Car Washing

Waste

There are some differences in the level of waste and resulting environmental damage derived from car washing, depending on the type of car wash (driveway versus professional). According to engineering studies, a 5/8-inch hose running at 50 psi uses approximately 14 gallons of water per minute. This means that a rather short domestic car wash can use between 116 and 180 gallons of water. Professional car washes consume approximately 60 percent less water than driveway washes, depending on the method they use (manual, conveyor, in-bay automatic, or self-service systems).

Pollution

Besides water-consumption issues, the dirt washed off vehicles as well as many of the materials used in the process of cleaning are generally harmful to the environment. Washing vehicles (both by hand or using a machine) on an impermeable surface can cause wash wastewater flow into storm drains. Soap from washing cars at home or charity car washes generally causes a lot of pollution, since soap and dirt flow freely through storm drains and ditches, ending up in streams untreated.

Contaminants in most of wash wastewater include the following:

• Petroleum hydrocarbons (such as gasoline, diesel fuel, motor oil, fluids, and lubricants) from automobile engines, leaks, and fuel combustion processes. Oil and grease contain hazardous materials such as benzene, lead, zinc, chromium, arsenic, and metals resulting from normal wear of auto brake linings (copper), tires, exhaust, and fluid leaks.
• Detergents, including biodegradable detergents. Surfactants that are present in detergents and cleaning formulations (both synthetic and organic agents) lower the surface tension of water, allowing dirt or grease to be washed off. Detergents can destroy the external mucus layers that protect fish from bacteria and parasites. Detergents can also damage the gills. Most fish will die when detergent concentrations approach 15 parts per million. Detergent concentrations as low as five parts per million can kill fish eggs.

Surfactant detergents are implicated in decreasing the breeding ability of aquatic organisms. Organic chemicals such as pesticides and phenols are then much more easily absorbed by the fish. A detergent concentration of only two parts per million can cause fish to absorb double the amount of chemicals they would normally absorb, although that concentration itself is not high enough to affect fish directly.

Phosphates and nitrogen-containing detergents (nitrates) that are plant nutrients could cause excessive growth of pest plants at or in nearby water bodies. Water naturally contains less than 1 milligram of nitrate-nitrogen per liter. State and federal laws in the United States set the maximum allowable level of nitrate-nitrogen in public drinking water at 10 milligrams per liter (10 parts per million). Infants who ingest water that is high in nitrate can develop methemoglobinemia.

This condition is also called “blue baby syndrome” because the skin appears blue-gray or lavender. This color change is caused by a lack of oxygen in the blood. Common sources of nitrate contamination include fertilizers, animal wastes, septic tanks, municipal sewage treatment systems, and decaying plant debris.

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