WO2015002999A1

WO2015002999A1 - Laundry effluent based water recovery system

Info

Publication number: WO2015002999A1
Application number: PCT/US2014/045135
Authority: WO
Inventors: Bruce R. Harrison; Eugene L. Langlais; Walter R. SMALL, Jr.
Original assignee: Aquacache, Inc.
Priority date: 2013-07-03
Filing date: 2014-07-01
Publication date: 2015-01-08

Abstract

A system for treating wastewater containing solid materials and one or more of fats, oils and grease, in which wastewater in a flow path through one or more screens disposed in said flow path, and continuously or intermittently refreshing the screen media in said flow path is refreshed to expose fresh free media, without interruption of flow of said wastewater, without interruption of the wastewater, whereby buildup of solids, fats, oils and grease on said screen media is avoided.

Description

LAUNDRY EFFLUENT BASED WATER RECOVERY SYSTEM

This invention relates to the field of wastewater treatment and recovery. The invention has particular utility in connection with the treatment and recovery of laundry effluent wastewater and will be described in connection with such utility, although other utilities are contemplated.

All commercial laundry facilities, laundromats, and dry cleaners with laundry facilities are required to install a lint trap or settling pits for discharge from washing machines.

Currently, the warm waste water from each wash cycle is first passed through a vibrating shaker screen, see Figure 1 which illustrates a shaker screen diagram according to the prior art to remove particles larger than 70 microns. With this system material feeds out of the hopper onto the shaker screen. The screen is vibrated vigorously causing the material flowing over it to rapidly bounce up and down. This shakes the finer material off of the larger material and allows it to pass through the mesh panel. The larger particles continue to bounce off the end of the mesh panel at the rear of the screen. This is the most common method for large laundry operations. Some laundries will use a simpler coarse stationary screen that may only be able to catch larger materials 200- 1000μ without plugging and overflowing rapidly. As indicated by the particle sizes shown in Table 1,

TABLE 1 - Material Size Range that could be found on Cloth these systems can only trap a modicum of the macro-fiber lint and very little if any of the micro-fiber lint. They are also not specifically designed to capture fats, oils and grease (F.O.G.). Once these systems get filled or plugged, they must be removed for cleaning and the laundry flow must stop; or, there needs to be a redundant installation so that the waste water flow can be re-directed from one system to the other while one system is being cleaned and screens are being replaced. The larger the system is the more laborious and time consuming the cleaning process will be.

Alternatives for this type of prior art system are stationary screens and baffles, as shown below in Figures 2, 3 & 4, in which Figure 2 shows simple static screen trap including a first "coarse" screen stage which captures "buttons"; Figure 3 shows a two stage "medium" screen capture system with removable and fixed straining baffles, which capture lint and some particles; and Figure 4 shows more complex filter screen, baffle and catch trap design.

These prior art systems are not geared to deal with the constant removal dynamics of particle/lint build-up and must be cleaned out frequently; nor do they deal with capture of finer particles, micro-fiber lint or F.O.G. Grease & Oil traps usually deal with flotation and/or skimming the oily materials from the surface of the water. See Figure 5 which shows a trap design that uses a box strainer for lint and larger items (e.g. buttons) and then uses baffles to allow Grease and Oil to gather at water surface for later extraction.

All of the above prior art systems require extensive maintenance and cleaning procedures, while only removing lesser portions of the unwanted materials compared to the present invention disclosed, as will be discussed below.

The present invention provides an improved system for extracting water exiting from laundry facilities in which the water is directed to pass through one or more dynamic screening sections thereby removing large quantities of grease, lint and debris. The result is a more convenient, efficient and complete extraction of unwanted materials than presently provided. The extracted materials are more easily discarded, and the water that has been processed through this device is more effectively treated, enabling the water to be post treated and post filtered more efficiently and thus recycled for reuse in many subsequent laundry cycles. This will result in water, power and materials savings without lowering laundry quality.

Figs. 1 -5 illustrate conventional prior art screening systems;

Fig. 6 is a micro-photograph of lint fibers with "powder particle" simulated objects superimposed for comparison;

Fig. 7 illustrates a first embodiment of the invention in which flow from water source direction is filtered from two different sides as mesh screens, and dynamic screens are motorized to unwind and wind at variable speeds; Figure 8 shows an alternative embodiment of the invention involving flow from two water source directions, filtered through screens of one mesh size and in which dynamic screens are motorized to unwind and rewind at variable speeds;

Figure 9 is a perspective view showing bi-directional-dual screen device for grease and lint extraction in accordance with the present invention;

Figure 10 is a top plan view of the device of Figure 9;

Figure 1 1 is a side view of the device of Figure 9;

Figure 12 illustrates lint fiber build-up on the screen mesh forming a "filter cake";

Figure 13 illustrates lint fiber trapping grease particles and particle clusters; Figure 14 is a side elevational view of a filter mesh illustrating how as the fiber "filter cake" builds thickness, smaller particles will be captured in the deeper levels of the fiberglass, further clarifying the fluid below the mesh;

Figure 15 illustrates the sieving mechanism of filtration and shows how particles that cannot fit through the openings of a filter material or filter cake won't pass;

Figure 16 illustrates how filtration mechanisms play an important part in a filtering process, namely, how particles caught in the fluid flow and interact with the "primary filter fiber" or with the "secondary filter fiber" captured as "lint" from the laundry stream;

Figure 17 illustrates progression filtration from sl ight to plugged with a static screen process;

Figures 1 8-21 illustrate, progressively, screens from clean to complete blockage and no flow;

Figure 22 illustrates filter screen material of different mesh sizes from coarse to fine;

Figure 23 illustrates the dynamic screen process in accordance with the present invention.

As used herein the following definitions apply:

Other "associated debris" can include such items as buttons, snaps, coins and other such items as can be carried into a washing machine in laundry items.

Laundry items include clothes, uniforms, aprons, towels, napkins, table cloths, bibs, overalls, caps and hoods, face masks, blanket, pillow cloths, wash cloths, wipes, grease rags and other such cloth related objects. These items can be fabricated from cloth or materials such as linen, cotton, polyester, nylon, cellulose acetate and similar fabrics most commonly used for the production of the aforementioned laundry items.

The term "grease" is often referred to as G&O (grease and oil) or F.O.G (Fats, Oils and Grease) in laundry applications, and in general connotes all lipid materials that need to be cleaned or removed from the soiled cloth in the washers. These unwanted grease related materials may be in the form of liquids, semi-solids, or solids; and can include fatty acids, fatty esters, amides, waxes and a large variety of other similar natural and synthetic organic chemicals. Typically, these materials would be considered as being hydrophobic and would not be water soluble, but may be capable of being emulsified or dispersed in water with the appropriate surface active materials, such as soap or surfactants.

The term "lint" (or "wet lint") in this application refers to the various fibers that are generated from the process of washing the cloth items in the laundry machines that are found suspended in the water discharged from those laundry washing machines, not to the dry lint found in the drying machines. This "wet lint" is comprised of macro- fibers and micro-fibers of the threads used to make the cloth and sew portions of that cloth together in the fabrication of the aforementioned "laundry items" and the like. Such lint fibers can be solitary or can be in tangles and clumps. The lint may be generated by the untangling and breaking of the threads in the cloth or may come from "dry lint" trapped in (e.g. in a pocket) or on the cloth (e.g. from static). The size of the lint (length and diameter) can vary widely. However, typical lint macro-fibers are 30- 100μ (1 μ = 1 μιη = 0.001 mm) long and 5-15μ in diameter. See Figure 6 which is a microphotograph of lint fibers with "powder particle" simulated objects superimposed for comparison. However, lint tangles and clumps can be much larger (>1 ,000 μ). Micro-fiber lint is much smaller, but with a wider range of sizes, and may not be visible to the unaided eye. Such micro fiber lint can range from 5-25μ long and 1 -5 μ in diameter. However, exceptions to these ranges are also possible depending on the fiber type, the age of the cloth; and the amount of friction it has experienced before, during, and after the wash and rinse cycles in the laundering process. The laundry chemicals, pH, and water temperature will also have an effect on the amount of lint generated, as can any previous chemical exposure the cloth has experienced (in a hospital, restaurant, laboratory, machine shop, print shop, etc.).

"Other Fibers" may also be present that did not originate from the cloth items. These fibers may come from paper (cellulose) or they can be "hair" from humans or animals (e.g. cats, dogs, horses, etc.) or they can come from other cloth contact not intended for the commercial laundry (e.g. wool). The size of these "other fibers" is quite variable. Human hair averages 70 micron in diameter, but could be many centimeters long (l cm = Ι Ο,ΟΟΟμ).

"Unwanted materials" can include a wide variety of items that will also vary with the source of the laundry and with events and timing. Such items can include sand and dirt, dust, pollen, talcum powder, human skin cells, animal dander, white blood cells, red blood cells and so on. (See Figure 6 and Table 2.) Other materials of much larger dimensions are also possible.

Figure 6 - Microphoto of lint fibers with "powder particle" simulated objects

superimposed for comparison

25 Microns _ Lint, Parfeies Visi le to the Naked Eye

10 Microns _m Heavy Dust, Lint, Fertilizer, Potten

5 - 10 Microns Average Dust, Plant Spores, Mold

1 - 5 Microns _ Bacteria, Light Dual Animat Dander

0.3 - 1 Microns _ Sacterfa, Tobacco and Cooking Smoke. MMaOe Fumes 0.001 -0.01 Microns Viruses Table 2 - Relative Size Comparison of Materials

All such materials as described above (and others) must be removed from the laundry cloth in order for it to be considered "clean". Likewise, the materials once removed from the cloth then reside in the water and must be removed from the water before this water can be used again in the laundry cycle, or the risk of these materials re- depositing on the clean laundry cloth is extremely high. The result will be dingy, dull, stiff, "unclean" laundry items.

In simplest form, the present invention, employs two or more different sized mesh screens through which wastewater may be flowed. Unlike prior art lint traps, the screens are motorized to unwind and wind as they fill with lint. This is shown

simplistically in Figure 7 which shows flow from one water source direction; filtered through two different size mesh screens; and in which the dynamic screens are motorized to unwind and rewind at variable speeds.

An alternative embodiment is illustrated in Figure 9 which shows bi-directional flow of water, and having a bi-direction/dual screen device for grease and lint extraction. This configuration allows for two inlet streams of washer effluent to be strained concurrently.

The overhead view. Figure 10 of the Figure 9 embodiment of the current invention shows the drive assemblies on the left for the two "dynamic screen" assemblies. NOTE: both webs of screen material have been disconnected between both sets of unwind and rewind rolls, and the inward located rewind rolls can be removed for discarding the "used dirty screens"; and "new clean screen" material can be loaded on the outward located unwind rolls for threading and connecting to the inward rewind rolls to begin a new cycle of extraction.

Unlike the static or vibratory screening systems in the previous existing art described, the present invention is a simple design based upon a "dynamic screen" extraction system intended to remove debris such as lint, grease and large particles more effectively than existing systems.

Dynamic Screen

A dynamic screen system refers to a continuous web of screen material that is powered to unwind and rewind allowing for a sufficient screen area to be available for capturing and holding a volume of unwanted grease and lint along with other adventitiously captured debris that is large enough to be trapped by the screen fabric and/or by the build-up of lint and other fibrous matter onto the screen fabric that acts like a "filter cake" to retain even finer particles.

A filter cake is formed by the substances that are retained on a filter device or media. The filter cake grows in the course of the filtration process and becomes "thicker" as particulate matter is being retained. The increased thickness and decreasing pore size of the filter cake retains ever finer particles. However, with increasing layer thickness the flow resistance of the filter cake increases. After a certain time of use the filter cake has to be removed from the filter media, e.g. by back-flushing, or the filter media replaced. If this is not accomplished, the filtration is disrupted because the flow resistance of the filter cake gets too high, thus too little of the mixture to be filtered can pass the filter cake and the filter plugs.

Dynamic screen advantages

In the present invention, the use of a "dynamic screen" takes advantage of the increased efficiency of particulate capture, and eliminates the possibility of filter plugging, by controlling the speed at which the screen mesh materials progresses through the fluid stream. The constantly "renewed" dynamic screen material maintains a consistent flow rate.

The dwell time of a static or stationary screen in the fluid stream will determine how long it will take for the screen to get plugged, along with volume of water being filtered, particle size of the contaminants, the % loading of contaminants in the fluid, the pressure exerted on the filter screen, the temperature of the fluid, the size of the filter pore, the % of open area on the screen, total area of the screen in contact with the fluid, degree of turbulence in the fluid, electrostatic effects, density of the materials to be filtered, the affinity of the contaminants for the screen materials or other materials captured on the screen (for example, lipids like grease will tend to be attracted to lipophilic surfaces like plastic screens), viscosity of the fluid, the extrudability of the contamination to be removed (grease is very extrudable semi-solid and becomes less viscous and more extrudable at higher temperatures) and similar variables.

The dwell time of the dynamic screen is determined by the speed at which it is unwound and exposed to the fluid laden with suspended contamination. The other variables will stay in effect. The width and exposed height of the dynamic screen will be chosen by volume needs.

The screen velocity may be simply controlled by motor RPM, or can be interactively controlled by a feedback loop to maintain a constant surface speed, or to advance periodically, as necessary. Surface speed will vary with the changing diameter of the spool of screen material on the unwind roll as the diameter diminishes and the diameter of the spool increases on the rewind roll.

As the flow of fluid progresses through the screen, materials begin to build up, as the screen approaches the wind-up roll that portion closest to the roll has been exposed the longest and has captured the most debris and thus is the dirtiest. Similarly, the portion of the screen that is closest to the unwind roll has had the least exposure and has captured the least debris and thus is the cleanest. The area of the screen that is midway between the two rolls theoretically is half clean and half dirty, assuming that the fluid flow rate and total suspended solids (and constituency, particle size and ratio of solids) has been maintained. By using a dynamic screen principle, this invention, with proper process controls, for example, by monitoring back pressure on the screen using a strain gauge, or by measuring flow rates, one can maintain a relatively constant filtration efficiency throughout the length of the web of filter screen material. This will prevent plugging and any ensuing overflow and spillage, as well as preventing an under-utilization of the filter screen materials and the ensuing extra cost. By choosing the right mesh size and proper web speed, the process will be very efficient and easily maintained.

Changing to new rolls of screen material will be dependent on fluid volumes and contamination levels; but are intended to be done no more than once per day, and could be done , for example, only once per week or longer.

Screen Materials

The screen material used is readily available and inexpensive, and in one preferred embodiment, plastic screen mesh normally used for insect control may be used. It is available in a variety of mesh openings and in a variety of widths and roll lengths. It is also available in several plastic types, (and metal as well). Fiber glass is a popular material for strength and cost; but mesh screen also is available in polypropylene, Nylon, polyester and other polymer types. Common mesh sizes available are: 12x12, 14x18, 16x18, 17x20, 20x20 and 20x30. The numbers refer to the number of "wire" strands in one direction and the other number of strands perpendicular to the first. See Table 3. The opening size, through which water can pass and through which materials cannot pass, is determined by the mesh count and by the diameter of the strands. The % open area is also important. These dimensions represent "minimum criteria" for choice of materials. These dimensions determine the "sieving mechanism" of filtration and exclusion of particulates, but other filtration mechanisms (discussed below) play an important role in filtration efficiency, as does the build-up of the filter cake as previously mentioned above.

It has been discovered that a synergy exists between the lint fiber and F.O.G nature of contaminants captured and the screen materials chosen that leads to higher capture efficiency.

Mesh Aperture Mesh Aperture

Number (mm) Number (mm)

2.5 ^" ^" 7 .925 ~ ^' 32 0.495

3 6.680 35 0.4 1 7

3.5 5.61 3 42 0.31 5

4 4.699 48 0.295

5 3.962 60 0.246

6 3.327 65 0.208

7 2.794 80 0. 175

8 2, 362 100 0. 147

9 1 .981 1 15 0. 1 24

10 1 .651 150 0. 104

12 1 .397 170 0.088

14 1 . 168 200 0.074

16 0.991 250 0.063

20 0.833 270 0.053

24 0.701 325 0.044

28 0,589 400 0.037

TABLE 3 - A list of standard mesh sizes (number) versus opening dimensions

(aperture) in millimeters (mm); 1 mm = 1,000 μηι

Filter cake mechanism

The combination of lint fiber lengths makes an excellent mat on the screen mesh material. Once captured, they can then begin to capture particles and globules of grease. Even before the lint covers the plastic screen, it is attracted to the polymer strands and covers them, which in turn can trap the lint. This simultaneous build-up of grease and lint forms an excellent "filter cake" which in turn can capture even finer particles as it continues to build. With the controlled speed of the "dynamic screen" process, no plugging occurs and an optimum level is achieved. See Figure 12 which illustrates lint fiber build-up on the screen mesh forming a "filter cake", and Figure 13 which illustrates lint fiber trapping grease particles and particle clusters.

As the fiber "filter cake" builds thickness, smaller particles can be captured in the deeper levels of the fiber mat, further clarifying the fluid below the opening mesh size. Multiple Filter Mechanisms

The straining of particles through a screen mesh is a fundamental mechanical mechanism of filtration known as the Sieving mechanism (see Figure 15 which illustrates the Sieving Mechanism of Filtration is the simplest and most obvious; particles that cannot fit through the openings in the filter materials or filter cake won't pass, and is dominated by the juxtaposition (i.e. placement of two particles near one another), of particles of a certain size and pore openings of a certain size to determine what particle dimension will pass through the openings and which ones will pass through. Particles larger than the pore size are trapped and those smaller should pass through. However, other filtration mechanisms such as illustrated in Figure 16, which shows other filtration mechanisms as described below may play an important part in the process. Thus, particles caught in the fluid flow can interact with the "primary filter fiber", or in this case, can also interact with the "secondary filter fiber" captured as "lint" from the laundry stream can enter into play. Juxtaposition can also invoke other mechanisms of capture.

Other Filtration mechanisms:

· Inertia! impaction: With this mechanism, particles having too much inertia due to size or mass cannot follow the fluid stream as it is diverted around a filter fiber and it impacts the fiber. This mechanism is responsible for collecting larger particles.

· Interception: As particles pass close to a filter fiber, or caught in a fluid eddy, they may be intercepted by the fiber. Again, this mechanism is responsible for collecting larger particles.

· Diffusion: Small particles are constantly bombarded by molecules in the fluid, which causes them to deviate from the fluid stream and come into contact with a filter fiber,, This mechanism is responsible for collecting smaller particles.

· Electrostatic attraction: Oppositely charged particles are attracted to a charged fiber. This collection mechanism does not favor a certain particle size and can happen in coordination to the other mechanism, or it can be an independent occurrence, assuming the particles approach close enough for the charge attraction to overcome the flow.

Other attractive forces:

· Adhesion: Particles that impact softer materials, like fats and greases, or sticky materials can adhere or become imbedded in the softer mass and become trapped. * Wetting: Surface energy can allow oils and greases to wet and spread on a like surface with a somewhat higher surface free energy, such as a polymer

In all cases, once a particle comes in contact with a filter fiber, as illustrated in Figure 17 which shows progression of filtration from slight to plugged with a "static screen process", or other attractive materials, it is removed from the fluid stream and strongly held by molecular attractive forces (dipole moment, hydrogen bonding, etc.). It is very difficult for such particles to be removed once they are collected.

Figure 18 shows a front view of a clean filter screen material - no contaminate capture, Figure 19 shows a front view of a static screen with partial contaminate capture, Figure 20 shows a front view of a static screen plugged with contaminates-no flow, and, Figure 21 shows a front view of a "dynamic screen" with an ongoing gradient of capture.

The dynamic screen process used in this invention provides a consistent and controlled capture of a large percentage grease and lint and other debris while providing a consistent fluid flow.

The exit stream is ready for the subsequent steps of chemical and physical treatment to provide a usable recycled water source for laundry applications and similar processes as described in our co-pending provisional application no. 61 /842,894 filed July 3, 2013 (attorney docket AQUACACHE 13.02-P) and co-pending application no. PCT/US14/ , filed July 1 , 2014, based thereon (attorney docket

AQUAC 13.Q2PCT), the contents of which are incorporated herein by reference. More lint is extracted than the typical static screen processes and with much lower cost than shaker screen installations, and with lower maintenance requirements than either system.

Furthermore, much more grease is extracted from the washer waste stream than is possible with the typical static screen systems currently in use. And, shaker screen systems typically need separate grease and oil traps or separation systems to prevent fouling of the shaker screens if they are to prevent even higher maintenance costs and system down time to wash the disassembled dirty shaker screen devices and reassemble them.

The device can use a variety of screen materials, and can be scaled to smaller or larger sizes with scant difficulty to meet the needs of commercial laundry installations using multiple washer installation or tunnel washing devices. Daily volumes of 20,000 liters to 200,000 liter per day can be handled by single devices of moderate size. The dynamic screen may be set to travel (unwind) at a nominal 1 -3 inches/minute, as needed.

Larger volume applications could use multiple units and/or larger size units with wider screen webs and longer screen lengths, and different unwind speeds.

Two operational configurations are possible: (1 ) Uni-directional flow (Figure 7) with 1 or 2 stage filtration; (2) Bi-directional flow (Figure 8) with 1 stage filtration. (1 stage filtration uses two screen webs with the same mesh size; 2 stage filtration using 2 mesh sizes - larger size first then smaller size second to improve filter efficiency as needed.) See also Figure 22 which illustrates the use of three mesh sizes, coarse, medium and fine.

Examples of different mesh sizes for two stage filtration configurations

Disposal Advantages: Unlike static screens (fixed or movable) that cannot be discarded and need to be cleaned, and de-ibuted, or shaker screens which must be taken out for similar maintenance, "dynamic screens" are easily removed and discarded at very low cost. (<2e7ft²). No additional water or chemicals are required for sanitizing the screens and preparing them for re-use.

Since the rolls are rewound under pressure, most of the water is squeezed out of the used screens. The screen materials is sliced and removed in flat packs of spent material which can then be dried further if needed. The used screens can be disposed in a land-fill since unlike fluid and sludge wastes, they do not require permitting.

Alternatively, the used screens can be incinerated.

Referring to Figure 23, which depicts the "dynamic screen" process resulting in a composite gradient of lint and grease and other debris. The gradient is dependent upon residence time in the effluent stream with the thickest deposit at the exit/re-wind position and the thinnest deposit at the entry/unwind position; the total residence time is dependent upon the speed (in/min or cm/min) of the continuous web of screen material through the fluid from entry to exit (T_exi, - T_e„,_ry = T,_otai), rate and/or level sensors may be included in the system that can cause the utilization of the "dynamic screen" movement, to speed up, slow down, or stop & start the screen to maximize grease and oil extraction while minimizing use of the screen media, thus reducing cost and waste.

In summary, the present invention uses a "dynamic screen" approach in which a filter screen media is moved across the flow of contaminated fluids, thereby always presenting new and unused filter capability to the fluid in a "continuous process". This prevents blinding of the filter and overflow of the trap and/or failure to remove grease and lint from the process fluid stream; and, once the roll of material is "finished" allows for quick removal and replacement, and disposal of a "solid waste".), instead of the prior art "static screen" approach (that keeps a the filter media "in place" in a "batch process" until the filter does blind and overflow and/or fails to remove grease and lint from the trap, and then needs removing, cleaning and replacement, and the disposal of sludge.); or, the prior art "vibratory shaker screen" approach than employs an expensive metal screen in-place and allows the contaminated effluent to flow over the screen as it vibrates and allow larger particulates to flow downstream to be collected as a sludge, while allowing the process stream and finer particles to strain though that shaker screen and be delivered into the next phase, until that screen fouls or blinds and overflows and/or prevents removal of the grease and lint from the waste stream, and then needs to be disassembled from the device for off-line cleaning and eventual re- installation.

The present invention removes grease and lint at the same time and takes advantage of the lint to act as a "second filter material" and/or as a "filter-aid material" to trap grease, and other particulates, more efficiently as the "filter cake" builds up on the "dynamic screen" while still allowing high fluid flow though the areas on the screen that are less built up; additionally, the grease acts as a trap to embed particulates and fibers more efficiently, while the controlled dynamic process eliminates the possibility of blinding or fouling. Prior art methods are more subject to grease fouling, and additional grease and oil traps may be needed prior to screening to maintain longer up-time before screen removal and cleaning.

While the present invention has been described in particular in connection with treatment and recovery laundry effluent wastewater, it should be appreciated that the invention may be used in any system where water is being processed to remove fats, oils and grease, lint including fibers from clothing, bed linens, table linens and other fabrics/textile items, and other forms of debris including sand, grit, cottons, coins, paperclips, woodchips, etc. Various changes may be made in the invention without departing from the spirit and scope thereof.

Claims

Claims:

1 . A method for treating wastewater containing solid materials and/or one or more of fats, oils and grease, which comprises directing the wastewater in a flow path through one or more screens disposed in said flow path, and continuously or intermittently refreshing the screen media in said flow path to expose fresh free media, without interruption of flow of said wastewater, whereby to avoid blocking buildup of solids, fats, oils and grease on said screen media.

2. The method of claim 1 , wherein said screen media comprises two or more screens having different mesh sizes.

3. The method of claim 1 or claim 2, wherein the screen media comprises elongate screens that are advanced through said flow path from a roll of said screen media.

4. The method of any of claims 1 -3, including the step of measuring flow resistance of said fluid through said screen media, and controlling refreshing of said screen media based on said sensed flow pressure.

5. The method of any of claims 1 -4, including the step of sensing a depth of said flow stream, and controlling refreshing of said screen media based on said sensed depth.

6. The method of any of claims 1 -5, wherein said wastewater comprises laundry wastewater, and including the step of recycling the water to the laundry facility after subsequent treatment.

7. The method of any of claims 1 -6, including the step of disposing of spent screens by incineration.

8. The method of any of claims 1 -7, including the step of disposing of spent screens in a landfill.

9. A filter apparatus for filtering wastewater containing solids as well as one or more of fats, oils and grease, comprising:

a tank having an inlet and an outlet for a flow of said wastewater;

one or more screen media disposed in a flow path of said wastewater through said tank; and

a mechanism for continuously or intermittently advancing fresh screen media to said flow path in said tank.

10. The apparatus of claim 9, further including one or more sensors for sensing buildup of solids, fats, oils and/or grease on said filter media, and a controller for controlling advancing of fresh filter media from a supply into said flow path.

1 1 . The apparatus of claim 10, wherein one or more of said sensors comprise fluid level sensors arranged in said tank for determining a rise of fluid in said tank due to filter loading.

12. The apparatus of claim 10, wherein one or more of said sensors comprise pressure sensors arranged to sense an increase in back pressure or tension on said screen media.

13. The apparatus of any of claims 9-12, wherein said screens comprise a plurality of screens of different mesh size.

14. A laundering facility comprising one or more washing machines, and one or more filters through which wastewater is flowed, wherein the filter comprises a mechanism for continuously or intermittently supplying fresh filter media to said flow path.

15. A laundering facility comprising one or more washing machines, and one or more filters through which wastewater is flowed, wherein the filter comprises a filter apparatus as claimed in any of claims 9-13.