The present invention relates to an apparatus for and method of removing pollutants from water and, more particularly, for removing the oily pollutants from the runoff due to rain before the runoff can enter streams and bodies of water.
In recent years, federal, state and local regulatory agencies charged with storm water management have required that storm water be pre-treated, that is, cleaned up, prior to being discharged into the receiving body of water.
Sources of such pollution include light industrial areas where oils and organic solvents are used for equipment maintenance, and streets and parking lots where oil from automobiles and trucks has leaked from engine crankcases. Oil is also deliberately applied in some rural areas to reduce dust and control pests. Another source of undesirable oils and the materials which make up road surfaces themselves such as asphalt which can release tars. Rainstorms and other sources of water wash oil and organic material from paved surfaces towards gutters. Other undesired oils reach streams, lakes and oceans from water flowing over lawns, rooftops, parking lots and outdoor work areas. Rainwater washes the oils up and they float on the surface of the flowing water which travels to nearby storm drains, where it begins to travel to downstream creeks, rivers, bays and oceans. Pollutants of primary concern found in storm water include oils and other organic hydrocarbons. It is the first sheet of water which runs across a paved surface that contains the most pollutants and is important to be pre-treated.
Pretreatment in open areas can be accomplished by filtering the storm water through grass swales, exfiltration trenches (underground filtration), or dry retention areas. However, these pretreatment arrangements are often not possible due to, for example, lack of sufficient area or the high cost of acquiring it, in the case of grass swales, or a water table close to ground surface, in the case of exfiltration trenches. As a result, regulatory agencies are forced to allow direct discharge of storm water containing pollutants into ground water, canals, lakes, streams, etc. This oil pollution problem is exacerbated in urban and suburban areas where surface waters are quickly channelled into underground conduits. In these collection and channelling systems, oil is not exposed to sunlight and weather which tends to break down or evaporate the oils, especially the lighter fuel oils.
Spills of oil or other hydrocarbons from tankers and from equipment loading the tankers usually occur on large open waterways such as harbors, bays, canals, oceans, estuaries and, on some occasions, flowing rivers. Spills from these sources are routinely treated by first retaining the spill within a confined area with booms and then mechanically removing the oil with skimmers or absorbent materials. There are a number of absorbent materials for both natural and synthetic oils, including synthetic fibers which absorb oils but not water. However, these oil abatement measures are designed to be temporarily deployed at oil spill sites. These materials are designed to float on the surface of the water and soak up oil and other organics. They are then removed and disposed of or, in some cases, are squeezed out and reused on the spill.
Less attention has been focused on the contamination of streams and bodies of water by oils and other organics from what are known as non-point sources, such as in runoff from rainfall. Water in small streams, irrigation ditches, storm drains and gutters can become contaminated with oil from a variety of sources both acute and chronic in nature.