The American Water Works Assn. (AWWA) announced the launch of its new ...
The state of Florida’s population is growing by more than 1,000 people per day. This phenomenal growth is certainly beneficial to the state’s economy, but it comes with a demanding toll on precious natural resources. Every person and business that migrates to Florida is competing for the finite supply of fresh water.
Traditionally, the primary source of water has been groundwater; however, the state of Florida has shown a great deal of foresight in encouraging the development of alternative water supplies to meet the ever-increasing water demands. Reclaimed water is one of these alternative supplies and the state of Florida is the nation’s leader in reclaimed water usage. More than 60% of all reclaimed water in the state of Florida is being used for agricultural and landscape irrigation, with the balance used for groundwater recharge and industrial use.
The Challenges of Going Alternative
Located in Palm Coast, Fla., the Dunes Community Development District is comprised of Hammock Dunes, Island Estates and Ocean Hammock. This rapidly growing residential and golf course community is bound by the Atlantic Ocean on one side and the Intercoastal Waterway on the other. The 2,120-acre development is an example of the efficient use of reclaimed water. The Dunes Community Development District supplies reclaimed water for irrigation to residential and common areas as well as two golf courses. Total usage is approximately 690 million gal per year (1.9 million gal per day). The reclaimed water is provided by the nearby wastewater treatment facility, Dunes Utilities. The reclaimed water coming from Dunes Utilities flows into three lined reclaimed storage ponds, and is then pumped throughout the purple reclaimed water piping system by three irrigation pump stations.
Properly filtering the reclaimed water proved to be a major obstacle. As the reclaimed water flows into the open ponds, the water quality significantly deteriorates when exposed to sunlight and the open atmosphere. One can commonly find sediment, algae, snails, mussels, bloodworms and other creatures present in reclaimed water ponds. Other than a coarse strainer, there was no filtration equipment previously installed on the system, resulting in constant sprinkler plugging. The first step towards resolving the problem was the installation of manual filters in 15 zone locations. This solved the problem of sprinkler orifice plugging; however, the manual filters proved to be labor-intensive, sometimes needing to be cleaned on a daily basis. Dunes Utilities sought out various filtration technologies that would handle the water quality present in the reclaimed water holding ponds while minimizing manual maintenance.
The filtration system was designed and manufactured by Miller-Leaman, Inc., Daytona Beach, Fla., which manufactures a range of filtration products, including a fully automatic, self-cleaning disc filter technology called the Turbo-Disc Filter. This filter is well suited for organic contaminants typical of open reclaimed water ponds (and surface water applications in general) because the filter media is three-dimensional unlike a screen filter, which is two-dimensional. As water passes through the disc media, the depth of the discs captures the soft fibrous contaminants, which can extrude through a two-dimensional screen filter. As the differential pressure across the filter system reaches an adjustable set point, the Turbo-Disc Filter goes through a backwash cycle, sequentially flushing each filter housing until the entire filter system is clean.
Centralizing the System
Initially the plan was to install 15 automatic Turbo-Disc Filters to replace the various manual filters at each zone location. After further discussion, it was concluded that a large central filtration system was the most cost-effective approach. In an effort to familiarize the Dunes with the filter technology, Miller-Leaman transported their fully operational demonstration trailer to the site. The demo trailer has the ability to pump water from the actual water source to determine the solids’ loading (ppm), the particle distribution size and other important variables. The filter housings in the demo trailer are transparent, allowing the customer to visualize the effectiveness of the filter, both in filtration and backwash modes.
After the demonstration, Miller-Leaman worked with Dunes personnel to properly size the system, as well as customize it for their needs. For example, because of the proximity to the ocean and the corrosive environment it presents, all the manifolds on the filtration system were fabricated out of Type 316 stainless steel versus standard Type 304 stainless construction. The system was also designed modularly, so it could be expanded over time as the Dunes development grows and the reclaimed water demand increases. Miller-Leaman was also contracted by the Dunes to fabricate custom stainless steel manifolds, allowing additional Turbo-Disc Filter modules to be added over time. The first system was designed to accommodate 3,000 gpm; since then an additional filter module has been added to accommodate the current demand of 4,500 gpm.