Dredged Materials 

Bioremediation Technologies

Typical bioremediation technologies are windrow composting, landfarming and land treatment.

Bioremediation Technologies

Biological treatment is used for decontamination. This method was first applied in sewage treatment plants where microorganisms consume organic matter. Bioremediation techniques are based on the consumption of contaminants, especially organics such as PAHs, by microorganisms as food or
energy resources.

Creating a favorable environment for optimal growth of the microorganisms requires providing sufficient oxygen and nutrient content as well as controlling moisture, temperature and pH-level.

The contaminant break-down by catabolism or biodegradation is generally more time-consuming than chemical and physical treatment and evaluation of the efficiency of biological decontamination may be difficult to determine

Fly ash spill cleanup

Typical bioremediation technologies are windrow composting, landfarming and land treatment.

For Jones Island CDF, Milwaukee, WI windrow composting has been applied. It requires placing the material in long piles and periodical mixing with mobile equipment. Thermophilic conditions (54-65°C) and correct moisture have to be maintained. Below a moisture of 40% biodegradation is slowed down considerably while above 50% moisture turning operations become difficult. Furthermore gas emissions are of concern.

Another way to treat dredge material biologically is by phytoremediation or phytoreclamation. It combines degradation by microflora or plant-associated bacteria and enzymes (metabolism), plant extraction, i.e. removal of contaminants through plant uptake and bioconcentration, and immobilization by reducing leaching pathways. Phytoremediation can be applied in-situ and has been conducted successfully at industrial sites.

Phytoreclamation or phytoremediation can be defined by three basic processes:

* Plant extraction is the removal of contaminants from a soil material or water through plant uptake and bioconcentration with possible volatilization by plant respiration and transpiration 

* Degradation is the metabolism and/or degradation by plant processes or plant-associated enzymes, bacteria, and other microflora

* Stabilization and containment is the in situ immobilization of contaminants by virtue of reducing soil erosion and minimizing uptake of particular contaminants.

Phytoreclamation of contaminated soils has been applied to industrial sites by commercial entities with documented success. It is fast becoming acceptable to the public and in most cases is less © expensive than traditional treatment technologies such as incineration, bioslurry composting, etc.

The U.S. Army Environmental Center (USAEC) estimated the cost for phytoreclamation of 1 acre of lead-contaminated soil to a depth of 50 cm to be $60,000 to $100,000 compared with excavation and landfilling at a cost of $400,000 to $1,700,000 (USAEC 1997). Also, phytoreclamation has high economic potential for commercial entities that can successfully demonstrate its effectiveness. The CE can benefit from these successes by developing and
demonstrating these new and innovative technologies for managing dredged material.

Plant based decontamination of metal contaminated soils-1
Plant based decontamination of organic contaminated soils
Plant based dredge sequestration containment strategies


Most industrial cleanup efforts deal with one contaminant or one class of contaminants at a time.

This is not the case with most dredged material. Heavy metals, petroleum hydrocarbons, poly-chlorinated biphenyls, organotins, dioxins, and other contaminants may be present in dredged material. Drastic physicochemical changes may also occur as a dredged material is removed from an anaerobic, aquatic condition and placed in an aerobic, terrestrial environment. This is especially true when the transition is from an aquatic saltwater to an upland freshwater site. All of these conditions must be addressed when considering phytoreclamation as an alternative for cleanup/stabilization of dredged material contaminants.

Evaluating the potential success of phytoreclamation of dredged material will include three basic assessments including sediment physical and chemical characteristics, plant exposure effects, and contaminant reduction effectiveness. Additionally, site management issues and goals must be considered prior to selection and implementation of a phytoreclamation process. The advantages and disadvantages of various phytoreclamation approaches, as shown for metals in Table 1, may require specific management considerations to implement the process. For example, phytoextraction may increase the bioavailability of some metals to animals such as earthworms that reside in the

Dredge material placement can support habitat development.

This includes the creation of wetlands, aquatic or upland habitats, and artificial islands. Over 2,000 man-made islands have been constructed in the Great Lakes, coastal and riverine areas utilizing dredge material [8].

Dredge material can be used as raw material for cement or lightweight aggregate production (rotary kiln} and the manufacture of glass tiles (plasma torch). Both processes involve high temperatures (more than 660°C} and are thus energy-intensive and costly [16]. However, high-value end products can offset these costs. Another approach is the production of so-called Eco-Blocks. These building blocks are produced with compression equipment, using mixes of lime, dredge material and sand. Decrease in contaminant concentration is achieved by blending with other materials and encapsulation . Dredge material may be also used in asphalt, so far tested without promising results, or in concrete applications.