Project Brief

A look at phosphate sand with the aid of an electron microscope reveals a jagged molecular landscape that offers a vast surface area to capture heavy metal ions.

The phosphate permeable reactive barrier is deployed with commonly used and available dredging equipment, making it cost-effective to handle and transport.

Trap & Treat
Patented reactive barrier traps and stabilizes toxic heavy metals in sediment.

Challenge
River and harbor sediment polluted with toxic heavy metals is a widespread problem with a common solution: put a lid on it. To avoid the risks of dredging—loss of habitat, dispersal of contaminants, and what to do with all that toxic sediment—many opt instead to spread several feet of sand over the contaminated site. However, since conventional caps must be thick enough to prevent pollution from migrating into the water column, they can be costly to install and maintain, hinder boat navigation, and put a damper on the growth of aquatic life.

Response
With a series of grants from CICEET, researchers at the University of New Hampshire have developed a new approach to capping: a phosphate-based permeable reactive barrier. Sand-based caps act as physical barriers that can only slow the spread of pollution. However, the new class of reactive barriers made from sorbent materials binds and stabilizes pollutants, removing them as a threat from the surrounding ecosystem. This phosphate reactive barrier uses natural minerals mined from ancient seabed deposits to stabilize heavy metals such as lead and zinc, and prevent their contamination from spreading.

Basic research in the lab has tested the technology’s ability to treat sediment from heavily polluted waterways such as Newtown Creek, N.Y. and Providence Harbor, R.I. In a field demonstration in the Anacostia River in D.C., an 8,000 square-foot test plot is showing promising results. Researchers have demonstrated that, compared to sand caps, a much thinner layer of this barrier can be used to remediate sediment, and that it can be deployed with conventional dredging equipment. A technology transfer grant from CICEET is allowing the researchers to explore ways to commercialize this technology so that it will be widely available.

Impact
The phosphate permeable reactive barrier is licensed and ready for full-scale use. Many of the technological hurdles for permitting and deploying the material have been overcome. Methods developed for this project led to the award of patent number 6,290,637, available at www.uspto.gov

Project investigators are part of a bi-coastal team that received a $1.1 million grant from the Department of Defense’s Strategic Environmental Research and Development Program (SERDP) to develop a single delivery system that combines different reactive barrier technologies to address site specific contamination. The prototype for this system will include two CICEET-funded technologies: the reactive phosphate barrier and one based on organoclays that treats toxic organic chemicals.

Learn More
Jeffrey Melton, Ph.D.
Research Assistant Professor
Gregg Hall
35 Colovos Rd.
University of New Hampshire
Durham, NH 03824
T: 603-862-2107
E: jeffrey.melton@unh.edu
http://unh.edu/phosphatebarrier

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