Why might Denmark need these units?
During the year salinity levels in the Denmark River vary, depending on the season and the amount of water flow in the river. During times when salinity levels are higher, the water needs to be treated in order to supplement the town’s drinking water supply. Portable desalination units can be used to ensure the water quality meets Australian Drinking Water Guidelines (ADWG).
Water Corporation is yet to operate the portable desalination units.
What is brackish water?
This desalination process produces rejected brackish (slightly salty) water as a by-product that consists of the salts naturally found in the Denmark River. The treatment process also uses a small amount of standard water treatment chemicals, including anti-scalant, which are approved by the Department of Health for use in drinking water.
Total dissolved solids (TDS) are made up of inorganic salts (calcium, magnesium, potassium, sodium, bicarbonates, chlorides, and sulphates) and small amounts of organic matter dissolved in water.
How will the desalination units operate, if required?
The desalination units are located at the Denmark Water Treatment Plant, adjacent to the Denmark River Dam. The treatment plant consists of 3 reverse osmosis (RO) units. The number of units required for operation is dependant upon different factors. The number of RO units operating will depend on the amount of water needed to supply Denmark. So, in low supply time, only 2 RO units will be needed, and in high demand times all 3 RO units will run. At full production of all 3 units, the units can produce up to 95% of treated water required to supply Denmark.
How long will Water Corporation run the desalination units?
The desalination units will run for as long as required to ensure Denmark’s drinking water meets (ADWG). Water Corporation aims to minimise the need to run the desalination units by using a combination of Quickup Dam and Denmark Dam water.
How much does it cost to run the desalination units?
It is estimated that it will cost around $1,000–2,000 per day depending on how the units are being operated. Water Corporation always aims for cost efficiencies.
How much energy do they require?
The average operating energy for running all 3 RO’s is 50.5 kilowatts per hour. This is about the same energy for a family-sized refrigerator to run for a week (https://www.keysenergy.com/appliances.php).
Where else are desalination units used in WA and how is brackish water disposed of?
Portable desalination units are used all over WA for both seawater and brackish water including Hopetown, Leonora, Gascoyne Junction and Yalgoo. The brackish water is disposed of by ocean outfall, evaporation ponds, infiltration and is reused for mining operations.
How much brackish water will be produced during treatment?
It is estimated the amount of brackish water could be up to 60–100 thousand litres a day. The amount of water produced will vary depending upon the salinity level in Quickup Dam and how much water is required to supply the down. The comparative volume of brackish water disposed of each day is about the volume of a large backyard swimming pool.