Water Treatment:
Using Natural Resources as an Integral Part of Filtering
By Owen Waters
When I was growing up, I lived in and visited countries where water was considered a precious resource. The lack of it made for eyesores that were justified—water treatment plants—giant colossal vats converting seawater into fresh drinking water, capable of providing water to societies. Manmade oases in a land surrounded by water, similar to the BVI.
We first encountered Rob Wassell of Caribbean Technology in the June issue of Property Guide, when we looked at the extensive water treatment plant at Nail Bay on Virgin Gorda. More recently, Robb and his engineer Calvin Williams took me to Long Bay Beach Resort at West End to look at their beach well system and reverse osmosis plant that uses minimum energy to produce enough water for the resort. I was impressed.
Tanks with fine-graded sand creating natural filters for passing Atlantic water. All photos by YachtShotsBVI.com
ADVERTISEMENT
Property Sales
Standing on the mile long beach with Yacht Shots photographer Brynley Rathbun whilst Calvin talked about the sunken beach wells, and as he said, “I think they are somewhere around here,” fascination took in at the underground wells that draw water through sand and that is then drawn up into the plant. The sand is the key concept. Sand has long been used as an abrasive natural filter. As Calvin pointed out, “Most living organisms won’t get through sand, and only water and minerals will get into the plant treatment room before it then goes through a series of finely graded media layers housing various gradients of sand to pass through a filtration system. From there into a carbon filter, and then the pumps will come into action.”
Caribbean Technology particularly prides themselves on energy-saving techniques. The emphasis, as Rob states, “is on efficient modular package plant with low maintenance and the minimum of operator training and supervision required.” Installed at Long Bay resort is the ERI PX pressure exchanger, an energy recovery turbine capable of converting water from the four beach wells that take the Atlantic’s finest and boosts the main water pump with high pressure, using minimum electricity, and then adds product water into the resort at 50 gallons a minute and then releases brine back into the sea. For a regular pump to be capable of this would require another plant room bigger than the one we are in, which if anything seems spacious. This is the latest technology in reverse osmosis, and though Long Bay used to use town water and rely solely on grid electricity, the combination of generator and new water treatment plant has saved them a small fortune. As those of who live in the BVI count as a blessing, it never and literally never runs out. (I happily secured a good hot shower, movie and a hot meal at Long Bay during Hurricane Earl.)
Bad weather does have its impact on the systems. Low tides and strong swells will affect the beach wells and ultimately make the pressure low. Pumps with turbines or impellors will run at 15,000 rpm. Add the electricity bill to that, and you might start to see the headache of providing water effectively. The PX exchanger has a ceramic rotor, and the model I saw was about 5 feet long and housed 3 feet or so, which tells me must be a budget’s dream.
To explain further how the device works, Calvin talked me through the flow of the water from the beach to the taps. The PX harnesses the power of the reject brine and boosts energy into the main pump and can reduce the main pumps size by up to 60 percent. Therefore, the energy passes through the ceramic rotor and then by boosting high pressure splits at required forces the fresh and rejects waters to their designated areas once through the system with less effort than standard pumps. The significant difference to conventional plants is that the main high pressure pump can be downsized by utilising the stored energy in the brine stream. Mixing of raw water and brine is avoided by maintaining accurate flow settings.
ADVERTISEMENT
Once installed, parameters are set on a daily and weekly inspection by the Caribbean Technology engineers. For the most part, as Calvin points out, things are usually in order with a safe water product and the system running efficiently without having to replace burnt out pumps or waiting on their parts. Due to the energy displacement and use of as much natural resources as possible, the investment in the equipment is rewarding. This is a key aspect of Caribbean Technology’s philosophy of supplying to the islands—that they have a firm understanding of the frustrations of importing and transporting equipment that has longevity and is energy efficient. On an island that still counts water as a contemporary issue, don’t expect to go short where Caribbean Technology has been installing their products, and don’t expect that technology to be seen or heard.
