Company to Feature New Pilot Unit at AWWA Show

USFilter will feature its new Actiflo® microsand ballasted clarification pilot unit at the American Water Works Show in New Orleans, LA, June 16-19. The new 140 gpm demonstration unit is part of the company's Kruger Products pilot program, which helps cities investigate performance, provide operational data and develop treatment experience prior to purchase of the full scale Actiflo process plant.

Each trailer mounted pilot unit contains all necessary process equipment, chemical feed systems, controls and laboratory equipment - forming a self-contained on site treatment process capable of demonstrating the performance of the Actiflo process across a range of operating conditions. USFilter pilot test engineers can set up and have the pilot system operational within 1-2 days. Typical test periods last from 2-3 weeks.

In the Actiflo® microsand ballasted clarification process, the raw water to be treated enters the coagulation tank where chemicals destabilize suspended solids and colloidal matter. Next, in the injection tank, polymer and microsand are added to initiate floc formation. The water then passes to the maturation tank where gentle mixing provides ideal conditions for the formation of polymer bridges between the microsand and the destabilized suspended solids.

The fully formed ballasted flocs leave the maturation tank and enter the settling tank. Here the microsand ballasted floc settles rapidly. The clarified water flows upward though the inclined plate or tube settlers. Clarified water exits the process through collection troughs or weirs for further treatment and discharge in the case of wastewater; or to filtration, disinfection, and distribution in the case of drinking water.

The sand-sludge slurry collects at the bottom of the settling tank, where it is collected and pumped to hydrocyclones for separation. The microsand is concentrated and discharged from the bottom of the hydrocyclone and re-injected into the process stream. The lighter density sludge is discharged at the top of the hydrocyclone and sent to thickening or final disposal.

The Actiflo process differs from conventional clarification in that microsand is used as a ballasting agent in the flocculation process step. The microsand plays several important roles:

• The large surface-area of the sand particles serves as a "seed" for the floc formation.
• The microsand and polymer produce a large, stable floc.
• The relatively high concentration of microsand in the mixing basin dampens the impact of sudden variations in raw water quality and low temperature waters.

The microsand and polymer ballasted flocs in the process have considerably higher settling velocities than flocs from conventional treatment and allow clarifier rise rates up to 100 times higher than conventional treatment processes.

The microsand ballasted clarification process can be applied wherever physical-chemical treatment including coagulation, flocculation and settling is used. The Actiflo process can treat raw waters containing both high and low turbidity, TOC, algae, particle counts, color, Cryptosporidium, giardia, iron, manganese, arsenic, and other typical water contaminants.