WO2021204795A1

WO2021204795A1 - Waste water treatment system and purification media for the same

Info

Publication number: WO2021204795A1
Application number: PCT/EP2021/058928
Authority: WO
Inventors: Bert Gustafsson; Stefan Berg
Original assignee: Kingspan Baga Ab
Priority date: 2020-04-07
Filing date: 2021-04-06
Publication date: 2021-10-14
Also published as: SE2050397A1

Abstract

In a method for treatment of waste water, there is used a filter bed (100, 100') which includes at least one foam glass layer (20).

Description

WASTE WATER TREATMENT SYSTEM AND PURIFICATION MEDIA FOR

THE SAME

TECHNICAL FIELD The present invention relates to a waste water treatment filter bed, and a waste water treatment system.

BACKGROUND

Purifying sewage water from hostile compounds, such as organic nutrients, is of great importance in order to avoid contamination of the environment. Unpurified sewage or waste water also imposes a large infection risk among humans and animals.

There are several products which purify waste water biologically available on the market. Methods using soil-based purification include the use of filter beds of different types. An infiltrating filter bed can consist of a drainage layer, comprising for instance gravel, arranged in the underground. Waste water is released above the drainage layer and trickles through the layer, and into the soil beneath it. Due to the direct infiltration into the soil below the drainage layer, such filter beds are dependent on the soil type in the terrain in order to have a sufficiently satisfying effect, i.e. the soil must be able to absorb the incoming water. In addition, the drainage layer has to be large enough not to saturate the soil with waste water, rendering a need for a lot of space.

Other filter beds involve the use of several stacked layers of materials, sometimes beneath spreaders plates. For instance, the filter bed may comprise an air- spreader plate, followed by a layer of sand beneath the spreader plate, and finally at the bottom a layer of gravel and a drainpipe. The waste water will flow through the layers before it is finally collected by the drainpipe and discharged into a recipient or infiltrate into the ground below the filter bed.

The materials in the filter bed serve to retain particles of various sizes. In even more advanced filter beds, the materials therein also serve as a carrier for micro organisms responsible for biological purification of the effluent. Even though biological purification processes are efficient, there is an increasing demand for further treatment of waste water effluent. Contaminants present in waste water such as phosphorous, nitrogen and E-coli bacteria need to be removed from the effluent prior to release.

New materials are being investigated whether they provide better results than the use of conventional materials, such as sand, in filter beds. The type of sand required for filter beds has also become a scarcer resource. Such materials should preferably provide both a filtering function and biological purification. However, few materials have succeeded to demonstrate both properties.

In EP2322487A1, coconut mesocarp is disclosed to be one of the most suitable materials capable of functioning as a mechanical filter and a carrier for the micro organisms. However, such system is prone to clogging and coconut mesocarp will degrade with time. Thus, this system requires constant maintenance and in time, the coconut mesocarp will have to be exchanged.

Another waste water purification apparatus disclosed in CN100497205 A has a porous granular culture soil in an artificial wet land system for sewage treatment. The porous granular culture soil is disclosed as a mixture of pumice, silicic acid sedimentary rock and charcoal.

From the above it is understood that there is room for improvements in this technical field and that there is a need for an improved filter bed for the treatment of sanitary waste water.

SUMMARY

An object of the present invention is to provide a concept which is improved over prior art and which solves or at least mitigates the problems discussed above. This object is achieved by the technique set forth in the appended independent claims, preferred embodiments being defined in the related dependent claims.

The present disclosure is - inter alia - based on the idea that foam glass can be used in a filter bed for treating sanitary waste water since it is a lightweight material, with long sustainability and comprising foam glass particles providing a large surface area, e.g. for the growth of biofilm inhabited by microbes. Such microbes will cleanse waste water passing the foam glass in the filter bed and therefore enhance the efficiency of the filter bed. In addition, foam glass in an abundant material which is sustainable and commercially available. It is also a lighter material than previously used filter materials for filter beds, such as filter bed sand. Further, foam glass will require low maintenance and is not prone to clogging, as many other filter bed materials are.

In a first aspect, there is provided a waste water treatment filter bed. The filter bed comprises at least one foam glass layer. This filter bed is advantageous in that foam glass particles in the foam glass layer filtrate the waste water from impurities and also act as a scaffold surface for the growth of microorganisms. Such microbes may further cleanse the waste water chemically and biologically to remove organic substances from the effluent.

In one embodiment, the waste water treatment filter bed further comprises a spreader plate arranged at a top of the filter bed, above the foam glass layer. This is advantageous in that the spreader plate helps to distribute the waste water over the filter bed and increases the air supply to the filter bed.

In a second embodiment, the waste water treatment filter bed comprises a drainage layer arranged at a bottom of the filter bed, beneath the foam glass layer. A drainage layer provides an additional filtration layer beneath the foam glass layer.

In yet another embodiment, the waste water treatment filter bed further comprises a drainage pipe arranged at a bottom of the filter bed. The drainage pipe is advantageous since it collects the filtrated waste water before it is discharged.

In one embodiment, the waste water treatment filter bed is arranged below ground level GL. This is advantageous since the filter bed need not take up space above ground level.

In another embodiment, the waste water treatment filter bed is arranged above ground level GL, or at least partly above ground level GL. This is advantageous for instance when the soil type at the location where the filter bed is to be used does not allow for a subterranean filter bed, e.g. when a ground water level is close to the ground level and a filter bed arranged underground would be placed too close to the ground water level. In yet another embodiment, the foam glass layer has a thickness TFG of between 10 and 80 cm, preferably between 20 and 70 cm, most preferred between 30 and 60 cm. These thicknesses are preferable since they allow for a satisfying filtration of the waste water, and are thick enough to maintain the waste water in the foam glass layer for sufficient time for biological and chemical purification to take place.

In another embodiment, the foam glass layer comprises a fractioned bulk of foam glass particles. The particles are in the size range of between 0.5 and 15 mm, preferably between 1 and 8 mm, in particular between 1.5 and 5 mm, and most preferred between 2 and 4 mm. These particle sizes are beneficial since they allow the waste water to trickle through the foam glass layer at a preferable speed.

In one embodiment, the foam glass layer has a density of between 100 and 500 kg/m³, preferably between 150 and 450 kg/m³, and most preferred between 350 and 400 kg/m³. This is advantageous since these densities are quite low, resulting in a filter bed which is easy to assembly due to its light weight. If thee filter bed is pre-manufactured at another site than that of use, transportation is facilitated by the light weight of the foam glass.

In another embodiment, the filter bed is covered by a geotextile. This is advantageous in that the geotextile prevents unwanted particles and soil to enter the filter bed.

In yet another embodiment, foam glass particles in the foam glass layer are covered by biofilm inhabited by microbes. The microbes are advantageous in that they may purify the waste water from organic compounds biologically through chemical reactions.

In one embodiment, the drainage layer comprises foam glass having a particle size larger than foam glass particles in the foam glass layer. This is advantageous in that the filter bed then has layers of different filtering capacity, which sieves unwanted particles of different sizes from the waste water.

In a further embodiment, the filter bed is arranged in a housing. This is beneficial since the housing including the filter bed may be pre-manufactured and transported to another location. Additionally, such housings may result in that the filter bed attains a certification, such as a CE-marking. In a second aspect, there is provided a method for treatment of waste water in a filter bed. The filter bed comprises a foam glass layer and the method comprises the step of supplying waste water to the filter bed, whereby the waste water flows through the filter bed.

In one embodiment, in a method for treatment of waste water in a filter bed, the filter bed is arranged below ground level GL.

In another embodiment, the waste water is led through the foam glass layer of the filter bed such that microbes present in the foam glass layer purify the waste water biologically and/or such that the foam glass layer filters the waste water.

In a third aspect, there is provided a waste water treatment system, comprising a filter bed and a biomodule arranged on a top surface of the filter bed.

In a first embodiment, the biomodule and the filter bed are covered by a geotextile.

In a second embodiment, the waste water treatment system further comprises a pre-treatment unit, in fluid communication with the biomodule through a pipeline extending from a pre-treatment unit outlet to the biomodule. Preferably, the pre treatment unit is a sludge separator. This is advantageous since it provides a pre treatment of the waste water before it enters the biomodule and subsequently the filter bed. Such pre-treatment separates sludge and larger items, such as sanitary pads and toilet paper, from the effluent, thus facilitating a more efficient purification process in the biomodule and filter bed.

In another embodiment, the filter bed and biomodule are housed inside a container having a container inlet connected to the pipeline and to a spreader pipe of the biomodule. This is beneficial since such container can be arranged above or below a ground level GL and can be transported to various sites.

In one embodiment, the container is arranged below a ground level GL or above the ground level GL.

In another embodiment, the waste water treatment system further comprises an air vent arranged in connection with the biomodule and/or a spreader plate arranged at a top of the filter bed. The air vent provides oxygen to the biomodule, thus increasing the capacity and efficiency of the biomodule. In a fourth aspect, there is provided the use of a foam glass layer in a filter bed or in a waste water treatment system. This is advantageous since it provides a filter bed or waste water treatment system with the use of a sustainable material of light weight.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be described in the following; references being made to the appended diagrammatic drawings which illustrate non-limiting examples of how the inventive concept can be reduced into practice.

Fig. 1 A is a cross section of a subterranean filter bed;

Fig. IB is a cross section of waste water treatment system, comprising a subterranean filter bed as shown in Fig. 1 A, having a biomodule arranged on top;

Figs 2A and 2B are exploded views of the filter bed of Fig. 1 A and the waste water treatment system of Fig. IB, respectively;

Fig. 3 shows a waste water treatment system comprising a filter bed, a biomodule and a pre-treatment unit;

Fig. 4 shows a perspective view of a waste water treatment system comprising a pre-treatment unit and a container according to another embodiment;

Figs 5A and 5B show the inside of the container comprised in the system in Fig. 4; and

Fig. 6 shows an inside of a biomodule comprised in said container.

DETAILED DESCRIPTION

With reference to Fig. 1, a subterranean filter bed 100, also referred to as a soil bed herein, arranged below ground level GL is shown. The filter bed 100 disclosed herein is used to treat and purify sanitary waste water, i.e. waste water in the form of sewage effluent stemming from flushed toilets and the like. Sanitary waste water is also referred to as blackwater, and is characterized in that it can contain feces, urine, water and toilet paper from flush toilets. Blackwater is distinguished from greywater, which comes from sinks, baths, washing machines, dishwashers and other kitchen appliances apart from toilets. Greywater results from washing food, clothing, dishes, as well as from showering or bathing. Since blackwater typically comprises pathogens and other impurities originated from stool and urine, sanitary waste water requires a higher level of purification than greywater.

The sanitary waste water treatment filter bed 100 in Fig. 1 comprises a plurality of layers, of which the first top layer 10 placed nearest the ground level GL is a spreader plate 10. A thickness TSP of the spreader plate 10 is indicated by a double arrow. The second layer 20 is a foam glass layer 20, having a thickness TFG indicated by a second double arrow in Fig. 1. Foam glass may also be referred to as porous glass herein.

At a bottom 110 of the filter bed 100, a third layer 30 in the form of a drainage layer 30 is arranged. A thickness TDL of the drainage layer 30 is indicated by a third double arrow in Fig. 1 A. Further, a drainage pipe 40 is embedded within the drainage layer 30. However, the filter bed 100 may comprise a plurality of drainage pipes 40.

Fig. IB shows a sanitary waste water treatment system 500, comprising the soil bed 100 beneath ground level GL and a biomodule 50. The filter bed 100 has the same layers as described with reference to Fig. 1 A. The filter beds 100 shown in Figs 1 A and IB may be placed above the ground level GL. In addition, the filter bed 100 with or without the biomodule 50 may be arranged inside a housing (for instance a container 200 as shown in Figs 4-5B).

The soil bed 100 in Fig. IB has a first layer 10 in the shape of a spreader plate 10, a second layer 20 of foam glass, and a third layer 30 in the shape of a drainage layer 30. The thicknesses TSP, TFG and TDL are indicated by double arrows of the left hand side of the bio bed 100. In addition, there has been placed a biomodule 50 below ground level GL, on a top surface 125 of the spreader plate 10. The biomodule 50 has a main body 54 and is provided with a spreader pipe 52.

Figs 2A and 2B show the filter bed 100 of Fig. 1 A and the sanitary waste water treatment system 500 of Fig. IB in an exploded view, respectively. The soil beds 100 have the first top layer 10 in the shape of the spreader plate 10, the second filter layer 20 being the foam glass layer 20, and the third layer 30 being the drainage layer 30. The drainage pipe 40 is embedded in the drainage layer 30. Fig. 2B also shows the biomodule 50 arranged on top of the soil bed 100.

The biomodule 50 may be any biomodule known in the art, and the disclosure herein is not limited to a biomodule as described with reference to the figures. For instance, the biomodule 50 may be a biomodule of the type disclosed in the applicant’s patent application WO2019053252A1.

Preferably, the spreader plate 10 is a spreader plate made from the material forming the carrier plates disclosed in WO2019053252A1. However, the spreader plate 10 may be of any type known in the art or material suitable for the use as a spreader plate in a soil bed 100. The thickness TSP of the spreader plate 10 may be between 1 and 15 cm, preferably between 2 and 10 cm, most preferred about 3 cm.

Foam glass is a porous material formed from glass (often recycled glass material), which is commonly produced by the addition of gases acting as blowing agent when the glass material is in its melted state. Therefore, it is a sustainable material, which is also commercially available. In addition, porous glass is a light weight material which in the present disclosure preferably has a density of about between 100 and 500 kg/m³, such as between 150 and 450 kg/m³, or 200 to 400 kg/m³, most preferred approximately 350 kg/m³.

The thickness HFG of the foam glass layer 20 may be between about 10 and 120 cm, preferably between about 20 and 100 cm, such as between 30 and 90 cm, most preferred about between 40 and 80 cm. For instance, the thickness TFG of the foam glass layer 20 may be 50 cm or 60 cm.

The foam glass forming the foam glass layer 20 is a fractioned bulk of material, comprising foam glass particles of varying sizes which preferably vary between 0,5 and 15 mm, such as between 1 and 8 mm, such as between 1.5 and 5 mm, most preferred between 2 and 4 mm.

A thicker foam glass layer 20 provides to possibility to use a fractioned bulk of foam glass particles with generally larger size, while a thinner foam glass layer 20 may require foam glass particles of a smaller size.

The foam glass particles have a large surface, since the surface area is rugged and uneven. Thus, the foam glass particles in the foam glass layer 20 provide an environment which allows waste water to flow there through in a preferable pace, such that microbes present in the foam glass layer 20 will be able to cleanse the waste water biologically and chemically. Furthermore, the waste water will be filtered by the foam glass layer 20, and the optional spreader plate 10 and the optional drainage layer 30. Optionally, the filter bed 100 shown in Fig. 1 A and the filter bed 100 and biomodule 50 shown in Fig. IB may be covered by a geotextile 60.

The drainage layer 30 is optional, and a basic filter bed 100 may have a spreader plate 10 at a top 120 of the soil bed 100 and a foam glass filter layer 20 arranged beneath the spreader plate 10. In such case, the drainage pipe 40 is preferably embedded in the foam glass filter layer 20 or lies beneath the foam glass filter layer 20.

The thickness TDL of the drainage layer 30 may be about between 10 and 50 cm, preferably between 15 and 45 cm, such as about 20 cm, 25 cm, 30 cm, 35 cm or 40 cm, most preferred about 20 cm.

The drainage layer 30 comprises materials such as gravel or foam glass. The particles forming the drainage layer 30 have a larger particle size than the particles forming the foam glass layer 20. The particle size of the particles forming the drainage layer 30 may be for instance 8 to 40 mm, such as 10 to 30 mm.

The thickness TFG of the foam glass layer 20 may be thicker than the thickness TDL of the drainage layer 30.

In Fig. 3, the sanitary waste water treatment system 500 has a filter bed 100 and a biomodule 50 as described with reference to Figs IB and 2B, and a pre-treatment unit 70, which may be a septic tank or a sludge separator. The soil bed 100 is arranged beneath ground level GL and the filter bed 100 has a first layer 10 in the form of a spreader plate 10, a second layer 20 of foam glass, and a third layer 30 in the form of a drainage layer 30. A biomodule 50 has been placed on top of the filter bed 100, and the biomodule 50 has a main body 54 and is provided with a spreader pipe 52.

The pre-treatment unit 70 in Fig. 3 is connected to the biomodule 50 through a pipeline 75, extending between an outlet 72 of the pre-treatment unit 70 and the spreader pipe 54. Water is led from a household, or other facility (not shown) to the pre treatment unit 70 through a pre-treatment unit inlet 71.

Additionally, two air vents 80 are placed at each end of the biomodule 50 to enhance oxygen supply to the biomodule 50. The air vents 80 extend from below ground level GL and above the ground level GL to create a draft and supply air/oxygen to the biomodule 50. A waste water treatment system 500’ according to another embodiment of the present disclosure, is shown in Fig. 4, and is formed of a pre-treatment unit 70’ connected by a pipeline 75’ from an outlet 72’ to a secondary treatment unit 200, also referred to as a container 200 or housing 200 herein. The pre-treatment unit 70’ may be a sludge separator, or a septic tank.

The container 200 has a container inlet 210 and is provided with two air vents 80’. Both the pre-treatment unit 70’ and the container 200 are arranged below ground level GL. Further, the pre-treatment unit 70’ is equipped with a control station 78’ above ground level GL and has a pre-treatment unit inlet 7G. Sanitary waste water arriving from i.e. a building (not shown) enters the pre-treatment unit 70’ through the inlet 71’.

Figs 5A and 5B show the inside of the container 200 being part of the waste water treatment system 500’ of Fig. 4. A spreader pipe 52’ embedded in an isolation layer 58’ extends from the container inlet 210 to the top of a biomodule 50’. The isolation layer 58’ may be made of polystyrene and provides structural stability, isolation and acts as a distance material. Preferably, the isolation material 58’ is water compatible. Air from the air vent 80’ is led into the biomodule 50’ through an air pipe 8G. One air vent 80’ is placed closer to ground level GL than the other, to achieve a draft and thus efficient air supply to and through the biomodule 50’.

Fig. 5 A shows a soil bed 100’ being arranged below the biomodules 50’. A spreader plate 10’ is arranged below the biomodule 50’, at a top 120’ of the soil bed 100’. Beneath the spreader plate 10’ there is a foam glass layer 20’, and at the bottom a drainage layer 30’, in which a drainage pipe 40’ is embedded. The drainage pipe 40’ in Figs 5A and 5B extends throughout the container 200 within the drainage layer 30’ and exits the container 200 through a container outlet 220.

The biomodules 50’ and the spreader plate 10’ are covered by a geotextile 60’. The spreader plate 10’, the foam glass layer 20’, the drainage layer 30’, the drainage pipe 40’ and the geotextile 60’ together make up the soil bed 100’ which is of the same character as the soil bed 100 described with reference to Figs 1A-3. The drainage layer 30’ and the geotextile 60’ are optional features of the soil bed 100’. Hence, a basic version of the soil bed 100’ is composed of the spreader plate 10’ and the foam glass layer 20’.

Moreover, in Fig. 5B, it is shown how a filling material 90’ is used to fill the remaining space inside the container 200. The filling material 90’ may for instance be foam glass, gravel, sand, or soil, preferably foam glass since this is a material having low density, rendering the secondary treatment unit 200 light and thus simple to install. The filling material 90’ may be any material which gives stability within the container 200 and which prevents unwanted movement within the container 200.

The biomodule 50’ is shown in more detail in Fig. 6. Each main body 54’ of the biomodule 50’ is housed in a framing 57’. On top of the biomodules 50’, the distribution pipe 52’ is embedded in the isolation material 58’. the main body 54’ is equipped with a plurality of carrier plates 55’ forming a sandwich like structure. Between each carrier plate 55’, there is provided a geotextile sheet 53’ and a net 56’.

The pre-treatment unit 70, 70’ disclosed herein may be a sludge separator 70, 70’ which is configured to distribute the water flow in the waste water treatment system 500, 500’ evenly throughout the hours of the day. Such sludge separator 70, 70’ comprises a water level sensor (not shown) which measures the water level within the sludge separator 70, 70’ during predetermined time periods, such as once each hour. If the water level is sufficiently high within the sludge separator 70, 70’, the sensor will indicate to a pump in the sludge separator 70, 70’ to pump a predetermined volume of waste water through the outlet 72, 72’ and through the pipeline 75, 75’ to the biomodule 50, 50’. If the sanitary water level is too low in the sludge separator 70, 70’, the sensor will indicate the pump to pump water at another predetermined time period, such as every other hour, or to pump lower volumes each hour. In this way, an even waste water distribution in the soil bed 100 and/or the container 200 comprising a soil bed 100’ and a biomodule 50’ is accomplished.

An evenly wetted biomodule 50, 50’ and soil bed 100, 100’ have been shown to be more efficient than soil beds and biomodules which are exposed to large amounts of waste water at the time followed by dry periods.

A method for treatment of waste water in a soil bed 100, 100’ will now be explained with reference to the Figs 1 A-6. If the waste water treatment system 500, 500’ comprises a sludge separator 70,70’, water is led from a household, or other facility,

(not shown) into the sludge separator 70, 70’ through the inlet 71, 71’. The sludge separator 70, 70’ acts as a primary treatment unit, and separates larger particles and items from the waste water, and partially purifies the sanitary waste water. The decomposition of particle impurities requires a lot of oxygen. Therefore, it is advantageous to remove - at least to a great extent - these impurities already in the sludge separator 70, 70’.

Partially rinsed sanitary waste water is then pumped, preferably at predetermined volumes and in predetermined time ranges as described above, out of the sludge separator outlet 73, 73’ and through the pipeline 75, 75’ to the biomodule 50,

50’. Preferably, the pipeline 75, 75’ is connected to the spreader pipe 52, 52’ which distributes the sanitary waste water in the biomodule 50, 50’ through openings along the spreader pipe 52, 52’ (not shown). If the soil bed 100’ and the biomodule 50’ is held inside a container 200, the pipeline 75’ is connected to a container inlet 210 which is in fluid communication with the spreader pipe 52’.

The sanitary waste water then flows through the biomodule 50, 50’ and is purified biologically while its passing through said module 50, 50’. The biomodule 50, 50’ provides surface area for microbial growth (also referred to as biofilm herein), which decomposes BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand).

In the biomodule 50’ shown in Figs 5 A to 6, since the geotextile sheets 53’ in the biomodule 50’ are covered by microbial growth, they are semi-permeable to water. Therefore, the water will partly pool on top of and flow along each sheet 53’, and thus flow through the carrier plate 55’ located above each sheet 53’. However, some water will trickle through the sheets 53’. Thus, the sanitary water flows slowly, mainly back and forth through each layer of carrier plates 55’, and partially through the sheets 53’ of the biomodule 50’, allowing the microorganisms to reduce the impurities (COD and BOD) carried therein. The net 56’ presses the geotextile sheet 53’ towards the plate 55’, causing the water to pool more evenly on top of the geotextile sheet 53’, and therefore a more even biofilm production is promoted. However, as stated above, any type of biomodule known in the art may be used in the waste water treatment systems 500, 500’.

Subsequently, the water arrives at the bottom of the biomodule 50, 50’ and trickles into the spreader plate 10, 10’ which distributes the sanitary waste water over the area of the soil bed 100, 100’. The waste water passes through the spreader plate 10, 10’ and further flows into the foam glass layer 20, 20’.

The surface area of the foam glass particles constituting the foam glass layer 20, 20’ also serve as a scaffolding for biofilm, created by microorganisms inhabiting the foam glass layer 20, 20’. Such microbes can purify waste water further from impurities with a biological process, before the waste water infiltrates soil below the soil bed 100 or after exiting the container 200.

Since the surface area of the foam glass particles is uneven and rugged, a large surface area for the growth of biofilm is provided. This enhances the efficiency by which the microbes may purify the waste water flowing through the foam glass layer 20

If the soil bed 100, 100’ is provided with a third layer, such as the drainage layer 30, 30’ shown in Figs 1 A- 3 and 5A-B, the sanitary waste water will continue to pass through the drainage layer 30, 30’ and exit the soil bed 100, 100’ through the drainage pipe 40, 40’. If the soil bed 100’ is housed within a container 200, the waste water exits the container 200 through the container outlet 220 in the drainage pipe 40’, and if the soil bed 100 is arranged directly on the soil beneath it, the purified waste water trickles into the soil below the soil bed 100.

The use of foam glass in a soil bed 100, 100’ hence provides additional biological purification and filtration when waste water flows through said soil bed 100, 100’. In addition, due to the low density of the foam glass, the container 200 of the sanitary waste water treatment system 500’ will be less heavy than if conventional soil bed sand is used.

The filter beds disclosed herein may be arranged below the ground level GL (shown in Figs la-b, 3 and 4) or above a ground level GL. When the filter bed is arranged underground, there should preferably be a certain distance between the bottom 110 of the filter bed 100, 110’ and a ground water level in the terrain. Hence, a filter bed 100, 100’ placed above the ground level GL is a preferable option if a ground water level in the soil does not meet the requirements of distance between the ground water level and the bottom 110 of the filter bed 100, 110’.

When the filter bed 100, 100’ is arranged above the ground level GL, a bio module 50, 50’ arranged in communication with the filter bed 100, 100’ is also arranged above the ground level GL. The filter bed 100, 100’ may be arranged below ground level GL while the bio module 50, 50’ is arranged above the ground level GL.

The filter bed 100, 100’ may also be arranged partly below the ground level GL and partly above the ground level GL. Finally, it should be mentioned that the inventive concept is not limited to the embodiments described herein, and many modifications are feasible within the scope of the appended claims. For instance, several biomodules may be combined into a larger water treatment installation used on top of a soil bed. The soil bed may consist of additional filter layers or other spreader plates than those mentioned herein. The drainage pipe may have varying dimensions. Furthermore, the foam glass particles may be of other fractions and particle sizes as disclosed herein.

Claims

1. A waste water treatment filter bed, said filter bed (100) comprising at least one foam glass layer (20).

2. The waste water treatment filter bed according to claim 1, further comprising a spreader plate (10) arranged at a top (120) of the filter bed (100), above the foam glass layer (20).

3 The waste water treatment filter bed according to claim 1 or 2, further comprising a drainage layer (30) arranged at a bottom (110) of the filter bed (100), beneath the foam glass layer (20).

4. The waste water treatment filter bed according to any one of claims 1 to 3, further comprising a drainage pipe (40) arranged at a bottom (110) of the filter bed (100).

5. The waste water treatment filter bed according to any one of the preceding claims, wherein the filter bed (100) is arranged below ground level (GL).

6. The waste water treatment filter bed according to any one of claims 1 to 4, wherein the filter bed (100) is arranged above ground level (GL) or at least partly above ground level (GL).

7. The waste water treatment filter bed according to any one of the preceding claims, wherein the foam glass layer (20) has a thickness (TFG) of between 10 and 80 cm, preferably between 20 and 70 cm, most preferred between 30 and 60 cm.

8. The waste water treatment filter bed according to any one of the preceding claims, wherein the foam glass layer (20) comprises a fractioned bulk of foam glass particles, said particles being in the size range of between 0.5 and 15 mm, preferably between 1 and 8 mm, in particular between 1.5 and 5 mm, and most preferred between 2 and 4 mm.

9. The waste water treatment filter bed according to any one of the preceding claims, wherein the foam glass layer (20) has a density of between 100 and 500 kg/m³, preferably between 150 and 450 kg/m³, and most preferred between 350 and 400 kg/m³.

10. The waste water treatment filter bed according to any one of the preceding claims, wherein the filter bed (100) is covered by a geotextile (60).

11. The waste water treatment filter bed according to any one of the preceding claims, wherein foam glass particles in the foam glass layer (20) are covered by biofilm inhabited by microbes.

12. The waste water treatment filter bed according to any one of claims 3 to 11, wherein the drainage layer (30) comprises foam glass having a particle size larger than foam glass particles in the foam glass layer (20).

13. The waste water treatment filter bed according to any one of the preceding claims, wherein the filter bed (100) is arranged in a housing (200).

14. A method for treatment of waste water in a filter bed, said filter bed (100) comprising a foam glass layer (20), said method comprising the step of: supplying waste water to the filter bed (100), whereby the waste water flows through the filter bed (100).

15. The method according to claim 14, wherein the filter bed (100) is arranged below ground level (GL).

16. The method according to claim 14 or 15, wherein the waste water is led through the foam glass layer (20) of the filter bed (100) such that microbes present in the foam glass layer (20) purify the waste water biologically and/or such that the foam glass layer (20) filters the waste water.

17. A waste water treatment system, comprising a filter bed (100) according to any one of claim 1, and a biomodule (50, 50’) arranged on a top surface (125) of the filter bed (100).

18. The waste water treatment system according to claim 17, wherein said biomodule (50, 50’) and filter bed (100, 100’) are covered by a geotextile (60, 60’).

19. The waste water treatment system according to claim 17 or 18, further comprising a pre-treatment unit (70), in fluid communication with the biomodule (50, 50’) through a pipeline (75) extending from a pre-treatment unit outlet (72) to the biomodule (50, 50’), preferably said pre-treatment unit (70) is a sludge separator.

20. The waste water treatment system according to claim 19, wherein said filter bed (100’) and biomodule (50’) are housed inside a container (200) having a container inlet (210) connected to the pipeline (75) and to a spreader pipe (52’) of the biomodule (50’).

21. The waste water treatment system according to claim 20, wherein said container (200) is arranged below a ground level (GL) or above the ground level (GL).

22. The waste water treatment system according to any one of claims 17 to 21, further comprising an air vent (80, 80’) arranged in communication with the biomodule (50, 50’) and/or a spreader plate (10) arranged at a top (120) of the filter bed (100).

23_. Use of a foam glass layer (20, 20’) in a filter bed according to any of the claim 1 or in a waste water treatment system according to any one of claims 17 to 22.