Tahmoor Coal wins 2014 PACE Water and Wastewater Award

PACE Zenith Awards 2014: Water & Wastewater Award sponsored by Bürkert Fluid Control Systems

WINNER: Tahmoor Coal (Glencore)
Tahmoor Coal Recycled Water Treatment Plant

Tahmoor Colliery is an underground coal mining operation situated in the Southern Highlands region of NSW, approximately 75km south west of Sydney. 

Tahmoor Colliery has historically purchased approximately 1.5 million litres of potable water per day from the Sydney Water main supply system, for virtually all underground and most surface processes, including all cooling and dust suppression water which are significant points of use). 

During the peak of the drought in 2006, Tahmoor Colliery was named in Sydney's top ten water users on the front page of the Sydney Morning Herald.

At that point, with Sydney's water supply dams at record low levels and residential water restrictions were in force, there was strong pressure from Government for industry to reduce water use.

The initial proposal to recycle water at Tahmoor was to utilise a reverse osmosis (RO) plant to treat mine waste water, and to produce approximately 1 million litres of potable grade water per day to offset the mine's existing water purchases.

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Tahmooor Coal project managers inspecting the recycled water treatment plant.

Detailed review of this concept revealed a significant increase in electricity consumption, and a brine waste stream that could only effectively be disposed by road tanker haulage to an ocean outfall. 

The Tahmoor Environment and Community team developed an alternative concept, which was more sustainable, producing fit for purpose water, with lower capital and operating costs, significantly reduced energy requirements, and no community impacts from increased road traffic. It is this improved system which has now been commissioned.

The treatment plant design involves utilising a clean stream of high quality groundwater from the base of the No.3 Ventilation Shaft approximately 450m below the surface.

Historically this clean water stream (approximately 1 ML/day) had been mixed with process water from the underground operational areas, and pumped to the surface sedimentation ponds to form part of Tahmoor's daily 3-4 ML/day mine discharge stream to the Bargo River (in accordance with mine dewatering licences and the site Environment Protection Licence). 

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The Recycled Water Treatment Plant utilises a simple and sustainable low energy water treatment process to produce fit for purpose water to the mine.

By separating the No.3 Shaft water, a fairly simple aeration, precipitation and filtration system was developed and installed to meet an output design specification recommended for industrial applications such as dust suppression and machine cooling (without risk of causing scaling and calcium build up in equipment). 

The project involved the construction and commissioning of a 1 ML/day Recycled Water Treatment Plant and two 250,000 litre concrete water tanks to provide a balanced supply of treated water to the underground mine. The fully automated system includes in-line real-time monitoring, which is monitored via the mine's computer control system (Citect SCADA).

The Recycled Water Treatment Plant has offset Tahmoor's daily potable water consumption by approximately 1 ML each day, utilising a simple and sustainable low energy water treatment process to produce fit for purpose water to the mine. 

The immediate benefit from the introduction of the water recycling system is the direct offset of purchased fresh water by recycled mine water.

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The treatment plant is saving the operation approximately 1 million litres per day – an operational cost saving of around $620,000 per year to the mine.

The operating cost of the treatment plant is less than the cost of purchasing water (approximately $150,000 per year). 

The capital cost of the plant has been assisted by a $2,000,000 Water Savings Funding Agreement with the Office of Environment & Heritage. The former waste water stream that was discharged to a local water course will now substantially offset fresh water purchases for the life of the mine.

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