UV disinfection

For drinking water for semi-arid island

Advanced ultraviolet water treatment technology being introduced to Australia by CST Wastewater Solutions has demonstrated its potential for applications here after being installed on a semi-arid Caribbean island.

Ten of Berson’s InLine UV disinfection systems were installed on the island of Aruba, where eight systems are used to disinfect drinking water and two are used to treat greywater prior to discharge.

The island opted for UV instead of chlorine as part of its ‘non-chemical’ approach to water treatment, says CST Wastewater Solutions Managing Director Michael Bambridge.

Five of the Berson UV units are installed at the Balashi water treatment plant, the site of gold mill ruins near Aruba’s capital, Oranjestad. Operated by WEB Aruba, which supplies drinking water and electricity to the island’s residents and businesses, Balashi also houses the world’s second largest desalination plant. Because Aruba has a semi-arid climate, desalination is necessary to supply its growing population with much-needed water.

Following the desalination process, the water passes through the UV systems before being transported to seven storage tanks situated at elevated locations around the island. The UV units, which are installed outdoors and controlled by DGtronic microprocessors, each disinfect 400 m³ of water per hour, rising to 600 m³/h during peak flow conditions.

No chlorine is used at any stage of the water treatment process. Chlorine was originally considered as an alternative to UV but was rejected after concerns over costs and safety. WEB Aruba also has an anti-chemical policy.

Two of the seven storage tanks situated around the island are also fitted with Berson’s InLine UV systems, providing an additional disinfection step prior to distribution. It is expected that all the tanks will eventually be fitted with UV. One of the storage tanks is situated in the harbour and supplies cruise ships with UV-treated drinking water.

In addition to disinfecting drinking water, two Berson UV systems are also used to treat greywater. One unit is installed at each of the island’s two wastewater treatment plants and the treated greywater is used to irrigate the island’s two golf courses.

Berson’s compact InLine medium-pressure UV systems use MultiWave lamps, which emit a wide spectrum of UV wavelengths with a very high energy output, causing the total and permanent deactivation of microorganisms. The small size of the lamps means that they are positioned perpendicularly to the flow of liquid, increasing disinfection efficiency and reducing the overall size of the disinfection unit.

Berson’s InLine+ medium-pressure closed vessel UV systems recently became the first in the world to gain formal approval for wastewater re-use applications. They underwent extensive third-party testing by Carollo Engineers in the US before being formally approved for post-filtration and reverse osmosis applications by the California Department of Public Health (Title-22 validation). The systems are now validated for wastewater re-use applications in accordance with AwwaRF/NWRI guidelines, which are internationally respected and some of the toughest in the world, says Bambridge. The guidelines are also the only ones offering guidelines on sewage treatment, which is a key factor in Australia.

“The Berson technology used on Aruba clearly has potential in Australia as well, because we not only have the same pressures on water in semi-arid areas, but also are looking increasingly to desalination as an alternative source of water supply.”