Robert Staniec

Cross-Reference to Related Application

This is a continuation in part of the earlier copending United States Patent Application 08/005,206, filed June 29, 1993, the disclosure of which is incorporated herein by reference in its entirety.

Technical Field

This invention relates to methods and materials for remediation of liquids, particularly anaerobically fouled large-volume liquids, and especially for remediation of cutting oil used in the machining of metal parts.

Background of the Invention

Traditional methods of treating industrial or municipal waste water, aquaria, and the like, is to provide an aerobic bacterial process in an otherwise stagnant basin. To achieve such an aerobic bacterial process, the liquid is aerated. Aeration is usually carried out by

injection of oxygen or air into the waste water by means of jets, airstones, diffusers, or the like.

One specific example of a potentially stagnant fluid reservoir is found in machining operations. Cutting oil is a generic term for that class of oils which are used in metal machining operations. Cutting oil is provided at the cutting surface where a metal-shaping bit is used to modify a metal workpiece. Cutting oil provides a lubricating film between the cutting bit and the workpiece, thus keeping the cutting area cooled. The continuous flow of cutting oil acts to retain metal shards or flakes formed during the cutting process, and to carry these flakes away from the cutting surface.

One example of a machining apparatus 110 is shown in Figure 1. A workpiece 112 (shown in cross section) is supported below a cutting bit 114. The workpiece 112 and the cutting bit 114 are moved relative to one another, either by motion controls such as the handle means 116 shown, or by computer controls (not shown). Generally, motion controls provide relative movement along each of the x, y and z axis.

A reservoir of cutting oil is maintained within the body of the machining apparatus 110. The cutting oil is pumped to a nozzle 118 located proximal to the cutting surface. The cutting oil is sprayed over the workpiece 112 and the cutting bit 114. A drain system (not shown) returns the cutting oil to the reservoir.

The presence of metal flakes in the cutting oil has traditionally limited the effective use life of cutting oils. However, a variety of methods have been developed to enhance the life of the cutting oil by

filtering the oil, either before it is sent to the cutting oil reservoir, while it is held within the reservoir, or as it is brought to the cutting surface. Generally, the larger flakes are removed by filtration or straining. The smaller metal flakes can be removed by skimming or other processes. Cutting oil can be filtered by the processes described in U.S. Patent 4,325,663, for example.

Cutting oil can become contaminated by anaerobic bacteria. The presence of anaerobic bacteria in the cutting oil reservoir causes rank and rancid odors, limiting the useful life of the cutting oil for aesthetic reasons. The presence of the anaerobic bacteria can also provide a source of irritation or contagion for the humans who must come into contact with the cutting oil in either liquid or volatilized form.

Figure 2 shows a cross-sectional representation of a machining apparatus of the parent application. A workpiece (not shown) is supported below a cutting bit 214. Cutting oil provides a lubricating film between the cutting device and the workpiece, thus keeping the cutting area cooled. The continuous flow of cutting oil acts to retain metal shards or flakes formed during the cutting process, and to carry these flakes away from the cutting surface. The cutting oil is removed from the cutting area by a retrieval conduit 220. This retrieval conduit 220 is adapted to deliver used cutting oil from the cutting area to a cutting oil reservoir 222. Within the cutting oil reservoir 222 is a recirculating pump 224 which returns cutting oil to the nozzle 218, continuing the cycle. One or more cutting oil reservoir 222 is generally located within the body of the machining apparatus 210.

In the pictured embodiment, an aeration system is located at least partially within the cutting oil reservoir 222. The aeration system 226 acts to increase the oxygenation of cutting oil in the cutting oil reservoir. If a standard machining apparatus is to be retro-fitted to include an aeration system, an aeration system including an air compressor (not shown) and air tubing 228 is generally used. compressors are generally designed to function in a clean, dry environment. Therefore, it is generally convenient to locate the air compressor outside the body of the machining apparatus 210. The air tubing 228 is generally connected to one or more air diffusers or airstones 230 which are placed in the cutting oil. It is generally preferred that the air diffuser or airstone 230 device be weighted or otherwise secured to remain at or near the bottom of the reservoir.

Aerobic and anaerobic bacteria are normally present as contaminants in cutting oil. The initiation of aeration will generally start the process of encouraging the proliferation of aerobic bacteria and discouraging the proliferation of anaerobic bacteria. The process of colonization of the preferred bacteria can be dramatically shortened by seeding the cutting oil with a starter culture 232 of the desired aerobic bacteria. Generally, the aerobic bacteria which are encouraged for proliferation in the cutting oil aeration system are those bacteria which facilitate an aerobic decomposition of the decomposable organic materials suspended in the cutting oil. Nitrifying bacteria, such as nitrobacter sp. and pseudomonas sp., are especially appropriate.

Preferably when a solid matrix starter culture 232 is used, it is weighted to remain at the bottom of the reservoir 222 while permitting

easy circulation of the aerated cutting oil. When a solid matrix is used to provide the starter culture, it can be attached to a string or other handling means for ease of retrieval from the reservoir 222. In the pictured embodiment, a string 234 is connected to a hook 236 to provide easy access to the starter culture.

The combination of aerator mechanism and bacterial starter culture on a solid matrix has been found to be very effective. However, because the starter culture matrix is relatively mobile, it can migrate to areas of the tank in which there is less aeration, and less current flow across the matrix. This is especially problematic in larger tanks.

Snmmarv nf the Invention

An apparatus of this invention provides a two-chambered aeration tube which is submersible into a liquid. The first chamber is the aeration chamber. The aeration chamber is connected to a compressor installed above the surface of the liquid. .Air is fed from the compressor to the aeration tube, and exits the tube by way of a multiplicity of perforations. Air bubbles are continuously formed to maintain the circulating liquid in an aerated state.

As air bubbles continuously rise from the perforations of the air tube toward the surface of the liquid, a negative pressure is created, drawing up liquid which is present just below and surrounding the aeration tube. The bubbles cause the movement of the mass of liquid in a predictable manner. Specifically, the liquid forms currents which flow upwards from the aerator, then away once the bubbles break at the surface. The current flows downward again, and then is brought

inward toward the aerator to repeat the cycle. The volume of air moved, the size of the bubbles formed, and the volume of the liquid each contribute in part to the strength of the current.

The second chamber within the aeration tube is a microbe chamber. This chamber contains a substrate which is appropriate to support aerobic bacteria upon its surfaces. A multiplicity of perforations permit relatively free liquid flow through the microbe chamber and across the aerobic bacteria. Biological remediation of the liquid takes place as the aerobic bacteria break down the byproducts of anaerobic bacteria which foul the system. Continued aeration acts to provide a suitable environment for the proliferation of the aerobic bacteria, and ensures that proper mixing of the liquid takes place, permitting all of the liquid to be remediated.

Brief Description of the Drawings

Figure 1 shows a machining apparatus of the prior art.

Figure 2 shows a partial cross-section view of a metal machining apparatus of the parent application, including a cutting oil recirculating system, an aeration system, and a source for cultured aerobic bacteria.

Figures 3a and 3b show partial cross-section views of an improved aeration/remediation apparatus of this invention. Figure 3a shows the two chamber subunits separated, while Figure 3b shows the assembled unit in use.

Figures 4a and 4b show alternate configurations of the aeration chamber and microbe chamber.

The Figures are drawn for clarity and are not drawn to scale. Similar numbers refer to similar structures throughout the Figures.

Disclosure of the Invention Including Best Mode

Figures 3a and 3b show the two chambers of an improved aeration/remediation tube 340 of this invention. The first chamber is the aeration chamber 342. The aeration chamber 342 acts as an airstone or air diffuser, to break up a stream of air or oxygen supplied by the compressor (not shown) into discrete bubbles, which escape from the aeration chamber 342 through a multiplicity of perforations 346. The rising bubbles produce currents of aerated liquid within the liquid being remediated.

The second chamber of the aeration/remediation tube 340 is the microbe chamber 344. The microbe chamber also includes a multiplicity of perforations 346, to permit the currents created by the aeration of the liquid to pass across the surface of a matrix 348 within the microbe chamber 344. The surface of the matrix 348 is seeded with aerobic bacteria which, under appropriate conditions, cause the biological remediation of the liquid in which the apparatus is placed.

The aeration/remediation apparatus can find use in a variety of anaerobically fouled liquids, including aquaria, ponds, waste treatment, and the like. However, the aeration/remediation apparatus finds particular use in the remediation of cutting oils. For purposes of example only, and not by way of limitation, the invention will be described with specific reference to a cutting oil remediation system. It

will be understood that the system herein will be useful in a variety of environments.

Cutting oil is a generic term for that class of oils which are used in metal machining operations. Cutting oil generally comprises one or more mineral oil, chlorinated or sulfurized mineral oil, fatty oil, or mixtures thereof. The cutting oil can also contain anti-corrosion agents, emulsifiers, and the like. It is preferred that the cutting oil used in the subject invention not contain any anti-bacterial agents which would interfere with the proliferation of aerobic bacteria.

Cutting oil is provided at the surface where a metal-shaping bit or blade is used to modify a metal workpiece. Devices which use cutting oil include lathes, cold-saws, milling machines, and the like. Cutting oil provides a lubricating film between the cutting device and the workpiece, thus keeping the cutting area cooled. The continuous flow of cutting oil acts to retain metal shards or flakes formed during the cutting process, and to carry these flakes away from the cutting surface. The cutting oil is removed from the cutting area by a retrieval conduit. This retrieval conduit is adapted to deliver used cutting oil from the cutting area to a cutting oil reservoir. Within the cutting oil reservoir is a recirculating pump which returns cutting oil to the nozzle, continuing the cycle. One or more cutting oil reservoir is generally located within the body of the machining apparatus.

In accordance with the invention herein, an aeration/remediation tube 340 is located within a cutting oil reservoir. The aeration system acts to increase the oxygenation of cutting oil in the cutting oil reservoir.

The aeration system is run constantly, whether or not the machining apparatus is being run. Failure of the aeration system can cause die-off of the aerobic bacteria within the microbe chamber 344. If the aeration system has been disconnected for 12 hours or more, it is generally recommended that the reservoir system be re-seeded with a new bacteria starter culture.

If a standard apparatus is to be retro-fitted to include an aeration system, an aeration system including an air compressor (not shown) and air tubing 328 is generally used. Air compressors are generally designed to function in a clean, dry environment. Therefore, it is generally convenient to locate the air compressor on a clean, dry surface adjoining the container of liquid being remediated. A variety of appropriate air compressors are known and are commercially available. Care must generally be taken during installation and use of the air compressor to ensure that cutting oil cannot escape the reservoir through or along the air tubing. If possible, the air compressor is placed above the level of the cutting oil in the reservoir to avoid siphoning in the event of power failure. Preferably, an anti-siphon valve is positioned along the air tubing 228.

Air tubing 228 is connected at one end to the air compressor, and at the other end to the aeration chamber 342. Air tubing 228 is commercially available in varying rigidity, diameters and lengths. Generally, the rigidity, diameter and length of the air tube will be dictated by the specific air compressor used and its proximity to the fluid reservoir.

If flexible air tubing 228 is threaded through curves having a small radius, a rigid pinch protection collar should be provided to avoid crimping of the tubing. In one embodiment, hooks or other such devices are provided to secure the air tubing 228 along its course from the air compressor to the airstone or air diffuser. By securing the air tubing 228 in place, inadvertent crimping of the tubing can be minimized or avoided.

The air tubing 228 is generally connected to one or more aeration chamber 342. When more than aeration chamber 342 is used, a "T" connector or splitter can be used to provide multiple tubing connections between a single air compressor and multiple aeration chambers 342. It is generally preferred that the aeration/remediation tube 340 be weighted or otherwise secured to remain at or near the bottom of the reservoir. For example, a weight 350, such as a lead weight, can be placed within the aeration chamber 342, the microbe chamber 344, or elsewhere within the housing.

The aeration chamber 342 is preferably a perforated tube. For example, a porous polyethylene tube having a 3-inch outer diameter and a 3/16-inch wall polyethylene tube can be used. The length of the tubing will vary with the application, but will commonly be from less than 2 inches to more than 12 inches in length. Generally, the pore size is from about 40 micron to about 80 micron, more preferably about 60 micron. Appropriate tubing is commercially available from Porex Technologies, Fairburn, Georgia, as Porex porous plastic tubing.

A cap 352 provides a male pipe thread or hose barb to connect standard air tubing 328 to the aeration chamber 342. When the aeration chamber 340 is three inches in diameter, the air tubing 328 will be, for example, 3/4 inch in diameter. Such air tubing is readily available commercially.

In alternate embodiments (not shown), the aeration chamber is a stone, ceramic, or polymeric airstone. Such airstones are commercially available in a variety of sizes and shapes, and can function as the aeration chamber 342.

The aeration chamber 342 is physically joined to the microbe chamber 344. Conveniently, the microbe chamber 344 can be removed for periodic replacement, and thus is readily separable from the aeration chamber 342. In a preferred embodiment (shown in Figure 3b), the microbe chamber 344 is joined with the aeration chamber 342 in an end- to-end configuration. Conveniently, a screw cap 453a on the microbe chamber 344 is fitted into a threaded receptacle 354b on the aeration chamber 342. Other temporary or permanent joining schemes and configurations will be readily apparent to those skilled in the art.

The microbe chamber 344 is preferably a perforated tube. For example, a porous polyethylene tube having a 3-inch outer diameter and a 3/16-inch wall polyethylene tube can be used. The length of the tubing will vary with the application, but will commonly be from less than 2 inches to more than 4 inches in length. Generally, the pore size is from about 250 micron to about 350 micron, more preferably about 250 micron.

Appropriate tubing is commercially available from Porex Technologies, Fairburn, Georgia, as Porex porous plastic tubing.

In an alternate embodiment (shown in Figure 4a), the microbe chamber 344 surrounds the lower surfaces of the aeration chamber. Liquid is carried through the microbe chamber 344 as it passes upward, drawn by the rising bubbles. In another embodiment, shown in Figure 4b, the microbe chamber 344 forms a collar about the airline tubing 328.

As shown in Figures 3a and 3b, the microbe chamber 344 is a perforated chamber which allows the currents generated by the aeration chamber 342 to flow in and out. The perforated housing can be made of any suitable material, such as polymers, ceramics, plastics, and the like. Like the aeration chamber 342, the microbe chamber 344 is conveniently capped 354a, 356 at each end.

Within the microbe chamber 344 is a matrix 348 which is suitable for the growth and proliferation of aerobic bacteria. An inorganic matrix 348 which is insoluble in surrounding liquid is preferably used. The inorganic matrix 348 includes cultured aerobic bacteria on surfaces upon and within the matrix. A suitable matrix 348 material is perlite. The matrix 348 is contained within the perforated chamber by use of perforations 346 which are too small for the matrix to fit through. In a less-preferred embodiment (not shown), a rigid or flexible housing structure having a plurality of relatively large holes therethrough can enclose a non-woven nylon filter membrane, for example, which in turn confines the particulate matrix. These materials can be hot-stamped to fuse them into a suitable container for a particulate matrix 348.

Aerobic bacteria can be cultured from native bacteria within an environment which is appropriate for the liquid being remediated. Alternatively, a commercially prepared bacterial starter can be used. A variety of suitable aerobic bacteria cultures are commercially available. The "Bio 520" starter culture, available from Harvey Universal, Inc. (Torrance, CA) is especially suitable. "Hi-Clean Σ" from Sankai

Chemical Co. (Tokyo, Japan) can also be used.

Generally, the aerobic bacteria which are encouraged for proliferation in the cutting oil aeration system are those bacteria which facilitate an aerobic decomposition of the decomposable organic materials suspended in the cutting oil. Nitrifying bacteria, such as nitrobacter sp. and pseudomonas sp. , are especially appropriate.

The temperature of the cutting oil reservoir will generally be about room temperature. Even while cutting oil is being used (and therefore heated) at the cutting surface, the aeration (using room temperature air) will act to stabilize the temperature within the reservoir. Generally, however, the temperature should be kept with the range of about 15°C to about 37°C. The pH of the cutting oil will generally remain in the range of about 6 to about 8.5.

If the temperature, pH, or other variable causes the bacteria die off and rank odors result, it is recommended that the cutting oil be discarded and fresh cutting oil, with an appropriate bacterial starter culture, be placed into the system.

While the invention has been described in connection with several exemplary embodiments, it will be understood that many modifications will be apparent to those of ordinary skill in the art in light of the above disclosure. Such modifications may include using substitute materials, smaller or greater dimensions, varying the number and placement of the aerobic bacteria chamber relative to the aeration chamber, using a variety of different aeration devices, and so forth, to achieve substantially the same results in substantially the same way. Reference to the following claims should be made to determine the scope of the invention.