The overriding principal behind regulating air emissions, water discharge and waste is protection of the public health and providing for the general welfare of the populace. Usually, the “populace” are considered to be those people living or working within the general area of the facility. However, wind currents may transport air pollutants from one area to another and even across national borders; discharges to water bodies may similarly travel nationally and internationally; and waste may be shipped across the country or the world.
Shipyards conduct a large variety of operations in the process of constructing or repairing ships and boats. Many of these operations emit water and air pollutants which are known or suspected to have detrimental effects on humans through direct physiological and or metabolic damage, such as cancer and lead poisoning. Pollutants may also act indirectly as mutagens (which damage future generations by affecting the biochemistry of reproduction) or teratogens (which damage the foetus after conception).
Both air and water pollutants have the potential to have secondary effects on humans. Air pollutants can fall into the water, affecting quality of the receiving stream or affecting crops and therefore the consuming public. Pollutants discharged directly to receiving streams may degrade the water quality to the point that drinking or even swimming in the water is a health risk. Water, ground and air pollution may also affect the marine life in the receiving stream, which may ultimately affect humans.
Air emissions can result from practically any operation involved in the construction, maintenance or repair of ships and boats. Air pollutants that are regulated in many countries include sulphur oxides, nitrogen oxides, carbon monoxide, particulates (smoke, soot, dust and so on), lead and volatile organic compounds (VOCs). Shipbuilding and ship repair activities which produce “oxide” criteria pollutants include combustion sources such as boilers and heat for metal treatment, generators and furnaces. Particulates are seen as the smoke from combustion, as well as dust from woodworking, sand- or grit-blasting operations, sanding, grinding and buffing.
Lead ingots may in some instances have to be partially melted and reformed to mould into shapes for radiation protection on nuclear-powered vessels. Lead dust may be present in paint removed from vessels being overhauled or repaired.
Hazardous air pollutants (HAPs) are chemical compounds which are known or suspected to be harmful to humans. HAPs are produced in many shipyard operations, such as foundry and electroplating operations, which may emit chromium and other metallic compounds.
Some VOCs, such as naphtha and alcohol, used as solvents for paints, thinners and cleaners, as well as many glues and adhesives, are not HAPs. Other solvents used primarily in painting operations, such as xylene and toluene, as well as several chlorinated compounds most often used as solvents and cleaners, especially trichloroethylene, methylene chloride and 1,1,1-trichloroethane, are HAPs.
Since ships and boats are constructed on waterways, shipyards must meet the water quality criteria of their government-issued permits before they discharge any industrial waste waters to the adjacent waters. Most US shipyards, for example, have implemented a programme called “Best Management Practices” (BMPs), considered to be a major compilation of control technologies to help shipyards meet the discharge requirements of their permits.
Another control technology used in shipyards that have graving docks is a dam and baffle system. The dam stops the solids from getting to the sump and being pumped out to the adjacent waters. The baffle system keeps oil and floating debris out of the sump.
Storm water monitoring has recently been added to many shipyard permits. Facilities must have a storm water pollution prevention plan which implements different control technologies to eliminate pollutants from going into the adjacent water whenever there is rain.
Many ship and boat building facilities will also discharge some of their industrial wastewater to the sewage system. These facilities must meet the water-quality criteria of their local sewage regulations whenever they discharge to the sewer. Some shipyards are constructing their own pretreatment plants which are designed to meet local water-quality criteria. There are usually two different types of pretreatment facilities. One pretreatment facility is designed primarily to remove toxic metals from industrial wastewater, and the second type of pretreatment facility is designed primarily to remove petroleum products from the wastewater.
Different segments of the shipbuilding process produce their own types of waste that must be disposed of in accordance with regulations. Steel cutting and shaping generates wastes such as scrap metal from steel plate cutting and shaping, paint and solvent from coating the steel and spent abrasive from the removal of oxidation and unwanted coatings. Scrap metal poses no inherent environmental hazard and can be recycled. However, paint and solvent waste is flammable, and spent abrasive may be toxic depending on the characteristics of the unwanted coating.
As the steel is fabricated into modules, piping is added. Preparing the piping for the modules generates wastes such as acidic and caustic wastewater from pipe cleaning. This wastewater requires special treatment to remove its corrosive characteristics and contaminants such as oil and dirt.
Concurrent to the steel fabrication, electrical, machinery, piping and ventilation components are prepared for the outfitting phase of the ship’s construction. These operations generate wastes such as metal-cutting lubricants and coolants, degreasers and electroplating wastewaters. Metal-cutting lubricants and coolants, as well as degreasers, must be treated to remove the dirt and oils prior to discharge of the water. Electroplating wastewaters are toxic and may contain compounds of cyanide that require special treatment.
Ships in need of repair usually need to unload wastes that were generated during the ship’s cruise. Bilge wastewater must be treated to remove oil contamination. Sanitary wastewater must be discharged to a sewage system where it undergoes biological treatment. Even garbage and trash may be subject to special treatment in order to comply with regulations preventing the introduction of foreign plants and animals.