The present invention relates to an apparatus for filtration of contaminants from water. In a second aspect, the present invention relates to a method for filtration of contaminants from water using such an apparatus.

Technical background of the invention

Some of the more common methods in water filtration techniques of today are filtration through sand, micro filtration through strainer screens or activated carbon, and ultra filtration through so-called ultra filtration membranes.

The water to be treated can originate from groundwater sources, lakes or different types of reservoirs or streams. It may also be recirculated water in industry to mention but a few.

Frequent occurring contaminations to be separated are organic suspensions, humus, particles, colour colloids, gels, and oxygen consuming substances.

The treatment of water by means of a sand filtration bed involves that the reduction of particles and suspensions will not be large enough without a previous flocculation or chlorination of the supplied water. If not done only the particles be- ing 10 m or larger are removed.

Another problem is that the filtration container and the sand together are a large, heavy and bulky part, which in turn bring about that the costs for manufacturing, storing and transport will be unreasonable high compared to the performance of the sand filter. Usually the sand filtration container is circular and has a pear-shaped lateral section, which means that it cannot be wall mounted and consequently it will cover a large floor area at the installation place.

The treatment of water by means of micro filtration involves that all the particles larger than the pores of the filtration medium will be collected onto the surface of the filtration medium. When filled up the filter has to be rinsed in some way or changed for another one.

The treatment of water with an ultra filtration membrane involves a separation of small sized contaminations, as e.g. humus, colour colloids or other small particles of different kind and low molecule weight ions. When applying the method often a pre-filtration is required as in effect in all types of water there are contami- nations of higher size order than that. Also the method involves a water loss of about 25% to 35%.

The treatment of water with activated carbon in a bed or inside cartridges can be used only for small units and is a method for filtration of already pre- filtrated water. A gram of activated carbon has an absorption surface of about 10 square metres, where very small particles are accumulated. Therefore in plants having large carbon beds it will be too expensive to change the carbon mass and introduce a new one, which at a continuous operation has to be done every fortnight.

If it is assumed that the water to be treated is not chlorinated it can be established that common for the methods mentioned above, except for ultra filtration, the contaminations are collected on the surface of the filtration medium resulting in that this deposition has to be removed in one way or another at regular intervals or that the filtration medium has to be changed for a new one.

A reason for the collection of substances onto the filtration medium is that the water being pressed into a filtration house and covers all the surface of the filtration medium, lacks an appreciable movement closest to the covering successively built up onto the filtration surface. This known phenomenon was the reason for the start of the development of the membrane filtration, where at the expense of lack of water and substantial more expensive plants than what previous alternative methods involved, where by means of a continuously flowing water layer over the surface of the filtration medium it would be prevented, that this coating layer could be prevented. With this method some 30% of the water was flushed away, which sometimes will be too much as most of the water sources have a very re- duced supply of water.

The facts mentioned above are known to the expert in the matter. Furthermore there is a need to develop improved apparatuses and methods for filtration of water having reduced water losses. Summary of the invention

The purpose of the present invention is to supply improved apparatuses and methods for filtration of water solving the problems mentioned above.

It is obtained with an apparatus for decomposition and removal of contaminations from water according to claim 1 , comprising a filtration house having an entrance part including an inlet pipe arranged for conduction of contaminated water into the filtration house and an outlet part including an outlet socket arranged for conduction of purified water away from the filtration house; a porous membrane including a bottom and an envelope surface and being arranged inside the filtra- tion house; a first transparent pipe, the two ends of which being open and which is arranged in the inlet part around the centre of the filtration house within the membrane, where the inlet part is in fluid communication with the outlet part through the first transparent pipe; a second transparent pipe with a closed bottom arranged within the first transparent pipe and a UV fluorescent lamp contained in the second transparent pipe and adapted to transmit radiation of ultraviolet light to hit a layer on the membrane to generate free radicals, which in turn give rise to combustion and decomposition of the contaminations in the water passing through the radiation area, wherein the lower end of the first transparent pipe is close to the bottom of the membrane in order to lengthen the water flow path from the membrane to the outlet part.

By the combination of the membrane filter, the UV radiation and the generation of free radicals a very effective arrangement is obtained for filtration and purification of water, which solves the problem mentioned above, which involves that more than one method for treatment has to be used for the treatment of water containing large as well as small contaminations.

In a preferred embodiment the apparatus further includes an air compressor arranged in connection to the outlet part of the filtration house and adapted to supply air to the water when the apparatus is back flushed and an ultrasound unit adapted to supply ultrasound to the membrane for obtaining rinsing of the mem- brane surface and its pores. By the supply of air and the use of ultrasound when back flushing one obtains an improved cleansing of the membrane surface without changing or removing the membrane from the filtration house.

Preferably the inlet part of the filtration house includes a separate outlet pipe which can be opened when back flushing to remove the back flushed contam- inations from the filtration house. Alternatively the back flush water and the contaminations are conducted away from the filtration house through the inlet pipe.

In another embodiment the apparatus further includes a dosage pump arranged in connection to the outlet part of the filtration house and adapted for adding an antioxidant to the water to interrupt the production of free radicals. As free radicals are very chemical active and harmful to human beings they have to be removed before the purified water leaves the apparatus. This is obtained in an effective way by introducing antioxidants to the water, which bind and render the free radicals harmless.

In an alternative embodiment the bottom of the membrane has a larger diameter than the end most close to the outlet part of the filtration house, whereby the membrane forms a truncated cone, the lateral section of which is inclined with respect to the length axis of the membrane by an angle of between 0 and 60 degrees, preferably 20 degrees. By giving the membrane an inclination with respect to the length axis the envelope surface can be made larger, which increases the effective purification surface and thus, the capacity of the apparatus.

In a preferred embodiment the layer arranged onto the membrane is made of sintered titanium oxide. Titanium oxide is used in sun-checking inhibitors due to its high refraction index and ability to reflect UV radiation. Titanium oxide also emits a large amount of free radicals when exposed to UV radiation which effectively purify the water.

In another embodiment the UV fluorescent lamp is adapted to transmit a radiation of ultraviolet light having a wavelength of between 175 nm and 260 nm, preferably 254 nm. This wavelength area is most effective to produce free radicals.

In an alternative embodiment the inlet pipe is arranged angled to the side wall of the filtration house to obtain a tangential water flow towards the membrane. By the tangential flow a continuous movement is obtained, a continuously loop flow, along the membrane surface which assists to keep the pores free from contaminations. By that the attachment of contaminations onto the filter surface is avoided. This is obtained with extremely small water losses whilst the apparatus can be kept operated during longer periods without rinsing or changing the membrane.

In a preferred embodiment the apparatus further includes an outlet pipe close to the bottom of the filtration house, the outlet pipe being connected to the inlet pipe through a valve and a pump and is adapted for delivering a loop flow to maintain the tangential water flow towards the membrane. By the loop flow it is ensured that contaminations built up do not remain between the inlet pipe and the membrane and thereby the forming of a coating onto the membrane surface is prevented. In another embodiment the apparatus further includes an outlet valve connected in parallel to the valve and adapted to drain water from the outlet pipe to an outlet. When the concentration of contaminations in the loop flow grows the outlet valve may be opened in such a way to remove the contaminations built up from the apparatus.

In another aspect of the present invention a method is supplied for decomposition and removal of contaminations from water comprising following steps: guiding the water to be purified into a filtration house through an inlet pipe; allowing the water is to pass through a porous membrane including a bottom and an envelope surface arranged inside the inlet part of the filtration house;

guiding the water further through a first transparent pipe, the two ends of which being open and which is arranged in the inlet part around the centre of the filtration house within the membrane, where the inlet part is in fluid communication with an outlet part of the filtration house through the first transparent pipe; and

guiding the water out from the outlet part through an outlet socket,

wherein the water is irradiated with ultraviolet light from a UV fluorescent lamp contained in a second transparent pipe having a closed bottom and being arranged inside the first transparent pipe, during the passage of the water from the membrane to the outlet part,

wherein the ultraviolet light is allowed to hit a layer on the membrane to generate free radicals, which in turn give rise to combustion and decomposition of the contaminations in the water passing through the irradiation area, and

wherein the flow path of the water from the membrane to the outlet part is lengthened by arranging one end of the first transparent pipe close to the bottom of the membrane.

The method according to the invention implies that contaminations like organic suspensions, particles, gels, colour colloids, and chemical solved oxygen consuming substances are removed in a way that results in a more far-reaching purification than what can be obtained with any method known per se.

In a preferred embodiment the method further includes the step of carrying out a back flushing to remove the contaminations from the outer surface of the membrane during supply of air from an air compressor arranged in connection with the outlet part of the filtration house and production of ultrasound to the membrane by an ultrasound unit. In another embodiment the method further includes the step of adding an antioxidant to the water to stop the production of free radicals.

In an alternative embodiment the water to be purified is introduced at an angle to the side wall of the filtration house to obtain a tangential water flow to- wards the membrane.

In a preferred embodiment some of the water in the inlet part of the filtration house is returned to the inlet pipe by means of an outlet pipe arranged close to the bottom of the filtration house, which outlet pipe being connected to the inlet pipe through a valve and a pump for providing a loop flow to maintain the tangen- tial water flow towards the membrane. Preferably the water from the outlet pipe is drained to an outlet by an outlet valve connected in parallel to the valve.

Short description of the drawings

Fig. 1 shows with a schematic cross section view an apparatus for purifi- cation of water according to the present invention during normal flow.

Fig. 2 shows with a schematic cross section view an apparatus for purification of water according to the present invention during back flushing.

Fig. 3 shows with a schematic cross section view an apparatus for purification of water according to a preferred embodiment of the present invention dur- ing back flushing.

Fig. 4 shows with a schematic view a flow arrangement for the apparatus according to a preferred embodiment of the present invention.

Description of the invention in detail

The method according to the invention is described by means of an apparatus to be found in Figs. 1 and 2.

In the following description some minor technical constructive details are left open, such as seals, method of connection, fittings, connection means, material thicknesses, closures etc. having no importance to the basic process technical arrangements being valid for the invention as such.

The filtration house 1 , as a whole made of steel, ceramic or a plastic material, has the form of a rectilinear pipe with a bottom and at the top provided with a flange 2 having a circular folding 3. Inside the filtration house 1 there is a membrane 4. This membrane consists of two layers. The layer first passed by the untreated water, which also constitutes a porous support layer for the following layer, may be made of a ceramic porous material or a sintered metal, such as for instance sintered titanium having a pore size of varied order from 20 μιτι to 0.1 μιτι, but preferably 10 μιτι. The following layer downstream in the water flow direction consists of a titanium oxide layer having a porosity which may be varied from 20 μιτι to 0.1 μιτι, but preferably 10 μιτι.

The membrane 4 has a larger diameter at the bottom than at the top. Its lateral section is characterised by a truncated cone, the secant of which with respect to the vertical plane can be varied between 0 and 60 degrees, but is preferably 20 degrees. Thus, the filtration surface of the membrane can be optimised and the largest possible surface can be obtained for an effective purification with a high capacity.

The lower end of the membrane 4 is provided with a bottom made of the same material as the envelope surface. At the upper part it has a perpendicular flange fitting in the folding 3 of the filtration house flange 2.

Inside the membrane 4 there is a first transparent pipe, preferably a glass pipe 5, being open at both the ends. In the upper part thereof it is fastened in a packing box 6. Inside the glass pipe 5 there is a second transparent pipe, preferably a glass pipe 7, the bottom of which being closed and the upper end thereof reaches the cover 8 of the filtration house and is maintained by packing box 9 arranged in the cover 8. The upper part of the second glass pipe 7 has a closure 1 1 . Within the second glass pipe 7 there is a UV fluorescent lamp (12), the power supply cable of which passes through the closure 1 1 . Within the framework of the present invention it is also possible to use other types of material or design of the pipes 5 and 7 for transmission of UV radiation.

In the cover 8 of the filtration house there is a horizontally clamped outlet socket or pipe 14 to conduct away treated water and to be the inlet for back flush- ing water.

In the upper part of the filtration house 1 there is a connection pipe 13 for water supply during the filtration action. This pipe may be angled such that the water supply is tangential. The supply method is such that the water is brought to circulation around the membrane surface. Fig. 1 shows the water flow progress through the apparatus during normal filtration. By help of the pump 18 the water is pumped to the filtration house 1 through the inlet 13 and then it passes though the membrane filter 4. There the water goes through the membrane filter 4 and is then conducted in a downward di- rection and thereafter going up between the outer glass pipe 5 and the inner glass pipe 7 to finally be conducted out from the upper part of the external glass pipe 5 to the outlet 14 for further transport through a multiple-way valve 10 as a return water to a tank or pool.

Fig. 2 shows the water flow progress through the apparatus during back flushing of the membrane filter 4. By help of the pump 18 the water is pumped to the inlet 14 and is brought further through the glass pipe 5 in a downward direction. Then it goes in an upward direction between the glass pipe 5 and the membrane filter 4, then out through the inlet pipe 13 for finally being drained through the multiple-way valve 10 to an outlet through the pipe 21 .

At the same time as the multiple-way valve 10 is set for back flushing an ultra sound unit 22 having a drownable transmitter 25 is started. The transmitter 25 is adapted to be inserted in the outlet part of the filtration house 1 and transmits an ultra sound to the membrane to separate most of the particles collected onto the membrane 4 surface and in its pores. Simultaneously, an air compressor 20 is al- so started, which is connected to the outlet part of the filtration house 1 , wherein air is blown into the back flushing water which also is pressed out through the membrane 4.

In operation an ultraviolet radiation is transmitted from the UV fluorescent lamp (12) within a wave length area of 175 nm through 260 nm, but preferably 254 nm.

When the ultraviolet radiation hits the titanium oxide layer free radicals are produced in the passing and retained microbe substance therein, which in turn produce a process in the water where decomposition of organic substance and also of chemically bound organic material occurs. This process occurs also in the wet area between the two glass pipes and within the wet area between the glass pipe 5 and the membrane 4 with its titanium oxide layer.

This process acts in such a way that certain atoms and molecules lose electrons from other atoms and/or molecules, which in turn proceeds in a similar way. The result is a chain reaction with a fast development, wherein contamina- tions of different types are reduced. When a free radical hits an antioxidant there is no formation of a new free radical. The chain reaction is stopped but at the same time the antioxidant is consumed.

As the free radicals have to be annihilated before the purified water is used the invention comprises that during the process an antioxidant is dosed into the water before it leaves out into the outlet water pipe connected to the outlet 14. Therefore the apparatus has a nipple 16 onto which a dosage arrangement can be connected for supply of an antioxidant to the wet area under the cover 8 of the curved filtration house.

To avoid building up of a preventive layers or covers on the membrane 4 the inlet pipe 13 is arranged at an angled to the wall of the filtration house 1 , which results in that the water between the wall of the filtration house 1 and the membrane 4 is brought to flow helically from the inlet 13. This arrangement, giving rise to that the membrane surface partly, but continuously is rinsed, prevent bacteria and other microorganisms together with ions and organic substances to form adhesive layers on the membrane 4 and in such a way the water can pass through the membrane in a continuous way.

In an embodiment shown in figs. 3 and 4 the apparatus also includes an outlet pipe 17 arranged close to the bottom of the filtration house 1 . In turn the out- let pipe 17 is connected to the suck side of the pump 18 by the pipe 19 and a valve 15. Then the water is returned to the inlet pipe 13 of the filtration house 1 through the pipe 22, such that the sucking force obtained by the pump 18 contributes to continuously maintain the helically formed water flow in the filtration house 1 .

The loop water flow is set by means of the valve 15, such that it will be between 1 and 2% of the water supplied to the filtration house through the inlet pipe 13. The loop water together with a high concentration of contaminations are emptied and drained off by means of an escape valve 24 at chosen intervals.

Unlike the methods mentioned by way of introduction, where the filter or membrane coatings are not removed continuously, which result in considerable costs caused by the frequent filter changes or obvious water loss due to frequent back flushing intervals, the apparatus according to embodiment described above in connection with fig. 3 permit that coatings on the membrane can be avoided at a minimum expense of a water loss. The flow arrangement for the apparatus is evident from fig. 4 and the references given below.

The purpose with the glass pipe 5 is to attain two flow paths inside the membrane 4, where one runs through the glass pipe 5 and the other one runs be- tween the glass pipe 5 and the membrane 4, wherein the water flow velocity is doubled and its thickness is reduced by halves and that the water within the two flow areas is exposed to the ultraviolet light at the same time.

When the water is more and more pure during the exposure time of the flow course the shadow zones of the UV radiation will be fewer, which means that in an ever higher extent during the water flow passage one obtains a killing of eventually unremoved micro organisms including bacteria and virus etc., when the water passes through the glass pipe 5 during the end phase. These are killed just by the UV radiation due to their DNA molecule being broken down.

The relation between the diameter of the inner glass pipe 7 and the exter- nal glass pipe 5 ought to be from 1 :2 to 1 :4, but preferably 1 :3. The relation between the diameter of the external glass pipe 5 and the membrane 4 ought to be from 1 :1 .2 to 1 :8, but preferably 1 :1 .3.

The glass pipe 5 being open at its two ends causes the water to flow a longer path within the UV irradiated area with the aim of minimising appearing shadow zones when the contaminations in the water mainly are constituted by substances causing turbidity.