TIGG Provides Groundwater Remediation Rental Success

 TIGG Provides Groundwater Remediation Rental Success

When an experienced environmental remediation company secured a contract to clean up a former manufactured gas plant in a New York community, the contractor realized the environmental remediation process would require a host of different technologies to address contaminated soil as well as ground and surface water.

TIGG Corporation was called upon to provide a solution for treating the contact water because of its ability to meet the company’s requirements of reasonable pricing, immediate rental equipment availability and technical expertise.

TIGG helped rescue the project, which initially employed one of its competitors, who provided inadequate engineering and a solution that was not meeting treatment objectives.

“With the goal of removing contaminants from groundwater in an area near a shopping center, we worked with the remediation contractor to help ensure the safety of the public,” said TIGG Director of Project Engineering Jeff Iman. “We delivered an idea and the apparatus to implement it in a little over three weeks.”

Initially, TIGG developed a water treatment system that combined various technologies to separate oil and coal-tar residuals from the contact water. This process included gravity separators, centrifugal pumps, bag filter units and vessels containing oil-absorbent media and activated carbon.

However, it was soon discovered that cyanide was prevalent in the water. The remediation contractor suggested that iron coprecipitation be used to treat the water and remove the substance. Prior to implementing this plan, the contractor asked TIGG to confirm the treatment process in the laboratory.

After meticulously bench-testing different treatment methods, TIGG identified an anion exchange resin as the best method for removing cyanide from the contact water.

Once the environmental remediation company saw the test results, TIGG incorporated a secondary bag filter skid into the plan and added two anion water filtration vessels. This additional equipment safely removed the cyanide from the water.

As part of its overall service agreement with the environmental remediation contractor, TIGG exchanged spent media with fresh media in the filtration vessels, while offering continuous technical support on the overall process.

“Thanks to our bench testing and ability to integrate various technologies to meet changing needs, the project was executed in a timely and effective manner,” said Iman. “The end result was clean water ready to be introduced back into the local ecosystem.”

For more information on this topic visit www.tigg.com/groundwater-treatment

Activated Carbons and Manufactured Gas Plants

Activated Carbons and Manufactured Gas Plants

A Presentation To The GTI Conference, TIGG Corp.

Authored by:

Michael Hasel PPL Service Corp.

Anthony Mazzoni TIGG Corp.

Johyn Mahfood Corp. Env. Solutions

 

 From the early 1800’s through the mid-1900’s gas for lighting, heating and cooking was produced from coal or oil at manufactured gas plants (MGP). The MGP sites were built on the outskirts of towns that have since grown.  Therefore, the sites are often located in inner city areas.

The process that was used yielded residues that included tars, sludge, light oils, spent oxide waste and other hydrocarbon products. Although many of these byproducts were recycled, excess residues remained at the site.  The residues contain polyaromatic hydrocarbons (PAH) which are present in the base contaminant, which is coal tar.

Approximately 1500 MGP sites have been designated to be cleaned up.  The clean up is triggered by regulatory pressure, mainly state agencies, property transfers and re-development as well as releases via ground water migration.  Due to de-regulation, site clean-up may also be triggered by sale of a utility or of a specific utility site to other utilities.

When considering the remediation of a MGP site, the owner desires to have few or no problems, at the lowest cost, with the neighbors or government agencies, during the remediation operation. To achieve this goal there are many factors that need to be considered. These include, but are not limited to owner costs, public and government relations, present and future liabilities and type of remediation protocol to use.

The purpose of this paper is to discuss the pros and cons related to each of these factors when using one of three accepted options in conjunction with the “hog and haul” method of remediating a site. The options are the use of (1) minimal controls, (2) extensive onsite monitoring and (3) a fabric structure with limited air testing.

As we are all aware, the government continues to react to public and media pressures relating to real or perceived environmentally caused health problems. Therefore, there is the possibility that new regulations will require more stringent guidelines for controlling emissions during the remediation operations and minimizing the need for further action in the future.

Regardless of the regulatory oversight and except for the most unusual of settings most MGP sites require a standard site investigation, risk evaluation and remediation often consisting of soils/materials excavation. At a minimum, the normal practice is to remove the extremely impacted (e.g. tar tanks, holders) soils for disposal/treatment. It is these soils that have the greatest impact to the environment and the neighborhood during a remedial action.

The complete remedial design is no longer limited to the evaluation of what technology, and their associated risks, to use for cleaning the site, but must also include the development of a comprehensive public relations campaign involving the neighbors, the media and the local government officials.  Satisfying neighbor concerns is the center of the public relations effort.  Their concerns are normally related to health, both during and after the clean-up, noise and property values.

The health concerns during remediation are usually related to odors and seeing personnel in moon suits. This is an indication to them that something is bad in the air.  Both of these issues must be addressed or the public will be upset.  This then leads to more media coverage, more government scrutiny, an adverse impact on the company’s image, and is likely to extend the time of the operation and increase costs.

Failure to manage risks for a single remediation could negatively impact the owner in many ways.  This could lead to extensive regulatory review, negative P.R., and possible impacts on the stock value, applications for future permits, and future job sitting (e.g. substation, power plants etc.).  For regulated industries, it could even impact the rate case and reduce the ability to collect all or a portion of the costs from the ratepayer.

There are many technologies that are used to remediate MGP sites. Some of these are bio remediation, capping and slurry walls, stabilization, sheet piling and thermal treatment of the soil. However, the excavation and hauling technique, commonly referred to as “hog and haul”, is an old idea but is still a core tool and is used alone or in conjunction with other technologies.

Whatever technology is used there are still factors that affect the success of the overall remedial operation. The weather, i.e. rain, snow, heat, wind and cold can cause delay in the operation if the site is not covered.  Also hours of operation could be limited by complaints about noise.

Following is a comparison of the three options that are used with the “hog and haul” technology:

1.   Excavation with Limited Monitoring of Air

In this option there are minimal measurements of VOC emissions. Foam or plastic may be put down to help control vapor emissions and reduce complaints by residents. Monitoring may include the use of hand held PIDs.

Pros:

• This is the lowest cost approach
• Probably appropriate for rural areas and industrial complexes

Cons:

• Work delays due to weather or uncovering unexpected “hot spots”
• Variation in emissions could go undetected by monitor but detected by neighbors and thus complaints
• Lawsuits due to perceived health effects
• Regulatory control when done in suburban and urban areas
• Delays due to having to put down foam or plastic
• Extra costs due to change orders because of delays
• Public can be upset by odors and seeing moon suits

2. Excavation with Extensive Real Time Monitoring of Air Emissions

Real time VOC monitors are installed around the site. When the monitors detect a contaminant work activity is slowed or stopped. Monitors provide individual gas constituents.

Pros:

• Extensive monitoring can detect fugitive emissions
• Provides legally defensive monitoring data
• Can be used in suburban and urban settings
  

Cons:

• Work delays due to weather or uncovering unexpected “hot spots”
• Lawsuits due to perceived health effects
• Regulatory control when done in suburban and urban areas
• Delays due to having to put done foam or plastic
• Extra costs due to change orders because of delays
• Public can be upset by odors and seeing moon suits

3. Excavation under Fabric Structure and Limited Monitoring of Air 

In this option a fabric structure is erected over the most contaminated area of the site.  Garage doors, large enough to allow heavy equipment to enter the structure, along with mandoors and lighting are installed in the structure.

The size and orientation of the structure is site specific and must take into account the work plan and truck traffic pattern. In addition to the structure, a well-designed air handling and purification system must be installed to capture VOC emissions generated within the structure and to allow workers to wear minimal personnel protection equipment. Generally the air purification system should be sized to provide 2-5 changes per hour. Once erected and operational a fabric structure with a properly sized air purification system enables work to proceed in most weather conditions and prevents escape of contaminated air.

Pros:

• Not affected by weather conditions
• Organics adsorbed on activated carbon so no odors released to atmosphere
• No visibility of operations
• Minimal visibility of personnel in moon suits
• Same cost as real time monitoring option
• Less noise
• Minimizes risk of lawsuits
• Structure can be moved to various locations on the site
• Better control of costs and schedule
• Much easier and more effect public relations
  

Cons:

• Presence of large visible structure
• A visible depiction of the foregoing discussion is presented in the accompanying table.  The code for interpreting the presentation is as follows:
• Meets or exceeds objectives 
• Meets objectives
• May not meet objectives

 

As is obvious from the chart, the most solid black circles are shown under the structure option.  The activities that are involved with this option are discussed below.

Objective:

Determine which and then select the operational option, when using the “hog and haul” technology, that would satisfy the Owner/Client, Regulators and public to complete the R/A with minimal problems.

Conclusion:

The use of a fabric structure in a residential setting: allowed for the successful completion of the core goals and objectives of the remedial design.

Benefits of Using a Fabric Structure:

•     A remedial plan to meet regulatory compliance
•      Balances project cost with current and future liability controls
•      Easier public and local buy-in for successful project completion
•      Better control of costs and schedules versus other options
•      No odors released to atmosphere
•      Minimizes risk of lawsuits
•      Not affected by weather conditions

 For more information on this topic visit www.TIGG.com

 

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 Activated Carbon is Ideal for PCB Removal

For more than 50 years, polychlorinated biphenyls (PCBs) were commonly used in industrial materials including, caulking, cutting oils, inks, paints and as dielectric fluids in electrical equipment such as transformers and capacitors. Concerns over health effects led to a North American ban of manufacturing PCBs in 1977. By the mid-1980s, an initiative was started to clean up contaminated areas and to phase out PCB-containing equipment and products that were still in use. This cleanup effort continues today.

Careless disposal practices and accidental discharges in the past contribute to the present amount of PCBs in groundwater and in sediments of rivers and lakes. Growing public and government concern over health hazards has led to new practices to safely remove and dispose of PCBs. Residual contamination has been effectively treated by systems using activated carbon adsorption media.

Activated carbon is widely used for the adsorption of many contaminants from liquid and air streams. The activated carbon is produced from carbonaceous organic substances including bituminous coal, coconut shell, lignite, bone, wood and other materials. It is used in many applications such as food production and liquid decolorization.

Adsorption results from a physical process in which layers of atoms or molecules of one substance are attracted onto the surface structure of another substance. Activated carbon’s extremely high surface area within its extensive pore structure makes it an ideal adsorbent. One pound of activated carbon has the surface area equivalent to six football fields.

Activated carbon exhibits a graphitic plate structure, and one may liken the formation of adsorption surfaces to a box of peanut brittle, with the highest energy adsorption sites formed at the intersections of the plates (see image below). The iodine number is used as a general measurement of the surface area of the activated carbon. These numbers generally range from 900-1100 for higher quality carbons.

Activated carbons tend to adsorb organic compounds with increasing affinity as adsorbate (the material being adsorbed) molecular weight, boiling point, and refractive index increase and as solubility decreases. Thus, activated carbon has a high affinity for PCBs due to their high molecular weight, high indices of refraction, and very low solubilities. PCBs have a very large molecular structure and for effective adsorption will require an activated carbon with a compatible pore size. Different base materials will yield different pore structures. For example, the pore structure of coal-based carbon will better accommodate these types of molecules as compared to coconut-based carbon. The latter are more suited to smaller molecular weight compounds with low boiling points and, therefore, are not as effective in this application.

The surface loading of adsorbate on activated carbon varies with the concentration and conditions in the fluid stream. In order to evaluate the economic potential of an application, the activated carbon isotherms can be developed for the particular compound at a given set of conditions. Many isotherms are already available for various compounds, including PCBs. They can be obtained from carbon manufacturers, purifications companies, and EPA literature. They also can be developed in the lab using simple procedures.

The figure below illustrates an isotherm for a PCB molecule with one chlorine atom on TIGG 5D 1240 coal-based activated carbon. As with any testing, these isotherms are performed under controlled laboratory conditions. Actual performance in the field can be affected by factors associated with the treatment system.
When dealing with PCB contaminated groundwater, the solubility of the PCB isomers molecules in the water can typically range between 20 parts per billion (ppb) and 60 ppb with solubilities generally below 1 part per million. Above these levels, the PCBs will be found as free product. As illustrated by the isotherm, PCBs are readily adsorbed by activated carbon, with the example of the PCB isomer with only one chlorine atom (the lowest affinity for all PCB isomers) showing excellent loading on the carbon, even at 1 ppb levels. The result is that effluent levels below 1 ppb are achievable.

Treatment of this water depends not only on keeping the carbon “clean” for proper kinetic transference of the molecules but also the contact time allowed for the adsorption to take place. Field experience has shown that often under turbid conditions, the PCB levels in the effluent following the carbon adsorbers in the treatment train can be as high as 5 ppb. The reason for the higher than expected levels in the effluent is that the PCBs will attach to colloidal material in the water or any carbon fines and pass through the bed without being adsorbed.

In order to decrease these residual levels, the treatment requires upstream and downstream filtration. Typically a 5-10 micron bagfilter is installed prior to the carbon bed and a 0.5 micron bagfilter is installed after the carbon bed, prior to discharge. These processes remove most suspended solids that may be entering the carbon and essentially “plugging” the bed of the carbon thus limiting adsorption; and, capturing any solids that may be making their way through to the effluent.

In addition to the pre- and post-filtration of the carbon bed, the carbon bed needs to be properly sized. Both the bed surface area and the carbon bed depth affect removal efficiency. About seven to eight minutes empty-bed contact time (EBCT, or time to pass fluid through a give actual volume of carbon present as a theoretically open volume) is optimal for proper adsorption.

Typically, a minimum of three feet carbon bed depth is required. The surface area is typically designed to promote a superficial velocity of four to six gallons per minute per square foot. Slower velocities can be used, but very low velocities should be avoided as this may promote the occurrence of channeling, or the liquid seeking a path of least resistance through the carbon bed, resulting in poor distribution.

Overall, activated carbon adsorption is an effective way of reducing PCB’s contamination in groundwater. Successful results can be achieved with a properly designed system that addresses both pre-filtration and post-filtration, along with proper carbon selection and bed design parameters including bed surface area, depth, and contact time.

For additional information on Activated Carbon’s role in Environmental remediation Applications, visit TIGG’s Activated Carbon Information Library at http://www.tigg.com/library