is being conducted.
[Floating Floc Aeration Method|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|Floating Floc Research]
* This page discusses the research into the floating floc phenomenon that is being conducted.
Floating Floc Team [Annotated Bibliography|Floating Floc Annotated Bibliography]
[Quiz|Floating Floc Quiz]
This quiz checks that you have a basic understanding of the principles behind this research. | 