Final Report: A Low-Impact Delivery System for In-Situ Treatment of Contaminated SedimentEPA Contract Number: EPD06029
Title: A Low-Impact Delivery System for In-Situ Treatment of Contaminated Sediment
Investigators: Menzie, Charles A
Small Business: Menzie-Cura & Associates, Inc.
EPA Contact: Manager, SBIR Program
Project Period: March 1, 2006 through August 31, 2006
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2006) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Small Business Innovation Research (SBIR) , SBIR - Cleanup of Contaminated Sediments
The purpose of this research project was to develop a product for delivering remedial materials to contaminated sediments for in situ remediation. Incorporating remedial materials, such as activated carbon, zero-valent metals, iron oxide, and calcium carbonate, into sediment reduces the concentration and bioavailability of contaminants through processes of chemical reaction or sorption. Current delivery methods rely on injection and/or mechanical mixing of remedial materials into the sediments. During this research project, Menzie-Cura & Associates developed a product that is an agglomerate designed to deliver remedial materials to sediment without the aid of mechanical mixing or injection. The agglomerate is deployed from the water’s surface, sinks to the sediment surface, breaks down, and mixes into the sediment by bioturbation, which is the physical mixing of sediment by benthic organisms.
The research involved four key objectives: (1) developing an activated carbon a gglomerate; (2) testing the behavior of the agglomerate in the laboratory (settling behavior, dissolution rates, formation of dusts, sorption property); (3) evaluating the effects of the agglomerate on benthic organisms; and (4) observing the mixing of the agglomerate into sediments in model benthic environments that reflect natural benthic invertebrate communities.
Development involved testing a variety of materials for the ability to form an agglomerate that is: dense enough to sink through the water column and provide a light, non suffocating layer on the sediment; resistant to resuspension while it is worked into the sediments; and capable of breaking down to release active agents over a period of days to weeks.
Activated carbon was selected as a proof of concept for the research and was tested with a variety of binder and additive materials to form the agglomerate. In addition to forming the agglomerate, the additives’ effects on activated carbon were evaluated for interference using the iodine number test.
The interaction between benthic organisms and the agglomerate included toxicity screening and using a fluorescent trace to evaluate the movement of the agglomerate by bioturbation.
The agglomerate was produced successfully in the laboratory with all the characteristics necessary for delivering remedial materials to sediment. The project included a review of the laboratory practices and agglomerate materials by an agglomeration industry expert, who concluded that the agglomerate could be produced on an industrial-scale by several agglomeration techniques.
The iodine number test ( ASTM D 4607) was used to evaluate if the additives had any effect on the ability of the activated carbon to adsorb iodine, which would indicate a reduced ability to adsorb contaminants. The iodine number test found that the binder and additive materials included in the agglomerate did not affect the adsorptive capacity of the activated carbon.
The toxicity screening, using the U.S. Environmental Protection Agency-approved Test Method 100.3 with Lumbriculus variegates, found no significant adverse effects in benthic organisms when the agglomerate was mixed into sediment.
A qualitative bioturbation experiment was used to observe the distribution of the agglomerate by benthic organisms. The experiment was modeled after a 28-day bioaccumulation test and used large tanks containing 10 inches of field-collected sediment, which contained natural fauna. To maximize the bioturbation for this experiment, the tanks were seeded with the estuarine amphipod Leptocheirus and polychaete Nereis. Activated carbon agglomerates containing a fluorescent tracer material were added to the sediment surface and left for 30 days. The movement of the agglomerate material throughout the sediment column was observed qualitatively using an ultraviolet lamp to fluoresce the tracer. The results show the agglomerate material being mixed into sediment to depths of 2 inches. There were no cases of observed avoidance or high turbidity in the tanks.
Menzie-Cura & Associates was successful in producing an agglomerate with the necessary characteristics for delivering activated carbon to sediment. In addition, the bioturbation experiments show that the activated carbon, as evidenced by the fluorescent tracer, can be mixed through the sediment by benthic organisms after delivery to the sediment surface as an agglomerate.
The agglomerate represents the first delivery method for remedial materials to sediment that does not require mechanical mixing into sediment. It is, therefore, applicable in areas where current in situ treatment practices are problematic, such as in deep water, through vegetation, or over large areas. The agglomerate can be designed to carry a number of remedial materials to sediment, allowing for in situ treatment of a variety of contaminants.