GB1601380A

GB1601380A - Process and apparatus for purification of effluents

Info

Publication number: GB1601380A
Application number: GB25203/78A
Authority: GB
Original assignee: ARMAFILT EGYESUELT MUESZAKI TO
Current assignee: ARMAFILT EGYESUELT MUESZAKI TO
Priority date: 1978-05-31
Filing date: 1978-05-31
Publication date: 1981-10-28

Description

(54) PROCESS AND APPARATUS FOR PURIFICATION OF EFFLUENTS (71) We, ARMAFILT EGYESSLT MOS- ZAKI TOMATO ES GEPSZAKMAI IPARI SZÖVET KEZET, a Hungarian body corporate of 1134 Budapest, Huba utca 24, Hungary, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention concerns a process and apparatus for purification of effluents e.g. for separating out suspended or emulsified contaminants, mainly for de-oiling oily effluents and thus producing drinking water or industrial water.

In the process according to the invention the so-called raw effluent to be purified is introduced into a purification space which is divided into a lower reaction space, a central or intermediate filtering space and an upper liquid space, the filtering space being bounded by a lower filter plate and an upper filter plate and accommodating a filter insert, a flocculating agent and the raw effluent is passed into the lower reaction space whereby to enclose the particles of the contaminants within cells formed by the flocculating agent, then the flocculated cells are passed into the pores of the filter insert, the thus bound contaminants together with the flocculated cells enclosing them are removed from the filter insert by the simultaneous application of liquid and air, whereby to render the filter insert capable again to bind flocculated cells, the purification of the effluent and the regeneration of the filter insert being performed in an alternating fashion and wherein the filter insert consists of a mass of particulate resilient material of a density such that the filter insert is lifted to be compressed by the upwardly flowing effluent against the upper filter plate, the purified liquid being withdrawn from the upper liquid space.

Apparatus according to the invention for carrying out the above process includes a vessel which contains a purification space, which can be pressurised and which is provided with the filter insert, with means coupled or associated with the vessel suitable for feeding into the purification space the raw effluent to be purified, the flocculating agent(s) and air, and for removing purified water, wherein the purification space of the vessel is divided into a lower reaction space, a central or intermediate filtering space and an upper liquid space, the filtering space being bounded by a lower filter plate and an upper filter plate, the lower or bottom reaction space of the vessel is connected to a raw effluent inlet pipe, a flocculating agent infeed pipe, and sludge-water draining pipe for flushing out the caught contaminant; the upper liquid space of the vessel is connected to a purified liquid removal pipe, while in the filter space there is placed the filter insert which is formed of a mass of particulate resilient material.

In engineering practice, it is a frequency task to produce drinking water or industrially usable water from contaminated waters e.g. from natural so-called surface water, or for environmental protection reasons from industrial effluents to the extent that such effluents should not damage the life conditions in these natural or artificial waters.

In principle, purification of liquids may be carried out in three fundamental ways; chemical methods, physical methods or a combination of these two. Due primarily to economic considerations, if at all possible an attempt is made to utilise physical water purification methods. A common characteristic of the latter is that the water to be purified is settled and/or clarified, then filtered and finally in given cases is subjected to some further treatment.

In the majority of modern water purification processes an attempt is made to omit the steps of settling and clarification and instead the water to be purified is passed directly through one or more filter layers so that in the meanwhile continuously or intermittently flocculating agents and other flocculation-promoting materials are added to the water. The flocculating agents are in the form of chemicals, passed into a treatment space where in the course of purification the formed flocks enclose within themselves the undesired contaminating components. After this enclosure of the contaminants has taken place the flocks and the cells enclosing the contaminants formed thereby can be retained by some suitable filtering material and removed from the water.

In the filtering processes used in practice, the filter inserts placed in the treatment space "saturate" after a certain length of time and become unsuitable for the further retaining and binding of additional flocks. Hence filter inserts must be regenerated from time to time in order to make them suitable once more for performing their tasks. From the point of view of performing the filtration and regeneration the known filters can be divided into two groups; filter beds and filter layers.

In the filter beds belonging to the first group the contaminated water is passed through a filtering medium consisting of some particulate material, principally or primarily quartz sand, anthracite millings, granulated active carbon or a synthetic resin.

The filter layer is generally one to two m. in thickness and the rate of filtration varies in the range of 5 to 15 m/h. Both the thickness of the layer and the rate of filtration can be selected in dependence on the extent of contamination of the water to be decontaminated, from the nature of the contaminant, from the requirements made of the purified water and on the duration of the so-called cycle time between each regeneration process.

A type of filter bed is also known wherein the filter insert is made of a porous and resilient synthetic material. The insert of synthetic material is made up of parallelepipedal pieces with an edge length of 3 to 5 cms. Such a filter layer is placed between plates, expediently perforated plates, and special care is taken in the selection of the pore size of the insert. In the course of filtration, the insert is held in a compressed state since the filtering material is of a lower density than water and therefore would loosely fill the filtering space. Consequently, without such pressure the water to be purified would pass virtually without resistance through the gaps between the pieces of the filter layer and the desired filtering effect would not be achieved.

The advantage of filter beds is that it can provide filtered water of the desired quality for a relatively long time without regeneration because the filtering material has a large number of pores of large gap volume for accommodating the contaminants. However, it is a disadvantage of filter beds that after their pores are clogged up, they require pure water for regeneration, particularly a large volume of pure or purified water and for loosening up the filtering material compressed air is also required.

Of the mentioned disadvantages, particularly the requirement for pure water is significant since according to experience, a considerable, proportion. even up to 10%, of the purified water is lost in the form of sludge water. It is also an economic disadvantage, particularly in the case of filtering highly contaminated waters, that a considerable amount of energy is required for feeding in the regenerating media. The situation is further complicated in the case of use of a synthetic filter insert because mechanical apparatuses require to be installed and operated for the compression of the synthetic filter inserts and for the circulation of the regenerating media. These mechanical devices are generally liable to breakdown.

To the second group of filters belong the so-called layer filters. Here some solid core or skeleton, such as porous porcelain or a sintered metal plate or a finely woven textile web receives a material of gel consistency, e.g. bentonite siliceous earth, a metal hydroxide etc., These gel materials or materials of gel-like consistency perform the filtering of the liquid to be purified. Filter paper is another layer filter which can be called conventional.

It is an advantage of layer filters that the liquid to be purified can pass through them at a relatively high speed (15 to 50 m/h) and even in the case of relatively small layer thickness, excellent quality purified water can be produced. Their disadvantage is however that the thin filtering layer is exhausted after a short time, its pores are blocked and thus the cycle time of such layer filters is significantly shorter than that of filter beds of similar throughput. It is also unfavourable that the active filter layer either cannot be regenerated at all or only at very high expense.

The characteristic type of known modern filter apparatus is described in Patent Specification No. 1,922,196 of the Federal Republic of Germany which concerns a continuously operating condensing-pulsating filter. The apparatus operates with one or more filter element of rigid construction, made e.g. from a ceramic material. It has a vessel for accommodating the concentrated suspension as well as for removing it, a pipe for removing the filtered liquid, the so-called filtrate and a respective pulsation chamber on the inlet and outlet side.

In this apparatus, operation is continuous and regeneration also takes place continuously simultaneously with the filtration. This is achieved in that when the filtering element is blocked or clogged up, the pressure in the pulsation chambers increases and the excess pressure tears off or almost "explodes off' by a sudden counter pulse pressure the contaminants deposited on the filtering element surface. There is also a possibility for enhancing the effect of the counter pulse in the pulsating chamber on the outlet side by utilising an external energy source, e.g. a compressor.

In the pulsating filter apparatus in question, highly contaminated liquids can be continuously filtered and simultaneously the filter insert can be continuously regenerated.

It is also favourable that the pressure changes taking place or arising during filtration are virtually automatically effective to perform regeneration.

However, it is a disadvantage that where the contamination is of a high concentration, very large filtering areas require to be used because otherwise the pulsation chambers would have to be operated all the time as a consequence of the rapid clogging up of the filters. It is also an unfavourable phenomenon that the filter elements must be subjected to large pressure changes of opposite sign in the course of filtration and regeneration.

If it is required to purify waters contaminated with synthetic material or oil by means of filtering elements of high mechanical strength capable of resisting the abovementioned high mechanical loads, generally ceramic filter elements, then their very fine pores would be so blocked up that they could not be regenerated purely and solely by mechanical pulsation. Thus this apparatus is not usable for filtering effluents of this character.

A filter apparatus of simpler construction is described in Patent Specification No.

1,436,294 of the Federal Republic of Germany. Its essence consists in a filtering tank which can be subjected to pressure and in which is placed a lower filtering plate of fixed position and an upper filtering plate which may be hydraulically or pneumatically displaced.

In the course of the filtration, the upper filtering plate is pressed on the filter charge or medium placed between the two filtering plates. In the course of regeneration, the upper filtering plate is raised to enable the filtering material to be loosened. The filtering material is not resilient and its specific gravity is approximately the same as that of the liquid to be decontaminated.

This apparatus may expediently be used in cases were the liquid is passed through a filter charge consisting of an ion exchanging synthetic resin. During filtration the filtering charge must be clamped down or compressed because it is of low specific gravity and would either float away or would loosen up to such an extent that the filtration would not be efficient. In the course of regeneration, the charge must be loosened and therefore the upper filtering plate is formed in a displaceable manner.

Although the basic principle of this apparatus is good, in the case of oily effluents its use is not expedient, although not all its disadvantages are connected with oily effluents. One reason for the disadvantage of this apparatus is that in the course of the filtering period the charge must be highly compressed in order to occupy only a small fraction of the space between the lower and upper filtering plates. For this reason, on the one hand the filtration is not sufficiently effective and on the other hand expensive machinery is required for the hydraulic or pneumatic displacement of the upper filtering plate, in operation and in installation.

There are also filtering apparatuses which operate with the aid of an excess pressure amongst which is the so-called REISERT type of filtering apparatus which is described in e.g. Kieser: Handbuch des Chemischen Technologie. The apparatus comprises a pressurisable closed filter tank, an air drum, a pump for feeding in raw water and a compressor for producing the air pressure in the air drum. Here also the filter medium or charge is an unresilient solid particulate material, expediently quartz sand. The filter ing medium is supported by a filtering plate mounted by so-called filter plugs. Beneath the filtering plate there is also an unperforated second filtering plate.

In the REISERT-typ filtering apparatus, filtering takes place intermittently. After blocking or clogging of the filtering charge compressed air is passed to the lower portion or space of the filtering tank. This compressed air suddenly pushes the already purified water collected at the bottom of the tank in an upward direction into the material of the filtering insert and thus the charge or filtering medium is loosened by the filtered or previously filtered water. When the purified water at the bottom of the tank has been completely used up then further air is passed in to loosen the material of the filtering medium in the course of which the contaminants deposited on its surface are cleaned off.

The removal of the contaminants may take place by highly pressurised filtered water.

The REISERT-type filtering apparatus is suitable for performing filtration in all cases where the material of the filtering medium consists of unresilient solid particles. The regeneration of this filtering medium also takes place at a high efficiency. However, it is unfavourable that a very high volume of filtered water is required for regeneration as well as expensive apparatus such as a hydrobore, air drum etc., This apparatus cannot be used with a filtering medium of resilient material.

The aim of the invention is to provide apparatus and a process for the effective purification of effluents, especially oily effluents, which eliminates or reduces the disadvantages of known apparatus and processes and which is suitable for the production of water of the required degree of purity, which utilises as a filtering layer a resilient readily compressible material which readily regains its original shape, with a filtering medium of long life which is simply and effectively regeneratable.

In addition, it is a task of this invention to produce apparatus which cleans or purifies water containing emulsified contaminants with the aid of the addition of flocculating chemicals wherein the flocks form cells encompassing the contamination and these flocks can be separated with the aid of the filter insert until any desired degree of purity has been achieved, while the contamination caught by the filter charge is removable without residue and the filter layer can be repeatedly regenerated over a long time.

The basis of the inventive concept is primarily the recognition that the so-called layer filters, (e.g. filter paper, membrane filters etc.,) filter with a very high efficiency but after becoming clogged either cannot be regenerated at all or only with great difficulty while the filter beds (e.g. sand, gravel, active carbon etc) filter at a lower efficiency but on becoming blocked can be relatively simply and efficiently regenerated.

The discovery on which the invention is based is signified by the experience that the utilisation of filtering materials of high efficiency and perfect relaxation can be carried out by using a process which combines in itself the advantages of layer filters and filter beds. In other words this means that the apparatus for carrying out the process of the invention filters as a layer filter and is regeneratable like a filter bed. The desired effect can be achieved with a filtering charge or medium which is made up of a foamed synthetic material milled to a particle size of 0.1 mm to 25 mm.

Further it is a part of this recognition, in contrast with conventional filtering processes, that the filtration is carried out by a flow of liquid which is not from above downwardly, and the regeneration with a flow which is not from above upwardly by in the very reverse direction, the filtration is carried out from below upwardly and the regeneration in the opposite direction. This concept on the one hand makes it possible to adjust the efficiency of the filtration and on the other hand it means that it is not necessary to use already purified water for the regeneration.

By filtering with a flow taking place from below upwardly, the filtering medium of low density is pressed against the upper filter plate of the filtering space or purification space while its layer thickness and porosity is influenced by the rate of flow of liquid passing therethrough. In other words, this means that by regulating a single parameter, the rate of flow of the water to be purified, the efficiency of purification can be regulated as desired.

During filtering, the filtering insert operates as a layer filter. When its pores become clogged up, the flow of liquid is stopped whereby to loosen the charge which will no longer be pressed against the upper filtering plate but instead will uniformly fill out the space, the filtering space between the filter plates. After this loosening, which takes place without the use of purified water the regeneration can be carried out simply by draining the liquid in the filter tank.

The efficiency of regeneration can be increased by removing the liquid from the purification space, not only by gravity but also with the aid of a high speed pump. The regeneration efficiency can also be increased by introducing air into the filtering medium before or during the draining or pumping off, because by doing so the particles of the material forming the filtering medium or charge can be very effectively mixed together.

In accordance with the set task or aim of the invention the process according to the invention is set out in appended claim 1.

Preferably, the degree of contamination of the purified liquid discharged in the purification process from the purification space provided with a filter insert--or at least that of the so-called prefiltrate discharged in the initial phase of purification-is monitored and the efficiency of purification is regulated or adjusted to the desired degree of purity by adjusting the rate of inflow of raw effluent into the purification space, and the regeneration of the filter insert is carried out by causing the purified liquid to flow through the filter insert from above downardly in the purification space itself.

A further characteristic of the process according to the invention may be that the degree of contamination of the prefiltrate and/or of the purified liquid is monitored either by intermittent sampling or by continuous observation, e.g. by placing a 'test instrument in the path of the purified liquid.

The regeneration of the filter insert may be carried out by the single or multiple draining of the raw liquid in the purification space or by the single or multiple pumping off of the raw liquid in the purification space, with the aid of a suitable pump. In the course of draining or pumping off the liquid the efficiency of the regeneration of the filter insert in the purification space can be enhanced with the aid of pressurised flushing air.

In the course of regenerating the filter insert, the material of the filter insert is mixed with the aid of liquid in a preferred embodiment whereby to remove the contamination from the surface of the particles of the filter insert and then, again with the air of air, the sludge liquid removed from the filter insert is removed or pressed out from the tank.

In this latter case, compressed air is used for draining the sludge liquid from the tank and thus the sludge liquid as well as the filter insert of the resilient particles are brought into an eddying or vortical movement to enhance the mixing of the filter insert, then in the final phase of the regeneration the filter insert is pressed by means of compressed air against the lower filter plate to cause the contaminants caught in the pores of the filter insert to be removed.

The apparatus according to the invention for the purification of contaminated effluents is defined in appended claim 10.

The apparatus according to the invention may also be further characterised in that the filter insert consists of a heap of porous particles or a milling of some sponge-like foamed synthetic material. Expediently the filter insert consists of particles of differing sizes of which the finest fraction is of 0.1 mm or greater and the coarsest fraction is 25 mm or smaller.

In an expedient embodiment of the apparatus both the lower filtering plate and the upper filtering plate is fixedly mounted in the purification space of the vessel.

In the vicinity of the vessel, the pipe for feeding in effluent (e.g. raw water) to be purified, the pipe for feeding in the flocculating agent into the tank and the pipe for removing sludge liquid containing the filtered contaminants are combined into a single common charging/discharging pipe.

In an alternative preferred embodiment the filtering medium or insert is divided into layers by means of separating plates expediently perforated plates. The perforated plates are fixedly secured within the tank.

Compared with known earlier solutions, the process and apparatus according to the invention for purification of raw liquid has numerous technical and economic advantages. The most important technical advantage is that it enables oily raw waters and other effluents containing emulsified contaminants to be efficiently filtered, which until now has not been solved. Moreover, not only does the invention make this possible but the purification takes place at a far higher rate and efficiency than hitherto. In contrast to the filtration rate of 5-16 m/h with conventional filtering apparatus with a process and apparatus according to the invention a filtration rate of 35-100 m/h may be achieved.

A further technical advantage is that the flocculation process needed for the removal of the suspended and emulsified contaminants can take place in the apparatus itself. It is extremely advantageous from economic considerations also that for the regeneration there is no need for already purified liquid and moreover extremely high regeneration efficiency can be achieved by simply removing raw liquid from the purification space by gravitation. It is further advantageous that the operation of the apparatus may be readily and fully automated. Having regard to the fact that the filtration rate is high the output of the apparatus is much more favourable than those of known devices and thus the specific investment costs are considerbly and significantly lower than those of conventional apparatuses.

Numerous further advantages also stem from the basic concept of the process and the construction of the apparatus. Such an advantage is for instance the fact that the upper and lower filter plates bounding the filtering space remain in place both in the course of regeneration and filtration and hence the construction is simple. It is also favourable that the air introduced into the tank not only loosens the material of the filtering medium but also mixes it and thus the contaminants are easily removable from the surfaces of the filter particles. The possibility arises furthermore that the air introduced in the second phase of the regeneration which may in given cases be compressed air, the filtering material or insert can be pressed against the lower filtering plate whereby to press out the contaminants that have passed into the pores of the filtering particles. This is because as a consequence of the resilience of the filtering insert the contaminants are absorbed by the filtering insert in the manner of a sponge while in the course of regeneration, due mainly to the squeezing effect, the contaminants are expelled without residue.

It is also a very great advantage compared with all conventional constructions that by changing the rate of throughflow of liquid to be purified, the porosity of the filter insert and thus the efficiency of filtration, i.e. the degree of purity of the purified liquid can be regulated. Since regeneration is carried out with purified liquid no special mechanical apparatus is required for regeneration and also due to the high rate of filtration and dimensions of the apparatus relatively small and these circumstances mean significant investment savings.

It is also advantageous that by introducing air not only is the filter insert loosened but is brought into quasi-vortical movement, can be perfectly mixed and therefore regeneration is far more intensive and rapid. Finally, one cannot ignore also the fact that the filter insert is in principle regeneratable an infinite number of times and in practice therefore its lifetime is practically unlimited.

A preferred embodiment of the invention is illustrated in the accompanying schematic drawing.

In the Drawing, Figure 1 is a schematic embodiment of one form of the invention and Figure 2 differs from it only in the internal construction of the main vessel.

The principal part of the apparatus is the main vessel 33 in which is fixedly secured a lower filter plate. Sa and an upper filter plate Sb. The lower filter plate Sa and the upper filter plate 5b divide the purification space in the interior of the vessel 33 into three separated parts, namely a reaction space 4, at the bottom, a filtering space 6 and an upper water space 8. The filter insert 7 is disposed in the filtering space 6. In the drawing, the filter insert 7 is shown in the course of filtration wherein under the effect of the raw water flowing in from below the filter insert 7 is pressed against the upper filter plate and thus fills only the upper portion of the filtration space 6.

Figure 1 illustrates the preferred embodi ment wherein the duct 22 feeding in raw water, the duct 25 conveying the flocculating agent towards the vessel 33 as well as the duct 28 serving for the removal of the sludge water containing the filtered contamination are united into a common charging/dis charging duct 35.

As can be seen from Figure 1 the raw water comes in via a foot valve 21 into the apparatus and then continues on its way via the duct 22 and the suction valve 2 towards the united or combined suction duct 24. The combined suction duct 24 not only conveys the raw water arriving from the duct 22 but also the chemical arriving from the chemical tank 13 via the chemical feeding valve 12 and duct 25.

The common or combined suction duct 24 debouches into a pump 1 which pressurises the raw water which now contains the flocculating agent. Thereafter, the raw water continues on its way towards the vessel and the combined charging/discharging duct 35 via a pressure valve 3 and pressure duct 27.

Expediently, the pressure duct 27 also con tains an output regulating valve 19 which is suitable for changing the flow rate of the raw water and thus also regulating the porosity of the filter insert 7 and the efficiency of the filtration.

It can be seen also from Figure 1 that the common or combined charging/discharging duct 35 has a lower junction point 38 to which is also connected the sludge water suction duct 23 provided with a suction valve 14. Thus when the filter insert 7 is being regenerated, the contaminated water, the so called sludge water can be removed from the purification space via the suction duct 23 for sludge water and the suction valve 14.

In the course of regeneration, the sludge water is conveyed via the combined or common suction duct 24, the pump 1 and the combined pressure duct 26 to the sludge water pressure valve 15 and is removed from the apparatus via the sludge water pressure duct 28. At such times naturally the suction valve 2 and the chemical feeding valve 12 must be in their closed position to ensure that the sludge water should be able to continue its flow in the desired direction. In the same way naturally the pressure valve 3 must also be in the the air compressor 17 that the compressed air should pass into the open air instead of into the vessel 33. A non-return valve 20 is expediently connected into the compressed air duct 31 to prevent air from flowing back in the direction of the air compressor 17.

Figure 2 refers to an embodiment wherein the filtration space 6 of the vessel 33 is divided into parts with the means of perforated plates 36 and 37. In this way, the filter insert 37 is divided into mutually separated layers 7a, 7b and 7c so that the layers cannot be. mixed together. The possibility is also opened up for the filter insert to contain fractions of different particle size in these portions.

Based on experiments performed until now, the process and apparatus according to the invention may expediently be employed not only for the de-oiling of oily effluents but also for the purification of raw waters or other liquids contaminated with other emulsions. It is particularly advantageously us- able as a treatment stage connected after chalky softening reactors for the filtration of softened water in the interest of achieving the desired degree of purity for ion exchanging charges or filter inserts. The apparatus according to the invention is advantageously usable in associated with the water removal works of any natural or artificial lake or river for the production of industrial or drinking water.

WHAT WE CLAIM IS: 1. A process for purifying effluents for separating out suspended or emulsified contaminants from liquids, wherein the raw effluent to be purified is introduced into a purification space which is divided into a lower reaction space, a central or intermediate filtering space and an upper liquid space, the filtering space being bounded by a lower filter plate and an upper filter plate and accommodating a filter insert, a flocculating agent and the raw effluent is passed into the lower reaction space whereby to enclose the particles of the contaminants within cells formed by the flocculating agent, then the flocculated cells are passed into the pores of the filter insert, the thus bound contaminants together with the flocculated cells enclosing them are removed from the filter insert by the simultaneous application of liquid and air, whereby to render the filter insert capable again to bind flocculated cells, the purification of the effluent and the regeneration of the filter insert being performed in an alternating fashion and wherein the filter insert consists of a mass of particulate resilient material of a density such that the filter insert is lifted to be compressed by the upwardly flowing effluent against the upper filter plate, the purified liquid being withdrawn from the upper liquid space.

2. A process according to claim 1, wherein the degree of contamination of the purified liquid discharged in the purification process from the purification space provided with a filter insertr at least that of the socalled prefiltrate discharged in the initial phase of purification-is monitored and the efficiency of purification is regulated or adjusted to the desired degree of purity by adjusting the rate of inflow of raw effluent into the purification space, and the regeneration of the filter insert is carried out by causing the purified liquid to flow through the filter insert from above downwardly in the purification space itself.

3. A process according to claim 2, wherein the degree of contamination of the prefiltrate and/or of the purified liquid is monitored by intermittent sampling.

4. A process according to claim 2, wherein the degree of contamination of the prefiltrate and/or of the purified liquid is continuously monitored, e.g. by a monitoring or testing instrument placed in the path of the purified liquid.

5. A process according to any one of claims 1 to 4, wherein the regeneration of the filter insert is performed by the single or multiple draining of the raw effluent disposed in the purification space.

6. A process according to any one of claims 1 to 4, wherein the regeneration of the filter insert is performed by a single or multiple pumping off of the raw effluent in the purification space with the aid of a pump.

7. A process according to claim 5 or claim 6, wherein in the course of draining or pumping off the liquid the efficiency of regeneration of the filter insert disposed in the purification space is enhanced by the use of pressurised flushing air flow.

8. A process according to any of claims 5 to 7, wherein in the course of regenerating the filter insert the material of the filter insert is agitated by means of air so as to remove surface contamination from the particles of the filter insert and then again with the aid of air the sludge liquid removed from the filter insert is expelled from the vessel.

9.- A process according to claim 8, wherein compressed air is employed to discharge sludge liquid from the vessel and the air is used to cause both the sludge liquid and the filter insert of resilient particles to move in an eddying movement to promote agitation of the filter insert, and then in the final phase of the regeneration the compressed air is used to press the filter insert to the lower filter plate to cause the contaminants caught by the filter to be expelled from the pores of the filter insert.

10. Apparatus for purifying effluents for separating out suspended or emulsified contaminants from liquids, wherein the contaminated or raw effluent is purified with the aid

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the air compressor 17 that the compressed air should pass into the open air instead of into the vessel 33. A non-return valve 20 is expediently connected into the compressed air duct 31 to prevent air from flowing back in the direction of the air compressor 17. Figure 2 refers to an embodiment wherein the filtration space 6 of the vessel 33 is divided into parts with the means of perforated plates 36 and 37. In this way, the filter insert 37 is divided into mutually separated layers 7a, 7b and 7c so that the layers cannot be. mixed together. The possibility is also opened up for the filter insert to contain fractions of different particle size in these portions. Based on experiments performed until now, the process and apparatus according to the invention may expediently be employed not only for the de-oiling of oily effluents but also for the purification of raw waters or other liquids contaminated with other emulsions. It is particularly advantageously us- able as a treatment stage connected after chalky softening reactors for the filtration of softened water in the interest of achieving the desired degree of purity for ion exchanging charges or filter inserts. The apparatus according to the invention is advantageously usable in associated with the water removal works of any natural or artificial lake or river for the production of industrial or drinking water. WHAT WE CLAIM IS:

1. A process for purifying effluents for separating out suspended or emulsified contaminants from liquids, wherein the raw effluent to be purified is introduced into a purification space which is divided into a lower reaction space, a central or intermediate filtering space and an upper liquid space, the filtering space being bounded by a lower filter plate and an upper filter plate and accommodating a filter insert, a flocculating agent and the raw effluent is passed into the lower reaction space whereby to enclose the particles of the contaminants within cells formed by the flocculating agent, then the flocculated cells are passed into the pores of the filter insert, the thus bound contaminants together with the flocculated cells enclosing them are removed from the filter insert by the simultaneous application of liquid and air, whereby to render the filter insert capable again to bind flocculated cells, the purification of the effluent and the regeneration of the filter insert being performed in an alternating fashion and wherein the filter insert consists of a mass of particulate resilient material of a density such that the filter insert is lifted to be compressed by the upwardly flowing effluent against the upper filter plate, the purified liquid being withdrawn from the upper liquid space.

of a flocculating agent in a purification space by enclosing the contaminants inside cells formed by the flocks and then the flocks contaning the contaminants are retained on a regeneratable filter insert and are then removed from the liquid, and accordingly the apparatus includes a vessel which contains a purification space, which can be pressurised and which is provided with the filter insert, with means coupled or associated with the vessel suitable for feeding into the purification space the raw effluent to be purified, the flocculating agent(s) and air, and for removing purified water, wherein the purification space of the vessel is divided into a lower reaction space, a central or intermediate filtering space and an upper liquid space, the filtering space being bounded by a lower filter plate and an upper filter plate, the lower or bottom reaction space of the vessel is connected to a raw effluent inlet pipe, a flocculating agent infeed pipe, and sludgewater draining pipe for flushing out the caught contaminant; the upper liquid space of the vessel is connected to a purified liquid removal pipe, while in the filter space there is placed the filter insert which is formed of a mass of particulate resilient material.

11. Apparatus according to claim 10, wherein the filter insert consists of a heap of porous particles or a milling of a sponge-like foamed synthetic material.

12. Apparatus according to claim 10 or claim 11, wherein the filter insert is a heap of particles of different particle size in which the finest fraction is of 0.1 mm particle size or greater, while the coarsest fraction is of 25 mm or less.

13. Apparatus according to any of claims 10 to 12, wherein both the lower filter plate and the upper filter plate is fixedly secured in the purification space of the vessel.

14. Apparatus according to any of claims 10 to 13, wherein the inlet duct for the raw effluent to be purified, the inlet duct for the flocculating agent and the duct for removing the sludge liquid containing the filtered contaminants are combined into a common charging/discharging duct in the vicinity of the vessel.

15. Apparatus according to any of claims 10 to 14, wherein the filter insert is divided into layers with the aid of partition plates, expediently perforated plates.

16. Apparatus according to claim 15, wherein the perforated plates are fixedly installed in the vessel.

17. A process for purifying effluents substantially as herein described with reference to Figure 1 or Figure 2 of the accompanying drawing.

18. Apparatus for purifying effluents substantially as herein described with reference to and as shown in Figure 1 or Figure 2 of the accompanying drawing.