Propeller Meters Stand Up to Harsh Source Waters

The City of Titusville, Fla., located on the east-central coast of the state is surrounded by many amenities including the Kennedy Space Center, Indian River Lagoon, and the undeveloped, pristine Canaveral National Seashore.

In spite of all of the natural beauty, geography has thrown a twist into the citys Water Resources Department: the local aquifer is shallow and isolated from the deep, fresh Floridian aquifer found inland. The high iron levels found in the area have long presented a maintenance problem for the city due to clogging of well screens, piping and meters.

Until recently, the city of Titusville Garden Street Water Plant used a combination of venturi and temporary propeller meters to record and monitor well flows. These meters were in constant need of maintenance due to the high iron deposit rate. In 1996, the city decided to construct 14 new replacement wells and abandon the originals. Bids were procured and due to the high cost, it was decided that the city would re-engineer the project and complete all construction internally with the exception of well drilling.

A project team was formed consisting of the City Water Production Division, Well Water Systems Inc. of Fort Myers and Barnes, Ferland, and Associates of Orlando. When selecting the well meters, it was decided that a propeller meter with a polyprop would be used in the hope that the iron deposition would not maintain adhesion to a high degree.

The McCrometer MW500 series was selected for its prop style and material, along with integral straightening vanes, instrument interface and relatively low cost. The McCrometer engineering team worked with the city to select the correct characteristics for the application. The meters were installed over a period of two years as the wells were completed.

A telemetry system was incorporated to provide control and monitoring of the wells from the Garden Street Water Plant. The plant operator can monitor the flow, pump status, water level, intrusion alarm, and voltage/phase status from a computer screen in the control center. An actuated butterfly valve was added in the discharge piping, allowing the computer to restrict flow when the pumping level begins to approach the top of the well screen. Use of the flowmeter ensures adequate flow for proper pump and motor cooling.

This arrangement has reduced iron bacteria colonies which were causing clogging of the well screens. (This effect is thought to be produced by avoiding exposure of the screens to air via heavy drawdown.) Maintenance intervals have increased significantly, reducing costs and equipment downtime. Sampling of the McCrometer flowmeters has indicated very little iron deposition, and the meters have exhibited no degradation in performance.

The wellfield project was completed ahead of schedule, and below the original low bid cost.