NL2020137B1

NL2020137B1 - Groundwater recharge system

Info

Publication number: NL2020137B1
Application number: NL2020137A
Authority: NL
Inventors: Willem Anna Bastings Ivo
Original assignee: Drainblock B V
Priority date: 2017-12-20
Filing date: 2017-12-20
Publication date: 2019-06-26

Abstract

The invention relates to a groundwater recharge system, comprising a mineral wool reservoir, suitable for retention of water; at least one passage for water to reach the mineral wool reservoir; 5 and at least one columnar conduit between the reservoir and the aquifer, which allows water from the reservoir to ﬂow to the aquifer through the action of gravity. The invention further relates to the use of mineral wool blocks in such a system, as well as to a method of producing such a system. [fig.2]

Description

GROUNDWATER RECHARGE SYSTEM

The invention relates to a groundwater recharge system.

Background

Waler management, in particular in densely populated areas, is a complex problem. On the one hand, groundwater is used as a water supply, and must therefore be replenished/recharged regularly. This may for instance be done by pumping water under pressure into the aquifer.

On the other hand, in times when of high intensity rainfall, or if there is a large influx of water for some other reason, flooding problems may occur. Many solutions involve having selective flooding, pumps, or other ways of redistributing water, but these tend to be complex, in need of monitoring and other human intervention, etc.

There is therefore a need for a groundwater recharge system which may improve water management capabilities, and which does not rely on either motorized elements or constant monitoring and adjustment.

Summary A solution may be provided by the groundwater recharge system the invention, which comprises a mineral wool reservoir, suitable for retention of water; at least one passage for water to reach the mineral wool reservoir; and at least one columnar conduit between the reservoir and the aquifer, which allows water from the reservoir to flow to the aquifer through the action of gravity.

Mineral wool is a natural and environmentally friendly material. Mineral wool is known primarily for its properties as a thermal insulator and sound absorber. It is also used in the field of hydroponics as a growth medium for plants, wherein its capacity to retain water is an important aspect. Mineral wool is further known as a filtration material.

The present invention is based on the inventive insight that the properties of mineral wool also makes it very useful in a large-scale buffer, in which water may be retained but from which it may also gradually flow under the influence of gravity. In particular, mineral wool has high water storage capacity and a long life-time, it is load bearing and it has good drainage capabilities. This combination of features makes it very suitable both for water retention and for recharge of the aquifer.

The mineral wool reservoir is preferably positioned underground, between the surface and the aquifer. Furthermore, mineral wool is load bearing. This means that this reservoir does not impede on above-ground space to be used for other purposes. In particular, the reservoir may advantageously be positioned under existing structures, for instance under parking areas, roads, parks, playgrounds, sports field, construction and the like.

The water from the mineral wool reservoir flows under gravity through the columnar conduits to the aquifer, in particular since, as the reservoir is higher than the aquifer, there is always positive pressure. If the reservoir inflow exceeds the column discharge capacity, which may for instance occur in times of heavy rainfall, the mineral wool reservoir has sufficient capacity to serve as a temporary water buffer. In dry periods the water stored in the reservoir will gradually drain to the aquifer.

The connection between the reservoir and the aquifer may be formed in different ways. It may for instance be formed by an open pipe, with walls of a suitable material. Alternately, a sand column may be used, or a column filled with mineral wool, which may or may not be of the same type as the mineral wool in the reservoir. While the columns may have a substantially constant, circular diameter, note that the invention is not limited in such a way: any conduit which allows water to gradually flow from the reservoir to the aquifer, regardless of size and shape. The skilled person will be able to determine the best choice of material and configuration for the columnar conduits, depending on factors such as cost, expected precipitation, desired flow speed, etc.

The ratio between the distance from the al least one columnar conduit to the closest edge of the reservoir and the distance from the at least one columnar conduit to the midpoint of the reservoir may be between 2:1 and 1:2. Preferably the columnar conduits are not too close to the edge of the reservoir, since somewhat centrally located columnar conduits tend to lead to an improved flow under gravity of water from the mineral wool reservoir to the aquifer.

Preferably, the system comprises at least four columnar conduits. In general, the larger the horizontal cross-section of the mineral wool reservoir, the more advantageous it is to have a larger number of columnar conduits, thus providing several points at which water may leave the mineral wool reservoir.

The passage for water to reach the mineral wool may comprise pipes. Alternately or additionally, the passage for water to reach the mineral wool reservoir may comprise a material through which water may infiltrate.

The groundwater recharge system according to the invention may further comprise means to filter water before it arrives at the mineral wool reservoir. These means may comprise mineral wool, which may or may not be of the same type as used in the reservoir.

There are many possible ways to collect water for the reservoir. The word “passage" is not meant to be limiting, and may also cover a passage through a material such as sand. Some possible ways of collecting water are already known in combination with other water collecting solutions, and in fact the present system may make use of already present water collection means. The below options are not intended to be limiting, and the various options may be combined with each other according to the desired application. Some or all of the passages for water to reach the mineral wool reservoir may comprise means to filter water before it arrives at the mineral wool reservoir. This may help prolong the lifetime of the reservoir, in particular since the filtering means will generally be closer to the surface and hence more accessible than the mineral wool reservoir itself. This means that these filtering means may be replaced regularly if necessary.

One category of possible passages is constituted by so-called pipe systems, in which a network of pipes guides the water to the mineral wool reservoir. Water, for instance rain water, may be collected with a street gutter, a roof gutter, and/or other channels, and then guided through pipes to the mineral wool reservoir.

Another category of possible passages makes use of infiltration through an open surface. For instance, the surface may comprise sand, pebbles, or porous paving. The latter is a specific form of covering is purposefully made to allow water to infiltrate through it.

Another category of possible passages in constituted by street gutters with grates. These gutters may for instance take the shape of trenches dug along roads or in other convenient places, wherein blocks of mineral wool are placed in these trenches, the remainder is filled with sand or a similar material, and a covering grate is installed. This configuration has as an added advantage that plants may grow on the surface, which makes the street gutters aesthetically pleasing as well. The skilled person will be aware of modifications that are possible with this set-up without losing its double functionality: collecting water to then guide is to the mineral wool reservoir, and filtration.

The above-mentioned means may be combined with a so-called central collection pit and sand trap. In these cases, the water is collected using one of the means described above, and the guided to and discharged into a large collecting pit, that also acts as a sand/sediment trap. Inside this collecting pit there may be filtration means. Furthermore, there may be outflow to the mineral wool reservoir, for instance through a central point.

The passages may also be formed substantially above the mineral wool reservoir, and may then take the shape of columnar connections between the surface and the mineral wool reservoir. These columnar connections may be formed by using mineral wool elements which allow for the passage of water and also serve as filtering means. The connection may be covered on the top and/or the bottom by a grating and/or pebbles. The mineral wool elements may be replaced as needed, for instance when the connection becomes clogged.

Note that while the above-described passages may work under the action of gravity, the use of pumps and other means to control the circulation of water is not excluded in the present invention.

The system further comprises means to guide overflow water to existing storm water drainage systems. The capacity of the mineral wool reservoir is limited by its size. Advantageously, therefore, the size of the mineral wool reservoir would therefore be chosen such that it may accommodate the extremes of rainfall to be expected at its location. However, it is difficult to rule out the possibility of overflow altogether, in particular due to the unexpected developments in weather and climate. Therefore it is advisable to provide means to guide overflow water to existing storm water drainage systems. For instance, these means may comprise pipes connected to an upper area of the mineral wool reservoir itself or to a potential central collection pit. The other end of the pipes may then be connected to an existing storm water drainage system. Alternately, overflow may simply be allowed to run out on the streets.

Preferably the area of a horizontal cross-section of the mineral wool reservoir is smaller towards the bottom than at the top. This assists with the flow under gravity of water from the reservoir to the aquifer, in particular also due to capillary slow.

This may for instance be achieved by building up the mineral wool reservoir from at least two cuboid layers, wherein the midpoints of these layers preferably coincide. A cuboid in the sense of this invention is a polyhedron of which each side is a rectangle. This shape has shown to be advantageous in ensuring the flow from the reservoir through the columnar conduits to the aquifer. Furthermore, mineral wool is often manufactured in cuboid blocks, and hence such a shape is easy to fill with such blocks without requiring them to be cut or adapted.

Alternately, the mineral wool reservoir may gradually taper towards the bottom of it. For instance, it may have a trapezoidal shape. Of course, the skilled person will be able to imagine many shapes for which the area of a horizontal cross section is smaller towards the bottom than at the top; in particular, the skilled person will be able to choose a size which is both conducive to flow from the mineral wool reservoir through the columnar conduits to the aquifer and convenient to dig and manufacture.

The invention also related to the use of mineral wool blocks in a groundwater recharge system according to any of the previous claims.

The invention also relates to a method of installing a groundwater recharge system, preferably the system as described above, comprising inserting at least one columnar conduit into a surface, with the bottom end reaching the aquifer; forming a mineral wool reservoir, wherein the reservoir is connected to the lop end of the at least one columnar conduit, and configured such that water from the reservoir may flow to the aquifer through the action of gravity; and ensuring that there is at least one passage for water to reach the mineral wool reservoir.

Brief description of the figures

The invention will be further elucidated based on the accompanying figures, wherein:

Fig. 1 shows a top view of an embodiment of the groundwater recharge system according to the invention;

Fig. 2 shows a side view of this embodiment of the groundwater recharge system according to the invention;

Fig. 3 shows a side view of an embodiment of the groundwater recharge system according to the invention including more detail of the passages for water to reach the mineral wool reservoir; Fig. 4a shows one embodiment of the surface end of passage for water to reach the reservoir; Fig. 4b shows the same embodiment, with the grate removed to know what is underneath.

Detailed description of the figures

Figures 1 and 2 show a top view and a side view, respectively, of an embodiment of the groundwater recharge system according to the invention. In the shown embodiment, the horizontal cross-section of the mineral wool reservoir 1 is a square; however, the cross-section may have any other shape. A rectangular cross-section may be preferred if pre-fabricated cuboid mineral wool blocks are used.

In Fig. 1, the mineral wool reservoir 1 has been virtually divided into four equally sized portions. In the middle of each of these portions, a columnar conduit 21, 22, 23, 24 may be seen. Dividing the mineral wool reservoir in such a way into equally sized portions, and positioning the columnar conduits substantially at the center of each one, is one advantageous method to determine good positions for the columnar conduits; however, other methods may also be used. Furthermore, while the columnar conduits are shown as having a circular cross-section, other cross-sections are also possible. The size, shape, number and distribution of the columnar conduits should be chosen to lead to the desired flow rate to the aquifer.

In Fig. 2, a side view of the same embodiment is shown. Here, it may be seen that in this embodiment, mineral wool reservoir 1 may be described as being comprised of two cuboid sections (without a separation between them). The top layer 11 is larger than the bottom layer 12. The midpoints of both layers substantially coincide. In this way, water may be led towards columnar conduits 21, 22, thus improving the flow rate. The length of columnar conduits 21, 22 is chosen such that water from the mineral wool reservoir may eventually reach the aquifer 100.

It may be seen here that mineral wool reservoir 1 in located underneath the surface 1, at a certain distance. There may be passages 30, 31 which allow water to enter the reservoir. Note that water may, aboveground, be guided towards these passages 30, 31. These passages 30, 31 may be provided with filtration means, for instance mineral wool blocks, which may or may not be of the same type as is used for the reservoir. Also, in some embodiments, water may infiltrate towards mineral wool reservoir 1 over the entire top surface of mineral wool reservoir 1.

Fig. 3 shows a more detailed, less abstracted embodiment. Mineral wool reservoir 1 is comprised of several cuboid portions 11, 12, 13, 14, 15, 16, 17, and lies just under surface 10. Two columnar conduits 21, 22 can be seen exiting mineral wool reservoir 1. Water may be supplied to mineral wool reservoir 1 in various ways. For instance, it may infiltrate from surface 1. At the left side, two collecting areas 43 and 43’ are shown, which are connected to mineral wool reservoir 1. The top of these may be for instance a grating 44 opening to the street, for instance connected to an existing street gutter.

Collecting areas 43 and 43’ may comprise filtration means, for instance sand. These filtration means may serve to filter water, for instance rain water, before it is transported to mineral wool reservoir 1. They may also, additionally or alternatively, comprise pumping means to convey water to mineral wool reservoir 1.

Collecting areas 43 and 43’ may further be supplied with water through conduit 42. Conduit 42 is connected to a filtration area 49, which lies underneath road 41, and may comprise for instance a granular filtering means. Filtration area 49 is at a slight incline, which may be sufficient to ensure water flow towards conduit 42 and collecting areas 43 and 43’. Filtration are 49 may be supplied with water in several ways. In the shown embodiment, it is supplied with a street gutter 48 as shown in Figs. 4a and 4b, which may further comprise mineral wool blocks 47 for additional filtration.

Note that the shown embodiment combines several possible ways of collecting water and conveying it to mineral wool reservoir 1. All the shown methods may also be used separately, or in combination with still other possibilities.

Figs. 4a and 4b show a street gutter 51, which is one possible way in which water may be collected for mineral wool reservoir 1. In particular, this street gutter may be located at the side of a road 60 or between two roads 60 and 61, but this is not meant to be limiting. In this embodiment, the street gutter is covered by a grate 50, as may be seen in Fig. 4a, which comprises openings which allows (rain) water to pass, but which stops larger objects such as leaves and detritus from entering.

In Fig. 4b, the grate has been removed. Underneath, blocks 47, which are preferably mineral wool blocks, which may or may not be the same mineral wool blocks as are used in mineral wool reservoir 1, are used to perform a first filtration step. The system may also work without these filtration means. However, an advantage of having first filtration means close to the surface, underneath a removable grate, is that these blocks may be easily replaced when they get clogged.

Turning back to Fig. 3, the water which passes through the street gutter of Fig. 4 may then optionally pass through a further filtration area 49, through conduit 42, onto collecting areas 43 and 43’, after which it is guided through conduits 45 and 46 to mineral wool reservoir 1.

Using a combination of the above-described methods, water from an extended area may be collected and guided towards mineral wool reservoir 1, where it may be stores even in cases of heavy rainfall, thus helping to prevent flooding. Furthermore, the water stored in mineral wool reservoir 1 may then gradually be guided to the aquifer 100 through columnar conduits 21, 22, 23, 24, in such a way both recharging the groundwater level and ensuring that space is created in the mineral wool reservoir to be able to receive water again during the next period of heavy rainfall. Thus, the system according to the invention, which is not limited to the above-described exemplary embodiments, serves a dual purpose, as both a groundwater recharge system and as a drainage buffer.

Claims

A groundwater change system, comprising: a mineral wool reservoir suitable for water retention; at least one passage for water to reach the mineral wool reservoir; at least one column-like conduit between the reservoir and the aquifer, which allows water from the reservoir to flow to the aquifer under the action of gravity.

Groundwater change system according to claim 1, wherein the mineral wool reservoir is placed ungrounded, between the ground surface and the aquifer.

3. Ground water change system according to claim 1 or 2, wherein the at least one column-like pipe is one of an open tube, a sand column or a column filled with mineral wool.

Groundwater change system according to any of the preceding claims, wherein the ratio between the distance of the at least one column-like pipe to the nearest edge of the reservoir and the distance between the at least one column-like pipe to the center point of the reservoir is between 2: 1 and 1: 2.

Groundwater change system according to one of the preceding claims, wherein the at least one column-like pipe comprises at least four column-like pipes.

Groundwater renewal system according to any of the preceding claims, wherein the passage for water to reach the mineral wool reservoir comprises tubes.

Groundwater change system according to any of the preceding claims, wherein the passage for water to reach the mineral wool reservoir comprises a material through which water can infiltrate lean.

A groundwater change system according to any of the preceding claims, wherein the passage for water to reach the mineral wool reservoir comprises means for filtering water before it reaches the mineral wool reservoir.

The groundwater change system of claim 8, wherein the water filtering means comprises mineral wool.

A groundwater drainage system according to any one of the preceding claims, wherein the system further comprises means for conducting flooding water to existing stormwater drainage systems.

Groundwater change system according to any of the preceding claims, wherein the surface of a horizontal cross-section of the mineral wool reservoir is smaller closer to the bottom than to the top.

Groundwater change system according to claim 11, wherein the mineral reservoir comprises at least two beam-shaped layers, the centers of the two layers preferably corresponding.

Groundwater renewal system according to claim 11, wherein the mineral wool reservoir preferably tapers gradually towards the bottom.

A groundwater change system according to any of the preceding claims, wherein the mineral wool reservoir comprises mineral wool blocks.

Use of mineral wool blocks in a groundwater change system according to one of the preceding claims.

A method for manufacturing a groundwater renewal system, comprising: inserting at least one columnar conduit into a surface, wherein the lower end reaches the aquifer; forming a mineral wool reservoir, said reservoir being connected to the upper end of the at least one column-like conduit, and being arranged such that water can flow from the reservoir to the aquifer under the action of gravity; ensuring that there is at least one passage for water to reach the mineral wool reservoir.

A method according to claim 16, which results in a groundwater change system according to any of claims 1-14