Click the icon below for detailed area map of water and electricity services currently available (before RO) in the Port St George and Stella Maris.
Drinking water solutions for the resorts of Port St George and Stella Maris, Long Island, Bahamas.
Reverse osmosis water purification units. These units use a membrane that is semi-permeable, a semi-permeable membrane is a membrane that will pass some atoms or molecules but not others. The membrane allows fluid that is being purified to pass through it, while rejecting the contaminants that remain. Reverse osmosis filter systems will allow the removal of particles as small as ions from a solution. This reverse osmosis process is used to purify water and remove salts and other impurities in order to improve the color, taste or properties of the liquid.
How reverse osmosis works. Water molecules are forced through a 0.0001 micron semi-permeable membrane by water pressure. Long sheets of the membrane are layered and rolled up around a hollow central tube in a spiral design. This rolled-up configuration is commonly referred to as a spiral wound membrane. The membrane is placed in a housing unit to maintain the membrane pressure. This pressure supplies energy to force the water through the membrane, separating it from unwanted substances.
If the water pressure is low, then the process of reverse osmosis requires a driving force to push the fluid through the membrane, and the most common force is pressure from a pump. The higher the pressure, the larger the driving force. Also, as the concentration of impurities in the water increases, the driving force required to reject the impurities needs to be increased. Substances that are left behind are automatically diverted to the waste drain so they don't build up in the system as with conventional water filtering devices. This is done by using a part of the unprocessed water (feed water) to carry away the rejected substances to the drain, keeping the membrane clean.
Reverse osmosis drinking water systems will allow the removal of particles, as small as ions from a solution and is capable of rejecting bacteria, salts, sugars, proteins, particles, dyes, and other constituents. Reverse osmosis filtration systems are used to purify water and remove salts and other impurities in order to improve the color, taste or properties of the fluid. It is applied to water purification and desalination, waste material treatment, and many other chemical and biochemical laboratory and industrial processes.
Here are a few photos of commercial RO units, plus a photo of the raw unprocessed water typically found here on the Out Islands of the Bahamas.
The following text is taken from a recent survey of the groundwater situation in the Port St George and Stella Maris areas of Long Island.
The ultimate source of all natural drinkable water on the Earth is rain, which is rarely used as a direct source, with the exception of certain islands situated in salt water environments.
The Caribbean islands, areas of Central, Southern and Northern America are forced to rely on rainwater as their only source drinking water.
Bermuda is a good example of this shortage. Historically there the rain is collected and led into cisterns to serve as the islanders' only available water supply. In an effort to improve matters, the Bermudan government have recently (October 2006) employed a Grand Cayman company to construct a seawater osmosis (desalination) plant near Tynes Bay. When finished this plant (500,000 GPD) should ensure fresh, clean drinking water for the entire island. By comparison, groundwater resources in the Bahamas have always been easy to exploit, and regular usage dates back to the earliest settlers. Today, in some areas, water is still privately obtained by bucket from shallow hand-dug wells. Public supplies are obtained from mechanically cut trenches, pits and seasonal freshwater marshes. Owing to the lack of rivers on these islands, fresh or brackish water can be still be found by the drilling of wells; in the latter case a simple RO unit is suggested to improve quality.
The Bahamian islands and, of particular note, the northern end of Long Island have an abundance of fresh potable water. This is due the island's geological limestone and coral formation.
The Stella Maris well fields (located adjacent to phase 2 section 3) are a valuable asset to the area. This natural source is easily and economically accessed utilizing simple well methods. "Town water" (see note below) is currently piped across a large section of the sub-division and could be distributed to most other areas without excessive cost should the requirement arise. However, town water, while a welcome addition, is not the most common form of supply. Rainwater catchment cisterns (see below) also commonplace throughout the island.
In practice a mix of rainwater catchment, town water, wells and in recent years reverse osmosis units are used, usually in a mix, to provide the best freshwater solution on a case by case basis. There are no areas of the Stella Maris sub-division where it would be impractical or economically enviable to use a mix of these to service a development, although the actual mix should always be decided upon according to the individual lot.
Given the many water extraction options available on this island, we have to report that the piped town water option would not be our favoured one. The reason for this is simply that the piped water has an undeniable saline flavour to it. This taste is due to the water being pumped directly from the Stella Maris well fields, and these fields are of sufficient size to make capping impractical. However a small private bore-hole can be very easily and economically capped and the resulting taste of capped well water is far superior.
Town water should not, however be dismissed, as it is perfectly acceptable for bathing, cooking and other domestic chores which involve the quality, but not the actual flavour, of the water. Connection to the town water distribution system often remains worthwhile, especially where the development of a small group of houses is taking place. Such connections would prove to be viable and cost effective.
However, the running of pipe work to a single dwelling may prove undesirable depending on the location of the building. A far more practical alternative would be to use the town water supply only as and when any area is developed with multiple constructions and rely upon a combination of the other sources for more isolated developments. Any group of 5 or more homeowners should find the inclusion of the town water supply in the mix to be a sensible decision.
Alternative extraction methods and approximate costings.
The traditional method (suitable for low lying land only) is a time honoured method, which dates back to the old "plantation days". It is a very simple, but effective way of well construction. It needs only one man who is armed with a long, heavy steel rod. He continually taps away at the limestone base and this constant tapping creates small seismic cracks. The stone collapses in onto itself, ever deepening. This tapping is maintained until he reaches clear and fresh water. This usually takes around 3-4 days and the cost is +/-$300 per day.
The more modern method of well construction involves drilling, using specialist boring machinery. The equipment, machine and operator are available on the island at a cost of around $1,000 per day (which includes transport to and from the site). The cost of a residential well will vary according to depth and can be calculated as approximately $25 per foot of depth with a minimum of $500. This figure includes capping, but excludes any piping, pumps and electrical connections which average $3000 per well. Each well would be capable of serving a number of dwellings and with some central co-ordination of the drilling work the cost per connection works out to be reasonable.
Note: Backhoes (JCB's) are also widely used throughout the islands for well excavations, but this type of machine would be a secondary choice as the finished well would be a very wide one (6-8 ft to allow for the movement of the excavating arm). The cost and duration of hire of a backhoe is similar to that of the specialist boring equipment mentioned above.
Also worth noting is the fact that in the flat and low land areas it may be necessary to drill a mere seven feet to access the fresh water table. A large amount of the high elevation lots we surveyed also contain water "bulges" and the depth of drilling needed from high land can, in many cases, be much less than the level of the low land.
The sub-division has a very sensible clause within its restrictive covenants making the inclusion of a rainwater catchment tank mandatory for all dwellings. Our recommended size for a residential cistern would be around 3,000 gallons, as water delivery trucks usually carry around 2,000 gallons. An average two or three person household would be expected to consume between 1,500 to 3,000 gallons of water per month.
As catchment tanks are normal in this part of the world the cost is usually included in most construction quotes at approximately $2 per gallon for a concrete tank. These tanks do of course allow any building to rely solely upon rainwater collection and delivered water if so desired.
Multiple abstraction schemes are used in the Bahamas for the extraction of ground water. Our primary recommendation for residential consumption in this particular area would be the use of bore hole wells (dependant on elevation) combined with catchment tanks.
However, as the water table here has a shallow depth, often around 1.5 meters, the drilling of wells on certain high ground areas may be impractical. In this case we would recommend a catchment tank system combined with water delivery.
Where multiple homes are planned, a connection to the town water system would be worthwhile to provide backup for domestic tanks.
The electricity supply situation in the Port St George and Stella Maris area of Long Island, Bahamas.
The supply of mains electricity around the existing sub-division is more than adequate as the power grid covers most of the main residential areas. The only recommendation we make is that the supply be laid in the various roadways as and when development takes place. This will avoid possible storm damage to overhead supply cables, given the extent of the current power distribution this should be a quick, easy, cost effective installation.