BACKGROUND It shall be made clear from the start that throughout this description expressions such as"waste water"and"waste water drain"are used to generally designate different kinds of polluted water and drains, respectively, that are employed to discharge such polluted water, namely storm water as well as drain water and sewer water.

Throughout the years, a large number of different methods and equipment have been employed to separate and collect contaminants and pollutants when purifying waste water. Such contaminants and pollutants are present in the form of coarser and finer particles as well as in the form of suspended contaminants such as oil and grease. In later years there has also been an increased focusing on the disposal of other substances that have been found to be harmful to man and/or to nature in general. Examples of such environmentally harmful substances are heavy metals and different kinds of harmful chemicals.

In earlier separating apparatuses, and in particular those that have been provided storm water drains or inlets for cleaning storm water flowing down into municipal sewer systems, a filter container has traditionally been employed and has been provided at the drain inlet. The filter container was often a wire mesh basket having a relatively open structure in which coarser contaminants, such as sticks, leaves and cigarette butts, were collected. Lately, the wire basket of this type of apparatus has often been replaced by a filter bag of a porous fabric that has been arranged with its upper end in connection with the inlet of the drain. Examples of such a separating apparatus are disclosed in U. S. Patents 5, 372,714 and 5,575, 925, that are specifically directed to an arrangement for supporting the filter bag in the inlet opening of the drain. Said arrangement shall also facilitate replacement of the filter bag.

However, there is a problem with determining the optimum filter fabric porosity for the above described separating apparatuses. On the one hand this shall secure an effective separation of

contaminants and pollutants of different size and type, and on the other hand it must not be clogged too fast, since maintenance in the form of clearing or replacement of the filter container involves substantial costs when the intervals between the service occasions are reduced. In accordance with a previously practiced method, performing the separation in two steps or stages has reduced said problems. Thus, U. S. patent no. 4,419, 232 discloses a solution where the largest or most coarse pollutants are separated in a relatively open wire mesh basket that is provided directly at the level of the inlet of the storm water drain and that is in turn provided inside a deeper container having the shape of a filter bag. With this solution, where a very shallow wire mesh basket is provided directly at the level of the inlet, there is an obvious risk that the wire mesh basket will be clogged very quickly by the above mentioned type of larger or coarser pollutants. Thereby, the capacity of water flow of the entire drain may be very dramatically reduced, such as by heavy rain.

Another method of performing the separation in two steps is described in Swedish Patent Application no. 9903366-4. Here, a separating apparatus is used that consists of a central perforated inlet pipe having"draining bowls"provided at its exterior. In the central pipe that at its lower end is connected to a closed collection chamber a first step or stage of the separation is carried out. At least one further separating step is performed in the bowls that are provided at its exterior. This apparatus provides good separation without any essential reduction of the flow capacity through the drain, but is relatively expensive to produce. For that reason it is less suitable for use in municipal storm water drains that within urban areas may be provided in large numbers.

Accordingly there is a great demand for a solution to the problem of providing an efficient cleaning and filtering of storm or run-off water, not least for storm water drains in municipal sewer systems, that is simple and inexpensive both with regard to the necessary investment and with regard to service and regular maintenance.

SUMMARY OF THE INVENTION The invention eliminates the above discussed drawbacks in an efficient and appropriate manner.

A general object of the invention is to provide a solution to the problem of efficiently filtering waste water, that is attractive for cost reasons and that is simultaneously practical to use.

Thus, it is a basic object of the invention to find a simple and appropriate method of providing an efficient separation and collection of contaminants and pollutants in waste water. Briefly, in accordance with the invention this object is achieved by employing inner and outer liquid permeable filter containers, respectively, in first and second steps or stages, respectively, of the filtering. The containers are formed from cloth or fabric that relatively speaking has more open and a less open structure, respectively. The effective filtering area of both the first and the second stages extends substantially from a first and to a second end of the separating apparatus in which they are included. By being able to separate and collect solid contaminants of different size in this manner in the different stages and over practically the entire filter surface a very high filtering capacity is achieved, without any danger of clogging. Hereby, a very high flow through capacity is provided and maintained for a long time.

According to an embodiment of the invention clearing of waste water is performed as it flows into a waste water drain, and in an alternative embodiment clearing is performed on waste water that is exists in connection with or within a separator, such as an oil separator, or that is discharged from such a separator. In a further alternative embodiment of the invention particle separation and clearing is performed on waste water from a manufacturing process, such as on concrete sludge from a concrete production.

According to another embodiment of the invention, the first and second separation stages are supplemented with an intermediate absorption stage for separating solved or suspended substances. This is achieved by conducting polluted water through dense felt provided between the inner and outer filter containers. With such an embodiment environmentally hazardous substances such as oil, heavy metals and various chemicals may also at demand be absorbed in an efficient way. The intermediate absorption stage is performed over at least a main portion of the surface of the filter containers. In other words, the dense felt is provided at least partially between the inner and outer filter containers.

According to a further embodiment of the invention, one or more intermediate separation stages are performed between the first and second stages. This is done by providing a further filter container between the outer and inner containers, and results in a very flexible and inexpensive

solution for adapting the capacity to the existing circumstances and to the expected load both with regard to the amount of water and to the amount or type of pollutants or contaminants.

According to a further embodiment of the invention one or several of the inner, outer and/or intermediate filter containers are formed of more than one cloth or fabric. In other words, they are designed having at least double walls. With this procedure the filter containers may be supplemented with other filter media, and in one practical embodiment especially with the dense felt of the absorption stage that in this embodiment may be positioned and thereby may be retained between the walls of the respective container.

According to a further embodiment of the invention, the filter containers are formed employing monofilament of synthetic material, preferably of polyester or polypropylene. Through this choice of material a very good temperature resistance is achieved, both for high and low temperatures. In a practical embodiment, the absorption stage felt is formed from calendered polypropylene fabric.

According to still another embodiment of the invention, it is suggested that the filter containers be inserted into the next outer filter container through an open upper end thereof. This embodiment makes it possible to easily combine different filter containers in a way that best favours the purpose of the filtering in question.

According to one embodiment it is suggested that through a carrier connected thereto the filter containers are positioned on and supported directly by a bracket that is firmly attached in an upper inlet portion of the waste water drain. It is also suggested that the filter containers be designed having a generally tubular shape with circular, oval or polygonal shape.

Another object of the invention is to provide an improved and very efficient separating and collecting apparatus for the filtering of waste water, which to a relatively low cost solves problem of clogging and related to a reduced flow through.

Thus, according to another aspect of the invention, a separating and collecting apparatus is suggested, which in accordance with the basic principles of the invention consists of filter containers of water permeable fabric of different openness and having an effective or active

filtering area extending over substantially the entire height of the apparatus. Embodiments of this aspect of the invention are clear from the associated dependent claims.

These and other objects of the invention are achieved by the invention as defined in the attached patent claims.

DESCRIPTION OF THE DRAWINGS Further objects, features and advantages of the invention as well as further embodiments thereof are clear from the patent claims and from the following detailed description referring to the enclosed drawings, on which: Fig. 1 is a partial side view, partially in section, of a first embodiment of a separating and collecting apparatus according to the invention, illustrating the apparatus installed in a very schematically indicated waste water drain; Fig. 2A is a partial side view, in section, of the separating and collecting apparatus of the embodiment of fig. 1, illustrating the two filter units being part thereof ; Fig. 2B is a section view taken along the line A-A of fig. 2A of the separating and collecting apparatus of the embodiment of fig. 1 ; Fig. 2C is a detail view of the attachment of a carrier in a filter unit of the separating and collecting apparatus according to fig. 1 ; Fig. 3 A is a detail view of the fabric of the outer filter unit according to figs. 1 and 2A; Fig. 3B is a detail view of the fabric of the inner filter unit according to fig. 2A; Fig. 4A is a partially schematic top plan view of an embodiment of a bracket for supporting the separating and collecting apparatus of the invention in a waste water drain; Fig. 4B is a section view of the bracket according to fig. 4A, taken along the line B-B;

Fig. 5A is a partial, partially schematic section view of the upper end of a further embodiment of a filter unit in a separating and collecting apparatus according to the invention, in open operating condition; Fig. 5B is a view corresponding to fig. 5B of the upper end of the further embodiment of a filter unit according to the invention, but illustrating this in closed handling condition; Fig. 6A-B are section views corresponding to fig. 2B of alternative embodiments of the sepa- rating and collecting apparatus according to the invention; Fig. 7 in a partial side view, and in section, illustrates another embodiment of an outer or alternatively inner filter unit of an apparatus according to the invention; Fig. 8 is a partial, partially schematic section view of the upper end of another embodiment of a separating and collecting apparatus according to the invention; and Fig. 9 is a very schematic illustration of a further embodiment of a separating and collecting apparatus according to the invention.

DESCRIPTION OF EMBODIMENTS The basic principles of the invention shall now be described with reference to the drawings and by means of embodiments thereof. This will also clarify the differences compared to the conventionally employed technique.

The invention and its basic principles will now initially be described with reference to the partially schematic illustrations of figs. 1 and 2A-B. Of these, especially fig. 1 illustrates an embodiment of the invention in an application by a waste water drain 1 of the type that is referred to as a storm water drain and that is frequently occurring within urban areas for collecting and processing above all rain water in municipal sewage systems. Such storm water drains 1 are normally buried in the ground 20, having an inlet portion formed by an upper end 1 A of the drain 1 and being provided at ground level 21. A grate 15 is provided over the inlet portion 1A and on the one hand serves to stop very large or coarse pollutants and other objects from falling down into the drain and on the other hand serves as a protection against stepping down into the drain. One end,

not illustrated, of the drain 1 opens into a sewage pipe that in turn conducts the storm water to a likewise not illustrated waste water treatment plant. These parts are well known to the man skilled in the art and do not require any further description or illustration.

Figs. 1 and 2A-C further illustrate a first embodiment of the central parts that are employed in the method suggested according to the invention for providing an efficient separation and collection of contaminants from the waste water. Specifically, they illustrate a separating and collecting apparatus 2, the first, and in this embodiment upper end 2A of which is provided substantially in the area of the inlet portion 1A of the waste water drain 1. The second and in the embodiment lower end 2B of the separating and collecting apparatus 2 is positioned in the interior of the waste water drain, that is inwardly of its side wall 1B, at a distance above its bottom, not illustrated.

The separating and collecting apparatus 2 consists of an outer, and in the below described filtering process second separating and collecting unit 5 that is referred to as a filter unit below and that is partially illustrated in fig. 1. This second filter unit 5 consists of a filter container or filter bag that here has a generally tubular shape of substantially circular cross section (see fig. 2B). The filter unit 5 has an open upper end SA and a closed lower end 5B or bottom. The filter container of the second filter unit 5 is formed of a liquid permeable fabric 6 (see especially fig. 3A) manufactured from monofilament 6A, 6B of a suitable material that in addition to the purely mechanical strength shall withstand the temperatures occurring in the intended application. In the illustrated embodiment that is intended for a storm water drain the material preferably consists of polyester withstanding temperatures down to-40° C. This material also withstands high temperatures, such as from a burning cigarette. Other conceivable materials include polypropylene.

In the upper end SA of the second filter unit 5 is provided a carrier 11B that in the preferred embodiment consists of a ring of metal, such as of stainless steel, or of a plastic material. In the case where the carrier consists of metal it may be advantageous to provide a rubber lining 22 on the ring 11B (see especially fig. 8) so that it will not damage the fabric or cloth 6.

The carrier is preferably sewed into an upper edge of the fabric 6 of the filter unit 5 that is folded onto itself, as is illustrated in the detailed view of fig. 2C. By means of the carrier 11B

the second filter unit 5 is supported on a bracket 12 that will described be more closely below and that is fixed against the inner surface 1B of the drain 1, at its upper end 1A. The bracket 12 has a tapered inner surface 14 against which the carrier 11B rests, whereby the rubber lining 22, where applicable, also provides an optimized seal therebetween.

A first, likewise with reference to the filtering process, separating and collecting unit 3 or filter unit (see especially fig. 2A) is positioned inside the second filter unit 5 and is inserted into the second filter unit 5 through its open upper end 5A. Like the earlier described second filter unit 5 this first filter unit 3 consists of a generally tubular filter container or filter bag of circular cross section (see fig. 2B) and having an open upper end 3A and a closed bottom 3B. The filter container of the first filter unit 3 is formed of a liquid permeable fabric 4 (see especially fig. 3B) that is likewise manufactured from monofilament 4A, 4B of a material corresponding to that discussed above.

However, it is clear from figs. 3A and 3B that the fabric 4 of the first filter unit 3 has a more open structure than the fabric 6 of the second filter does unit 5. In other words, the openings 4C formed between the axial threads or warp 4A and vertical threads or weft 4B of the fabric 4 are larger than the corresponding openings 6C of the fabric 6. In a presently preferred embodiment according to figs. 3A-B, the fabrics 4,6 are also produced such that the openings 4C, 6C are generally rectangular and that the long sides 4D, 6D of the openings are directed perpendicular to each other. In this way, by the combination of rectangular openings and their mutually rotated arrangement in the different filter units, a very good separation of solid particles and simultaneously a very high flow through capacity is achieved.

A carrier 11 A is likewise provided in the upper end 3A of the first filter unit 3, said carrier consisting of a corresponding material and being sewed into the fabric 4 of the filter unit 3 in the corresponding manner. By means of this carrier the first filter unit 3 is supported on the tapered inner surface 14 of the bracket 12, below the second filter unit 5.

An example of a presently preferred embodiment of the bracket 12 in the separating apparatus 2 of the invention is illustrated in greater detail in figs. 4A-B. It consists of an outer ring 18 that is preferably rubber lined with a material that is resistant to chemicals, to provide an enhanced fit as well as seal against the inner wall 1B of the drain 1. An inner ring 14 is extended inwardly

from the upper end of the outer ring 18 and forms the tapered surface against which the carriers 11A, 11B of the filter containers 3,5 are intended to rest. Angular supports 16 are preferably provided between the inner and outer rings 14 and 18, respectively, to strengthen them. The inner ring 14 is also designed having"smooth"bends, that is bends having a large radius, in order to avoid sharp edges that might otherwise damage the fabrics.

It is clear from the figures that the bracket 12, namely the outer as well as the inner ring 14 and 18, respectively, is split by a continuous slit 17. A clamping means 13 in the shape of a rigging screw is provided such that it bridges the slit 17. The clamping means 13 is attached to the inner surface of the outer wall 18, alternatively to the underside of the inner ring 14, below an aperture 2 formed in the inner ring 14. By means of a corresponding maneuvering of the clamping means through the formed aperture 23, the bracket may accordingly, by virtue of the elasticity of the material, be expanded into firm contact with the inner wall 1B of the drain 1 during installation and may be released therefrom during dismounting, respectively. In fig. 4A is indicated an alternative embodiment where the inner and outer rings are formed of two generally semicircular parts, indicated through the further slit 17', that in one end are connected to each other by a simple hinge 19. Installation and dismounting is carried out as described above, and the only difference is that the hinge 19 is used instead of the elasticity of the material, to expand and retract, respectively, the bracket 12.

When practicing the invention, a separating apparatus 2 is positioned in the upper inlet end 1A of a waste water drain 1 after removal of the grate 15. Then, the apparatus is expanded by means of the clamping means 13, until it is firmly clamped to the inner wall 1B of the drain 1. With the bracket 12 in position, the second filter unit 5 is inserted into the drain 1 until the carrier 11B at its upper end 5A rests on the tapered surface of the inner ring 14 of the bracket 12. By virtue of this design, the filter unit 5 will be effectively sealed against the inner ring 14, especially if the carrier has been provided with a rubber lining 22, since the carrier will be forced harder against the inner ring 14 the heavier the filter unit 5 becomes during operation. Finally, the first filter unit 3 is inserted into the drain 1 through the upper, open end 5A of the second filter unit, until the carrier 11A provided in its upper end 3A engages the inner ring 14 just below the carrier 11B of the second filter unit 5. The first filter unit 3 is sealed against the inner ring 14 in the corresponding manner and in the installed condition its bottom 3BD is positioned just above the bottom 5B of the second filter unit 5. In other words, both filter units

have an effective filtering area extending over substantially the entire height of the separating apparatus 1, from its upper to its lower end 2A and 2B, respectively. Expressed otherwise, an effective filtering may when required-primarily at high water flow rates and/or a large accumulation of separated particles in either or both of the filter units 3, 5-be performed over a main portion of the height of the separating and collecting apparatus 2. This is very advantageous with regard to a long term optimization of the function of the separating apparatus 2.

When the apparatus 2 is in operation, storm water or the like that flows down through the inlet portion 1A of the drain 1 will first be conducted into the filter container of the first filter unit 3, said container being formed by a comparatively wide-meshed fabric 4, i. e. having a relatively open structure. The specific nature or character of the fabric is adapted to each application and the relevant conditions, but from a general point of view it may be stated that a typical fabric for the first filter unit 3 has an openness of between 45 and 55% and is formed of monofilament having a dimension of 0,25-0, 30 mm. With the indicated openness, this means for instance that the warp 4A has a density of approximately 10-13,5 threads/cm and that the weft 4B has a density of approximately 7-10 threads/cm. Having such a structure, the fabric 4 of the inner filter unit 3 collects or accumulates particles in an order of magnitude from 0,5 mm and upwards.

Thus, a first step or stage of separating and collecting comparatively coarse solid pollutants is performed as water passes through the first filter unit 3 and into the second outer filter unit 5. The latter is formed of a fabric 6 with comparatively more narrow mesh, i. e. having a less open structure. The specific nature or character of the fabric 6 is likewise adapted to the application in question and to the conditions prevailing there, but from a general point of view it may be stated here too that a typical fabric for the second filter unit 5 has an openness of between 20-35% and is formed of monofilament having a dimension of 0,2-0, 3 mm. With the indicated openness, this means that here the warp 6A has a density of approximately 14-30 threads/cm and that the weft 6B has a density of approximately 15-30 threads/cm. Having such a structure, the fabric 6 of the outer filter unit 5 collects or accumulates particles in an order of magnitude from 0,25 mm and upwards. In view of these indications, it is clear that for clarification the fabrics 4,6 have been drawn in the drawing figures with a greatly exaggerated openness.

A second step or stage of separating and collecting smaller solid pollutants is performed after the first separating and collecting step or stage, as the waste water passes through the second outer filter unit 5, and then the filtered water flows out into the drain 1.

Apart from the fact that the now described invention results in a very efficient clearing of waste water, maintaining a very good flow through capacity, it also brings about an advantageous flexibility that makes it possible to optimize the result in different applications having varying conditions.

Specifically, it is possible to combine the different types of material and monofilament thereof in various ways in order to obtain fabrics and combinations of filter units that best promotes the purpose of the filtering. Thus, with comparatively simple means it is possible to provide a complete system that in addition to the collection and accumulation of solid particles also results in a certain absorption of environmentally hazardous substances that flow with the storm water down into street inlets and further on to the variable existing recipients. With regard to filtering capacity and effect, the favorable result is achieved that the fractions of solid pollutants or contaminants, such as sand and gravel, collected in the filter units contribute to the filtering out of heavy metals and oil. In other words, this type of accumulated solid particles has an effect that may be compared to that of an esker.

A further advantageous aspect of the invention is that the design of the separating and collecting apparatus 2 and its manageability make it possible to store the accumulated solid material in its entirety, together with the filter cloths or fabrics, at a waste deposit site until the particles, such as sand, gravel etc. may be recovered through sand washing and sorting.

From a general point of view the collected amount of pollutants in the form of solid material, such as sand and gravel, referred to as sediment, may advantageously be washed and recovered but may also, after solidification, be used as fill material for the establishment of deposit site bases or bottoms, since the content of minerals, nitrogen, phosphorous and nutrient salts i. a. is an important ingredient of the biological degradation.

The dense filter cloth or fabric that is described below, in connection with fig. 7, and that has the form of a calendered woven fabric that is not necessarily heat treated, may be used in or may be included as a component part of ground rehabilitation of leachate or used as part of a deposit site base where it may consist of several layers for absorbing and filtering leachate.

In order to further simplify the manageability and facilitate storage at a deposit site, it is suggested in accordance with a further embodiment that is schematically illustrated in fig. 5A and B, that the filter units 403, of which only the inner one is illustrated, at the upper portion 403A thereof are provided with two closure pieces 424,425. At one side 424A, 425A thereof, the closure pieces 424,425 are firmly joined to the fabric 404 of the filter unit 403, close to the attachment of the fabric to the carrier 11A. In an opposite, free side thereof the closure pieces 424,425 are each provided with one part of a closure means 426 consisting of complementarily engageable parts 427 and 428, respectively.

This closure means may consist of a zipper or similar closure means that is easily engageable and disconnectable. In the illustrated embodiment the closure pieces 424,425 consist of the same fabric as the filter unit 403, but they may also consist of another material that is suitable for this purpose.

In the normal operating position where the filter units are mounted in a drain the closure 426 is open and the closure pieces 424,425 are folded down along the filter unit, fig. 5A, but when a filter unit becomes full or is removed from the drain for another reason, the closure pieces are unfolded and interconnected by means of the closure means 426. Closing the filter container in this way considerably facilitates managing the same until it can be disposed of, i. e. until the material is recovered and the fractions are washed and sorted for re-use. With the illustrated design, it is possible to close the container both for the actual handling and during the time of deposit.

Since the closure pieces may be folded up over the upper portion 403A of the filter unit 403 and may be brought together to then be interconnected, it is possible to make use of them to efficiently close a filter unit that has been fully utilized and that is filled up to the brim.

Figs. 6A-B illustrate two alternative designs of the filter unitslO3, 203,105, 205. Whereas the circular shape of the cross sections of the filter units 3,5 illustrated in fig. 2B is adapted to a substantially circular upper end 1A of the waste water drain 1, the two alternative cross section shapes of the filter units 103,203, 105,205 are adapted to drains (not illustrated) having corresponding square and rectangular upper ends, respectively. It will be realized that in these alternative designs the carriers (not illustrated) are designed having a corresponding shape. Here, brackets (not illustrated) of the corresponding kind are also used, having an inner surface formed of

walls provided in a corresponding square or rectangular arrangement and converging in a direction towards the bottom of the separating means.

In fig. 7 is illustrated a further developed embodiment of the invention, where filtering is supple- mented with a stage for separation and absorption of pollutants or contaminants, such as oil, heavy metals and other chemicals, that are dissolved or suspended in the waste water. This is accomplished in an absorption stage by conducting waste water through dense felt 7 that is functionally provided between the inner and outer filter containers 3, 5. Specifically, the inner or outer filter container 3 and 5, respectively, or alternatively a further filter container 10 described in connection with fig. 8, is supplemented with such felt 7. Throughout this application, the felt is referred to as"dense". The pur- pose of this expression is to indicate that compared to the fabrics 4, 6 the felt has a dense structure to enable it to absorbe dissolved and suspended substances, but that it is still liquid permeable.

In a presently preferred embodiment the dense felt 7 consists of a calendered woven fabric of poly- ester or polypropylene, not necessarily heat treated, having warp of 0,2 mm monofilament with a density of approximately 19 threads/cm and having weft of fibrils, split-film yarn with a density of 9 threads/cm. In the case where the outer filter unit 5 is combined with such a dense felt 7 its fabric 6 will not always have to be produced having a very high density. In certain situations it may instead with advantage consist of a fabric 4 corresponding to that of the inner filter unit. It is possible to provide the dense felt 7 both in the sidewalls 3C, 5C (see fig. 2B) and in the bottom 3B, 5B of the filter units 3,5, but in most cases it is regarded as more advantageous with regard to the flow through capacity to leave the bottom 3B, 5B of the filter unit without felt 7.

In an alternative embodiment the dense felt 7 consists of a combination of calendered fabric of polyimide having a thickness of 2,8 mm, calendered fabric of 100% Nomex'E'having a thickness of 2,2 mm and calendered fabric of 100% Polyphenylenesulfide, or alternatively a fabric of cellulose strengthened with cotton fibres, such as the material used in cloths named Wettexg, having a thickness of 2,0 mm. all of these materials have good thermal endurance that for the different named materials lies between 180° och 250°.

The dense felt 7 is preferably applied to the separating apparatus 2 by making the inner filter container 3 of the first separating stage or the outer filter container 5 of the second separating stage, or

alternatively said further filter container 10 for performing the further separating stage, at least double- walled. In other words they are made of at least two separate layers 8 and 9, respectively, of the comparatively coarse mesh or alternatively fine mesh fabric 6 and 4, respectively, and the dense felt 7 of the absorption phase is provided between the two separate layers 8 and 9, respectively, of cloth or fabric 6 and 4, respectively, of these filter containers 5,3 and 10, respectively. As was mentioned above, it is in most cases most advantageous to provide the felt only in the sides of the filter containers and to leave their bottom free from felt.

Naturally it falls within the scope of the invention to provide the dense felt 7 in different designs and compositions by more than one filter container 3, 5, 10 of a separating apparatus 2 in order to thereby further reduce the amount of heavy metals and different groups of chemicals in the waste water.

Practical tests have shown that an embodiment of the invention as described above works very satisfactorily both with regard to the separation of solid pollutants and contaminants and the above mentioned suspended or dissolved pollutants and contaminants and with regard to short term as well as long term flow through capacity. An example thereof appears from the test results indicated in the table below. The test results presented in the table refer to sampling performed at three occasions, Sampling occasion 1, Sampling occasion 2 and Sampling occasion 3, respectively, of sludge water from storm water drains. On each occasion the sampling concerned one sample of untouched sludge water (Storage tank) serving as a reference value; one sample of sludge water diluted with rain water prior to filtering; and one sample of the sludge water diluted with rain water after filtering in accordance with the invention. These tests were performed in a situation where dissolved and suspended substances have been a problem, and therefore they were solely per- formed using apparatuses that were provided with the dense felt 7. Considering the presently in- creased focusing on environmentally hazardous substances it was generally also regarded to be of specific importance to confirm the effect of such an embodiment. On the sampling occasions the used separating and collecting apparatus consisted of filter units with the following specifications: Sampling occasion 1 Inner filter unit:-fabric of polypropylene having an axial thread density of 13,5 cm and a peri- pheral thread density of 7,0 cm and an openness of 47%. Collection of fractions from 0,5 mm

Outer filter unit:-fabric like that of the inner filter unit (13,5 threads/cm and 7 threads/cm, respektively, of Polypropylene); calendered woven fabric having warp of 0,20 mm, density of 19 threads/cm and weft of fibrils, split-film yarn with a density of 9 threads/cm. Outer fabric without calendered woven fabric in the bottom. Collection of fractions in the outer fabric from 0,5 mm; collection of fractions in the calendered fabric from 0,1 mm Sampling occasion 2 Inner filter unit:-same as for Sampling occasion 1 above.

Outer filter unit:-same as for Sampling occasion 1 above.

Sampling occasion 3 Inner filter unit:-same as for Sampling occasion 1 and 2 above.

Outer filter unit:-same as for Sampling occasion 2 above, but in this case also with calendered woven fabric, same as above, in the bottom..

On the sampling occasions sampling has been performed with the purpose of determining the metal contents of the filter fabric or cloth after filtering. This sampling is presented without any direct reference to any specific sampling occasion or to any specific fabric, and therefore the primary object of said presentation is to give a general idea of the collecting capability in this regard. The sampling provided the following result: Metal contents in the filter cloth prior to and after exposure to water from storm water drain mg/kg DS mg/kg DS mg/kg DS mg/kg DS mg/kg DS mg/kg DS mg/kg DS mg/kg DS mg/kg DS Arsenic Cadmium Lead Cobalt Copper Chrome Nickel Vanadium Zinc Filter cloth, 1 0,2 2 0,5 0,92 0, 5 I 2 0,89 reference Filter cloth, after 1 0, 21 15 1, 9 18 3>2 2 5 56 filterring Sampling was also performed directed to the separating and collecting effect in other regards, of the separating and collecting apparatus according to the invention and designed in accordance with the above specification. This sampling provided the following result: SAMPLING CONCERNING SEWAGE FILTER APPARATUS IN MUNICIPAL SEWAGE SYSTEM PERFORMEDO JULY-AUGUST Station Place Desig- Precipi- Temp Cond. Alc. pH TOC Tot N Tot P COD Susp. Susp. Note nation tation °C mS/m mg/l mg/l mg/l g/l (Cr) mg/l gf. mm mg/l mg/l Street inlet Storage inlet 1-3 20,5 65,4 280 7,8 100 39 1,9 460 190 110 graphite-grey Filter tank excluding foamy flocs in (Ref) rain tank surface water apparatus Street inlet Before inlet 1-3 22,2 55,9 190 7,2 140 30 1,8 720 260 170 Greyish-brown SAMP- filtering including Filter color of water LING 1 rain apparatus Street inlet After outgoing 1-3 20,0 10,6 37 7,2 27 5,6 0,55 310 250 130 Grey filtering water after color of water Fitler filtering apparatus Street inlet Storage inlet 3-5 21,1 74 350 6,7 26 39 0,79 120 97 74 graphite-grey tank excluding foamy flocs in Filter (Ref) rain tank surface water apparatus Street inlet Before inlet 3-5 20,0 9,0 27 5,0 29 5,3 0,33 140 85 49 Greyish-brown SAMP- filtering including Filter color of water LING 2 rain apparatus Street inlet After outgoing 3-5 19,8 5,0 13 5,0 17 3,0 0,17 66 12 5,4 brown color of filtering Filter water after water filtering apparatus Street inlet Storage inlet 5-10 22,7 87,1 500 7,1 37 53 2,6 140 740 550 graphite-grey tank Filter excluding foamy flocs in (Ref) rain tank surface water apparatus Street inlet Before inlet 5-10 19,2 0,852 2,8 6,1 4,8 0,65 0,48 30 9,6 7,4 Greyish-brown filtering SAMP- Filter including color of water LING 3 rain apparatus Street inlet After outgoing 5-10 19,2 2,01 6,0 5,1 7,4 1,3 0,14 30 11 5,0 brown color of Filtering Filter water after water filtering apparatus

It shall be clarified that in the table: COD-is a designation for pollutants or contaminants in water that consume oxygen, i. e. high COD content is a sign of rotten water. The results show that the pollutants settle after filtering; in sewage treatment plants chemicals are added to clean the water and to thereby eliminate the pollutants.

Susp. and Susp. gf, respectively-indicate the total amount of suspended substances and calcined residue of said substances, respectively, in the water.

TOC-indicates the total amount of carbon in the water, particles of carbon atoms.

The above indicated values are those that are of the greatest interest when estimating the clearing effect of the apparatus. In the obtained sampling results the mean value of COD in the storage tank is at a value of 240, before filtering the value is at 297 and after filtering a value of 135 has been obtained. In other words, the clearing in the apparatus has resulted in that the original value before filtering has been reduced to less than half said original value.

Tot P-indicates the total amount of phosphorous.

Tot N-indicates the total amount of nitrogen.

Alc.-indicates the alcality of the sample.

Cond. -is a measure of the electrical conductivity of the water and the value is obtained from the amount of particles in the water.

It shall also be noted that the results from Sampling 3 are not quite relevant with regard to the proportion of pollutants absorbed by the calendered woven fabric. The reason for this is that said sampling was disturbed by very heavy rain causing flooding of the unit having calendered woven fabric also in its bottom. By the flooding, substances that were to pass the filter were flushed over its edges and entered the container for collecting water after filtering. Although said sample is not quite relevant it still gives an indication of what has been stated above, namely that this embodiment indeed provides slightly further improved values with regard to the absorption of suspended and dissolved substances, but in many situations still is not optimal since the outer filter unit may be too dense for a normal flow.

The sampling results indicate unambiguously that with the method/apparatus of the invention a very satisfactory clearing effect is generally obtained with regard to solid particles, irrespective of

whether the inner or outer filter units are supplemented with the absorption stage or not. With the supplement of the dense felt, the clearing effect will also be very high with regard to suspended and dissolved substances. In all, the design used by samplings 1 and 2, without felt in the bottom of the filter unit, provides an effect that is optimal in most situations, since it makes it possible to maintain a desired high flow through capacity. This combination of filter cloths and dense woven fabric is recommended, especially for the absorption of oil and chemicals.

Fig. 8 illustrates a further embodiment of the invention that has been briefly discussed above.

In accordance therewith at least one intermediate separating and collecting stage is performed between the first and second separating stages for the purpose of even further optimizing the separation and collection of solid pollutants and contaminants. In this embodiment, a further filter container 10 is provided between the outer and inner filter containers 5, 3 for performing the further separating and collecting stage.

Alternatively, a separating and collecting apparatus 2 may also be provided with more than one further filter unit 10. In the embodiment of fig. 8 or in other embodiments having even further filter units provided in each other, it is mostly preferable to give the cloths of all units a denser structure the further out from the first filter unit 3 that they are positioned. Referring to the embodiments of figs. 3A-B having vertical apertures between monofilaments, it is also many times preferable in such a case of several filter units, to provide the rectangular apertures of adjacent filter containers with their long sides directed at an angle of 90° relative to each other.

Although the invention has been described above with reference to the specific embodiments that are illustrated in the drawings and that are especially adapted to a presently preferred use for filtering water that flows into storm water drains, it shall be emphasized that the invention also covers other variants that employ the basic principles of the invention. Thus, it also lies within the scope of the invention to use other geometrical shapes of the filter units or to use other cloth and felt materials therefore, for adaption to other specific applications. Examples of such conceivable applications are the three-compartment septic tanks that are predominantly used for managing sewage water from private households and also industrial waste water that is conducted to a collection tank, whereby particle separation and clearing is performed before the collection tank.

Furthermore, the invention has been illustrated and described solely with reference to an embodi- ment having separate filter units or containers supported by separate carriers. However, it shall be emphasized that the invention also covers embodiments that in principle correspond to the embodi- ment of fig. 7, i. e. with the inner as well as outer filter unit, i. e. its cloth or fabric, and in the applicable case also further filter units, joined at an upper end and supported on one and the same carrier.

It shall be emphasized with regard to the absorption stage, that the calendered woven fabric may be arranged covering the entire surface of the filter unit in question, including its bottom; covering only the side wall or side walls of the filter unit; or covering only an optional portion of the side wall or side walls. Thus, there is complete flexibility present, for adaption to different situations.

With regard to the cloth or fabric of the different filter units, this has only been illustrated here in an ambodiment having rectangular apertures between the monofilaments. However, the invention is not restricted to such an embodiment, but it lies within the scope of the invention to use cloth or fabric formed with square apertures between the monofilaments as well as with other geometrical shapes of the apertures being suitable for the intended application. Basically, the employed cloth or fabric shall secure a separation and collection of fractions from 0,25 mm and upwards.

It has been indicated above, that the cloth or fabric of the filter units at first hand shall consist of monofilament since this provides for a high flow through capacity and strength. It shall be noted though, that i all embodiments, depending upon the application, the cloth or fabric material may consist of monofilament, multifilament, spun or non-textured warp threads.

The invention also covers variants without separate bracket and clamping means, i. e. in a not illustrated embodiment where the filter units are supported directly i a specially designed waste water drain having an integrated bracket or corresponding supporting part.

Fig. 9 shows a further very schematically illustrated embodiment of a separating and collecting apparatus 502 according to the invention, in an application for clearing outgoing water from e. g. an oil separator 501. Liquid that has been cleared by means of flocculation and particle separation in the oil separator 501, but that still contains pollutants that are bound to particles or suspended, is conducted from an outlet 501A from the oil separator 501, through a line 530 and to an inlet 531A

at a first or inlet side 502A of the separating and collecting apparatus 502. The liquid that has been cleared in the separating and collecting apparatus 502 is conducted from an outlet 531B at a second or outlet side 502B of the separating and collecting apparatus, through a schematically illustrated outlet line 532 and to a waste treatment plant or the like (not illustrated).

In the illustrated embodiment the separating and collecting apparatus 502 is positined horizontally but like in the earlier illustrated embodiments it may be positioned vertically, and it may either be buried in the ground or placed in a basement or the like. In this embodiment where the separating and collecting apparatus 502 is not supported in a waste water drain, it comprises a container 531 that receives and supports filter units 503,505 that may correspond to the above described embodiments of filter units and that are therefore not illustrated or described in detail here.

However, it shall be emphasized that in an application after an oil separator 501 the filter units preferably comprise one or more units having dense felt in accordance with the embodiment of fig.

7. The filter units 503, 505 may likewise be supported in the container 531 by means of brackets designed in accordance with what has been described above, but in the illustrated horizontal arrangement the are supplemented with a frame or cage 512A, 512B that partly surrounds them and that in fig. 9 consists of relatively loosely or openly arranged longitudinal and transversal ribs 512A and 512B, respectively, in which the filter units are suspended in order not to collapse.

The embodiment of fig. 9 may with the same advantage be employed for particle separation and clearing of residue from manufacturing processes, such as waste water from concrete production.

In the latter case it is preferred that the concrete sludge formed during production is first particle separated through separation in one or several filter stages, whereupon liquid that is obtained after separation is conducted through the dense filter fabric that absorbes the remaining particle bound chemicals.

It will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departure from the scope thereof, which is defined by the appended claims.