Location : a small lake situated about 10 kilometers downstream of a paper-mill Paper-mill handled the recycling of waste paper containing PCBs How serious? Approx. 400 kg of PCBs Coverage : whole bottom of the lake Thickness: 0.4 m to 2 m

PCB is a fat-soluble, water-insoluble hydrocarbon containing chlorine Organic compounds originally widely used in industrial processes Extremely stable Withstanding temperatures of up to 870°C Fire-resistant

Ecology : Damages to fishes ’ internal organs, development and reproduction were expected PCBs are not readily biodegradable Dermal contact with PCB-contaminated sediment (or PCB-contaminated fish or other consumable aquatic organisms )is a potential concern to human health

Phytoremediation Plants extract Cd from the soil and transport into shoots and leaves where it can accumulate

Hydraulic dredging Mechanical dewatering and disposal of the sediments in a landfill Activated carbon Eliminate pungent odors and to reduce bioactivity of the PCB

Advantages: Generates little to no secondary wastes In the form of In-situ treatment Aesthetically pleasing Reduce erosion of soil Much cheaper than most other remediation techniques Disadvantages: Time consuming Volatilization can release contaminants into the air Depth limitations Possibility of contaminant entrance into the food chain

Advantages:  Removes organics such as petroleum hydrocarbons & pesticides  Removes taste and odour-causing agents such as hydrogen sulphide  Removes chlorine and ozone  Removes radon Disadvantages:  Needs to be replaced frequently  Hard to determine if the carbon is saturated with contaminants  Do not effectively remove bacteria, nitrates or metals  Provides an excellent medium for bacterial growth

Advantages: Permanently removes contaminated sediment No blockades for draining required Entire water surface area can be reached by the dredge, Sediment-water mixture is pumped & discharged safely Minimal disturbance to surrounding land Disadvantages: Residual sediment Sediment re-suspension/ downstream migration Presence of boulders/debris Costly

Hydraulic Dredging  Although costly but:  Most efficient way of removing the contaminated settlement  Minimal disturbance to surrounding land  Equipment and specialist readily available

Horizontal auger or basket-type cutter heads removes contaminated settlement Contaminants pumped to sludge de-watering equipment with aid of slurry and Geotextile screen Uncontaminated sediments pumped to upland dredge disposal areas for natural de-watering and re-use of material.