WO2013176616A1

WO2013176616A1 - Continuous sand filter plant with fluid distributors

Info

Publication number: WO2013176616A1
Application number: PCT/SE2013/050586
Authority: WO
Inventors: Hans F Larsson
Original assignee: Nordic Water Products Ab
Priority date: 2012-05-23
Filing date: 2013-05-22
Publication date: 2013-11-28
Also published as: CN104736215A; EP2852451A1; CN202822936U; EP2852451A4; IN2014MN02597A

Abstract

A continuous sand filter plant comprises a plurality of filter modules at least one fluid distributor. By designing the fluid distributor with a length adapted to extend across at least two filter modules of the filter plant, the costs are lower than in prior art filter plants.

Description

CONTINUOUS SAND FILTER PLANT WITH FLUID DISTRIBUTORS Technical field

[0001 ] The present invention relates generally to the treatment of

water/ waste water, and more particularly, to a new and improved continuous sand filter plant with fluid distributors.

Background art

[0002] In connection with municipal and many industrial water treatment systems, the water/ wastewater needs to be purified. For example, one such system may be a drinking water system where drinking water is produced from surface water and another system may be a municipal wastewater treatment wherein the wastewater needs to be treated so that it can be discharged or reused in industry or for irrigation and similar purposes.

[0003] The use of two different, separately operated sand filters can be avoided if a continuously operated sand filter of the type disclosed in United States Patent Nos. 4, 1 26,546 and 4, 1 97,201 is utilized. In such a continuous sand filter plant, the filter bed is continuously cleaned while the filter is in operation. In this regard, the dirtiest sand is taken out of the filter bed, washed and returned to the clean part of the filter bed. In this way, the filter does not have to be taken out of operation for back-washing. A similar type of continuously operating sand filter also is disclosed in United States Patent No. 4,246, 1 02. As disclosed in that patent, the liquid is treated with chemicals before being treated in the sand filter.

[0004] In the sand filters of these patents, the liquid is introduced into the lower part of the filter bed. Filtration takes place upwards through the filter bed which is moving downward. In case the sand filter is operated with chemicals being added as disclosed in United States Patent No. 4,246, 1 02, then precipitation/coagulation and/or flocculation occurs during this filtration process. Most of the suspended solids in the feed will be separated near the feed level, which results in the dirtiest sand being in the lower part of the filter. The sand bed is kept in a slow downward motion by an air-lift pump that removes the dirtiest sand from a location close to the bottom of the filter tank. In the air-lift pump, the sand is subjected to a thorough mechanical agitation by the action of the air bubbles within the pump such that the dirt is separated from the grains of sand. The separated dirt is rinsed from the sand in a sand washer near the top of the airlift pump, the sand washer being disposed concentrically around the upper part of the air-lift pump. The clean sand is returned to the top of the filter bed. Reject water is continuously removed from the sand washer and discharged from the sand filter whereas the filtrate exits from the sand filter as an overflow.

[0005] Such sand filters can also be adapted for removing nitrogen from water. The presence of oxygen is needed for nitrification and COD reduction . Some prior art sand filters are therefore provided with an aerator. Process air is supplied by a blower or compressor and is admitted to the process via non-clogging aeration hoods in the filter.

[0006] US 5,472,61 0 discloses an apparatus for blowing a gas into a granular filter bed comprising elongate hoods adapted for a single filter bed.

[0007] However, such hoods add to the cost of the filter plant. Summary of invention

[0008] An object of the present invention is to provide a new and improved continuous sand filter plant which is more cost efficient than prior art plants.

[0009] The invention is based on the insight that one single device for supplying a fluid to a filter plant can be used for a plurality of filter modules. [001 0] Accordingly, according to the invention there is provided a continuous sand filter plant comprising a plurality of filter modules and comprising at least one fluid distributor, characterized in that the at least one fluid distributor has a length adapted to extend across at least two filter modules..

[001 1 ] By providing a fluid distributor with a length adapted to extend across at least two filter modules, a plant is provided with a cost efficient device to

simultaneously supply a fluid to several filter modules. Also, the attachment of the fluid distributor is simplified since there is no need to provide separate attachment devices for the different filter modules and the radial arms of prior art devices can be omitted.

[001 2] Also, by providing a single fluid distributor for supplying a fluid for several filter modules, a more even distribution of the fluid is achieved.

[001 3] In a preferred embodiment, the at least one fluid distributor exhibits at least one straight section, which lends itself to easy manufacturing. It is also preferred that the fluid distributor is made of plastic.

[001 4] The at least one fluid distributor can be a water or a gas distributor, whereby the advantages of the invention can be applied to more than one application.

[001 5] It is preferred that the at least one fluid distributor is provided with a plurality of holes, whereby an even distribution of the fluid is achieved.

[001 6] In one embodiment, the device comprises a first and a second fluid distributor, wherein the first fluid distributor is provided at a higher level than the second fluid distributor. A stable design is thereby achieved, wherein the upper level of the fluid distributors relieve the lower level from part of the pressure exerted by the filter bed material. [001 7]

[001 8] In one embodiment, each filter module is partly defined by a bottom cone. This is a suitable shape for providing a filter module.

[001 9] Further preferred embodiments are defined in the dependent claims. Brief description of drawings

[0020] The invention is now described, by way of example, with reference to the accompanying drawings, in which:

[002 1 ] Fig. 1 is an overall view of a first embodiment of a filter plant according to the invention provided with a plurality of fluid distributors in the form of water and air distributors.

[0022] Fig. 2 is a detailed side view of the filter plant shown in Fig. 1 .

[0023] Fig. 3 is a detailed side view of the filter plant shown in Fig. 1 illustrating the operation thereof.

[0024] Fig. 4 is a detailed end view of the filter plant shown in Fig. 1 .

[0025] Fig. 5 is a detailed view of the filter plant shown in Fig. 1 .

[0026] Fig. 6 is a detailed view of an air distributor comprised in the filter plant of Fig. 1 .

[0027] Fig. 7 is an overall view of a second embodiment of a filter plant according to the invention provided with a plurality of fluid distributors in the form of water and air distributors.

[0028] Fig. 8 is a detailed side view of the filter plant shown in Fig. 7. [0029] Fig. 9 is a detailed view of an alternative air distributor comprised in a filter plant.

[0030] Fig. 1 0 and 1 1 are overall views of alternative embodiments of a filter plant comprising an air distributor in the form of a hose.

[003 1 ] Fig. 1 2 is an overall view of an embodiment of a filter plant wherein the water distributors extend across a plurality of filter modules.

Description of embodiments

[0032] In the following, a detailed description of a device for supplying a fluid into a filter module and a filter plant comprising such devices will be given . In this context, the term "fluid" should be construed broadly to incorporate all kinds of fluids in a filter plant, such as the water to be purified, a denitrification gas, such as air, etc.

[0033] Fig. 1 shows an overall view of a filter plant, generally designated 1 . The filter plant comprises a plurality of filter modules, generally designated 1 0, conventionally comprising sand as filter material. Each filter module is partly defined by a bottom cone made of concrete, for example.

[0034] The plant is provided with a plurality of inlet water distributors 20 and the water to be denitrified is admitted there through. Each water distributor 20 has a length adapted to extend across at least two filter modules. In the embodiment shown, there are four parallel water distributors running above each filter module.

[0035] Above the inlet water distributors, there are provided a plurality of process air distributors in the form of elongated hoods 30 having a length adapted to extend across at least two filter modules. [0036] In the filter plant 1 0, a device for continuous cleaning is provided for each of the filter modules. Thus, for each filter module 1 0, there is provided an air-lift pump 40 adapted to transport contaminated sand from the bottom cone.

[0037] A sectional view of the plant 1 is shown in Fig. 2. Filter material in the form of sand (not shown in this figure) is provided as inverted cones in the respective filter module 1 0. The air-lift pumps 40 extend down close to the bottom of the respective filter module for removal of contaminated filter material, preferably sand. Thus, a filter module is defined as a filter unit having a separate system for the removal of contaminated filter material.

[0038] In the illustrated embodiment, each water distributor extends across two filter modules 1 0, although it is envisaged that they can extend across more than two filter modules. Each water distributor 20 is supported in its middle section by concrete pyramids forming the base of the filter plant 1 and is at the two ends thereof supported by a respective bracket 22. Similarly, each air distributor 30 is supported at the two ends thereof by a respective bracket 22. A beam 32 is provided at the centre of the air distributors for supporting a plurality of air distributors, see also Fig . 1 .

[0039] Water is supplied to the water distributors 20 by means of a respective water inlet conduit 24 while air is supplied to the air distributors 30 by means of a respective air inlet conduit 34.

[0040] The air distributors 30 are provided with a plurality of holes 30a, through which air is allowed to escape. All holes are provided at the same level and this provides even distribution of air bubbles rising through the filter material of the module in question. It is preferred that the holes 30a on the two sides of each air distributor are provided mutually displaced so as to achieve even distribution of the air bubbles. [0041 ] The operation of the filter plant 1 will now be explained with reference to Fig. 3. Water is supplied through the water inlet conduit 24 and is evenly

distributed in the filter modules by means of the water distributors 20. This is indicted in Fig. 3 by the arrows designated "W". Simultaneously, air is supplied through the air inlet conduit 34 and is evenly distributed in the filter modules by means of the air distributors 30. This is indicted in Fig. 3 by the arrows designated "A". Since the water distributors are provided below the air distributors, water rising through the filter material of the module in question will be aerated when passing the air distributors by the air therefrom .

[0042] Fig. 4 is a detailed end view of the water and air distributors showing the water inlet conduits 24 supplying water to the water distributors 20 and the air inlet conduits 34 supplying air to the air distributors 30.

[0043] Fig. 5 is a view showing the shape of the water distributors 20 and the air distributors 30. In the detailed view of an air distributor shown in Fig. 6 it is seen that the holes 30a on the different sides of the air distributor are mutually displaced.

[0044] An alternative embodiment of a filter plant will now be described with reference to Figs. 7 and 8. In this embodiment, there is provided a plurality of air distributors 30 extending across two filter modules while the water distributors 1 20 are of a conventional type in the form of arms extending radially from the water inlet conduits 1 24. Thus, as in the previous embodiment, water rising from the water distributors is aerated by the air bubbles leaving the air distributors 30.

[0045] An alternative design of the air distributors will now be explained with reference to Fig. 9. Each air distributor 1 30 is constituted by a hood 1 32 preferably made of a plastic material, although it is also possible to use stainless steel or the like. The hood 1 32 has a ridge and two essentially planar slanting sections 1 32b extending at an angle from the ridge. At the lower edge of the slanting sections 1 32b, a plurality of notches 1 32c are provided, which are adapted to release air enclosed by the hood 1 32. By providing these notches, even distribution of the air is achieved and the size of the notches determines the size of the air bubbles leaving the air distributor 1 30.

[0046] In yet an alternative embodiment, the air distributors are in the form of a perforated hose 230, which is provided above the water distributors, see Figs. 1 0 and 1 1 . In Fig. 1 0, this kind of air distributor is combined with water distributors 20 extending across two filter modules while in Fig. 1 1 it is combined with water distributors 1 20 of the conventional form of arms extending radially from the water inlet conduits 1 24.

[0047] The hose 230 is preferably made of polyurethane or other suitable plastic material and can thus be arranged in different configurations depending on the layout of the filter plant 1 .

[0048] It will be appreciated that the inventive idea can be applied on the water distributors without applying it to the gas distributors. Thus, in Fig. 1 2 a filter plant 1 is shown, wherein the water distributors 20 extend across a plurality of filter modules 1 0 but each filter module is provided with a separate air distributor 330. In this embodiment, each air distributor comprises a plurality of essentially straight tube-like sections provided with holes, wherein these sections are interconnected so as to form a circle.

[0049] Preferred embodiments of a filter plant according to the invention have been described. It will be appreciated that these can be varied within the scope of the appended claims without departing from the inventive idea.

Claims

1 . A continuous sand filter plant comprising a plurality of filter modules (1 0) and comprising at least one fluid distributor, c h a r a c t e r i z e d i n t h a t the at least one fluid distributor (20; 30; 1 30; 230) has a length adapted to extend across at least two filter modules ( 1 0) .

2. The continuous sand filter plant according to claim 1 , comprising a plurality of housings, each housing enclosing a respective filter module (1 0) of the plurality of filter modules, the filter plant further comprising a support structure (32) attached to the housings and supporting the fluid distributor.

3. The continuous sand filter plant according to claim 1 or 2, comprising, for each of the filter modules (1 0), a device (40) for continuous cleaning of the filter bed.

4. The continuous sand filter plant according to any one of claims 1 -3, wherein the at least one fluid distributor comprises a water distributor (20) .

5. The continuous sand filter plant according to any one of claims 1 -4, wherein the at least one fluid distributor comprises a gas distributor (30; 1 30; 230).

6. The continuous sand filter plant according to any one of claims 1 -5, wherein the at least one fluid distributor (20; 30; 1 30; 230) exhibits at least one straight section.

7. The continuous sand filter plant according to any one of claims 1 -6, wherein the at least one fluid distributor (20; 30; 1 30; 230) is made of plastic.

8. The continuous sand filter plant according to any one of claims 1 -7, wherein the at least one fluid distributor comprises a hood (1 32) with a ridge and two essentially planar slanting sections (1 32b) extending at an angle from the ridge, wherein a plurality of notches ( 1 32c) are provided at the lower edge of the slanting sections (1 32b).

9. The continuous sand filter plant according to any one of claims 1 -8, wherein the fluid distributor is a hose (230) provided with a plurality of holes.

1 0. The continuous sand filter plant according to any one of claims 1 -9, comprising a first and a second fluid distributor (20; 30; 1 30; 230), wherein the first fluid distributor is provided at a higher level than the second fluid distributor.

1 1 . The continuous sand filter plant according to claim 1 0, wherein the first fluid distributor is a gas distributor (30; 1 30; 230) and the second fluid distributor is a water distributor (20) .

1 2. The filter plant according to any one of claims 1 -1 1 , wherein each filter module (1 0) is partly defined by a bottom cone.

1 3. The filter plant according to any one of claims 1 0-1 2, wherein the walls of the filter modules (1 0) are made of concrete.