OCETA ENVIRONMENTAL TECHNOLOGY PROFILES

• sediment treatment
• chemical injection
• in situ

Limnofix In-situ Sediment Treatment - LIST - is an in situ process for the remediation of contaminated aquatic and marine sediments, developed by the National Water Research Institute of Environment Canada. LIST uses specially-designed equipment to inject chemicals directly into contaminated sediments that will enhance bacterial activity and hence contaminant degradation. A flowchart of the LIST process is shown in Figure 1.

There are three major phases:

1. An investigation to determine the type and concentration of chemicals necessary to treat the site contaminants. This is done through bench-scale and pilot-scale tests.
2. A material handling system to prepare the chemical mixtures and deliver them to the injection site, and
3. Patented injection equipment to directly inject the treatment chemicals into surface sediments.

The LIST process is more cost effective and environmentally superior than traditional sediment treatments involving dredging and treatment or disposal on shore.

Figure 1

• bioremediation
• sediment oxidation
• sediment stabilization
• sediment dewatering

LIST technology can be used to enhance the bioremediation of contaminated aquatic sediments. It can be used specifically for:

1. biodegradation of simple organic contaminants including PAHs, BTXs, and petroleum hydrocarbons;
2. sediment oxidation to control problems created by anoxic sediments such as odours, nutrient release and toxicity caused by sulphides;
3. enhanced dredging efficiency through in-place sediment dewatering pre-treatment; and
4. sediment consolidation and flocculation to produce stable marine sediment surfaces.

The LIST technology is capable of remediating to a sediment depth of about 0.5 meters. At the time of printing, remediation projects had been carried out in water as shallow as 3 meters and as deep as 24 meters. LIST has been applied, on a pilot scale, to several sites in Hamilton Harbour, Ontario; the most comprehensive project involving a heavily contaminated boatslip. Over two years, the treatment has resulted in the reduction of PAHs and TPHs from 730 ug/g and 50 mg/g to 260 ug/g and 10 mg/g respectively. Figure 2 shows graphically the biodegradation of volatile organics at the same site.

Figure 2

• boom arm
• oxidants
• nutrients
• flocculant

The chemicals in the LIST process are applied via a specially designed boom arm which is attached to and dragged behind a boat or barge. The boom arm currently being tested is 8 meters wide and consists of a series of nozzles, tines and injection ports. The size of the boom is limited by the size of the vessel. Another requirement is that the boat be able to carry a minimum of 1 ton of treatment chemicals. Chemical preparation and mixing is carried out on shore and the material is transferred, as needed, to the application vessel. Chemicals injected include oxidants to oxidize any sulphides (which are toxic to bacteria) into non-toxic sulphates and nutrients (phosphorous, nitrogen, carbon) to encourage bacterial proliferation and activity. A flocculating agent is also added along with the chemicals which prevents sediment re-suspension as the chemicals are injected. The LIST process is illustrated in Figure 3.

Figure 3: Limnofix In-situ Sediment Treatment (LIST) Process

Figure 4: The LIST process being applied in Hamilton Harbour

* This technology has been successfully tested at the pilot-scale level
While OCETA has reviewed this product/process with the Vendor and conducted limited independent investigation,
OCETA assumes no responsibility for the accuracy and completeness of the information.

Profile Print Date: 10/95
Catalogue # 01-003-H

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