Patent Application
20120087730
When oil or similar hydrophobic chemicals are spilled into waterways, they typically float, forming a layer or “slick” on the surface. The removal of this slick is essential to prevent the fouling of beaches, riverbanks, and other areas that the oil might come into contact with, and also to permit the entry of oxygen and sunlight essential to the aquatic ecosystem. It has been well known in the art to use sorbent booms for this purpose. Such booms are long sock-like tubes filled with a material which absorbs oil and similar hydrophobic liquids, but does not absorb water. These tubes are often linked end-to-end to create a chain of booms intended to surround a spill (or in the case of a spill in a river or stream, span the flow). However, although this design has been in use for many years, it has not proven satisfactory in practice. Such booms typically permit substantial quantities of oil to pass underneath them rather than being absorbed. Their round shape limits the surface area which can be exposed to oil, and prevents them from being weighted to float at an appropriate depth. Attempts to mitigate this problem have typically involved the placement of a hard barrier boom behind the sorbent boom so that the oil is trapped in close proximity to the sorbent and therefore more likely to be absorbed. This solution is expensive, because two booms are employed, requiring two deployment and recovery efforts using redundant equipment. Hard booms are also very heavy, and therefore difficult to transport and deploy, as well subject to damage by wind or current. In addition, a hard boom may not be practical for use in rapidly flowing water such as small streams.
Another approach to dealing with spills in flowing water has been the use of “filter fences.” These are literally fences, consisting of posts and water-permeable netting or fabric, which are built across streams. By themselves they do little to stop oil, so oil-absorbing particulate material is placed on the upstream side to absorb oil as the water passes through. Although more effective than sock booms, this method is labor intensive. Fences must be built by hand and the oil absorbent must be placed and removed by hand. The absorbant material near the top is largely wasted, because it floats above the oil and is therefore unable to absorb it. It is difficult to place fenceposts in hard-bottomed streams or concrete-filled drainage ditches, and difficult to affix fenceposts with the necessary permanence in areas with fast flowing water or soft silt bottoms. In the event of a loss of fence integrity or unexpected water volume overtopping the fence, contaminated oil-absorbing particulate can be scattered downstream, creating a secondary environmental hazard to complement the oil spill.
Mechanical skimmers of the type used to remove oils from industrial wastewater have also been employed, but they suffer from even more severe deficiencies in real-world conditions than the above approaches. They do not handle waves or tides well, require a power supply to function, and have no barrier qualities at all, meaning they must be combined with hard booms or some other means of concentrating oil to allow it to be removed.
The problems of the prior art are solved by a sorbent boom having multiple compartments of similar size in a single panel, permitting it to absorb oil more effectively than sock booms without halting the flow of water through the boom as hard booms do.
Referring to
Compartments 18a, 18b, and 18c are filled with an oil absorbing fill material. Preferably, this fill material absorbs oil but not water, so that water may flow easily through the boom as a whole, but oil is trapped. The fill material should be lighter than water so that the boom 10 can float while absorbing oil rather than sinking. Meltblown polypropylene is preferred, and virgin rather than reclaimed polypropylene is especially preferred. Other oil absorbing fill materials are also available and well known in the art. Each compartment is closed in whatever manner will retain the fill material.
The boom 10 will preferably have some means of attaching it to other booms, to fixed structures, to boats, or to winches, reels, and other means of deployment. These attachment means 20 may be any well-known device, such as grommets, fabric or wire loops, or clips. These attachment means 20 are already in use on conventional sock booms. For illustrative purposes only, fabric loops are shown. Preferably, some of these attachment means 20 are located at or near the corners of the boom 10. This permits the booms 10 to be joined in such a fashion as to keep them substantially parallel with each other and prevent twisting. Additional attachment means 20 may be along the edges of the boom 10 to permit the booms 10 to overlap each other to maximize oil absorption. In addition, weights 22 may be attached to the attachment means 20 along one edge so as to hold it upright in the water.
The booms 10 of the invention may be deployed in a number of ways. For spills of limited scope in enclosed and relatively static bodies of water, they may simply be placed upon the water's surface and permitted to absorb any oil they encounter. This is an inexpensive means of cleaning the water. Somewhat greater efficiency can be achieved by connecting a plurality of booms 10 together and permitting the booms to float horizontally in an extended string. This method is simple and quick to set up and gives superior absorption compared to sock booms because the flat design puts more oil-absorbing material near the surface of the water, where it is needed. A flat-floating panel boom 10 or string of panel booms 10 also deals with wave action better than sock booms because waves that push the leading edge up tend to drive the trailing edge downward, into the oil requiring absorption.
A preferred method for deploying booms 10, as shown in
The weighted chain of oil booms 10 may be positioned in any way which maximizes the chance of encountering oil. For instance, a set of booms 10 may be deployed across a harbor mouth so that tidal action will cause bilge oils to be collected before they escape the harbor. The chain may be positioned to surround or “blockade” an environmentally sensitive section of shoreline so that oil spills from the open sea will not affect that area. It may be strung across a river or stream to capture oil from upstream and prevent it from doing further damage, and in this application it is much more efficient than filter fences because all of the sorbent material is located near the surface of the water, where the oil is. A chain of booms 10 may be deployed in a circle around the source of an oil spill or leak to contain it. It may be towed behind two or more towing boats 24 in a “purse seine” action to surround and mitigate an otherwise uncontrolled spill, as depicted in
Because the booms 10 are not made of biodegradable materials, they may be left in place indefinitely until saturated with oil. They may then be removed and optionally replaced with fresh booms 10. This permits cleanup to occur naturally over an extended period of time with minimal human intervention. For instance, a tanker truck carrying some quantity of oil may crash on the roadways, leaking oil into drainage ditches or storm drains which lead to local streams. While the bulk of the oil may be cleaned up fairly promptly, some may cling to rocks or the roadway and leach into the water only gradually. Booms 10 may be placed in the stream and left in place for extended periods of time to catch this residue until it has been reduced to an acceptably low level by the natural water flow.
The terms and expressions that have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims that follow.
| Number | Date | Country | |
|---|---|---|---|
| 61403411 | Sep 2010 | US |
