Floating Flocs

Overview

Rising flocs in the sedimentation tanks have been a problem from the very beginning at the plant in Tamara. The plant in Ojojona is also having this issue but to a lesser degree. Initially the rising of the floc was thought to be caused by alum overdosing but the problem persisted even after the dosage was changed. The speed with which the floc particles rise in the tank suggests that air bubbles are lifting them to the surface. Some water treatment facilities purposely make the flocs rise to the surface but since the Tamara and Ojojona plants are designed to have the flocs settle out at the bottom of the sedimentation tanks the layer of particles at the surface of the tank pollutes the effluent.

The water source for Tamara is a mountain stream below a large waterfall. Thus the water at the intake is likely in equilibrium with atmospheric oxygen. The supersaturation with oxygen most likely occurs in the transmission line since some sections of the pipeline carry a mixture of air and water into regions of high pressure.

A procedure is needed that will either prevent supersaturation of air in the transmission line or a method to remove dissolved oxygen prior to sedimentation to increase the effectiveness of the water treatment plant.

Floating Floc team goals and meeting minutes