TECHNICAL AREA

The present invention relates to a system for water purification and in particular a system that is designed for very low maintenance demands.

TECHNICAL BACKGROUND

Pure water is becoming more and more important in the world and many believe that the issue of access to pure drinking water will be one of the major issues in the world in the near future.

The applicant has been working with systems and devices for treating water and has developed a water treatment reactor based on AOT (Advanced Oxidation Technology), which utilizes a number of important components for treating water flowing through the filter. One is UV- generating means, i.e. wavelengths within the ultraviolet spectra, < 380 nm, of energies sufficient for photocatalysis and/ or direct elimination of microorganisms and/ or direct formation of free radicals in the liquid or components dissolved therein and/ or direct formation of ozone from oxygen present as gas or dissolved in the liquid. Catalysts are arranged in the reactive zone where ozone and free radicals are produced, in order to increase the amount of free radicals.

The AOT process is highly effective in removing microorganisms and other organic contaminants, which are broken down by the free radicals when exposed to them. Thereby all types of harmful microorganisms are removed, such as amoebas, parasites like Cryptosporidium, which causes diarrhoea, and bacteria such as Legionella. However, there are other types of components in water that could adversly affect those who drink the water. These components include salts that are dissolved in the water such as nitrate. These dissolved salts can be removed in industrial processes by ion exchange which work through adsorption of contaminant ions onto a resin exchange medium. That is, one ion is substituted for another on the charged surface of the medium, which usually is a synthetic plastic resin. The exchange medium is saturated with the exchangeable ion before treatment operations.

During ion exchange the contaminant ions replace the regenerant ions because they are preferred by the exchange medium. When there are no ions left to replace the contaminant ions, the medium has to be regenerated with a suitable solution, which re-saturates the medium with the appropriate ions. Solutions that could be used for regenerate the exchange medium in ion exchangers are sodium chloride or potassium chloride, amongst others.

Even though the above mentioned technologies have proven their potential in water purification, there is still a demand for systems that can be used in geographic areas where the possibilities for continuous maintenance and service are small, i.e. systems that have very low maintenance demands.

BRIEF DESCRIPTION OF THE INVENTION

The aim of the present invention is to provide a system for water purification that is capable of operating during long time periods with minimum maintenance and service work.

This aim is obtained according to the present invention with a system characterised by the features of the independent patent claim.

Preferable embodiments of the present invention form the subject of the dependent patent claims. According to a main aspect of the invention it is characterised by a system for treating water, comprising conduits to be arranged between a water source and water outlet, a pump connectable to said conduit, a filter connectable to said conduit downstream said pump, an ion exchange unit connectable to said conduit downstream said filter, a photocatalytic treatment unit connectable to said conduit downstream said ion exchange unit, characterised in a control system comprising control means, monitoring means and sensor means capable of automatically controlling the operation of said system.

According to another aspect of the invention, said ion exchange unit comprises at least two ion exchange treatment vessels connected in parallel, for enabling regeneration of one treatment vessel while operating the other treatment vessel.

According to a further aspect of the invention, said ion exchange unit comprises storage means for regeneration material, and wherein the regeneration is performed during time periods when the water demand is low.

According to yet an aspect of the invention, said filter further comprises back-flushing means, capable of back-flushing filter elements in said filter.

According to another aspect of the invention, back-flushing is initiated by a sensed pressure drop over the filter exceeding a certain preset value.

According to a further aspect of the invention, said catalytic treatment unit comprises an advanced oxidation technology reactor capable of creating radicals in the water flowing through said reactor. According to yet an aspect of the invention, it comprises further a buffer tank downstream said catalytic treatment unit.

According to another aspect of the invention, it comprises a further catalytic treatment unit connected to said buffer tank, through which further catalytic treatment unit water in the buffer tank is circulated.

There are a number of advantages with the present invention. The system provides a complete cleaning and purification process including both ion exchange and oxidation treatment of the water where a control system is automatically handling the operation of the system. Thereby the maintenance and service needs are greatly reduced while still providing a complete purification system.

Thus the system according to the present invention may be placed in geographical locations where service personnel are scarce. The maintenance and service needed is limited to refilling of regeneration material for the ion exchange unit and refill/ replacement of cleaning liquid, these measures may, depending on the size of the material tanks, be limited to once every three months. Preferably the system may be housed in a container or the like enclosure that is shipped and lifted in place. Then, the only thing that is needed is to connect the conduits from the water source, arrange for a buffer tank and provide electricity to the system. With such a solution, there is a reduced risk for either sabotage of the system or tampering with components of the system.

Preferably the ion exchange unit comprises at least two treatment vessels, which enables the regeneration of one vessel while the other is still in operation. Thus the system does not need to be shut down due to regeneration. This is important because the regeneration is the maintenance operation that is done most frequently. The regeneration is performed automatically according to the control system and preferably during periods of low demand for water such as during night time. Also the backflushing of the filter is performed automatically according to the control system. In this respect it may also be initiated by a measured pressure drop over the filter. The major factor is that the control system handles these maintenance measures completely automatic without the need for service personnel. This is also the case for the cleaning of the AOT reactors, which is performed by the cleaning equipment according to the control system.

When a buffer tank is used, which is preferred so that treated water can be temporary stored in order to handle differences in water demand, an AOT treatment unit may be connected to the buffer tank whereby the water in the tank is circulated through the treatment unit. Thereby the risk for organisms growing in the water of the buffer tank is minimised.

These and other aspects of and advantages with the present invention will become apparent from the following detailed description and from the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed description of the invention, reference will be made to the accompanying drawing schematically showing an example of a system according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

An example of a system according to the present invention that is disclosed in the drawing comprises a pump 10 connected to a water source via suitable conduits 12. The pump is further connected to a filter 14, which could be of any suitable type that is capable of removing larger particles and organisms in the incoming water. A preferable type of filter is an automatically back-flushing mechanical filter, whereby the filter could be back-flushed with liquid from a source 16 via a pump 18 when the pressure drop over the filter reaches a certain preset threshold. One example of such a filter is manufactured by Bollfilter GmbH, which is arranged with a number of generally cylindrical filter elements, through which the water flows. When the filter elements are to be back-flushed, the flow direction is reversed. A closing valve 20 is arranged between the pump 10 and the filter 14.

The filter 14 is in turn connected via conduits to an ion exchange unit 22 for the removal of nitrate. It comprises two ion exchange treatment vessels 24, 26, which are connected in parallel. Each vessel is further connected to tanks 28 with regeneration media. Closing valves 30 are arranged on all conduits to and from the vessels and tanks. The ion exchange unit is further connected via conduits to an Advanced Oxidation Technology (AOT) treatment reactor 32.

The AOT reactor utilises UV lamps emitting light within specific spectra. The liquid to be treated is exposed to UV radiation with a spectral distribution within the range of 180 - 400 nm. The present invention utilises the principle of using free radicals for purifying water. One reactor part consists of at least one substantially straight pipe, preferably made of titanium or some other material lined with titanium on the inside in order to obtain a ceramic titanium oxide. The titanium oxide acts as a catalyst during the forming of free radicals, i.e. the titanium oxide increases the amount of free radicals produced per time period. In one variant, a plastic pipe has been used, lined with titanium oxide. It is of course possible to utilize other highly resistant materials and to use catalysts as described in document WO 96/20017.

A UV radiating light source is arranged in the pipe. A drive unit for the UV lamps is also provided, not shown. A control unit 34 for controlling one or several of the drive units is also provided. The design and function of the drive units and the control unit is mere routine work for the man skilled in the art and will not be described in more detail. An inlet is arranged on the pipe wall, which inlet is arranged with suitable flanges or other suitable connection means for connection to other piping. The end of the pipe opposite the UV lamp is arranged as an outlet, provided with suitable flanges or other connecting means for connection to other piping.

As shown, the AOT reactor comprises two reactor parts described above connected by a pipe bend such that water flows through both reactor parts via the bend. Closing valves 36 are arranged at the inlet and outlet of the AOT reactor, which valves are automatically controlled by a control system.

The AOT reactor is further connected to a cleaning unit 38, a so called CIP (cleaning in place), capable of cleaning the AOT reactor. It could comprise a comprising a tank filled with cleaning media in liquid form. An inlet pipe from the tank is arranged with a pump 40 and a closing valve downstream of the pump. The pipe is then connected to the AOT reactor downstream of its inlet closing valve. After the reactor in the direction of flow and before the closing valve, a branch is arranged, which is also arranged with a closing valve, where each branch is connected to a return pipe back to the cleaning unit.

The AOT reactor is further connected to an outlet conduit, which could run either directly to the tap places 44 or directly to buffer tanks 46, and from there to the tap places, or branch to both the tank and the tap places.

The system comprises further a control system 42 and sensors for automatically controlling and operating the system. The control functions could comprise the following: Regeneration of the ion exchange unit.

The ion exchange unit needs to be regenerated quite often, such as about every week. Because there are two treatment vessels, it is possible to regenerate one while the other one is in operation. For the regeneration, brine tanks are connected to the vessels. When the control system indicates that a treatment vessel has to be regenerated, the inlet and outlet valves to that vessel are closed automatically and the regeneration liquid is pumped into the vessel. The regeneration is preferably performed during nights when the demands for water are low because of the lower production capacity when only one treatment vessel can be used. In a variant the control system could be self- adaptive in that it over time learns when the demand for water is at its lowest point and then performs the regeneration during those time periods.

Cleaning of the lamps of the AOT reactor and back-flush of the filter. When the AOT reactor needs to be cleaned, the control system shuts down the pump, switches off the lamp of the AOT reactor and closes the inlet and outlet valves to the AOT reactor and the pump 40 is started. For a period of time the reactor is thus flushed with treating liquid from the tank. The treating liquid could preferably have a low pH-value since the film of deposits on the lamps is basic. One example of a treating liquid comprises lactic whey and citric acid, which are harmless to the environment. Most of the cleaning liquid is reused in subsequent cleaning processes. However when a certain number of cleaning processes have been performed, the cleaning liquid contains so much deposit and other pollution so that it has to be replaced. The tank of the cleaning unit could be arranged with level sensors, capable of sensing the level of cleaning liquid. All sensors are connected via electrical lines to the control system 42 containing the appropriate means for handling signals from the sensor, perform necessary actions based of the type of signals. Further, when the system is switched off, the filter can be back-flushed. In this case liquid is pumped in the reverse direction for flushing away all particles and the like that has been caught in the filter elements.

Further treatment measures

When a buffer tank is used, it might be advantageous to treat the water stored there in order to minimize the risk of contaminants growing there. In this case an AOT reactor 50 could be connected to the buffer tank via a pipe branch and a pump, through which the water in the tank is circulated by the pump. This effectively prevents any growth or build-up of harmful organisms.

Preferably the system may be installed in a suitable enclosure such as a container and be shipped and installed at the proper location where it is connected via suitable piping to the water source. The only further measure is to arrange a buffer tank and electricity to the system. After this the operation of the system is performed automatically. It is to be understood that the system may include some sort of communication means that is capable of sending information for example to a service centre where service personnel monitors the different purification units placed at different geographical locations. The information that is transmitted from the units to the centre may be operation data, service intervals or if some of the components or functions of the system does not function as it should, which can alert the service personnel to perform a service in place. The information could also include alarms that the system is malfunctioning and requires immediate attention.

It is to be understood that the embodiment described above and shown in the drawings is to be regarded only as a non-limiting example of the invention and that it may be modified within the scope of the patent claims.