Pilot Plant Flocculation
Overview
The flocculators at the pilot plant allow the team to investigate flocculation, the process in which particles collide together to form flocs, in raw water. Two experimental set ups, a tube flocculator and a vertical flow hydraulic flocculator, are used at the plant. The velocity gradients (G) created as flocs travel through systems result in floc collisions and aggregation. The amount of mixing (Gθ) is a result of the velocity gradients and the residence time in the flocculator. Research has shown that as flocs grow they are more prone to shearing stresses and break apart when exposed to the same velocity gradients that formed them.
The original set up, built by the Spring 1997 Aguaclara team, is a small scale vertical flow hydraulic flocculator similar to those built in Honduras. This flocculator has been used to examine tapered flocculation. Using tapered flocculation the flocs are exposed to high velocity gradients in the beginning of the tank and lower gradients as they travel through the tank. This summer a tube flocculator similar to the one in the Aguaclara lab was constructed, (See tube flocculator for more information). Previously the tube flocculator experiments were only conducted with clay particles. It has be shown that organic particles in the water affect flocculation. The tube flocculator allows the team to investigate the effects of raw water on coagulation and alum dosing.