Although some consultants believe that flotation systems provide the most bang for the buck, many companies end up using them in combination with filtration and other treatments. As their name suggests, flotation systems generally separate solids by allowing them to float to the top naturally or with the aid of chemicals or other treatments. The addition of chemical flocculants to the effluent causes the suspended matter to join into larger particles that rise more quickly. Stirring the effluent can also promote the formation of larger particles. With this method, the air bubbles join with suspended particles and lower the specific gravity of the resulting air-particle agglomerate to less than that of water.
Particles then float to the surface for removal by a skimmer system.
As with other flotation system types, the process can be enhanced by adding coagulants and flocculants to increase particle size. To generate the air bubbles, the stream is saturated with air at several times atmospheric pressure. When the pressure is released, air in excess the saturation comes out of the solution as microscopic bubbles that attach to the solids. The units, manufactured by Precision Environmental Controls, also assured continued municipal discharge compliance for a projected wastewater flow increase resulting from the plant's expansion. The system includes two units for an initial stage of pretreatment and a third unit for a second-stage pretreatment, including a flocculation tube assembly.