Initial Particle Growth Effect on Settling of a Flocculating Slurry

In this study we found unusually high settling velocities in freshly precipitated, undisturbed ferric hydroxide floe. Even though during our operation the overflow from the reactor-clarifier did not meet suspended solid effluent discharge standards, we were confident that we could devise operating procedures that would produce satisfactory effluent. For example, we conducted all our studies without the use of polyelectrolyte addition. Such additives would surely remove the small particles which were causing the suspended solids to exceed standards. Of most importance is to develop the discovery of the increased settling velocities with freshly precipitated floes. It would seem reasonable to first quantify the power-energy picture so that floe size was predictable from known energy inputs. From this relationship we should proceed to determine the optimum energy-floe size combination which would produce the desired overflow concentrations. The potential here is to be able to increase the solids application rate for any reactor-clarifier, thereby increasing the throughput of the device without the need for additional capital investment. In addition, when designing new equipment, smaller vessels at less cost could be used.