IL45834A - Device for the treatment of water - Google Patents

Abstract

1475570 Disinfecting water MINES DE POTASSE D'ALSACE SA 1 Nov 1974 [5 Nov 1973] 47412/74 Heading ClC Apparatus for the treatment of water by the action on bromide ions of hypochlorite ions the quantity of which is regulated in response to measurement of the amount of active bromine present in the treated water, comprises a main circuit with pumping means which effect the circulation of the treated water and filtering means, wherein the system includes (a) a first branch circuit comprising a pipe connected to the main circuit having a valve the opening of which is controlled by measurement of the amount of active bromine in the treated water, said pipe feeding into a storage vessel which provides a supply of the hypochlorite, and a pipe for the discharge of the hypochlorite and its introduction into the main circuit downstream of the filtering means, and (b) a second branch circuit comprising a pipe which is connected to the main circuit before the point of injection of the hypochlorite, a cell for the measurement of the amount of active bromine in the treated water and a pipe for the delivery of the water from the cell. Specification 1,327,531 is referred to. [GB1475570A]

Description

Device for the treatment of wa e 4 MINES DE POTASSB D'ALSACE S.A.

The present invention relates to a new device for the treatment of waters by an antiseptic agent, more particularly to a simplified device enabling a continuous and regular in- 1 troduction of an antiseptic agent into a water to be treated. The invention can be used in the treatment of industrial waters such as for example the waters of refrigerating systems but it is most suitable for sterilizing swimming pool waters, and particularly small swimming pools.

It is known that chlorine and bromine are frequently used for the treatment of waters. Indeed in aqueous medium these halogens form respectively hypochlorous or hypobromous ions which are oxidising agents and possess bactericidal, power.

It is also known that in a slightly alkaline medium such as swimming pool waters, bromine, or more exactly the hypobromite formed by the introduction of bromine into said alkaline medium has a bactericidal power higher than that of the hypochlorite. Moreover, after having been treated by bromine, the waters have no unpleasant odour and do not irritate the mucous membranes as do the chlorinated antireptic agents. Bromine also has the advantage of being an algicidal agent.

But the use of liquid bromine as an antiseptic agent requires a severe control of the quantity of bromine introduced into the water and several devices have already been devised for the treatment of waters by liquid bromine. One of these earlier devices allows a controlled introduction of bromine into the water to be treated and enables the bromine content to be kept within predetermined limits with security and precision.

The use of liquid bromine as a sanitizing agent for waters is however not always easy since it can in some instances show drawbacks generally related to difficulties in the handling of this liquid. For example, for small size installations, plants or swimmin'g pools, it is sometimes difficult to have adequate space and/or workers to guarantee a safe storage and handling of the containers of liquid bromine. In other cases, the remoteness of the bromine sources can give rise to transport problems.

It is well known that bromides react on hypochlorites to form hypobromites and chlorides according to the following reaction : Br" + CIO" > BrO~ + :C1~ (1) This reaction is almost instantaneous and it has been foun that by operating under suitable conditions it is the thus for med hypobromite which, due to its oxidising power, acts as a bactericidal agent, when needed, by transforming itself again into the bromide as shown by the following reaction : BrO~ Br" + 0 (2) Applicant has already devised a method for the treatment of waters using the above-shown reactions (1) and (2) which takes profit of the antiseptic qualities of bromine without it being necessary to handle liquid bromine. This method described in British Patent Specification No., 1,327,531 comprises continuously maintaining in solution at least a predetermined minimum concentration of bromide and oxidising the bromide in situ according to the antiseptic requirement by means of a hypochlorite, the quantity of which is regulated in response to a continuous measurement of the amount of active bromine in the water.

By hypochlorite there is meant any compound which in water causes the formation of hypochlorous ions. There can thus be used chlorinated water or a N-chlorinated compound but there is preferably used a water soluble hypochlorite and more particularly sodium hypochlorite which is relatively cheap and easily available in commerce. In the following description the term "hypochlorite" is used in it^s wide acception as defined hereabove. _ There will also be recalled that "active bromine" is the term generally used to designate the oxidising power of the oxidising compounds of bromine. It represents the amount of elementary bromine which is capable of liberating the same quantity of oxygen than the given compound. In tlie case of an hypobromite for example, the active bromine content is equal to twice the quantity of bromine present in the hypobromite.

The present invention relates to a simplified device which allows an "easy practising of the above-described indirect method. This device has'" in particular the advantage of requiring very little monitoring and maintenance, which makes it mostly recommended for small size installations such as, for example, private swimming pools.

Other advantages of the device according to the invention will appear more clearly from the following description.

' The device according to the invention for the treatment of waters by the reaction between bromide ions and hypochlorite ions, tne quantity of which is regulated in response to the measurement of the amount of active bromine present in the treated water, comprises a main circuit with a pumping system which allows the circulation of the treated water and a constituted by a pipe branched on the main circuit, with a valve, he opening of which is controlled by the measurement of the amount of active bromine in the treated water, said pipe dipping into a storage vessel for the hypochlorite source and by a pipe for the withdrawal of the hypochlorite and its introduction into the main circuit covn.stream of the filtering system, and by b) a second connection line constituted by a pipe branched on the main, circuit before the point of injection of the hypochlorite, with a cell for the measurement of the amount of bromine in the treated water and a pipe for the withdrawal of the water coming out from the cell, optionally branched on the main circuit upstream of the pumping system.

The first connection line is advantageously branched on the main circuit between the pumping system and the filtering system, the pressure drop due to the filter being sufficient for the water to flow in the connection line when its valve is open. Should such an arrangement not be possible, the connection line can be branched downstream of the filtering unit but it is then necessary to create a pressure drop on the main circuit between the branching point of the connection line and the hypochlorite injection point. In such a case, there is provided on the main circuit a valve or a diaphragm or any other blocking system, which slightly decreases the rate of water in circulation or requires the use of a slightly more powerful pump.

The storage vessel is made out of a material which is inert to the chlorinated compound and which resists without deformation the pressure of the water stream, said pressure being mostly comprised between 0.3 and 1 bar. There can of course be used glass vessels since the satisfy both these generally used vessels out of plastic material, preferably relatively rigid, such as for example low pressure polyethylene. Such vessels are both light and hardly fragile. These vessels are advantageously stored sheltered from light and sharp variations of temperature.

The connection line for the continuous measurement of the amount of active bromine comprises a cell of a known type, operating as has already been ddvised by applicant. Said cell, with a continuous feeding of a small fraction of the treated water, continuously delivers an electric current the intensity of which is proportional to the concentration of active bromine in the treated water. After having been amplified, this current is sent to a control device which automatically activates the opening of the valve on the first connection line. This amplified current can also, if desired, be fed to a device for the direct reading of the bromine amount.

The pipe which brings the water to the measuring cell is preferably branched off the main circuit after the filtering system in order to avoid the plugging of the entering opening of the cell by any impurity which might be in the water. This pipe can also be branched off before the filtering system but in this case it is necessary to provide on the pipe a filter with small dimensions to protect the measuring cell.

It is generally advantageous to introduce the water coming from the measuring cell back into the main circuit : in this case, the pipe for the withdrawal of the water. joins the main circuit ahead of the pumping system. Where a loss of water does not create problems, it is not necessary to recycle the water coming from the cell. It is then sufficient to send the 45834/2 ^ 3 with a swimming pool of 50m , the rate of flow of water in 3 the main circuit being comprised between 5 and 10m /hr, the amount of water which flows through the cell amounts to about 50 liters per hour.

With the device of the invention which permits the injection of hypochlorite in response to the measurement of the amount-of active bromine in the water, it is possible to use i as a hypochlorite source a solution in which the concentration of active product varies continuously. This device makes it unnecessary to have a constant concentration of antiseptic in the storage vessel.

There is given hereunder, reference being made to the annexed drawing, a detailed description of the use of the device of the invention for the sanitation of swimming pool waters. It must be understood however that said device can be ur.ed in an analogous manner for other purposes.

In the embodiment shown in the drawing, there is represented schematically a swimming pool 1 with its main circuit constituted by a recycling pipe 2 provided with a pump 3 and a filter 4 of classical type, for example a sand filter. A pre-filter 5 can be placed ahead of the pump : it retains the largest fragments which may pollute the water and which could disturb the operation of the pump.

The hypochlorite is stored in a vessel 6 of a plastic material, and which has a capacity which varies according to the consumption which is expected. For example, there are fre~ guently used vessels with a capacity of 100 liters for swimming pools of 50rr3. These vessels are closed with a plug which is generally made of the same plastic material as the body of the vessel and which comprises two openings : one for 45834/2" the dipping pipe which brings water to vessel 6 and the other for a withdrawal pipe.. A first connection line comprises a pipe branched on the recycling pipe 2 at a point 20 located between the pump and the filter, with an electric valve 9 protected by a small filter 10 : this pipe brings the treated water to the vicinity of the bottom of the storage vessel.

The opening of electric valve 9, by way of a control device which will be described hereinafter, regulates the amount of water fed into the vessel. The withdrawal pip<> 8 is branched on the recycling conduit at a point 21 located downstream of the filter. The extremity 11 of the withdrawal pipe 8 penetrates into the recycling conduit so that hypochlorite is injected within the water itself. Should a heating system 12 be necessary, it is located on the recycling conduit, upstream of the point where hypochlorite is injected in order to protect it from the corrosive action of the chlorinated product and, preferably, after the filter. On-.the withdrawal pipe 8 there is advantageously provided a valve 13 or any other non-return system which isolates the storage vessel from the swimming pool tank. In order to avoid the introduction of chlorinated product into the recycling circuit when there is no circulation of water, the sterilising system can be in electrical connection with pump 3. When pump 3 is stopped and when, therefore, no water flows, the antiseptic content drops down to a value lower than a reference level but it reaches said level back as soon as the pump is in service again, i.e. during the period of normal use of the swimming pool. This discontinuous operation is particularly, advantageous for inside pools and generally speaking for small family or private installations.

The device comprises a second connection line for the continuous measurement of the active bromine content of the treated water. This second connection line comprises a conduit branched off the main circuit at a point 22 located downstream of the filtering system, the return being provided on a point 23 located upstream of the pump. On this conduit is placed a measuring cell 14. This cell is of the type comprising two electrodes of different type, for example one of platinum and the other f&vrb- of silver, both immersed in the water to be treated. The difference in voltage existing between these two electrodes creates a current the. intensity- of which is directly proportional to the amount of f.ctive bromine in the water which flows through the cell. This current, after having passed through an amplifier 15 , is sent to a voltmeter 16 with a graduated dial which allows a direct reading of the bromine content of the treated water. The amplified current is also sent to a control device 17 which automatically actuates the electric valve 9.

The duration of the opening of this electric valve, according to a given cycle, is determined by the position of a potentiometer 18 connected to the control device 17. The injections are made at regular intervals until the desired bromine content is reached in the pool. This content can be fixed to a certain value or can be modified according to the attendance of the pool or its degree of pollution or according to the risk of formation of algae. In order to facilitate this modification, a contacting device 19 with two or more positions, also connected to the control device 17, permits to choose the desired bromine content.

This device operates as follows. When the apparatus is put in service, there is added a bromide to . he water to be treated. This addition can be made at any point of the circuit but the simplest method consists in introducing sodium bromide tablets into the pool, in an amount sufficient to keep the bromide content at about 30mg/litre. The storage vessel is filled with concentrated (48-50 chlorometric degrees) sodium hypo-chlorite solution. As the injections take place repeatedly, that is to say as water penetrates into the vessel, the sodium hypochlorite solution is diluted and its active chlorine content drops. This continuous dilution is automatically counterbalanced by an increase in the number of injections until the desired bromine content is reached in the pool. When the concentration of active chlorine in the sodium hypochlorite solution becomes too low, the injection times governed by the position of the potentiometer 18 become insufficient to counterbalance in a reasonably short time the lowering of the bromine content of the pool water. The injection times are then increased by modifying the position of the potentiometer 18. Thus for example, in a private pocl of 50m? where an active bromine content of 0.6mg/l should be kept, the injections of the hypochlorite solution initially take place between 5 and 10 seconds each four minutes. When half the service life of the vessel is reached, the injection time is doubled by merely changing the position of the potentiometer control button. Under such conditions a 100 litres vessel has been found to last 4 months.

In a family pool normally used, the filtration usually takes place during night time when electrical energy is less expensive. The device of the invention can be used without

Claims (4)

45834/2 CLAIMS:

1. Device for the treatment of waters by the action of hypochlorite ions on bromide ions the quantity of the hypochlorite ions being regulated in response to the measurement of the amount of acti e bromine present in the treated water, comprising a main circuit with a pumping system which allows the circulation of the treated water and a filtering system, characterised by a) a first connection line constituted by a pipe branched off the main circuit with a valve, the opening of which is controlled by the measurement of the amount of active bromine in the treated water, said pipe dipping into a storage vessel for the hypochlorite source and b a pipe for the withdrawal of the hypochlorite and its introduction into the main circuit downstream of the filtering system and b) a second connection line constituted by a pipe branched off the main circuit before the point of injection of the hypochlorite, with a cell for the measurement of the amount of active bromine in the treated water and a pipe for the withdrawal of the water from the cell, optionally branched off the main circuit upstream of the pumping system.

2. Device for the treatment of waters as claimed in Claim 1 wherein the first connection line is branched off the main circuit between the pumping system and the filtering system.

3. Device for the treatment of waters as claimed in Claim 1 wherein the pipe bringing the water to the measuring cell is branched off the main circuit after the filtering system.

4. Device for the treatment of waters as claimed in Claims 1 and 3 wherein the pipe for the withdrawal of the water coming out from the cell is branched off the main circuit upstream of the pumping system. For the Applicants