Keeping the water supply safe is a responsibility the Mount Isa Water Board takes very seriously.
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The Water Board runs two main pieces of water infrastructure in Mount Isa, the water clarification system at Lake Moondarra and the reservoir on May Downs Rd. Together they form what MIWB CEO Stephen Farrelly calls a “natural system combined with a space age facility.”
The water clarification system is a unique system based on natural processes at Clear Water Lagoon adjacent to Lake Moondarra.
Originally Mount Isa’s water came straight out of the lake but during the rainy season the river water was highly turbid (cloudy) so in the 1960s Mount Isa Mines looked at establishing a water treatment plant, and recommended a clear water lagoon as a separate reservoir. The lagoon was installed in the 1970s and aquatic plants act as sedimentation plates keeping turbidity low.
MIWB continues to use Clear Water Lagoon to perform primary water treatment for supply to industrial customers and as pre-treatment before filtration.
Today the Clear Water Lagoon holds 2400 ML of water (Isa uses up to 27ML a day) and is only topped up from the Lake when the turbidity is low.
Water is pumped from Lake Moondarra into the Clear Water Lagoon via the Pontoon Pump Station or from Lake Julius via separate pump stations. Water first enters the flume where it runs over rocks and aquatic plants which aid in the initial filtration, aeration and oxygenation of the water.
The water is channelled into settling pond where solids and dissolved matter are filtered and absorbed by rush grasses and a weed called hydrilla. From the settling pond water enters Clear Water Lagoon where it resides for about three weeks allowing contaminants to settle.
The Lagoon is still recovering from an outbreak of blue-green algae in 2013 which triggered the water board to commence filtering the water. MIWB CEO Stephen said they remove any blue green toxins prior to filtration via oxidation.
Water from the Lagoon is pumped to town via a station named for former MIM power and water manager Col Popple.
The water is pumped to the Mount Isa Terminal Reservoir where it is chlorinated three times before it is delivered to Mount Isa Mines.
Water for the city requires further quality assurance and MIWB has installed a state-of-the-art $9m membrane filtration treatment plant opened in 2015 where CEO Stephen Farrelly says “this is where the magic happens”.
The filtration plant filters any remaining blue-green algae by putting water through a one tenth of a micron sieve which can provide 30ML of filtered water a day to Mount Isa City Council.