Innovative Public/ Private Collaboration Integrates Resort Growth and Nassau, Bahamas Water Resources Management
Abstract:The Commonwealth of the Bahamas faces water resources management challenges due to on-going topography, climate, and demographic changes in its islands. In order to facilitate the demand for increased development and growth in tourism, the Bahamas Water and Wastewater Corporation (BWSC) has embarked on an innovative and collaborative public/private approach with developers to provide cost-effective enhanced wastewater treatment with utilization of the high-quality reclaimed water in lieu of potable water for greenscape irrigation. One such opportunity is with the well-known, highly visited resort area of Paradise Island. The collaborative effort offers possible private capital funding to assist in making the innovative project a reality. Chester Engineers was directed by the BWSC Board to work with its talented professional staff to determine the technical / cost feasibility of redirecting sanitary sewage flows from existing wastewater treatment facilities on Paradise Island to a new reclaimed water production plant to be located across the bay on the north coast of New Providence Island; then returning the treated effluent back across Potter's Bay to Paradise Island to be used for irrigation on the golf courses and other acceptable non-potable water needs.
Paradise Island has three wastewater treatment plants that are located just west of the Ocean Club golf course on the east side of the island. There is a concrete in-ground facility and two above-ground plants. Average wastewater flows (ADF) from Paradise Island were estimated to be 3.3mgd (2.75imgd). The proposed project will allow the land currently occupied by the Paradise Island wastewater treatment plants to be used for future resort development. The new reclaimed water treatment facility will also process wastewater that currently flows from the downtown Nassau and areas west and east along Bay Road to an existing treatment plant located in Malcolm Park. The existing Malcolm Park facilities are over 15 years old and have satisfied their intended service life.
Two advanced treatment alternatives were evaluated in the feasibility study and conceptual design report. The first was a“conventional activated sludge wastewater treatment”system. Required treatment steps included preliminary treatment, aeration, clarification, filtration, disinfection, effluent disposal, and solids handling. Due to the limited size of the proposed new plant site, several changes to the conventional design were necessary to save space. One of the more significant changes includes the use of a Vertical Loop Reactor (VLR). The VLR process was first introduced in 1986 and is useful where land area is limited, where biological nutrient removal is required, and when wet weather I/I flow rates are high and organic loadings fluctuate widely. The second alternative evaluated used an “immersed membrane bioreactor process (IMB)” that enables the facility to save even more space than achieved with the first alternative. All of the steps in the IMB process are the same as in the conventional activated sludge system except that membranes are used instead of clarifiers and filters to remove suspended solids from the final effluent.
In addition to the new reclaimed water production facility, the project will require two separate new force mains to transport wastewater from Paradise Island across the bay to the advanced wastewater treatment plant site and return the reclaimed water to Paradise Island for irrigation use. The primary use for the reclaimed water will be irrigation for the Ocean Club Golf Course and common green areas on Paradise Island.
The Engineering and Cost Feasibility Study produced for the BWSC presented conceptual designs developed for alternatives evaluated with associated capital and lifecycle costs for final design, construction and operation of the proposed new facilities for treatment at and conveyance to the proposed new plant site. Negotiations between the BWSC, the purveyor, and the private developer are underway to share equitably in the financing of capital costs and the recovery of O & M costs for the project.
The expected result will be the establishment of a state-of-the-art advanced wastewater treatment/ reclaimed water production facility that will offer Bahamians, tourists, and commercial businesses a more cost- effective water resources management means of delivering high quality effluent for irrigation in lieu of using more expensive, less abundant reverse-osmosis water needed for meet the islands potable water demand.
Document Type: Research Article
Publication date: January 1, 2008
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