Grantee Research Project Results
Final Report: Low-Cost Activated Carbon for Permeable Contaminant Barriers
EPA Contract Number: 68D98137Title: Low-Cost Activated Carbon for Permeable Contaminant Barriers
Investigators: Kelly, John T.
Small Business: Altex Technologies Corporation
EPA Contact: Richards, April
Phase: I
Project Period: September 1, 1998 through March 1, 1999
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (1998) RFA Text | Recipients Lists
Research Category: SBIR - Waste , Hazardous Waste/Remediation , Small Business Innovation Research (SBIR)
Description:
Many military, and industrial installations include disposal or storage sites that contain underground plumes of VOCs, PCBs, and toxic metal substances. The migration of contaminants from these sites threatens water resources. Conventional approaches for cleaning these sites is expensive. A better approach is to use Permeable Reactive Barriers (PRB). These systems destroy or adsorb pollutants and allow clean water to pass through unimpeded. For this method to be effective and economical, a low cost and effective sorbent is needed. Altex has identified a Low-Cost Activated Carbon (LCAC) that can be used in PRBs. LCAC is made of 100% biosolids. The negative cost biosolids help reduce sorbent costs. The LCAC process produces an activated carbon that can be used in conjunction with other nonactivated sequestering agents to form an effective, and enduring reactive barrier that traps contaminants, and allows clean water to pass through.The purpose of the Phase I effort was to show the technical and economic feasibility of LCAC production. To achieve this goal, several efforts were performed, including:
* Defining the characteristics of LCAC
* Setting up test equipment
*
Producing samples of LCAC
* Testing LCAC for surface area and strength and
comparing its performance to PRB needs
* Designing the full-scale LCAC
plant
* Defining capital and operating costs
* Defining LCAC economic
viability
Needed characteristics of LCAC were defined by reviewing contaminated site pollutant information, including the sorbents currently being used in PRBs. It was found that over 217, 000 sites are contaminated and need to be remediated. Under the current requirements of federal and state regulations, remediation of these sites will cost $187 billion. Contaminant groups that were found to be common to most of the remediation programs are petroleum products, solvents, and metals. In particular, VOCs are the most frequently occurring contaminant type, present at more than two-thirds of the of the Superfund, Resource Conservation and Recovery Act (RCRA), and DOD sites, and almost half the DOE sites. These VOCs, primarily in the form of BTEX (Benzene, Toluene, Ethylbenzene, and Xylene) are also the primary contaminants at Underground Storage Tanks (UST).
Currently the two sorbent that are used in PRBs are Zero valent Iron (Fe0), and Granular Activated Carbon (GAC). Fe0 is not effective on VOC's and BETX, and cannot be used for these sites. GAC is effective, but is also very expensive. Given that approximately 30% of the PRB cost is associated with the sorbent, a lower cost and effective sorbent is required.
From the information gathered, it was concluded that the first LCAC application will be the remediation of sites contaminated with VOCs , BETX and other oil processing and use related hydrocarbons. This first application would be the basis for evolving LCAC to other contaminants and other sites. It is anticipated that this sorbent will also be effective on metals, with proper treatment. Also is was concluded that LCAC should be priced well below GAC, and competitive with Fe0. These characteristics require granular activated carbon with a surface area above 700 m2/gr, and at 80% below GAC price.
The main challenge in producing a good sorbent from biosolids was the high content of the ash in the biosolids, that is carried over into the final product. Tests showed that conventional ash separation methods failed to reduce this ash. Altex then used an innovative technique to convert the biosolids carboneous material into activated carbon, and leave the ash behind. Small-scale test equipment was then used to produce samples of LCAC material that were then tested for surface area and strength. Samples of LCAC were found to be stronger than commercial granular activated carbon. These tests demonstrate the technical feasibility of LCAC. A sample of LCAC was sent to the Micromeritics Instrument Corporation, Norcross, GA for analysis of surface area and porosity. Micromeritics performed a multipoint BET determination. This test is widely accepted for the evaluation of activated carbons, and is used universally by activated carbon manufacturers to specify their products. The surface area of the LCAC sample, as determined by the multi point BET, was 685 m2/g. This is a high degree of surface area development, and, to our knowledge, the highest ever achieved by any program utilizing waste municipal biosolids. These results show that the LCAC product can have surface area and adsorption characteristics similar to those for commercial activated carbon. Given the expected low cost, this suggests that LCAC has a significant potential for use as a sorbent in PRBs and other pollutant reduction systems.
To show the economic feasibility of LCAC, a 1000 lb/hr LCAC plant was designed. Inputs from manufacturers were used to identify the needed equipment to convert biosolids into LCAC. Capital and operating costs were identified and combined to arrive at the LCAC production cost. The negative cost of the biosolids is an income to the plant. LCAC plants also use the equipment and infrastructure existing at Waste Water Treatment Plants (WWTP). This also reduces the capital need. It was concluded that with the savings associated with the use of existing WWTP equipment and the income from biosolids, the LCAC product can be sold at 80% below the commercial activated carbon price and still make a substantial profit. It was found that even at this low sale price the LCAC plant return on investment is more than 50%. This is a return that should attract several investors.
In summary. this program showed that biosolids can be converted into a low cost activated carbon for use in PRBs. In addition to barrier applications, LCAC can be sold as a substitute for high priced granular activated carbon. Together, these applications represent a LCAC market of over $170 million per year. Considering the high level of LCAC return on investment, and this market potential, the LCAC commercialization potential is high.
Supplemental Keywords:
Economic, Social, & Behavioral Science Research Program, Scientific Discipline, Toxics, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, Hydrology, National Recommended Water Quality, Environmental Chemistry, Contaminated Sediments, Remediation, Fate & Transport, Environmental Engineering, Groundwater remediation, Engineering, Chemistry, & Physics, Market mechanisms, fate and transport, polychlorinated biphenyls (PCBs), soil sediment, soil and groundwater remediation, adsorbents, contaminated sediment, VOCs, groundwater plumes, chemical contaminants, soils, contaminated soil, Polychlorinated Biphenyls PCBs:, PCB, activated carbon, granular activated carbon, soil and groudwater remediation, groundwater contamination, cost effective, control technologies, heavy metal contamination, vadose zone, groundwaterThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.