Fall 2008 Research

Will be updated as soon experiments can be conducted!

Introduction

This semester, the pilot plant sedimentation team is experimenting with the parallel sedimentation tanks to get closer to the goal of 1 NTU water. Because the two tanks are identical, experiments now have a control, and the effluent differences cannot only be attributed to the turbidity of the inlet water or alum concentration changes. While leaving a sludge blanket in the control, experiments will be performed on the other sedimentation tank to see how effectively lamella and sludge blankets can interact. Some of the experiments include determining if there is minimum required tank depth below the lamella for blanket formation, dimensions of the lamella themselves, and spacing between lamella. Each of these experiments will be performed at various upflow velocities, since the plant flow rate in Honduras is also variable.

The chief research goals this semester were:

• Determine if there is minimum required tank depth below the lamella for blanket formation, and what that minimum depth is
• Determine the optimal relationship between the floc blanket and the bottom of lamella before performance is affected
• Determine the minimum how short can the lamella (vertical distance) before they are ineffective.
• Test lamella spacing to determing a minimum and the optimal spacing
• Determine if a combination sed tank can be used, and determine if that is the most efficient set-up.

Methods and Results

Set-up
The set-up is generally the same for all experiments conducted this semester.

• Two tanks: one without lamella, one with lamella placed so that the bottom of the lamella are at 1/2 the depth of the tank
• There is a small hole at the top of each tank that is usually plugged. To collect data on the turbidity of the water above the floc blanket, a thin tube is inserted in the hole. The tube is connected to a peristalic pump that pumps water to a turbidimeter.

Effects of Lamella at Different Depths
Lamella Depth
Lamella Spacing