Preventing discharge of contaminated bilgewater

Over the past two decades, U.S. regulations dealing with bilgewater discharge for all types of vessels have grown increasingly stringent. Even the presence of an oil sheen is punishable under federal law. Environmental technology has struggled to keep pace, but until recently no removal method has been capable of eliminating sheen and extracting all harmful contaminants from bilgewater. Federal regulations set a high standard for bilgewater. Even the tiniest drop of bilgewater oil has been demonstrated to kill hundreds of thousands of lobster eggs, just one example of the enormous threat to all aquatic life.

An on-board filter device for vessels has now been developed to remove 100 percent of sheen generated from oil, gas, diesel fuel and other hydrocarbons from boat bilgewater. The device works in a single pass in "real time." Having completed successful testing this year, the new system is currently being marketed nationwide under the product name of BilgeKLEEN by Mother Environmental Systems of Gainesville, Ga.

Bilgewater discharge regulations
The development of the new filter device is timely in light of increased regulatory scrutiny and penalties. For example, the Federal Water Pollution Act - also known as the Clean Water Act - disallows even the appearance of a visible sheen on the water, punishable by a $5,000 penalty. More specifically, the act "prohibits the discharge of oil or oily waste into or upon the navigable waters of the United States or the waters of the contiguous zone if such discharge causes a film or sheen upon, or causes a sludge or emulsion beneath the surface of the water."

Under 4301 (a) and (c) of the Oil Pollution Act of 1990, the fine for failing to notify the appropriate federal agency of a discharge has increased from a maximum of $10,000 to a maximum of $250,000 for an individual and $500,000 for an organization. The discharge of oil regulation, or "sheen rule," establishes the following criteria for determining a harmful oil spill:

  • Discharges that cause a sheen or discoloration on the surface of a body of water;
  • Discharges that violate applicable water quality standards; or
  • Discharges that cause a sludge or emulsion to be deposited beneath the surface of the water or on adjoining shorelines.

This sheen rule applies to both petroleum and non-petroleum oils - e.g., vegetable oil.

The discharge regulations also have been toughened for U.S. military vessels. The National Defense Authorization Act of 1996 amended Section 312 of the Federal Water Pollution Control Act to require the Secretary of Defense and the administrator of the U.S. Environmental Protection Agency (EPA) to develop UNDS for vessels of the armed forces for "discharges, other than sewage, incidental to normal operation." Previously, this section only addressed the regulation of sewage.

Mother Environmental is working with General Dynamics to provide solutions to ensure a clean bilge discharge from the new U.S. Marine Corps advanced amphibious assault vehicle (AAAV). A General Dynamics representative said that the technology "shows great promise for ensuring that the vessels' bilge discharge meets all uniform national discharge standards (UNDS) requirements with a cost-effective, environmentally safe solution."

Bilgewater content analysis
From an environmental perspective, the increased regulatory activity in bilgewater discharge limits is warranted. The cumulative effect of vessels ranging from small recreational boats to large surface ships dumping even small amounts of bilgewater could - and likely already has - wreak damage upon fragile aquatic ecosystems.

According to nature of discharge (NOD) reports obtained from the U.S. Navy, the composition of untreated bilgewater is a varying assortment of oil and grease, oxygen-demanding substances, and organic and inorganic materials. These materials, the reports say, include volatile organic compounds, semi-volatile organic compounds, inorganic salts and metals. The common metals collected in bilgewater samples include arsenic, copper, cadmium, chromium, lead, mercury, selenium and zinc, while organics include benzene, isomers of hexachlorocyclohexane, ethyl benzene, heptachlor, heptachlor epoxide, napthalene, phenols, pthalate esters, toluene, trichlorobenzene and trichloroethane.

The primary sources of these contaminants are vessel propulsion systems and auxiliary systems that use fuels, lubricants, hydraulic fluid, antifreeze, solvents and cleaning chemicals. Certain wastestreams such as steam condensate, boiler blowdown, drinking fountain water and sink drainage located in various machinery spaces can also drain to the bilge.

Existing bilgewater control devices
In worst-case scenarios, environmentally irresponsible vessel operators have dealt with excess bilgewater by dumping it overboard. Others have tried to hide the telltale sheen with emulsifiers, though the damage is still done.

Currently, commercial and military surface ships primarily employ two different methods in dealing with bilgewater treatment and removal. Many of these vessels use oil water separator systems to reduce the oil content of bilgewater prior to overboard discharge. Most of these larger vessels also have an onboard system for collecting and transferring bilgewater to a holding tank for later removal and disposal on shore.

Testing with new bilgewater filter
Lab testing and analysis were performed on the BilgeKLEEN system, utilizing solvent extraction followed by infrared spectroscopy (IR) (see Table 2). The test filter was a 10-inch spunbound polypropylene, 5-micron filter infused with the MYCELX chemical compound. Using a dwell time of one second and a flow rate of 20 gallons per minute, the filter reduced all contaminants to below detectable limits (BDL) at varying percentages of oil contamination. The test results included removal of all sheen and visible discharge.

The MYCELX technology used in the new system represents a new class of molecular compounds with the ability to solubilize and remove from water the full range of mixed emulsions and lipophilic and hydrophilic organic compounds in addition to many chelated and non-chelated metals. The chemistry is infused into a filter developed from any number of a wide range of substrate materials.

In treatment applications with bilgewater, the chemistry has demonstrated an extremely high affinity for hydrocarbons, especially aromatic and poly-aromatic hydrocarbons, as well as hexachlorocyclohexane, halogenated hydrocarbons and benzene derivatives.

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This article originally appeared in the 08/01/1999 issue of Environmental Protection.

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