Keeping cool, calm and hydrated underground

By Dineo Phoshoko

Working in an underground mine is one of the most dangerous jobs in the world; the possibility of a fatal rock fall underground is a reality faced by many mine employees, as is dehydration and heat stress.

Working in an underground mine operation is a very labour-intensive job in addition are the extreme and dangerous conditions faced by mine employees regularly. South Africa is known for having some of the world’s deepest underground mines, with depths of up to 3 000m.

The further you go underground can lead to extremely hot temperatures. Underground mines in South Africa can reach high temperatures over 40°C and these conditions can be physically taxing on the body, with a high potential of heat stress and dehydration.

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The Hydros 150-litre water purifier has an air-cooled condenser.
Image credit: MineARC Systems


In Petrus Schutte’s 2009 paper titled ‘Heat stress management in hot mines’ he explains that occupational heat stress is considered a health and safety hazard in South Africa’s mines. “The consequences of high occupational heat loads can be expressed in terms of impaired work capacity, errors of judgment with obvious implications for safety and the occurrence of heat disorders, especially heat stroke, which is often fatal,” he says.

Schutte explains that a review of the occurrence of heat stroke over a 10-year period shows that the origin of heat stroke is multi-factorial. “The main causal factors are interactions between strenuous work, suspect heat tolerance, excessively hot environments and concurrent dehydration. On the basis of this analysis, a basic framework with the following elements can be derived for work practices in ‘hot’ environments.”

Understanding and dealing with heat stress and heat stroke

The first heat stress related death in South Africa occurred in 1924, at a gold mine. After the fatality, the industry became proactive and took steps to address the heat stress challenge – with the introduction of heat acclimatisation in 1925. In his paper Schutte states that the, “Rudimentary method of heat acclimatisation was followed by a research programme aimed both at obtaining a better understanding of human heat tolerance and at developing improved heat acclimatisation procedures.”

According to Schutte, heat stress management (HSM) is one of the solutions to dealing with heat stress and heat stroke underground. He describes HSM as, “A multi-faceted approach to promoting health, safety and work performance through minimizing human heat strain and the incidence of heat disorders.”

Drinking water on mine sites

Access to clean and cool drinking water is one way mine employees can keep cool while working under extremely hot temperatures underground. Unfortunately access to quality drinking water on African mine sites is a major concern. A shortage of drinking water combined with high underground temperatures and a physically strenuous working environment can lead to dehydration and heat stress in mine employees. “Miners suffer high levels of dehydration and poor hydration is very common,” explains Mike Lincoln, MineARC general manager.

“Miners suffer high levels of dehydration and poor hydration is very common.” — Mike Lincoln

Chilled, treated water is essential for any underground mine operation, however the facilities and technology are not easily accessible. “An ideal system will be treated cold and readily available mine water,” Lincoln says. He also adds that on average, most mine employees consume between 3 to 5ℓ of water per shift, and up to 1ℓ per hour in mines with extremely hot temperatures. Many mine sites rely on bottled water or municipal water if available.

A new solution: Hydros Water Purifiers

One of the best ways to deal with heat stress underground is for mine employees to keep cool. While mine operators ensure that a mine has the required ventilation and cooling practices to ensure that there is sufficient air flow through the mine, geographical distribution of heat loads and micro-ventilation considerations, are properly dealt with. Although this is helpful, it is not enough to lower temperatures underground.

The new Hydros Water Purifiers from MineARC Systems address the issue of a lack of chilled treated water underground. Hydros Water Purifiers are designed to provide easily accessible, drinkable water – using either reverse osmosis or UV light filtration systems, depending on the site water quality and volume requirements.

Developed by MineARC’s R&D engineering team in Australia and Johannesburg, the water purifiers were officially launched in January 2018. A prominent South African refrigeration contractor was involved in the development of the water purifiers – making it possible for the units to be made in South Africa and exported globally. Lincoln explains that the purifiers were trialled and tested in various mines in Africa.

Reverse osmosis vs UV light filtration

Reverse osmosis (RO) is a technology that is used to remove contaminants from water by pushing the water under pressure through a semi-permeable membrane.

Osmosis is a process by which a weaker saline solution will display a natural tendency to migrate to a stronger saline solution. For example, if there is a container of water with a low salt concentration and one with a high salt concentration separated by a semi permeable membrane, the water with the lower salt content would begin to migrate towards the container with more salt.

The semi-permeable membrane is one that allows certain molecules to pass, but not others. RO is the process of osmosis in reverse. Energy (pressure) is required to force the concentrated solution through the semi-permeable membrane – leaving behind the majority of dissolved contaminants including salts and bacteria Nd pyrogens. The resulting, desalinated water is called permeate water and usually has about 99% of contaminants removed.

The UV light filtration system is designed for contaminants limited to bacterial concerns and where trace metals are negligible.

Ultraviolet (UV) water purification is an extremely effective method of removing bacteria from water. UV rays work to penetrate harmful pathogens within the water by attacking their genetic core, eliminating its ability to reproduce.

UV systems are environmentally safe and destroy 99.99% of harmful microorganisms without the need for chemicals. While effective for bacteria removal, UV filtration does not work to eliminate chlorine or heavy metals. Should sites require removal of such contaminants, reverse osmosis is the recommended alternative.

High and low volume water

Two options are available for the water purifiers: the Hydros 500 and the Hydros 150 water purifier. The Hydros 500 water purifier is ideal for high volume water requirements on site and can provide 500ℓ per hour of clean, chilled water. The Hydros 500 also meets the SANS 241:2015 standard on drinking water. The unit reticulates water from the tank, and then feeds the chilled water to multiple areas such as toilets, kitchens and ice machines as and when required.

The Hydros 150 also meets the SANS standard and also provides clean, chilled water. The difference with this water purifier is that it is more suitable for lower water volume requirements – with a size of just 650 x 650mm. The unit is ideal for drinkable water underground allowing mine personnel to refill on-the-go. Although the unit is smaller than the Hydros 500, the 150 is built to withstand the harsh underground mining conditions. It is very mobile and housed within a 304 stainless steel enclosure and includes an IP54 electrical rating feature.

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The Hydros 150-litre water purifier has an air-cooled condenser.
Image credit: MineARC System

Maintenance of water purifiers

Well-maintained equipment can usually last for a very long time in the mining industry and water purifiers are no different. “There is no reason if serviced regularly and not mistreated the water purifiers will last more than 10 years. We recommend a regular service that includes replacing water filters and checks of ultra violet or reverse osmosis units along with water tests to assure water quality is to South African potable water bottling standard SANS 241:2015,” says Lincoln.

According to Lincoln, Hydros water purifiers are different from other on the market because of the high-quality industry internationally recognised parts that are available worldwide, such as the stainless-steel compressors and switching components . “Hydros water purifiers are designed to not only maintain bottling standard water but importantly in high temperature mines deliver cold drinking water below 8°C at high volume 150ℓ per hour (Hyd-RO-150) and larger (Hyd-RO-500) at 500ℓ per hour,” Lincoln adds.

An added benefit is the purifiers can be used on open pit mine operations in addition to underground mine operations. Stephen Curry once said that, “drinking water is essential to a healthy lifestyle.” With the Hydros water purifiers, mine employees who work long shifts underground in scorching temperatures can have access to clean and healthy drinking water. This protects them from the dangers of heat stress and dehydration, in addition to maintaining a healthy lifestyle.

Hydros water purifiers quick facts

  • Air-cooled condenser and temperature controlled
  • Powder coated and Grade 3CR12 stainless steel enclosed unit
  • 240ℓ insulated integrated stainless-steel tank
  • Complete electrical panel with isolator and controls


‘Heat stress management in hot mines’ by Petrus Schutte.
‘The analysis of ventilation and cooling requirements for mines’ by J Van Der Walt.


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