Efficient Oil Removal Plays Critical Role in Water Recovery and Re-Use at Mines
Written by Jim Petrucci at Oil Skimmers, Inc.
In the mining industry, the process of washing down heavy-duty equipment is viewed as a critical aspect of routine maintenance. Regular cleaning not only simplifies maintenance and extends the life of fleet equipment but also optimizes the heavy-duty equipment before going back into operations.
To accomplish this, equipment wash processes are used to clean dirt, mud, clay, and other corrosives off mining machinery, trucks, and other heavy-duty equipment. For the largest earthmoving equipment, high-powered vehicle cleaning systems efficiently pressure wash the vehicle from top to bottom, from chassis to tires and wheels. Often applied at the rate of hundreds of gallons per minute, the water can remove thousands of pounds of debris containing diesel, oil, mud, and dirt caked with grease.
Given the volume of water involved, the mining industry is increasingly seeking new ways to reduce the consumption of fresh water through more efficient and environmentally friendly water treatment and recycling efforts. Along with a mandate to implement more sustainable water management practices in the face of a global water shortage, operators can also realize significant economic benefits. The potential cost savings include reducing water replacement through commercial suppliers, lowering chemical dosages, and lessening the burden (and requirements) of other aspects of the water treatment process.
“In mining, water recycling is critical and every gallon that can be reused counts,” says Jim Petrucci, Vice President at Oil Skimmers, Inc., a Cleveland, Ohio-based manufacturer specializing in oil skimming and separating equipment for a variety of industries. “Given that mines are often located in remote areas with limited access to fresh water, the cost to replace lost or evaporated water is particularly prohibitive. So is the cost of treatment and disposal if the water is not recycled.”
To treat water that collects in sumps or pits, the accumulated substances in the water must first be removed to achieve the level of quality required for re-use. As a result, heavy-duty equipment washing systems are typically designed with wash water reclamation systems that continuously treat and recycle hundreds of gallons per minute. To recover as much water as possible, these systems typically settle out the bulk of the mud and solids first in sumps or pits to eliminate any oils before the water is further processed.
“In equipment washing systems, oil that is not removed contaminates wash solutions and serves as a barrier to recycling the water for reuse,” adds Petrucci.
Heavy equipment washing is not the only place where oil can accumulate in mining. Due to the extreme demands on the equipment, small amounts of hydraulic fluid, lubricating oil, and fuel can emanate from joints, hoses, and other connection points on vehicles over time. When rainwater washes over the equipment, it can generate an oil-water mixture that is typically collected in a large sump or pit nearby. In underground mines, groundwater infiltration and condensation can have a similar effect as rain.
No matter how it is generated, any oil in collected water must be removed before it can be recycled or discarded. One cost-effective and simple method to remove the oil is using an oil skimmer that continually draws off surface oil from a sump, pit, or rainwater collection pond. These systems can be customized to meet the specific requirements based on the location and size of the pit.
“The easiest way to remove oil from water in a sump or pit is with a skimmer,” says Petrucci. “After skimming the oil, the water can be recycled, returned to the collection pit, or re-routed wherever it needs to go.”
The most efficient type of oil skimmer uses a free-floating collector tube that actively and continuously removes the oil as it rises to the surface of the water. As the tube moves across the surface, oil adheres to the outside, and then goes through a series of ceramic scrapers that constantly remove the oil, which then drains by gravity into a collection vessel. The skimmer is not affected by water level fluctuation or floating debris and solids, removes very little water in the process, and operates continuously with minimal attention or maintenance.
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An oil separator may also be required for situations where oil does not separate naturally by gravity or there is a reason to speed the process. Separators utilize a coalescing media that encourages separation and is designed to provide the necessary surface area required for non-emulsified oil droplets to combine or coalesce, forming larger, more buoyant droplets which rise to the surface more quickly and easily.
Petrucci notes that when mines use an oil skimmer along with a separator it reduces the costs for downstream wastewater treatment by decreasing the replacement of filters, and addition of chemicals and flocculants.
“Removing any oil in the water prior to additional wastewater treatment allows the entire system to operate more efficiently and reduces the costs,” says Petrucci. “For example, oil that is not removed first can ‘blind’ filters and lead to premature replacement. There are also maintenance costs when changing a filter.”
Whether oil in collection sumps or pits accumulates from heavy equipment washing, rainwater, condensation, groundwater infiltration, or solvent extraction techniques, mining operations can benefit by installing economical, effective oil removal solutions. In addition to the potential savings from water recycling and improvements in the wastewater treatment process, mining companies will be doing their part as good stewards of the environment as well.
For more information about oil skimmers, oil separators, or how to design the ideal oil removal system for your application, contact Oil Skimmers, Inc. at 440-237-4600 | info@oilskim.com | www.oilskim.com.