Difficult to remove and dangerous to the health of the environment and humans, DNAPLs are a persistent thorn in the side for many areas. Still, there are many ways to treat DNAPLs; the key is to find the correct method for the individual site.

What is a DNAPL?

DNAPL is short for dense non-aqueous phase liquid. Common DNAPLs include creosote, coal tar, and heavy oils; common DNAPL applications include degreasing and acting as a solvent. On the other hand, DNAPLs can also be the byproduct of industrial processes; in particular, a form of DNAPL known as multi-compound waste is a common type of waste oil.

Which method is best for Treating DNAPLs?

Each of the following methods have their advantages and disadvantages. The conditions present in each treatment site determine the effectiveness and cost of individual methods and is the largest factor in choosing treatment method. As such, a good working knowledge of the treatment site is key to effective remediation.

Excavation

Excavation, where an environmental remediation firm will dig to the DNAPL and remove the pollutant, is by far the most effective method and has close to 100% efficiency. Excavation is also expensive and impractical, since the DNAPLs are often deep underground and require significant amounts of manpower and machinery to reach the aquifer.

Bioremediation

Bioremediation is a much more common method. By introducing or encouraging the growth of organisms that can digest the DNAPL, bioremediation breaks down the pollutant into ecologically friendly substances. Bioremediation not only treats the DNAPL effectively, but can also potentially treat other pollutants in the remediation area and does not require the removal of waste.

Belt skimmers

Belt skimmers can be an effective means of DNAPL treatment. Having an oleophilic belt gives the belt oil skimmer an inherent way to attract floating oils and emulsified fluids without relying on pumps or other like means. In addition, a belt oil skimmer like the PetroXtractor requires far less daily maintenance than pumps or other means of collection.

Air sparging

Air sparging involves pumping pressurized air into the groundwater, causing the hydrocarbons in the water to become a gas. This gas is then sucked up by vacuum extraction. Air sparging is unable to function with low air permeability and functions inefficiently when the air permeability is too high.

Soil vapor extraction

Soil vapor extraction (SVE) is similar to air sparging, but focuses on removing contaminants from the surrounding soil rather than groundwater. As such, the technique shares may of its advantages and disadvantages with air sparging. Both techniques are focused on environmental remediation; although some industrial processes may be able to accommodate air sparging, most will find the introduction of gas into a potentially polluted tank will propagate foul smells and potentially harmful gases.

Solidification

Solidification involves immobilizing the contaminant via chemical or physical means. Often, this method relies on trapping contaminants in soil, either reducing contamination of the aquifer or making the contaminant easier to remove. Inorganic pollutants, such as radionuclides, can be collected more easily and with fewer health risks like radiation poisoning.

In situ oxidation

In situ oxidation involves the injection of chemical oxidizers, materials such as oxygen or the halogen family that encourage the loss of electrons, into the contaminated area. The chemical reaction between the chemical oxidizer and the pollutant renders the pollutant harmless. Often, oxidation is used for chemical pollutants. Oxidation still needs to react with the substance; if the pollutant is not easily oxidized, the treatment will have no effect.

In-situ chemical reduction

In-situ chemical reduction is similar in concept to In-situ oxidation. Usually used to treat chromium and the solvent trichloroethene, the method introduces a reducing agent such as zero-valent iron nanoparticles to reduce the number of electrons in a contaminant and change the contaminant to something less harmful.

Pump and treat

Pump and treat refers to the process of pumping out the groundwater from the aquifer and subsequently treating that groundwater through any number of means, including most of the methods listed above. Pumping out the water makes the water easier to treat since the conditions can be adjusted for better collection and the aquifer may not be suited to the optimal method of remediation.

Collecting DNAPLs can be a difficult task but is possible with enough foresight and planning. By understanding the nature of the contamination and the unique environment the treatment occurs in, an effective treatment method can be selected.

To learn more about oil skimmers, please contact our experts at 440-543-7400 or visit our website: www.abanaki.com

How Does a Well Oil Skimmer Work? 

Sometimes, an important technological advance begins with a small step-back! Such is the case with remediation of hydrocarbons from groundwater utilizing existing recovery and monitoring wells.

For the past few years, state government has based decisions on the amount of clean up that they require by the risk posed to the environment. Risk Based Corrective Action, commonly called “Rebecca” (RBCA), is a process that utilizes the principles of exposure assessment, toxicity and mobility to make corrective action decisions on sites that are cost effective while still protecting human health as well as that of the environment. Many times, all they require is removal of the free-phase product, allowing any emulsified contaminant to degrade with time. RBCA has saved many millions of dollars both for taxpayers and for businesses. With state regulatory agencies taking this approach, oil skimming devices have emerged as one of the most cost-effective groundwater remediation equipment choices.

Oil Skimmer is the Solution in Groundwater Remediation

Wastewater engineers in industrial settings have, for many years, understood the value of oil skimmers in the removal of hydrocarbons from water. Food processing plants, the metals industry, machining firms and utilities have all used oil skimmers with great success for wastewater treatment. Recently, oil skimmer manufacturers have modified their product as groundwater remediation equipment. The belt oil skimmer’s ability to get into tight spaces and remove relatively large amounts of hydrocarbons lends itself perfectly to groundwater remediation.

Since most oils, fuels and other hydrocarbon liquids have the tendency to float on water, oil skimmers are designed to remove only the top, free-phase, product layer. With only product being removed, the cost and maintenance of other down-well and water treatment equipment can be eliminated. Another cost advantage to oil skimming is that in many cases the product can be salvaged for reuse – further reducing the overall price by eliminating the disposal cost.

Belt Oil Skimmers are the Most Cost-Effective Method

The options for remediation equipment through recovery wells are practically unlimited since these wells come in a variety of sizes; any of the available technologies such as pump and treat of bio-remediation can be used in the correct size recovery well. Monitoring wells, however, are small, typically less than 4 inches in diameter. Initially installed for the monitoring of groundwater they are cheaper to construct and just large enough to allow a baling device or oil/water interface detector to pass through. As a cost savings measure, these small diameter wells are increasingly being used for product removal. With the increase in this new use, it is only natural that a number of devices are showing up claiming the ability to remove product through monitoring wells.

With the requirements for groundwater remediation systems becoming more reasonable, the use of skimming devices in lieu of pump and treat systems is increasing. The enormous expense involved with treating millions of gallons of water including the remediation equipment, monitoring and related maintenance is being replaced with a much more common-sense attitude. Oil skimmers, especially belt oil skimmers, as a means of remediation equipment, not only meet the challenge but, most times exceed. Pump and treat still has a place in this industry, but the small step “backward” to time proven skimming, a more reasonable and cost-effective method, cannot be overlooked.

To learn more about oil skimmers, please contact our experts at 440-543-7400 or visit our website: www.abanaki.com

How Does a Well Oil Skimmer Work? 

Oil skimmers usually incur a low initial cost, install easily, offer rugged construction, reliable operation and minimal upkeep. Training personnel for operation, monitoring and routine maintenance is nil.

Still, there are different types of skimmers, and each application requires some analysis to make the best selection. Also, the water collection system must be set up properly in order to get maximum performance from the skimmer.

Reservoir Design

Because skimming acts on floating oil, the water must be in a reservoir where separation can occur. The reservoir should be designed with quiet areas, weirs and sufficient volume to allow adequate residence time for oil/water separation. Avoid turbulence by having water return to the reservoir below the liquid surface at as low a velocity as practical. Tanks without nooks and crannies for oil to accumulate in are best.

If you have an irregular shape, put the skimmer where the largest amount of oil accumulates. Consider a means of directing oil toward the skimmer medium to improve removal efficiency.

Turbulence

All skimmers work more efficiently in quiet water with a relatively thick oil layer. The greater the turbulence, the lower their efficiency due to emulsification. Turbulence also affects the physical performance of a skimmer. For example, a tube-shaped medium may get kinked due to turbulence, which could cause damage or impair its drive mechanism.

Mop type oil skimmers may require a tail pulley with its axle secured to the side of the tank. Belt types may be fitted with a tether or stabilizer bar assembly to resist twisting of the tail pulley.

Skimmer Reliability and Maintenance

Skimmers require a certain amount of routine maintenance, primarily periodic cleaning and checking wiper blade adjustment. Easy removal of safety covers shielding the moving medium and its pulleys will reduce maintenance time.

In terms of drive designs, those with separate gear reducers tend to be somewhat more robust than unitary gear motor drives. Chain drives, which are found on a few models, need to be lubricated regularly and the chain should be protected from debris and other impediments.

Installing an Oil Skimmer

The biggest installation issues are the amount of space required and cost. With regards to space, there are two areas that need to be considered: mounting area and water surface area. Installation of a suction skimmer also may involve sensors and a control box.

Moving medium skimmers require some sort of rigid mount on or near the reservoir. Some require the drilling of holes into the tank, which can be costly, depending on the reservoir design. Because of drive design, drum types tend to require more elaborate mounting methods and space. Belt, disk, tube and mop drive units consume a moderate amount of space.

An advantage of some belt skimmer drives is the use of a flat surface mount or bracket, neither of which require tank modifications. Mounting stands, brackets and adapters help make skimmer installations easier and faster.

Portability is a plus in some applications. For example, in plants and mobile equipment service shops, a portable skimmer can sometimes service both a parts washer and a drain water retention sump.

Belt and disk type skimmers tend to be the best designs for portability, and can be made small enough to weigh only a few pounds.

As most hydrocarbons spread fairly quickly over the top of water, it is not necessary to use more of the surface than the skimmer medium contact area. However, a skimmer’s design may actually take up more of the surface than the minimum required. A drum skimmer may require up to five square feet depending on drum size.

A tube skimmer requires four to five square feet due to the tube snaking out over the surface of the liquid. Unless a mop medium is constrained by a tail pulley, it moves around and takes up surface real estate. This is particularly true when there is turbulence.

Disk skimmers generally require from one-half to one square foot of liquid area.

Belt skimmers require from a few square inches to about one square foot, which is determined by the belt width and diameter of the tail pulley.

To learn more about oil skimmers, please contact our experts at 440-543-7400 or visit our website: www.abanaki.com

Abanaki Model 8 Belt Skimmer in Operation

Selecting an oil skimmer can be a complex decision-making process. There are various factors you have to consider about your application when choosing the right skimmer. Here is a guide to help you avoid the 7 common mistakes that are made when purchasing an oil skimmer.

Under-Sizing Your Skimmer

Improper Placement of Oil Skimmers

Planning is important! Before spending money on a concrete pad and mounting arrangements, check where the oil actually collects in your process. Oil skimmers should be located opposite from the inflow and the tail pulley should be submerged two inches below the surface of the liquid in order to be as effective as possible.

Paying for a Complicated Solution

Oil skimming usually beats ultra-filtration systems in many applications. More often than not, installing large, complicated systems to remedy oil problems will not provide ideal results. You can save costs by using a relatively inexpensive oil skimming system to handle the free-floating oil and then a smaller treatment system to handle the oil that has remained suspended in the wastewater.

Not Telling Your Consultant or Vendor Everything

Oil skimmer selection can be a very complex process. There are numerous factors that go into selecting the right oil skimmer for your particular application. If the oil skimmer vendor does not know what chemicals or heat you have in your application, the wrong oil skimmer and belt materials could be selected, and the job will not get done correctly.

Choosing the Wrong Oil Skimming Material

There are several things to consider when choosing a belt or tube material for your oil skimmer. Some plastics will not stand up to heat or strong chemicals. Certain metal belts will not skim coolants effectively. Smooth belts do no pick up floating emulsified oils. Specific plastic belts do not last in heated applications, while other types of plastic belts will.

Lack of Maintenance and Basic Care

An oil skimmer will only remove oil if it is properly maintained. There are basic maintenance tasks that should be done regularly to keep your oil skimmer up to snuff. Are the wipers contacting the belt smoothly? Is the belt riding away from the sides of the pulley? Are the troughs and wipers clear of debris?

Buying from an Unknown Vendor Based on Price

Like most things in life, you get what you pay for. Buying from small, unheard of oil skimmer manufacturers will probably result in no customer support when maintenance issues pop up and little to no knowledge of how to resolve those issues. Furthermore, parts will need to be replaced over time, units might have to be changed or upgraded, or different belt materials need to be used. Disreputable vendors typically do not have a selection of materials or parts to choose from.

To learn more about oil skimmers, please contact our experts at 440-543-7400 or visit our website: www.abanaki.com

HOW TO TELL WHAT SKIMMER YOU NEED FOR YOUR MACHINE COOLANT

Have you ever looked at your coolant and wondered what type skimmer would work best in your machine sump? In this video, we talk about what oil skimmer works well in various coolant applications.

DNAPL is short for dense non-aqueous phase liquid. Common DNAPLs include creosote, coal tar, and heavy oils; common DNAPL applications include degreasing and acting as a solvent. On the other hand, DNAPLs can also be the byproduct of industrial processes; in particular, a form of DNAPL known as multi-compound waste is a common type of waste oil. The defining aspect of DNAPLs, density, causes the mixture to sink in liquids like water or coolant. Because the sludge sinks, surface skimmers like rope skimmers have issues treating DNAPLs. Additionally, the density tends to cause problems with devices requiring a pump for collections because of its density, clogging the pipe or even breaking the pump itself.

Why are DNAPLs a Problem?

DNAPLs are common forms of wastewater pollution. Having DNAPLs leak into local groundwater is a violation of EPA regulations. In addition, DNAPLs can worsen working conditions in manufacturing. Often, these oils will emit a smell akin to sulfur as they break down.

DNAPLs may also reduce the effectiveness of machinery. The density can interfere with pumps or other methods of liquid conveyance, while the chemical properties of the DNAPL, depending on composition, can have adverse effects on the liquid it is suspended in.

These problems can actively interfere with the intended function of the machinery, leading to productivity loss or even damage to the machine.

How are DNAPLs Collected?

For DNAPLS, there are two general means of treatment: extraction and destruction. Extraction denotes the removal of the DNAPL from the liquid, while destruction means breaking down or neutralizing the DNAPLs to a level of minimal impact.

Methods of treatment include bioremediation, in situ methods like oxidation, reduction and flushing, barriers, soil vapor extraction (abbreviated as SVE) and air sparging, solidification and stabilization, pump and treat, and excavation. Skimmers are often used as supplements for in situ methods like flushing to hasten the removal of free-floating DNAPLs.  

Belt Oil Skimmers are the Best Method?

Belt oil skimmers can be an effective means of DNAPL treatment. Having an oleophilic belt gives the belt oil skimmer an inherent way to attract floating oils and emulsified fluids without relying on pumps or other like means. In addition, a belt oil skimmer like the PetroXtractor requires far less daily maintenance than pumps or other means of collection.

When pumps break down from clogs or internal mechanical failures, additional time is needed to correctly assess the problem and repair the problem. The pump also collects excess water, which is expected to be pumped back in the well and adds extra cost. Oil skimmers circumvent these problems.

The streamlined design of the PetroXtractor makes for easy assessment and repair in case of malfunction. Belt oil skimmers do not face the same clogging issues pumps do simply because there is almost nothing to clog.

Upkeep is straightforward and easy on a skimmer, often requiring a visit only once a week. The design of the PetroXtractor focuses on the collection of LNAPLs and DNAPLs without collecting water, preventing excess fluid from being collected. The PetroXtractor also can operate in fluctuating water levels as well as in more extreme conditions that pumps may have issues handling.

To learn more about oil skimmers, please contact our experts at 440-543-7400 or visit our website: www.abanaki.com

How Does a Well Oil Skimmer Work? | Abanaki

This animated demo shows how the PetroXtractor well oil skimmer works great with a large vertical drop making it ideal for wells and other small openings. Depths of 100 feet or more can be handled without the use of pumps.