Air Emissions and Waste Water Discharges

April 7, 2009

Waste Treatment-Metals

The objective of this project was to perform a survey of U.S. shipyards and similar industries to determine what technologies are currently being implemented or planned to prevent or reduce air emissions and wastewater discharges from facility operations.

There are numerous reports available, summarizing and comparing various “clean technologies”, which have potential application in the shipyard environment.

Biological treatment capabilities include activated sludge, nitrification and denitrification, anaerobic and aerobic digestion, and wetlands.

Internet Address: Pacific Northwest National Laboratory works in all phases of the technology development cycle from Research and Development to industrial implementation.

They are studying carbon dioxide (CO2) pellet blasting, FLASHJETTM coating removal, laser paint stripping, plastic media blasting, sodium bicarbonate wet stripping, water blasting and wheat starch blasting.

The final product contains approximately 20% alumina (attributes to the abrasives hardness of 6-7 Mohs) and 54% silica (provides fracture characteristics) and other components including calcia and soda.

Carbon dioxide pellet blasting is a paint removal and/or cleaning technology that turns liquid carbon dioxide into pellets and blasts them through a nozzle or centrifugally towards the surface being cleaned.

As the dry ice pellets strike the surface, they induce an extreme temperature difference between the coating and the underlying substrate, weakening the chemical and physical bonds between the surface materials and the substrate.

– difficult to focus and control laser beam to allow stripping of curved or complex parts [1] – coating removal efficiency is affected by coating color and gloss [1] – requires use of Class 1 laser enclosure to ensure worker protection [1] – see the contact points in the the Bibliography cooresponding to the references below for more information [1] U.S. EPA.

Plastic media blasting (PMB) is a dry stripping process that projects plastic media at a surface through either low-pressure air (10 to 60 psi) or centrifugal wheels.

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