Protecting liquid assets

Government and industry are so dependent on water that the efficient harvesting, storage and management of water is becoming a critical factor in the viability of existing and new development projects.

Government and industry are so dependent on water that the efficient harvesting, storage and management of water is becoming a critical factor in the viability of existing and new development projects.

Evaporation is the single biggest cause of water loss in open water storage facilities.

Rio Tinto and Nylex recently took up the challenge to solve the problem, and have introduced a device that is said to reduce evaporation from open surface dams and water storages by up to 85%.

Facing the challenge of managing water in a highly visible/water-intensive industry, Rio Tinto embarked on an ambitious project to develop an effective solution to reduce evaporative loses from the range of open water storage facilities associated with its mining operations.

The challenge was to develop a cost-effective product that reduced solar and wind evaporation, allowed rain to pass, maintained water quality, was easy to assemble and transport and be wind, hail and debris resistant.

The product trials, beginning in 2006 (and concluding in 2007), were conducted at Rio Tinto’s Northparkes Mine and were designed to demonstrate the ability of a modular system, designed to reduce water loss through evaporation, from a working mine.

With water losses of up to 75% through mining and processing operations, the reduction of the losses with evaporation was critical, as in many instances replenishment is achieved through the appropriation of fresh water from supplies shared by local communities, towns and other industry sectors.

With changing climatic conditions and increasing competition for this basic resource, Rio Tinto and other mines face the issue of harvesting, storage and management of water as critical investment considerations. Nylex worked with Rio Tinto to produce and prove a technology for evaporative loss reduction.

The result is the AquaCap, which the Nylex, the company that developed the technology, claiming an average reduction of water loss by 85%

The trial was monitored by The National Centre for Engineering in Agriculture (NCEA).

The product is a 1,150 mm diameter, circular, modular disc made of non-toxic, white polypropylene that floats, semi-submerged, on the surface of the water.

The surface of each disc is solar reflective and curved to reduce solar and wind evaporation.

When fully deployed, the circular discs cover up to 90% of the water’s surface, allowing sufficient natural light to penetrate and minimise ecological disruption, prevent the build up of hazardous gases, and maintain water quality.

According to the company, each stackable disc is self-cleaning and is UV treated.

The product is 200 mm high and weighs three kilograms, and is tested to withstand wind speeds of up to 130 km/h.

The product floats semi-submerged and is deployed in a modular array with external tether/anchor points at the perimeter of the array.

According to Nylex National Marketing Manager Colin Harvey, with the increased focus on the cost of water for industrial application, the use of the technology addresses four critical business issues including sustainability, risk mitigation, improved productivity, and reduced costs.

The initial concept was an element of PhD research at RMIT University in Melbourne Australia, and was subsequently developed by Rio Tinto Technology together with the Rio Tinto Foundation for a Sustainable Minerals Industry.

In trials conducted by the National Centre for Engineering in Agriculture (NCEA), a number of evaporation control technologies were evaluated.

The Independent report by the NCEA on the effectiveness of Nylex AquaCap Floating Module Technology at the Rio Tinto Northparkes Mine1 found that during the trial period the covered storage lost 210 mm in evaporation and the control storage (uncovered) lost 1,445 mm, resulting in a saving of 1,235 mm or an 85% reduction in evaporative loss.

For every hectare of water surface, this is equivalent to 13.0 ML per year.

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