Archive for the ‘White Papers’ Category

Dry Cleaner Remediation (ERH) – White Paper

July 9th, 2013

Electrical Resistance Heating  Small Site RemediationDry Cleaner Remediation

Electrical Resistance Heating (ERH) is an aggressive in situ remediation technology that can simultaneously remove chlorinated solvents from vadose and saturated soil. It can treat pools of dense nonaqueous phase liquids (DNAPL) found deep below the groundwater table and clean flowing aquifers. ERH systems have quickly cleaned acre sized source areas to depths of over 100-feet below grade. The technology is robust enough to return highly contaminated groundwater to drinking water quality.
Developed for US Department of Energy sites, a large ERH system applies high voltage utility-line power to electrodes placed in a grid pattern across an impacted site. As the subsurface resists this flow of electricity it is heated to the boiling point of water producing steam and contaminant vapors. These vapors are then collected just above the heated zone and treated.

Dry Cleaner Remediation

However, not all chlorinated hydrocarbon impacted properties are multi-acre Superfund sites. Many are former dry cleaner sites with small, but persistent, source areas.  They require Dry Cleaner Remediation.  Currently, no In Situ Thermal Remediation (ISTR) vendors configure their technologies specifically for the treatment of these dry cleaner remediation sites.

Global Remediation Solutions (GRS) is a national provider of ERH ISTR technology and services. We manufacture our own custom ERH equipment and can match it to any site configuration. We have developed a Small Sites Program specifically for the remediation of small chlorinated and fuel hydrocarbon source areas. Our program is based upon the following key concepts:

  • Competitive pricing based on a project life cycle costing.
  • Safe, green remediation technology providing no rebound.
  • Fast and complete remediation.  Clean-up goals met in months, with NFA letter 12 months later.
  • Mobile, customized compact ERH delivery systems requiring 440/480 electrical service.
  • Drilling and electrode designs and applications to maximize access, minimize cost, and provide full commercial use of properties during clean-up..

GRS would be happy to review any size project for the use of ERH for your Dry Cleaner Remediation.

Electrical Resistance Heating (ERH) White Paper

June 9th, 2013

When chlorinated hydrocarbons, such as dry cleaning fluids and industrial solvents, are released into the environment, they migrate downward until they reach groundwater. Because they are heavier than water, they continue sinking through the aquifer until they find a layer of tight soil where they form pools of pure product. As these solvent pools slowly dissolve into the groundwater, they feed large contaminant plumes capable of impacting human health and the environment well down gradient of the impacted site.

These solvent pools are often found at depths of over 30-feet below ground surface and 20-feet below the water table, making them impossible to access using conventional remediation technologies. For example, the shoring and dewatering requirements for soil excavation and disposal at these depths represent insurmountable safety, engineering, and cost challenges. grs-3Phase-Diagram

Electrical Resistance Heating (ERH) is an aggressive in situ remediation technology that can simultaneously treat the solvents found in saturated and unsaturated soil, groundwater, and pools deep below the groundwater table. ERH is often used to clean sites where other technologies have had limited success. Using ERH, even large sites can be remediated quickly and completely. The technology is so robust that it can return highly contaminated groundwater to drinking water quality.

Developed for the US Department of Energy, ERH takes power from standard utility lines and applies it to electrodes placed in a grid pattern across an impacted site. As the subsurface resists this application of electricity it is heated to the boiling point of water producing steam and contaminant vapors. Installed to the maximum depth of contamination, ERH systems can heat to over 100-feet below grade.

During ERH, pools of solvents located below the water table are boiled first and this large contaminant mass is quickly removed from the subsurface. Next, steam formed in the subsurface starts driving contaminants out of soil and groundwater. As steam tries to escape from the subsurface, it sweeps contaminants to the recovery wells where they are collected and carried to the surface for treatment.
At the surface, steam and contaminant vapors are condensed into water, liquid contaminants, and cool contaminate vapors. Liquid contaminants are collected for recycling while condensate water and contaminant vapors are treated prior to release to the local sewer system and the atmosphere.

ERH can be applied in flowing gravel aquifers, heterogeneous glacial tills, and tight clays. It can treat fuel hydrocarbons, chlorinated solvents (dry cleaners), and polycyclic aromatic hydrocarbons (PAHs) such as creosote and coal tar. It can be safely used under roads, parking lots, and occupied buildings without disruption of traffic or occupancy. GRS would be happy to review any site for the use of ERH, and an easy to use site evaluation tool can be found on our web site.

Dalton’s and Raoult’s Laws

June 3rd, 2013

Dalton’s Law of Partial Pressure states that “the pressure of a mixture of gases is equal to the sum of the pressures of all of the constituent gases alone.”

Mathematically, this can be represented as:

Pressure Total = Pressure¹ + Pressure² … Pressuren

Dalton’s Law explains that the total pressure above a solution, such as a chlorinated solvent in water, is equal to the sum of the partial pressures of the parts. This mixture will boil when the vapor pressure above it is equal to ambient pressure. Thus, the boiling point of the solvent/water mixture is depressed below the boiling point of the solvent. For example, tetrachloroethene (PCE) boils at 121 °C in air and at approximately 81 °C when immersed in water or in contact with soil moisture. Similar reductions in boiling points are observed for all chlorinated solvents in contact with water.

Raoult’s law states that “The vapour pressure of a solution is dependent on the vapor pressure of each component and the mole fraction of the component present in the solution”.

It may also be expressed as follows: At a given temperature, the partial vapor pressure of a component in a mixture is equal to the vapor pressure of the pure component at that temperature multiplied by its mole fraction in the mixture.