Fugitive dust management

A few interesting articles from Mining Weekly (please follow the links to the original articles) regarding dust and waste management.  Enjoy the read!

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Comprehensive package facilitates fugitive dust management – Mining Weekly
BY: TASNEEM BULBULIA 18th May 2018

“Fugitive dust emissions pose risks to mining companies, surrounding communities and the receiving environment, and require proper management to mitigate their effects, and environmental management company I-CAT is well poised to do so through its comprehensive solution offering.

I-CAT Environmental Management and Consulting divisional manager Leon Janse van Rensburg says fugitive dust emissions are inherently part of the mining industry, owing to the nature of mining activities, such as blasting, minerals processing activities and fugitive dust emissions emanating from haulage roads. Emissions are especially prevalent in opencast mining and associated activities, the processing of raw mine materials using crushing and screening plants, and on waste rock dumps or mine tailings through windblown activities.

While not the biggest contributor, dust emissions contribute to the overall ambient PM10 (the fraction of particulates with a diameter of 10 μm or smaller) concentration in the atmosphere. Therefore, it is still a problem that should be properly managed, Janse van Rensburg emphasises.

In terms of the environmental impact of dust emissions, dust particles can become entrained in the atmosphere, resulting in the quality of ambient air decreasing and, in some cases, cause visual impairment near the source of emission. Further, surface waterbodies can become contaminated by dust particles settling on the surface, while the biodiversity of fauna and flora in areas surrounding mining activities can also be negatively affected by dust fallout.

Janse van Rensburg highlights that surrounding communities can be affected in two ways: socioeconomically, dust contributes to the devaluation of property in a mine’s surrounding area; in terms of health, inhaling dust particles over time can lead to a range of negative health effects.

For mining companies, the impact manifests financially, such as increased maintenance for mining equipment; and operationally, such as an increase in downtime often because of visual impairment when the dust emissions become too excessive.

From a health and safety perspective, mineworkers can inhale dust emissions, resulting in a range of occupational illnesses and diseases, which could further result in increased liability to mining companies.

Comprehensive Solution

Janse van Rensburg indicates that I-CAT’s dust management package constitutes the actual planning and implementation of dust management measures and technologies for mines.

In terms of operational control measures, this can include something as simple as implementing speed limits on the roads, and avoiding the excessive clearing of natural vegetation on mining sites. This mitigates the prevalence of areas that are void of vegetation, as these areas contribute to excessive dust emissions as particles are mechanically entrained in the atmosphere through windblown activities.

I-CAT aims to deliver a customised solution geared specifically for the challenges of clients. The type of solution is usually dictated by the source of the dust, which can either originate from a point or non-point source. Point source dust emissions are created from a static point, such as dust emissions created from a processing crusher, while a non-point source is variable, such as dust emission originating from haulage roads.

Technologies for point source systems include misting systems, which can contribute towards restricting particles from becoming airborne by addressing the problem at the source. Essentially, a misting system encourages the binding of water molecules with dust particles, resulting in the formed particle being heavier and drawn down to the surface under gravity.

In terms of technologies for non-point systems, water can be used in conjunction with road dust palliatives for primary and secondary roads. Dust palliatives aim to bind soil particles together over a longer period while using less water, as the application frequency of using dust palliatives in an aqueous solution is far less than the application of a water-only solution, Janse van Rensburg indicates.

He emphasises that using water only is not a feasible solution for dust management and suppression, owing to the scarcity of this resource in the country. Water also tends to evaporate quickly, which, in turn, allows for small particles to become entrained in the atmosphere in a short time period.

Other measures entail enclosing conveyor areas of mining plants’ offloading points and associated extraction, and collecting the dust particles into dust-filtering and storage infrastructure.

I-CAT has been designing and supplying these solutions and technologies since 2009, with numerous clients indicating that implementing the company’s technologies has had a positive effect on mitigating the negative effects of dust emission at mines, says Janse van Rensburg.””

For more please follow the link above………

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Sustainable solutions possible for AMD treatment – Mining Weekly 
BY: ERIN STEENHOFF-SNETHLAGE

“Multidisciplinary engineering consultancy WSP Africa states that, while acid mine drainage (AMD) decants in the Witwatersrand goldfields and surrounds should be dealt with urgently, there is no company large enough to start a large-scale water rehabilitation programme.

“The Witwatersrand goldfields is the area most threatened by AMD. After 120 years of mining in the area, the Western basin started to decant AMD in 2002. There are no large companies currently mining in this area, so no one [can] initiate a project of the scale needed to prevent the decant,” says WSP Environment and Energy Africa senior associate Karen King.

The onus to develop, own and operate AMD treatment facilities falls on the mines, with “mine closure plans supposed to adequately account for AMD prevention solutions, new mines should not be allowed to open without such plans”, she points out.

However, the responsibility also lies with government to oversee and govern mine closure plans, King adds. “[Some] of the country’s environmental policies, centred on mining and polluted water, are far better today than what they were in the past, but they need to be more strictly enforced,” King puts forward.

To date, AMD has caused considerable damage to the Wonderfonteinspruit, Tweelopiespruit, the Tudor dam and Robinson lake areas, King emphasises. The flooding of the Central basin in the Witwatersrand area has also been linked to seismic activity.

There is no short-term solution to the AMD issue, as the “effects of AMD can never be entirely reversed”, King states. Considering the existing pollution, the AMD needs to be pumped out of the mining areas and treated. This exercise is often started but not continued, as it is an expense which could bankrupt some mines, she reiterates. Older AMD-generating mines have been closed for many years, with companies unable to afford treatment and rehabilitation programmes.

Sustainable Solutions

King believes that there are sustainable solutions that can be used to treat AMD and help restore the natural environment.

Treatment will depend on the extent, volume and the make-up of the AMD, as well as the geographical area that it affects. Solutions include the diversion of clean surface water from sources of pollution, and the prevention of seepage and groundwater infiltration into affected sites. The placement of acid- generating water also needs to be controlled.

Flooding of potential AMD-generating areas before oxidation can occur is another option, as is the development of the Western Utilities Corporation mine water reclamation project. The project entails a plan to pump the water to a central treatment plant where it can be treated and sold to water utility Rand Water at a profit, but is being received with mixed enthusiasm, claims King. “There needs to be greater market understanding and recognition that polluted water can be a resource – and not a liability – if it is appropriately treated.”

Further, King points out that some considerations need to be taken into account when building an AMD treatment facility. The most important consideration is the standard – for potable, industrial or agricultural use – to which the water will be treated, as this will impact on the design and construction costs of the facility.

The potential AMD decant volumes, AMD chemistry and pretreatment methods also need to be considered. Thereafter, the best methodology must be selected to treat the specific type/s of AMD, King illustrates. Financing, maintenance and personnel training are also important factors to consider.

These factors can also be challenges because the lack of properly managing them could lead to the failure of the AMD treatment plan, she adds. For example, poor maintenance could lead to mechanical failures in machinery, as the aeration equipment can become clogged when the calcium sulfate levels are too high.

Further, an estimated 1.6-million people live in informal settlements next to mine waste residue deposits in South Africa, the majority of which are radioactive, King says, pointing out that long-term exposure to AMD-polluted drinking water and mine-residue deposits can lead to cancer, decreased cognitive function and mental retardation in fetuses.

“AMD needs to be addressed adequately and urgently,” King concludes.”

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