Shipyard processes and pollutant sources

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The shipbuilding and repair industry processes include surface preparation, painting and coating, metal plating and surface finishing, solvent cleaning and degreas-

ing, machining and metal working, welding, vessel cleaning, and fiberglass operations. They consume various types of products and produce solid, liquid, and gaseous pollutants. Many different production processes employed in shipbuilding and repair require a vast amount of material inputs and generate huge amounts of waste and considerable emissions. Raw material inputs to the shipbuilding and repair industry are primarily steel and other metals, paints and solvents, blasting abrasives, and machine and cutting oils. In addition, a variety of chemicals are used for surface preparation and finishing such as solvent degreasers, acid and alkaline cleaners, and plating solutions containing heavy metal and cyanide ions. Pollutants and wastes generated include volatile organic compounds (VOCs), particulates matter (PM), waste solvents, oils and resins, metal-bearing sludges and wastewater, waste paint, waste paint chips, and sent abrasives. Figure 39.1 shows basic shipyard processes (Celebi and Vardar, 2006). There are 42 shipyards for new shipbuilding and repair in Istanbul of Turkey. Figure 39.2 is a map of Istanbul including Tuzla region where shipyards are located.

c

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WELDING

AND

CUTTING

V_

4

SOLVENT CLEANING AND DEGREASING

SOLVENT CLEANING AND DEGREASING

MACHINING AND METAL WORKING

Fig. 39.1 Basic shipyard processes.

MACHINING AND METAL WORKING

Fig. 39.1 Basic shipyard processes.

Some of the important shipyard processes and waste emissions from these operations are discussed briefly in the following sections.

39.1.2 Surface preparation process and wastes

Surface preparation is an important step in the shipbuilding industry. Common surface preparation methods adopted by shipyards are dry and wet abrasive blasting, hydroblasting, thermal, chemical, and mechanical stripping. Material inputs used for preparing surfaces include abrasive materials such as steel shot or grit, glass, garnet, copper, or coal slag; cleaning water; detergents; and chemical paint strippers. In the case of hydroblasting only water and occasionally rust inhibitors are required.

Various methods are available to prepare metal surfaces for painting. The choice of the method to be used is based on several factors such as -whether the surfaces are painted or covered with a rust scale, which surface characteristics are required by the paint that is to be applied, the size and shape of the surface to be prepared, and the type of metal. Common surface preparation methods adopted by the shipyards are dry abrasive blasting, wet abrasive blasting, hydroblasting, thermal stripping, chemical stripping and mechanical stripping. Material inputs used for preparing surfaces include, abrasive materials such as steel shot or grit, glass, garnet, copper, or coal slag; cleaning water, detergents, and chemical paint strippers (e.g., methylene chloride-based solutions, caustic solutions, and solvents). In the case of hydroblasting only water and occasionally rust inhibitors are required. Air emissions from surface preparation operations include particulate emissions of blasting abrasives and paint chips. Particulates emissions can also contain toxic metals which is a concern both in the immediate area surrounding the work and if they are blown off-site or into surrounding surface waters. Other air emissions that could potentially arise during surface preparation operations are VOCs and hazardous air pollutants arising from the use of solvent cleaners, paint strippers, and degreasers. The primary residual waste generated is a mixture of paint chips and used abrasives. Blasting abrasives and paint chips that collect in tank vessels, ship decks, or drydocks should be thoroughly cleaned up and collected after work is completed or before the drydock is flooded or submerged. Particular attention should be paid to the cleanup of paint chips containing the antifouling tributyltin compounds which have been shown to be highly toxic to oysters and other marine life. A significant quantity of wastewater can be generated when cleaning ship cargo tanks, ballast tanks, and bilges prior to surface preparation and painting. Such wastewater is often contaminated with cleaning solvents, and oil and fuel from bilges and cargo tanks, paint chips, and surface contaminants (Celebi and Vardar, 2006).

Fig. 39.2 Map of Istanbul and Tuzla shipyards area (scale 1/600,000).

Abrasive blasting materials as aluminum, arsenic, chromium (III), chromium (VI), cobalt, copper, iron, manganese, lead, tin, zinc can be grouped as hazardous air pollutants. The long- and short-term exposure of these HAP's may cause respiratory irritation, manganism, chronic lung inflammation, pulmonary fi-brosis headaches, subclinical neurological disturbances, allergic dermatitis with skin contact, lung and nasal cancers, and asthma.

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