DALLAS, PA, July 2008 -- The Huntsville Water Treatment Plant is supplied by the 25 foot deep Huntsville Reservoir and is operated by Pennsylvania American Water. The facility was originally constructed with four heavy media up-flow clarifiers. The clarifiers were fitted in a concrete basin and fed four media beds. The reservoir; which is a reserve, supplies a stable supply and typically exhibits a seasonal algae plume in the summer. The facility was only observing minor reductions in turbidity and was experiencing maintenance problems with instrumentation and physical restraints caused by "fines" from the clarifier.
In contrast, the nearby Ceasetown WTP facility was equipped with a Microfloc Adsorption Clarifier®. Though both facilities were designed to utilize air scour during the clarifier cleaning or flushing sequence, the Ceastown facility was seeing a 60% reduction in turbidity without the maintenance or physical restraint issues.
After comparing the performance at the two facilities it was anticipated that longer filter bed run times, improved functional performance and lower maintenance costs could be achieved by converting the Huntsville facility to the Microfloc technology.
The Microfloc Adsorption Clarifier® clarification process was selected due to its operational flexibility and successful experience at the Ceasetown facility. The heart of the Adsorption Clarifier uses rolled and scarified high-density polyethylene (HDPE) beads about 2.5 mm in diameter. Coagulant is added upstream of the clarifier allowing the coagulated particles to collect within the media bed. The Microfloc Adsorption Clarifier® utilizes only one screen on the top to restrain the buoyant media while the heavy media system utilizes retention screens at the top and bottom of the media.
The clarifier conversion was done during the summer/fall of 2007. To prevent capacity and operational disruption at the facility one clarifier at a time was converted.
• Existing upper and lower retention screens were removed.
• Heavy media was removed from the clarifier.
• New influent headers and laterals replaced the old headers and laterals for the influent water and air.
• Newly designed diffusers were installed on the air laterals and new supports for the Adsorption Clarifier retention screens were installed.
• The clarifier was filled with the buoyant media and held in place with new retention screens.
The conversion of the first retrofitted clarifier was initiated and positive results were immediately observed. Over the next few months the remaining clarifiers were retrofitted to the new design.
The retrofit of the heavy media clarifiers with the Microfloc Adsorption Clarifier® resulted in a "World of Difference" in the performance of the water plant in general as noted by the Plant superintendent. While flush cycles of the clarifier did not substantially change, dramatic reductions in clarifier turbidity were seen all across the retrofitted clarifiers. As the Microfloc Adsorption Clarifier® efficiently captures coagulated particles, filter runs were increased from a typical run of 40 hours to an excess of 100 hours. The end result was that the facility has seen a 40% increase in capacity with a 50% reduction of filter wash water.