EP1896371A1

EP1896371A1 - An apparatus for treating small river water

Info

Publication number: EP1896371A1
Application number: EP06757683A
Authority: EP
Inventors: Ba Do Lee
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-05-16
Filing date: 2006-05-10
Publication date: 2008-03-12
Also published as: EP1896371A4; WO2006123868A1

Abstract

The present invention relates to an apparatus for treating urban small river water in the path of flow of a river comprising; a pit type bath built below a river bed in the path of flow, and aeration means equipped in the pit type bath for aerating and whirling the water which flows into the pit type bath. The apparatus of the present invention has following merits; i) it does not require a large additional space. ii) it is durable against violent natural phenomena and cost-effective with simple structure and easy maintenance. The pit type bath is not easily filled up and does not need frequent maintenances since turbulent flows or whirlings exist in the bath by aeration. iii) it is compatible with environments. iv) it treats river water effectively and raises self- purificability of a river.

Description

AN APPARATUS FOR TREATING SMALL RIVER WATER

Technical Field

[1] The present invention relates to an apparatus for treating small river water and, more particularly, to an apparatus for treating urban small river water in the path of flow of a river. Background Art

[2] Acceleration of pollution caused by concentrated population and urbanization may change an urban river to an outlet for discharging pollution so that the water of an urban river may be used as neither for drinking nor for other ends. By buildup of a sewage system in modern cities, wastewater is collected separately from rain water and delivered via sewage lines to a terminal wastewater treatment plant, treated in it, and then discharged to a river. Accordingly, river water looks as if it would not been exposed to pollution sources. However, inflow of sewage and domestic wastewater due to wrong connections of sewage lines to drain lines, inflow of polluted surface water, illegal dumping of contaminants and drying of river by rapid drainage of rain due to paved grounds and etc. cause water quality of an urban river to be degraded below self- purificability. Loss of self-purificability in an urban river results from decrease of length of flow and decrease of breadth of riverside by shaping of an unban river for use of space, decrease of amount in flow of river by drying and by acceleration of contamination. Since an urban river provides environments which tens of thousands or hundreds of thousands of people contact and enjoy, attempts have been continued to improve the water quality of urban rivers to a considerable level in order to satisfy the desire of citizens for comfortable environments and to use them as water resource effectively.

[3] Water qualities of rivers can be graded based on bio-chemical criteria such as dissolved oxygen(DO), biological oxygen demand(BOD), chemical oxygen demand(COD) and etc., or based on the inhabited living organisms(indicator living organisms). As BOD and COD in the river water increase, more oxygen is needed and DO decreases drastically so that the self-purificability of the river may be lost. A river with weak self-purificability not only smells bad but also restricts the inhabitation of the living things. When an urban river loses the self-purificability, it is graded as 4th or 5th Grade, or out of grade when a river has tens of ppm in BOD or COD value. The water quality of such a river may not be recovered unless inflow of pollution source is prevented or a proper treatment is implemented.

[4] There are some points to be considered for the improvement of water quality of a river, especially an urban river.

[5] First, a solution for improvement of water quality should be compatible with ecological environments for living organisms. The solution should satisfy habitation conditions of living organisms including fishes such as living, ascending and descending conditions.

[6] Second, since the neighborhood of an urban river is utilized already by shaping a river and by building banks around it, a space available for construction of water treatment facilities is quite limited.

[7] Third, the solution should have durability and be easily recovered in case of a great flow caused by a heavy rain including a flood.

[8] Fourth, the expense for construction of treatment facilities ought to be moderate since improvement of water quality of river cannot generate direct economic advantage.

[9] Fifth, a change in the path of flow of a river ought to be minimized, and the facilities should be effective while they do not spoil natural appearance of a river.

[10] The main conventional methods to improve water quality of a river selectively adopt conventional wastewater treatment technologies. Japanese Patent Publication No. 7000983 A2 disclosed a method for treating stream water. The method is similar to a conventional sewage treatment process in which tanks are arranged to treat stream water. Since such a treatment requires large-scale facilities which have problems of high cost for construction and operation, and other disadvantages that a large-scale plant has in common.

[11] Japanese Patent Publication No. 61230787 A2 disclosed a method for treating stream water in which a structure for diverting the path of water stream is built and ceramic particles are trapped in the structure to contact the water treated. Also, Japan Patent Publication No. 7016586 A2 disclosed a method for treating stream water by means of porous particulate materials.

[12] Such techniques have problems such that there is no fundamental countermeasure against provable losses or damages of apparatus or devices concerned when a great amount of water flows by a heavy rain.

[13] As another traditional method, there is a contact oxidation method that uses a fixed bed of pebbles as contact media with aeration or without aeration. This method needs baffles for evenly sufficient contact with media, which causes resistance of flow. In addition, soil carried by heavy rain would clog voids between pebbles which are used as paths of flow. Aeration would not work well with resistance of the media. Other methods adopting other contact media would not work well outside a laboratory on the same reason.

[14] Further, fishes may not pass through the treatment facilities having such fixed contact media since there are not gaps big enough between contact media for fishes to make through them.

[15] There is another conventional method for improving quality of stream water by maintaining a stream as natural as possible and by utilizing self -purification of a stream. For example, slopes of river-bed are adjusted to form riffles or small cascades or etc. so that more oxygen may be dissolved in the water to improve self-purificability of a river. Dissolution of oxygen in river water may be accelerated by forming cascades, but a retention time of water in the riffles or cascades is no more than several seconds or several minutes at most. This method is not so effective since the total incline of river-bed is already determined and once riffles and cascades are formed artificially in one region, flow rate will become slower in the neighborhood. Also, the slopes made artificially may be easily spoiled by deposition of soil or corrosion due to a heavy rain although a stream looks as close as natural state. Further, water plants or waterside plants may be used to increase the dissolved oxygen in the water by respiration of plants and to increase self-purificability of a stream. However, there may not be a space big enough to accommodate such a method owing to stream maintenance projects already done.

[16] There is another technique in which wire- wound and screen formed pipes and a collecting well are used. In this technology screen pipes are disposed under the bottom of a river so that underground water may be collected to the collecting well via the screen pipes. The collected underground water is discharged to the river by a pump. This method uses not only underground water but also the soil layer under the riverbed as a filter for stream water. However, it is obvious that soil layers under a river-bed block air supply and sunlight and they would not serve as a filter bed for a long time.

[17]

Disclosure of Invention

Technical Problem

[18] Accordingly, an object of the present invention is to provide an apparatus for effectively treating river water which does not require a lot of additional spaces with a few working parts and simple structure, and is durable against violent natural phenomena, and which is cost effective for installation and maintenance without spoiling much an appearance of a natural river and without doing harm to habitation conditions such as living, ascending and descending conditions of living organisms including fishes.

[19] Another object of the present invention is to provide an apparatus for treating water of a small river that can improve water quality from the lower grade to the third or higher grade. [20]

Technical Solution

[21] The present invention provides an apparatus for treating water of a small river, comprising a pit type bath built below a river bed in the path of flow, and aeration means equipped in the pit type bath for aerating and whirling the water which flows into the pit type bath.

[22] Preferably, the present invention provides an apparatus for treating a river water, comprising a pit type bath built below a river bed on the path of flow, the pit type bath being wider than half of an effective flow width of the river, being more than 2 meters deep and having length of more than 10 minutes retention time, and aeration means equipped in the pit type bath for aerating and whirling the water which flows into the pit type bath.

[23] The apparatus for treating river water of the present invention is preferably applied to an urban river, but it may be applied in its entirety to a common river which lost self-purification capability.

[24] The aeration means desirably comprises diffusers installed near the bottom of the pit type bath, pipes connected to the diffusers and pressurized air sources to supply air to the diffusers via the pipes.

[25] More preferably, the pit type bath of the present invention is wider than two thirds of an effective flow width of the river, 3 m to 5 m deep and having length of more than 30 minutes retention time. For example, a typical small urban river has water depth of about tens of centimeters, flow rate of about several meters per minute and flow width of about tens of meters. If it is assumed that mean water depth, mean flow rate and mean flow width of an urban river are respectively 20cm, 5m/min and 30 m, and then the size of the pit type bath of 4m depth and 1 hour retention time would have a dimension of 30 m x 15 m x 4 m.

[26] Inflow and outflow of river water into and from the pit type bath are implemented by flow of a river by itself without using pumping means. Since the height of the front wall and the rear wall of the pit type bath are adjusted to be similar to the slope of a river-bed, the flows near the inlet and the outlet of the pit type bath form smooth stream or a low fall or a small cascade at most. The front wall and the rear wall may have low thresholds to form cascades of flow. It is preferable that the pit type bath is built in a region in which a slope of the river-bed is gentle so that the thresholds of the front wall and the rear wall may not make high falls, and thus aquatic living organisms may ascend or descend through the bath.

[27] The diffusers or aerators in the pit type bath are disposed to provide water being treated by aeration in the bath with whirling upward and downward by which most of river water stays in the bath evenly for a mean retention time without being discharged directly. Preferably, the aerators are disposed in plural lines in flow direction of a river near the bottom of the pit type bath so that a plurality of whirls may be formed. An air generating means such as a blower or a compressor supplies pressurized air to the aerators through pipes with or without an air tank interposed between the air generating means and the aerator. Types of aerators or diffusers are not specially restricted. For example, disk types or porous plate types for aerators may be used. Aerators or diffusers may be simply holes formed on the pipes located in the bath to supply airs. A pump is not used basically to supply or to discharge river water into or out of the pit type bath, but pipelines and a pump connected to the pipelines may be used to drain water for its maintenance.

[28] The pit type bath typically has a front wall, a rear wall and two side walls and a bottom. The bath, especially the walls preferably is made of concrete for durability and for convenient construction. Generally, the bottom is made of impermeable concrete, but it may have a permeable bottom structure in order to allow underground water below a river bed to flow into the bath. At the inlet threshold of the pit type bath, screens may be mounted in order to prevent big and heavy bodies such as rocks or pebbles from coming in the bath.

[29] Near the rear wall inside of the bath, an ejector, an air jet or a water jet may be equipped to intermittently scatter precipitated particles to whirling area in the bath.

[30] The rear wall of the pit type bath may slant, preferably by less than 60 degrees, most preferably by 15 to 45 degrees, from the vertical line. With aerators intentionally removed, or structurally eliminated by the slant wall, near the rear wall in the pit type bath, whirling of river water may decrease, and therefore particles suspended by whirling may settle down. A sump for collecting particles settled down may be provided on the bottom near the rear wall inside the pit type bath. Pipelines for pumping may be connected to the sump so that the precipitated particles may be intermittently suctioned by means of a pump, an air jet or an ejector to be carried into whirling region or to be separated. Alternatively, an additional hopper type pit for precipitating particles may be built downstream of the pit type bath and the precipitated particles may be carried out to the pit type bath or may be removed periodically by pumping through connected pipelines.

[31] A pump for picking up settled particles may preferably move along guidance rails installed under a bridge constructed above the rear wall of the pit type bath and may suction and remove the particles collected in the sump. The removed particles may be sent back to the forward portion of the pit type bath so that they may be used as contact media or may be treated separately.

[32] Contact media for fluidizing may be fed into the pit type bath of the present invention. The contact media are preferably particles which suspend in whirling region and settle in a region where whirling is attenuated. Porous natural or artificial ceramic particles, mineral particles, for example, primary-fired ceramic ball or zeolite particles may be used for contact media. The contact media for fluidizing used in accordance with the present invention preferably have relatively higher specific gravity not to flow away and not to be too consumptive. Also the present invention may use heavy particles such as sand. Since such heavier particles may settle in the attenuated region so as to be recovered, only the amount of loss may be replenished.

Advantageous Effects

[33] The apparatus for treating small river water in accordance with the present invention has merits as follow; [34] i) it does not require a large additional space since the pit type bath is built under a river bed. [35] ii) it is durable against violent natural phenomena and cost-effective with simple structure and easy maintenance since there is no operational mechanism except for the aeration means. The pit type bath is not easily filled up and does not need frequent maintenances since turbulent flows or whirlings exist in the bath by aeration. [36] iii) it is compatible with environments without spoiling much an appearance of a natural river and without doing harm to habitation conditions such as living, ascending and descending conditions of living organisms including fishes. [37] iv) it treats river water effectively and raises self- purificability of a river with effective increase of dissolved oxygen and use of particulate media which naturally flow into and suspend in the apparatus.

Brief Description of the Drawings [38] The above and other objects, features and advantages of the present invention will become apparent as described in the preferred embodiments given in conjunction with the accompanying drawings, in which: [39] Fig. 1 is a side cross-sectional view for schematically illustrating one embodiment of the present invention; [40] Fig. 2 is a side cross-sectional view for schematically illustrating another embodiment of the present invention; [41] Fig. 3 is a side cross-sectional view for schematically illustrating another embodiment of the present invention; [42] Fig. 4 is a side cross-sectional view for schematically illustrating another embodiment of the present invention; and [43] Fig. 5 is a side cross-sectional view for schematically illustrating another embodiment of the present invention. Best Mode for Carrying Out the Invention

[44] Hereinafter, preferred embodiments of the present invention will be supple- mentarily described with reference to the following drawings.

[45] Fig 1 is a side cross-sectional view for schematically illustrating an embodiment of the present invention, wherein a pit type bath(lθ) has a front wall and a rear wall, the heights of which are adjusted to be similar to the slope of a river-bed(l) with low thresholds, so that the flow near the inlet of the bath forms a small cascade and the flow near the outlet of the bath forms a smooth flow. Aerators(22) in the pit type bath are disposed to provide the river water in the bath with whirlings upward and downward and thereby for any of the river water flowed in not to be directly discharged. The aerators(22) are disposed in plural lines in flow direction of a river near the bottom of the pit type bath so that a plurality of whirls may be formed. An air generating means(21) such as a blower or a compressor supplies pressurized air to the aerators(22) through pipelines. Types of aerators are not specially restricted. For example, disk types or porous plate types for aerators may be used.

[46] Fig. 2 is another side cross-sectional view for schematically illustrating another embodiment of the present invention, wherein the pit type bath(lθ) has a rear wall slanted toward a flow direction from the vertical line. Whirling is attenuated without aerators present for the rearward portion of the bath corresponding to slanted wall, and some of suspended particles (primarily sands) settle, slide down along the slant of the rear wall and go back into a whirling region to sustain some density of particles in the bath. Fig. 3 shows the pit type bath (10) which provides the means for picking up the settled particles. On slant of lower portion of rear wall in the bath air jet(25) is mounted to intermittently scatter settled particles into whirling area in the bath.

[47] Figs. 4 and 5 shows the structure of the pit type bath(lθ) in which a sump(15) is formed on the bottom near the rear wall of the pit type bath. Referring to Fig. 4, an ejector(27) is mounted in the sump(15) so that the collected particles may be carried to the forward portion of the pit type bath. Referring to Fig. 5, a pump moves along a guidance rail(42) installed beneath a bridge(40) constructed above the rear wall of the pit type bath. The pump suctions collected particles in the sump(15) with water through a suction pipe(31) and then, the filtered water is drained through a drain pipe(32). The picked particles may be provisionally stored for disposal or carried back to the forward portion of the pit type bath(lθ) to be supplied into the bath.

[48] It will be apparent to those skilled in the art that various modifications and changes can be made thereto within the spirit and the scope of the present invention. Therefore, it is obvious that the true scope of the present invention should be defined by the appended claims.

Claims

[I] An apparatus for treating water of a small river, comprising a pit type bath built below a river bed in the path of flow, and aeration means for aerating and whirling the water in the pit type bath which flows into the pit type bath.

[2] An apparatus as claimed in claim 1, wherein the pit type bath is wider than half of an effective flow width of the river, is more than 2 meters deep and has length of more than 10 minutes retention time. [3] An apparatus as claimed in claim 1, wherein the pit type bath has length of more than 30 minutes retention time. [4] An apparatus as claimed in any one of claim 1 through 3, wherein the aeration means comprises diffusers installed near the bottom of the pit type bath, pipes connected to the diffusers and pressurized air sources to supply air to the diffusers via the pipes. [5] An apparatus as claimed in claim 4, wherein Inflow and outflow of the river water into and from the pit type bath are implemented by flow of a river by itself without using pumping means. [6] An apparatus as claimed in claim 5, wherein aquatic living organisms may ascend or descend through the pit type bath [7] An apparatus as claimed in claim 6, wherein the height of the front wall and the rear wall of the pit type bath are adjusted to be similar to the slope of a river-bed, and thus the flows near the inlet and the outlet of the pit type bath form smooth stream or a low fall at most. [8] An apparatus as claimed in claim 7, wherein the pit type bath is built in a region of a river in which a slope of the river-bed is gentle so that the thresholds of the front wall and the rear wall may not make high falls. [9] An apparatus as claimed in claim 8, wherein the aerators are disposed in plural lines in flow direction of a river near the bottom of the pit type bath so that a plurality of whirls may be formed. [10] An apparatus as claimed in claim 9, wherein the rear wall of the pit type bath may slant.

[I I] An apparatus as claimed in claim 10, wherein the rear wall of the pit type bath may slant by less than 60 degrees from the vertical line

[12] An apparatus as claimed in claim 11, wherein the apparatus as claimed in claim

2, wherein a wall of the outflow portion in the pit type bath is slanted by 15 to 45 degrees toward a flowing stream direction from the vertical line.

[13] An apparatus as claimed in claim 12, wherein a sump for collecting particles settled down may be provided on the bottom near the rear wall inside the pit type bath. [14] An apparatus as claimed in claim 13, wherein the precipitated in the sump are suctioned by a pump, an air jet or an ejector. [15] An apparatus as claimed in claim 14, wherein the pump moves along guidance rails installed beneath a bridge constructed above the rear wall of the pit type bath, suction and remove the particles collected in the sump [16] An apparatus as claimed in claim 15, wherein the particles suctioned by the pump are carried back to the forward portion of the pit type bath and are supplied into the bath.