WO1998021153A1

WO1998021153A1 - Device for cleaning polluted water

Info

Publication number: WO1998021153A1
Application number: PCT/NL1997/000622
Authority: WO
Inventors: Antonius Paul Leo Maria Winters
Original assignee: H.T. Research B.V.
Priority date: 1996-11-14
Filing date: 1997-11-14
Publication date: 1998-05-22
Also published as: AU4970597A; NL1006507C1

Abstract

A device and a method for cleaning polluted water in a reservoir, which device comprises supply means for supplying the polluted water to the reservoir upstream of the reservoir, discharge means for discharging cleaned water downstream of the reservoir, as well as plants which are rooted in the reservoir, characterized in that the reservoir is a movable container.

Description

DEVICE FOR CLEANING POLLUTED WATER

The invention relates to a device for cleaning polluted water m a reservoir, which device comprises supply means for supplying the polluted water to the reservoir upstream of said reservoir, discharge means for discharging cleaned water downstream of said reservoir, as well as plants which are rooted m said reservoir.

A device of this kind is generally known. In particular m agricultural enterprises and farms the reservoir is an open ditch, whereby a hole is first dug into the ground, which hole is subsequently filled with successive layers of water permeable materials, such as sand, gravel, lava rock, peat and the like. The supply means supply the polluted water m the direction of the ditch (or a pond having dug-out walls) , whilst the discharge means function to transport the cleaned water to the surface water, for example.

One drawback of the known device is that the polluted water which is caught m the ditch is m open communication with the ground water via the bottom and the side walls of the ditch, which is no longer allowable for environmental reasons. The fact is that it has become apparent m practice that tne polluted water leads to serious pollution of the ditch bottom and the ground water. In order to obviate this drawback it has already been proposed to place a water impermeable foil on tne bottom and against the side walls of the ditch as a separation, but m practice this measure has appeared to be inadequate. It so happens that m particular the roots of the plants appear to pierce the foil after some time, with all its negative consequences, whilst the foil material is furthermore weakened as a result of weatnermg. Another drawback of the known device is furtnermore the fact that it takes a considerable amount of excavation work to dig a ditch - often the ground is hard - which is time-consuming and for that reason economically unattractive in many cases. The excavation work is furthermore made more difficult when the ground water level is high, and when conduits, cables, pipes and the like are present in the ground. Finally the known device has the drawback that time-consuming and costly excavation work is necessary again when after a number of years the vegetation in the ditch is to be replaced.

The object of the invention is to eliminate the drawbacks of the known device that have been indicated above, and in order to accomplish that objective a device of the kind referred to in the introduction is characterized in that the reservoir is a movable container. The container, which is preferably placed on or at least partially in the ground, is in particular provided with means for loading and unloading it on/from a container-carrying lorry, thus providing a mobile water cleaning system. In another preferred variant a fork-lift truck or a trailer is used instead of a lorry, whilst the container may be fitted with one or more lifting eyes or be movable on a slide. A major advantage is thereby the fact that the container can be placed at any desired location, whilst it is also possible to give the container any desired dimension and shape - depending on the user's requirements. The invention is in particular intended for use by private individuals and companies who are not connected to a sewage system yet and who are no longer allowed to discharge polluted water into the surface water. The invention also provides a solution for existing water purification plants which have to cope with an excessive amount of polluted water. Private individuals can connect the container according to the invention directly to outlets and overflows from their homes (shower, washing machine, sink, etc.), whilst companies, such as carwashes, washing companies and the like, can connect said container directly to all water outlets from their facilities, or for example from their canteens. An important advantage of the invention is furthermore the fact that in case of serious pollution of the contents of the container, the container can be picked up as a whole in order to be transported to a location where the contents can be cleaned, whilst in the meantime a new, already operative container is placed at the original location. Another advantage is finally the fact that a user may place several containers beside, behind or above one another, depending on his requirements.

In one preferred embodiment of a device according to the invention the plants which are rooted in the container are deep-rooting plants, in particular said plants have a length of 30 - 100 cm. Preferably the plants have hollow stalks, which leads to an ideal aerobic environment in the container. In addition phosphates, nitrates and salts can readily be absorbed by the plants and be converted in the plants. The plants preferably belong to the group of heliophytes, in particular they are reed plants. If desired separate means may be used for introducing oxygen and/or other gases into the container in order to stimulate the breakdown of contaminations that takes place within the container.

In another preferred embodiment of a device according to the invention the container is at least partially filled with a filter, which is preferably made up of layers of material, in particular a layer of sand, a layer of lava rock, a layer of coarse plastic material, a layer of porous plastic granulate, and a layer of vegetable mould.

In another embodiment of a device according to the invention the supply means are arranged to enable uniform irrigation of the container. With the known device this takes place on one side of the ditch, as a result of which nutritional substances for the plants mainly flow into the ditch on one side, so that the plants grow mainly on that side. When the water supply takes place over the entire area, the plant growth and the purification will also take place over the entire area of the container, which leads to an increased capacity whilst the surface area remains unchanged. Preferably the supply means comprise horizontal pipes, which are perforated and which are spaced maximally 1 m apart and maximally 0.5 m from the edge of the container. This results in a uniform supply of water over the entire area of the container.

In another preferred embodiment of a device according to the invention a water permeable layer is provided under said supply means, whilst it is furthermore preferred to provide a layer of vegetable mould or another layer that stimulates plant growth above said supply means. The result of this measure is that the water being supplied can disperse in horizontal direction and migrate downwards, whilst in addition transport of gas (air) can take place within the container to or via the roots of the plants which are rooted in the container and the micro-organisms which live near or on said roots.

According to another preferred embodiment of a device according to the invention the discharge means are constructed to make it possible to vary the ground water level in the container. The discharge means are preferably made in the form of an overflow thereby. This makes it possible to adapt the ground water level to the desired plant growth and climate. Furthermore it is possible to keep the ground water level low for a period following the planting of the plants, which stimulates root growth. When the container is used as a water purification system at a later stage, the ground water level will be raised again. The advantage of the overflow is that the ground water level in the container remains more or less constant and does not depend on water being supplied via the supply means or on rain falling into the container. It is thereby preferred, however, to prevent rain water from being mixed with polluted water as much as possible.

In another preferred embodiment of a device according to the invention the lowermost layer in the container is a water-permeable layer, which is in communication with the discharge means. As a result of this there is a flow in more or less vertical direction through the various layers in the container, and the entire area/capacity of the container is optimally utilized. The supply means are preferably adapted to ensure a recurrent supply of water to the container. The advantage of this is that the supply of water to the container can be evenly spread over time, thus preventing the plants and the uppermost layer in the container from drying out .

It is preferred to connect a pump to a storage space for untreated water. This makes it possible to feed the water, which is often supplied in varying quantities, to the container in an even flow. If a connection that can be shut off is present between the suction side of the pump and the outlet of purified water, it will be possible to circulate part of the water during periods of a prolonged absence of sufficient polluted water, this in order to prevent the uppermost layer and the vegetation in the container from drying out.

The invention also relates to a method to be used with a device according to the invention, wherein polluted water is supplied to a reservoir in the form of a movable container, upstream thereof, and cleaned water is discharged downstream of the container, wherein said cleaning is effected by plants which are rooted in the container and by a filter comprised of layers of material, which is present therein.

The invention furthermore relates to a container to be used in a device according to the invention.

The invention will be explained in more detail hereafter with reference to figures illustrated in a drawing of a preferred embodiment of the invention, in which:

Figure 1 shows a diagram of an agricultural enterprise comprising a cleaning or purification plant;

Figure 2 is a diagrammatic side view of the purification plant of Figure 1;

Figure 3 is a diagrammatic plan view of a container in which water purifying vegetation is present; and

Figures 4 and 5 are diagrammatic sectional views of the container of Figure 3.

The diagrams illustrate the various parts schematically, conventional constructions and known constructions are not shown. Like parts are numbered alike as much as possible in the various Figures.

Figure 1 and Figure 2 show a production facility 1, where vegetables, for example, are cleaned and/or cut. During said cleaning and/or cutting waste water may be produced, which contains contaminations to such an extent that it is not allowed to discharge it into the surface water. The waste water from production facility 1 is discharged into a storage space 5. A farm 2 is present at the same facility, at which farm domestic waste water is produced, which is discharged into a septic tank 3, from where it flows to storage space 5 via a grease trap 4.

Storage space 5 houses a pump 6, which can pump the polluted water from storage space 5 into a purification container 7. The water that has been cleaned in purification container 7 flows into an effluent pond 8 via a discharge pipe 10, and from there, via a discharge pipe 9, to the surface water or to another destination. Part of the water may be returned from effluent pond 8 to storage space 5, after which it can be pumped into purification container 7 again (diagrammatically illustrated in a dotted line in Figure 1) . It is also possible to reuse part of the cleaned water in production facility 1, or in the toilet group of farm 2, for example .

As is shown in Figures 2 and 3, purification container 7 consists of a closed steel container 12 fitted with a supply pipe 11 and discharge pipe 10, with container 7 being filled with a number of layers of material in which heliophytes grow. Supply pipes 11 are disposed above a porous layer, and are spaced apart and from the wall so far that the entire area of the container is irrigated. The height of container 7 is about 1.20 m, which is appropriate in most circumstances. It is also possible to use deeper containers, however, whereby it must be taken into consideration that it must remain possible to transport the container in order to replace it in a simple manner. Steel container 7 may be fitted with hoisting eyes and/or a slide. According to an alternative embodiment container 7 may be made of another dense material, such as concrete, plastic and the like.

The cleaning effect of purification container 7 is obtained in that heliophytes H, which are deep-rooting plants having hollow stalks, provide a good structure and ensure a proper aeration of the soil, which enables many micro-organisms to grow and stay there. The water is cleaned in that said micro-organisms take in the contaminations and convert them into vegetable materials or mineral sludge, for example. The aforesaid aeration provides an aerobic environment within container 7. It is possible to introduce additives into the container in order to accelerate the breakdown by micro-organisms.

Figure 4 shows an example of the arrangement of purification container 7. The figure thereby shows that a ground water level G is achieved by causing discharge pipe 10 to overflow. The position of ground water G can be set in a simple manner by adjusting the highest point of discharge pipe 10, for example by rotating the pipe.

Ground water level G is of importance for the correct operation of container 7, since the micro-organisms are very active near the separation between wet and dry soil . When container 7 is to be provided with new plants, the very first thing to do is to strongly reduce the ground water level, which will stimulate root development. During this period only little polluted water is supplied. After the plants have sufficiently developed, ground water level G will be raised to a level of about 0.5 m below the upper side.

Layers of different materials are present in steel container 7. Starting from the bottom said layers include a layer of sand 13 , a layer of sand and shingle 14, with discharge pipe 10 lying in said layers, so that the discharge from container 7 can take place evenly. On top of that lies a layer of lava rock 15, a layer of coarse plastic material 16, a layer of porous plastic grains 16, a layer of sand and gravel 18, a layer of vegetable mould and sand 19, with a layer of vegetable mould 20 on top. Supply pipe 11 lies on top of the layer of sand and gravel 18, as a result of which the water flowing in is evenly distributed over the upper side of the container.

Closing the upper side of container 7 with evaporation- reducing materials will prevent excessive evaporation. The occurrence of excessive evaporation is undesirable, since this may very well result in surface panning of the soil.

In order to maintain the plant growth and the growth of the micro-organisms, the supply of water must take place very regularly. A dry period of for example more than one week may be fatal for the organisms, and consequently measures have been taken to ensure that pump 6 can supply water regularly. Said measures comprise the provision of a time clock, for example, which sets the pump going for a few minutes every hour, but also provisions for recirculating the cleaned water from effluent pond 8.

By stopping the supply of water regularly and maintaining a minimum ground water level G it can be ensured that there are recurrent periods of rest in container 7, which is conducive to the growth of the micro-organisms and thus to the purifying action.

Purification container 7 may also be used in another manner, whereby use is made of the possibility to install the container without digging it into the ground and to replace purification container 7 by a clean purification container 7 after the lapse of a certain period of time or in case of the occurrence of toxicosis in the container. Of course it is important for container 7 to be liquid- tight. In a special variant several series-connected containers 7 may be installed at a private or industrial building, with the number of containers depending on the capacity that is required.

Figure 5 corresponds with Figure 4, with this understanding that the layers are composed as follows: various plants 13 - vegetable mould and peat moss 14 lava rocks 15 recycled plastic 16 porous hard foam 17 gravel 18 - sand 19 peat moss 20 sand and drainage means 21 sand.

Claims

1. A device for cleaning polluted water in a reservoir, which device comprises supply means for supplying the polluted water to the reservoir upstream of said reservoir, discharge means for discharging cleaned water downstream of said reservoir, as well as plants which are rooted in said reservoir, characterized in that said reservoir is a movable container.

2. A device according to claim 1, wherein said container is placed on or at least partially in the ground .

3. A device according to claim 1 or 2 , wherein said container is provided with means for loading and unloading it on/from a container-carrying lorry.

4. A device according to claim 1, 2 or 3, wherein said plants which are rooted in the container are deep- rooting plants, in particular having roots which have a length of 30 - 100 cm.

5. A device according to claim 4, wherein said plants have hollow stalks.

6. A device according to claim 4 or 5 , wherein said plants belong to the group of heliophytes, in particular said plants are reed plants.

7. A device according to any one of the preceding claims 1 - 6, wherein said container is at least partially filled with a filter.

A device according to claim 7, wherein said filter is made up of layers of material, in particular a layer of sand, a layer of lava rock, a layer of coarse plastic material, a layer of porous plastic granulate, and a layer of vegetable mould.

9. A device according to any one of the preceding claims 1 - 8, wherein the supply means are arranged to enable uniform irrigation of the container.

10. A device according to any one of the claims 9, wherein said supply means comprise horizontal pipes, which are perforated and which are spaced maximally 1 m apart and maximally 0.5 m from the edge of the container.

11. A device according to any one of the claims 1 - 10, wherein a water permeable layer is provided under said supply means.

12. A device according to any one of the preceding claims 1 - 11, wherein a layer of vegetable mould or another layer that stimulates plant growth is provided above said supply means .

13. A device according to any one of the preceding claims 1 - 12, wherein said discharge means are constructed to make it possible to vary the ground water level in the container.

14. A device according to claim 13, wherein said discharge means are made in the form of an overflow.

15. A device according to any one of the preceding claims, wherein the lowermost layer in the container is a water-permeable layer, which is in communication with the discharge means.

16. A device according to any one of the preceding claims 1 - 15, wherein said supply means comprise a pump for periodically supplying water to the container .

17. A method to be used with a device according to any one of the preceding claims 1 - 16, wherein polluted water is supplied to a reservoir in the form of a movable container, upstream thereof, and cleaned water is discharged downstream of the container, wherein said cleaning is effected by plants which are rooted in the container and by a filter comprised of layers of material, which is present therein.

A container to be used in a device according to any one of the preceding claims 1 - 16.