WO2001077028A1

WO2001077028A1 - A method and a device for purifying water

Info

Publication number: WO2001077028A1
Application number: PCT/SE2001/000487
Authority: WO
Inventors: Per Axelsson
Original assignee: Per Axelsson
Priority date: 2000-04-06
Filing date: 2001-03-08
Publication date: 2001-10-18
Also published as: SE0001259L; SE0001259D0; AU3961801A

Abstract

A method for purifying water contaminated with organic compounds. The contaminated water is led forth to a bed of composted wastes and thereafter brought to pass the bed, wherein at least the main part of said organic compounds are absorbed. A device for purifying water contaminated with organic compounds, which comprises an absorbent and is arranged so that the contaminated water passes the absorbent, wherein at least the main part of said organic compounds are absorbed. The device comprises a bed with composted wastes (4), wherein at least one part of said wastes constitutes the absorbent.

Description

A METHOD AND A DEVICE FOR PU RIFYING WATER

DESCRIPTION

FIELD OF THE INVENTION

The present invention relates to a device for purification of water contaminated with organic compounds, which comprise an absorbent and is arranged so that the contaminated water passes the absorbent, wherein at least the main part of said or- ganic contaminations is absorbed, and a method for purifying water containing organic compounds.

Examples of fields where there is a need for purification of water contaminated with organic compounds are everywhere where there is a risk of spillage of environmentally hazardous substances like different types of oils, diesel, petrol and organic solvents. Areas that are in need of purification are for example beneath fuel deposits, at parking spaces, industrial stores, and decontamination plants. Contaminated water from such areas should be collected and led to a purification plant. Another field of application for the invention is for purification of surface water in residential areas.

PRIOR ART

Different methods and devices for purification of water containing contaminations are known, and a known environmental problem is to let out contaminated water in the environment. To let contaminated water pass an absorbent where the contamina- tions are absorbed is also known. To decrease the load on the environment it is desirable to use an absorbent that gives as high a degree of purification as possible. In the Swedish patent document SE 51 1 731 a method and a device for purification of contaminated water is shown where the absorbent consists of peat. The device shown comprises a collecting tank for the contaminated water, which is connected to a purification device containing several on top of each other laid layers containing peat as an absorbent. The layers of absorbent are separated by perforated bottoms for dispersion of the passing liquid, whereby the contaminations are absorbed in the peat. A drawback with peat is that the supply of peat is limited and it is not renewable within reasonable time.

From the American patent document US 5,240,61 1 it is also known to use excrements from, for example, horse as absorb- ent. To achieve a high degree of purification when excrements are used as absorbent, cellulose needs to be added, if the excrements do not already contain undigested remainders of hay, and the water needs to pass a filter of active carbon. The method to purify contaminated water described in the document is very complicated.

SUMMARY OF THE INVENTION

The purpose of the invention is to indicate a method and a de- vice for purification of water contaminated with organic substances, which is simple, environmentally friendly, and gives a very high degree of purification.

This purpose is achieved by leading the contaminated water to a bed of composted wastes and thereafter bringing it to pass the bed, at which at least the main part of said contaminations are absorbed.

The purpose is further achieved with the previously mentioned device characterised in that it comprises a bed of composted wastes, at which at least a part of said wastes form the absorbent.

Measurements have shown that usage of composted wastes to purify contaminated water gives a very high degree of purification. The degree of purification is considerably better than by using peat. This effect is very surprising. The supply of composted wastes is almost unlimited. Composted wastes are not only a renewable resource, but constitute also a rest-product from waste disposals and need to find a market within suitable areas of application. From an environmental point of view it is therefore more advantageous to use the composted wastes instead of peat as absorbent.

The composted wastes contain already what is needed for an effective purification and therefore no extra additives are needed, such as cellulose or active carbon. The method to purify contaminated water with composted wastes therefore becomes simple and inexpensive._.

According to one embodiment of the invention, the composted wastes contain at least partially moulded organic material.

When the bed of composted wastes after a time is at least to some extent saturated with contaminations, it needs to be changed and the used bed needs to be taken care of. In one embodiment of the invention, in which the absorbed contaminations mainly contain organic compounds, the used bed is deposited for some time, whereby the absorbed organic compounds are degraded by bacteria and fungi contained in the compost. This degradation is an aerobic process and in one embodiment of the invention the deposition takes place in a ventilated container. The time for the deposition varies between two months and one year depending on the composition of the compost. When the degradation is finished, the compost and the absorbed organic compounds have changed into topsoil. The soil can then, for example, be used on the fields or in the garden. This method of taking care of the contaminated absorbent is both simple and advantageous in an environmental point of view. Instead of creating an environmental load afterwards, it creates a resource, i.e. topsoil.

In a further embodiment of the invention, the bed contains peat as well. The ability of the composted wastes to absorb the organic compounds is high, but their ability to retain the absorbed compounds is lower. By adding peat to bed, the ability of the bed to retain the organic compounds is increased.

In one preferred embodiment the share of composted wastes in the bed is larger than the share of peat, the share of composted wastes comprises preferably more than 70%. Since the share of composted wastes is higher than the share of peat in the bed, the properties of both the absorbing materials are utilised in an optimal way.

In one preferred embodiment of the invention, the bed comprises one layer of composted wastes and one layer of peat, and the contaminated water is first led through the layer of composted wastes and then through the layer of peat. In such a way, a high absorption of the organic compounds is first ob- tained in the first layer comprising the composted wastes, and then the peat in the second layer takes care of the organic compounds emitted from the first layer.

DESCRIPTION OF THE DRAWINGS

One embodiment of the device according to the invention will hereafter be described with support from the appended drawings.

Figure 1 shows a device for purification of water. Figure 2 shows a container for storage of the used absorption material during the time the absorbed contaminations are degraded.

DESCRIPTION OF EMBODIMENTS

Figure 1 shows a collecting vessel 1 for the contaminated water, for example rain- or groundwater. The collecting vessel is connected to the purification device 3 by means of a pipe 2. The water is contaminated with organic compounds, for example in form of different types of oils, such as diesel , and petrol, organic solvents, organic pesticides and tensides. The purification device 3 contains a container 7 of for example plastic, concrete, or metal. I n the container 7, a number of layers are inserted which each contains a filtermass in the form of a bed of composted wastes 4. In the filtermass the contaminations are absorbed . The container 7 is at least partially open in order to allow for an exchange of air between the tank and its surroundings. The absorption thus takes place under aerobic conditions.

With wastes means garbage and trash from households, gardens, and industries. The wastes must at least to some extent contain organic material that must be mouldable in order to function as an absorbent. The wastes do not necessarily need to be sorted, rather are they useful even if they contain non- mouldable materials such as plastic or glass. The absorbent comprises the mouldable parts of the wastes. In order to absorb efficiently, the wastes should be at least partially moulded, the moulding should preferably be in a far advanced state. The de- nomination compost refers hereafter to compost from composted wastes.

The different layers in the purification device 3 are separated by bottoms 5, which comprises plastic perforated over the entire cross section . The purpose of the bottoms 5 with perforations is to distribute the liquid over the whole absorbent cross section and thus to utilise the whole bed effectively. A purification unit of a number of on top of each other piled layers can easily be put down into the container 7. The now effectively purified water is tapped from the bottom of the purification device through a piping 6. According to a preferred embodiment, the container 7 contains one outer, upright container and one inner container, which is insertable and detachable from the outer container. The inner container can, for example, be a sack of plastic or textile. When the filtermass is saturated with contaminations, the sack is lifted out of the upright container and a new similar sack containing a purification unit with unsaturated filtermass is inserted into the container.

In the collecting vessel 1 , contaminated water is collected which thereafter is led by an inlet member 2 to the purification device 3 which comprises one or several layers each of which contains a bed of composted wastes. The contaminated water is brought to pass the compost, thus the main part of the contaminations in the water are absorbed in the compost. Thereafter the contami- nated water is led away through an outlet member 6. The contaminated water flows downwards through the purification device under the influence of gravity. In one embodiment of the invention, no outlet member is needed, instead the water is allowed to flow directly down into the ground beneath the purification de- vice.

After some time of usage, the filtermass becomes saturated with contaminations and needs to be changed for a new unsaturated filtermass. The saturated filtermass is deposited for some time in an aired container in order for the absorbed organic contaminations to have time to be degraded. The degradation takes place with the help of bacteria and fungi naturally present in the composted wastes. This is mainly an aerobic process. The time for the deposit depends on the composition of the composted wastes and the relationship between different types of fungi and bacteria in the compost. At optimum conditions, only two months can be enough, but it can take up to one year before the degradation is finished. When the organic contaminations have disappeared from the compost, topsoil remains, which can be used for example in gardens or on fields.

Fresh compost is rich in nitrogen. When the water passes through the absorbent during the purification, a soaking leaching of the nitrogen takes place, which brings the saturated compost to become deficient in nitrogen. In order to obtain an enhanced degradation of the absorbed organic compounds, the deposit can be carried out in two steps. In a first step the absorbent deficient in nitrogen is deposited without additives for two to four months. During this first step, white and red nitrogen avoiding fungi are grown. These fungi actively assist in the degradation of the absorbed organic contaminations, and in particular to the degradation of organic pesticides. In a second step, fresh compost rich in nitrogen is added to the absorbent. In the nitrogen rich environment created, the red and white fungi no longer thrive. On the other, hand bacteria prosper, assisting in further degrading the organic contaminations, in the nitrogen rich environment.

The deposit can suitably be carried out in an open container 9, see figure 2. The container 9 can, for example, be a sack, pref- erably of plastic. The plastic can be LDPE (low density polyethylene). In a preferred embodiment of the invention, the deposit is carried out in the container 7 in which the purification unit is inserted during the purification process. If the container 7 comprises an inner container in the form of a sack, the sack with the purification unit can be lifted out of the outer container and be put away for depositing. When the degradation is finished, the sack with contents is transported to a suitable place where the topsoil is spread out.

For further enhancing the ability of purification, the bed may also contain peat. The peat can be added directly together with the compost or be put in separate layers beneath the layers of compost. The contaminated water should first pass a layer of compost and then a layer of peat. The task of the peat is to absorb the organic compounds that the compost cannot retain. A suitable distribution between peat and compost is about 75% compost and 25% peat.

The invention can be varied within the scope of the claims below.

Claims

1 . A method for purifying water contaminated with organic compounds where the contaminated water is led to a bed comprising composted wastes (4) and thereafter brought to pass the bed, in which at least the main part of said organic compounds are absorbed.

2. A method according to claim 1 , wherein the composted wastes comprise at least partially moulded organic material.

3. A method according to claim 1 , comprising that when the bed with composted wastes are at least to some part saturated with contaminations, it is deposited for some time, whereby the ab- sorbed organic compounds become degraded.

4. A method according to claim 3, wherein the absorbed compounds are degraded by bacteria and fungi contained in the compost.

5. A method according to claim 3 or 4, wherein the bed of composted wastes is transferred to an aired container (9) for deposition.

6. A method according to claim 3 or 4, wherein, during the time the contaminated water passes the bed of composted wastes, the bed is kept in a container and the same container is used during the deposition.

7. A method according to claim 3, wherein the time of deposition is varied between two months and a year.

8. A method according to any one of the claims 3-7, wherein, during the time of deposition, fresh compost is added to the used composted wastes.

9. A method according to any one of the previous claims, wherein the bed contains peat.

10. A method according to claim 9, wherein the share of com- posted wastes in the bed is larger than the share of peat.

1 1 . A method according to claim 9 or 10, wherein the share of composted wastes in the bed is larger than 70%.

12. A method according to claim 9, wherein the bed contains one layer of composted wastes and one layer of peat, and the contaminated water is first led through the layer of composted wastes and then through the layer of peat.

13. A device for purification of water contaminated with organic compounds, which comprises an absorbent and is arranged so that the contaminated water passes the absorbent, at which at least the main part of said organic compounds are absorbed, characterised in that the device comprises a bed of composted wastes (4), at which at least a part of said wastes forms the absorbent.

14. A device according to claim 1 3, characterised in that the composted wastes contains at least partially moulded organic material.

15. A device according to claim 13 or 14, characterised in that it comprises a collection member (1 ) to collect the contaminated water which is connected to a purification device (3) which con- tains said bed with composted wastes (4).

16. A device according to claims 1 3-15, characterised in that it comprises a container member (9) arranged to keep the bed of composted wastes both during a phase of absorption when the contaminated water passes the bed and during a phase of depo- sition when degradation of the absorbed contaminants takes place.

17. A device according to claim 16, characterised in that the container member (9) contains a sack of plastic material.

18. A device according to claim 1 3, characterised in that said bed comprises peat.

19. A device according to claim 18, wherein the share of composted wastes in the bed is larger than the share of peat.

20. A device according to claims 18 or 19, wherein the share of composted wastes is larger than 70%.

21 . A device according to any one of the claims 18-20 , where in the bed comprises a layer of composted wastes and a layer of peat, and that the layers are arranged so that the contaminated water first passes the layer of composted wastes and then through the layer of peat.

22. The use of composted wastes for purifying water contaminated with organic compounds.