Dauphin Island Reverse Osmosis Water Treatment Plant

Dauphin Island, AL

Dauphin Island Water and Sewer Authority (DIWSA) selected Ardurra (fka Constantine Engineering) to plan, permit, design, and manage construction of the new Well No. 6 and a new 1.3 million gallons per day (MGD) water treatment plant (WTP). The new WTP replaced the existing Dauphin Island water treatment plant, and included pretreatment, reverse osmosis membranes for chlorides removal, aeration for H2S and CO2 removal, new finished water storage, new high service pumping, and a new operations building.

Ardurra worked with DIWSA from the early conceptual design of the water production improvements that included the new WTP, a new 1,200-gpm raw water well, a new 1 million-gallon (MG) ground storage reservoir, installation of 6,000 feet of 12-inch raw water main and 21,000 feet of 6-inch, 10-inch, and 12-inch water distribution mains, and the decommissioning/demolition of the existing water plant. The new water plant had to be constructed on the same site as the existing plant while keeping all existing facilities in operation. Because DIWSA has no other source of water for the island’s customers, maintaining water service during construction and startup was critical. By careful planning, design, and construction management, Ardurra was able to complete the project on time, within budget, and without disrupting water service to the island.

Well No. 6 is a new source in the Deep Sands Aquifer in the western edge of the Upper Floridian Aquifer. Ardurra completed extensive hydrogeological studies and modeling for the Coastal Zone Permitting for the well. Other permitting included the ADEM Permit to Construct a Potable Water Well, ADEM Permit to Construct the WTP, SRF/ARRA permitting for Environmental, Historical, Archeological, and Fish & Wildlife, and Army Corps of Engineers Nationwide permit and Coastal Zone Management permit. The new storage reservoir is a 1.0 MG prestressed concrete tank with a degassifier for H2S and CO2 removal. The tank includes corrosion-resistant materials for the aerator internals and epoxy-coated tank interior. The high service pumps include two 40-Hp variable speed end suction centrifugal pumps at 750 gpm each, and one 75-Hp variable speed end suction centrifugal pump at 1500 gpm.

The new operations building was designed to house the RO membrane skids, the chemical storage and feed systems, the high service pumps, the electrical room, the SCADA/Control room, and a wet chemistry laboratory. The new plant also included a new 250-kw emergency power generator.

DIWSA financed construction of the facility through the State Revolving Loan funds as a part of the American Recovery and Reinvestment Act (ARRA). Ardurra assisted DIWSA through the complete loan process and provided technical assistance that helped to secure financing that included $4.2 million in grant assistance and $2.7 million in a low interest loan. Ardurra and DIWSA were committed to provide a low energy treatment facility. In an effort to provide an energy efficient, environmentally friendly and employee friendly work environment, DIWSA chose to pursue Leadership in Energy and Environmental Design (LEED) certification for the new WTP. The third-party certification process validates and quantifies energy efficiency, and environmental achievements, while allowing the building to model better building practices to the community. The new water treatment plant is a unique LEED building, in that it is targeting increased efficiencies in process loads as well as in the base building envelope and systems. With the energy modeling process in place, DIWSA has a metric to benchmark their energy use, and can measure the return on investment in energy efficiency and environmental upgrades.

The DIWSA WTP was the first LEED Silver-Certified municipal water treatment facility in the southeastern United States. All materials and installed equipment used in the facility are American made as defined by the ARRA.

Project Highlights