"Providing Innovative Water and Wastewater Solutions"

EXAMPLE: RO System Diagnostics & Operating Solutions - St. Lucie West Utility Service District

Project Status: Design Build Solutions Completed 2007

The St. Lucie West Service District consist of a 4.0 MGD Reverse Osmosis Water Treatment System which is supplied by way of three deep Floridian Aquifer wells with a permitted capacity of 3.4mgd. U.S. Water Services Corporation (USWSC) was retained after the facility went into operation, due to start-up and operating problems which was impacting water quality stability. The project costs for construction were substantial and shortly after going on-line the District began taking exceedences for lead in the drinking water. USWSC provided an on-site, hands-on process evaluation of the calcite media to determine solubility and a design-build solutions to correct the malfunctioning units. The problem of lead exceedences in the water supply was highly publicized in local newspapers and became a significant regulatory and community issue. USWSC mobilized the necessary personnel resources with the required technical and operational experience to both diagnose and correct the operational problems. Although the primary cause of lead being dissolved into the water supply was due to improper stabilization and buffering of the finished water, there were numerous technical and design issues impacting the operation of the facility.

Troubleshooting, diagnostics, re-design with installation and repair oversight was provide by our engineering department. Additionally, USWSC provided an overall RO system evaluation, operator training, revised O+M manuals, revised SCADA controls, design/build of a polyphosphate feed system and performed various repairs and redesigns to the system hydraulics. We are proud to say that the system is now performing well. USWSC continues to work for the District providing consultation support and technical resources to the ongoing utility operations as needed.

Examples of redesign and corrective measures by USWSC impacting the St. Lucie West WTF:

Calcite Contactors:
Calcite Contactor calibration and process control, which consisted of installing calcite bed depth indicators, flow meters for each contactor, and installation of sample taps that allow the performance of each calcite contactor to be measured and thereby allowing improved operator process control prior to distribution.

Sulfuric Acid Tank Replacement:
Replacement of the bulk sulfuric acid storage tank due to corrosion that had occurred.

Polyphosphate Chemical System:
As a result of the lead and copper exceedences, a polyphosphate chemical feed system was installed to help stabilize the product water. This permanent system consists of three variable speed chemical feed pumps and a new fiberglass chemical building that includes containment, and replaced the district installed single chemical feed pump. The new chemical feed system also provides redundancy to the treatment process in the event of a pump failure.

Installed Rupture Disks:
USWSC installed two rupture disks that are designed to prevent damage to the membranes due to a sudden or unexpected pressure increase. The rupture disks are designed to “rupture” at a pressure prior to membrane damage.

Process Flow Diagram:
USWSC provided an updated process flow diagram of the WTP.
 

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