Hamilton Island

Location

Hamilton Island is a medium sized Island in the Whitsunday's group of Islands. The Island infrastructure comprises a large Resort complex, a number of condominiums and small businesses. Population varies between 2000 and 5000 depending on holiday seasons.

Plant Design

The plant was designed to provide 1.3 ML/day of potable water with <400 ppm dissolved salts with supply from a seawater intake. Seawater pick up was from two vertical turbine pumps installed on a purpose made jetty.

To address the issue of organic matter causing cloudiness in the water and the propensity for high levels of coral polyps at certain times of the year, Ausmos engineers used a coarse self backwashing screen filter followed by a foam fractionation column (this device is used successfully in marine aquariums to remove protein from seawater).

The foam fractionator comprises a 900 mm diameter by 5 meter tall fibreglass tower where the seawater is introduced in a downward direction and a mixture of fine air and low levels of ozone are introduced at the bottom. The foam produced is concentrated in a cone at the top and isdecanted to the desalinator reject outfall line. The foam fractionator exceeded all expectations removing virtually all-visible organic suspended matter.

The fractionated water is then passed to a 10,000-litre break tank to provide sufficient time for the ozone to disperse and additionally allow some buffering for the flow interruption during screen filter backwash. This water is then pumped through two banks of filters each comprising four 1100 diameter sand filters and four 1100 diameter carbon filters, followed by two banks of cartridge filters each comprising four vessels in each of which were eight 40" 1 micron cartridges and from there into two interconnected 10,000 litre break tanks.

Four independent low-pressure boosters then pump the final filtered water to four PEI high-pressure turbine pumps and energy recovery turbine boosters each feeding a bank of 30 8" high rejection seawater membranes fitted in 5 x 6 long vessels. The PEI pumps operate at 45 bar and the additional required membrane operating pressure boost to 61 bar is achieved entirely by the PEI purpose built energy recovery turbine that provides both the boost and backpressure control.

The filtered seawater fed to the membranes is divided by the membranes into two streams, permeate or treated water stream and a reject or wastewater stream. The recovery ratio between permeate to reject is 30%. The permeate quality is < 450ppm.

Permeate or treated water is then discharged to the island's existing storage tanks where it is chlorinated prior to distribution. The reject is discharged to a pit where it gravitates to an ocean outfall well away from the seawater intake.

The control system was, at the time of installation in 1996, a world first for this type of plant, in as much as it was possible to remotely monitor and control the entire plant from anywhere in the world.

Features

• Full PLC controls.
• Remote monitoring control.
• Ease of monitoring and operation.
• Reliability and durability - operating successfully since 1996.
• Quality components & construction which minimize repairs and downtime.