Dust control sprays have long been proven to be extremely effective to use for dust control purposes in mining operations as well as civil and construction projects. They can be easily applied to stockpiles or haul roads via water bowsers or fog cannons. Such products work by creating a uniform layer over the surface of the applied area and once dry, form a malleable membrane that stops dust from blowing up in the wind or running off during normal rain events.
Despite their effectiveness, concerns have been raised within the industry as to whether these sprays pose any environmental concerns. In the past, some dust control products were known to have a range of negative side effects on the environment. Chloride-based road salts, for example, are highly corrosive. When used to suppress dust on roads, the salts inevitably cause rust on vehicles and machinery and are also very harmful to roadside vegetation.
However, many modern dust control chemicals are based on concentrated, environmentally friendly, polymer based formulations. There are many different types of formulations available on the market, each with specific benefits for specific applications. In this blog post, we take a look at 3 of the most commonly used dust suppression formulations as well as how each can impact on the environment - bitumen emulsions, lignosulfonates and surfactants.
A bituminous emulsion is a two-phase mixture of fine bitumen droplets and emulsifiers, dispersed in water. The binding and sealing properties, robustness and reworkability of bitumen makes this a reliable dust control solution, particularly for treating and maintaining haul roads. Bitumen emulsions are specifically formulated to minimise wheel generated dust, as well as bind, seal and suppress fugitive dust.
For dust control applications, bitumen emulsions can either be sprayed onto existing road surfaces via a series of light dilutions or otherwise incorporated into the wearing course layer of haul roads and access roads which are being newly established. As soon as the diluted mixture cures, it forms a water-impermeable layer that doesn’t leach into permeable pavement materials and the underlying natural soils. Bitumen emulsions can be diluted in a water bowser at a concentration of 2.5% right up to 50%, depending on the specific requirement.
There has been some debate in the industry as to whether there are any environmental risks associated with using bitumen emulsions, due to the fact that bitumen is an oil based product. However, since bitumen emulsions are largely water based, and often highly diluted, they have minimal impact on the environment. Also, once the water-impermeable layer is formed, there is no risk to surrounding vegetation or the underlying soil.
Particular care does need to be taken when there is a likelihood of rain falling before the emulsion breaks and the bitumen layer agglomerates and cures. So for this reason, specially trained experts should always be used to apply, monitor and reapply bitumen emulsions.
Learn more about Dust-A-Side’s proprietary bitumen emulsion - DASProduct
The overall impact on the environment from applying lignosulfonates for dust suppression purposes is almost negligible.
Emulsified lignosulfonates are by-products from sulphite paper and timber making processes in which sulfonated lignin, a polymer built up of phenyl propane subunits, is dispersed in an aqueous solution. These binding properties of lignin are enhanced by the addition of sugars which helps bind surface road particles together. Water evaporates from the lignosulfonate as it dries and the dust particles are trapped by the high-viscosity, naturally sticky material.
The manufacture of lignosulfonates involves evaporation and this evaporation process drives off any volatile contaminants such as acetic acid. As a result, lignosulfonate based products have very low toxicity towards plants, low order of toxicity towards fish and present no risk of contaminating groundwater. In fact, lignin is natural enough to be used as a binder product in animal feed, depending on the type of white liquor / aqueous used during the cooking phase.
The non-hazardous features and abundant supply of lignosulfonate based suppression sprays make for an excellent dust control solution on roads.
Plain water is commonly sprayed onto roads and stockpiles as a means of dust suppression. However, the effects of water are short lived once the water evaporates. Surfactants (or wetting agents) are formulated to reduce the surface tension of water when used for dust suppression.
Ratio feeding surfactants to water sprays softens the water by enhancing the attraction of treated water molecules to the dust particles and increases the water droplets’ performance. Dust particles are therefore less susceptible to becoming and remaining airborne. The most effective surfactants increase the ability to suppress overall dust levels by 85%+ when compared with plain water.
Many surfactants available today are environmentally friendly and some are even biodegradable. Formulations are based on organic surfactants rather than synthetic polymers. They are often solvent-free, non-corrosive and water based.
Studies have shown surfactants to be non-toxic to humans, animals, marine life and plants. Therefore, modern surfactants are definitely safe for the environment and can be used in mining operations, construction sites, landfills and on unpaved roads. The additional benefit they offer to the environment is they help cut water usage significantly by improving the effectiveness of the water that is used.
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