AUSTRALIA Patents Act COMPLETE SPECIFICATION (ORIGINAL) Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: Zapf Wassersysteme GmbH Actual Inventor(s): Waldemar Schutz Address for Service and Correspondence: PHILLIPS ORMONDE & FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: FILTER SYSTEM AND METHOD FOR OPERATION THEREOF Our Ref: 764235 POF Code: 1108/476176 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): 6006q - 1A 11 January 2006 Zapf Wassersysteme GmbH Z105936 Bd/Sg/hei Filter system and method for operation thereof This application claims priority from German Application No.10 2006 001 486.3 filed 11 January 2006, the contents of which are to be taken as incorporated herein 5 by this reference. The invention relates to a filter system with a clear water storage tank and at least one filter element, wherein the wastewater side of the filter element is surrounded by the wastewater to be treated and wherein the wastewater, having passed 10 through the filter element, is then available on the filter side of the filter element in the form of clear water or filtrate. The invention further relates to a method for operation of such a filter system. Generally, such filter systems, which convert wastewater into clear water by filtra 15 tion, are used at municipal level, e.g. in the outflow of municipal sewage treat ment plants, for the production of drinking water, in industrial applications for the recycling of process water, as well as in private applications, such as in the pro duction of drinking water from rainwater, for decentralized water supply. 20 The aforementioned filter applications may employ, for example, membrane fil ters of the kind described e.g. in connection with European patent specification EP 1 016 449 B 1, which describes filter inserts with filter pockets which are disposed side-by-side on a carrying plate and which are provided above a filtrate collection chamber with a base with penetrations extending transversely to the filter pockets 25 in the region of recesses. Such filter inserts of membrane filters can be used, for example, for the treatment of wastewater. Generally, in the case of prior-art filter systems and, in particular, in the case of prior-art filter systems employing membrane filters, there is the problem that, over 30 the long term, said filters lose in their filtering effect, because dirt is accumulated on the wastewater side of corresponding filter elements, thereby restricting the -2 filtering effect. Furthermore, it is necessary, in order to maintain or in order to guarantee the filtering effect in the first place, for the filter to have a certain per meability. Conventionally, this is accomplished, for example, by extracting the filtrate on the filter side of the filter, this ensuring that there is always an 5 appropriate permeability for the wastewater which is to be filtered. However, such filter systems are relatively complex and cost-intensive, because special pumps must be provided in the water circuit. Furthermore, the necessary cleaning of such filters is time-consuming, because the filters must be removed for this purpose. 10 Therefore, the present invention describes a filter system and method for operation of a filter system which overcome the disadvantages of the prior art and which, while, in particular, being of simple and cost-effective design, provide safe and reliable operation with constantly good filtering effect, are easy 15 to clean and have a reduced degree of fouling over time. The present invention describes a filter system having the features according to claim I and by a method for operation of such a filter system having the features according to claim 10. Preferred embodiments are defined in the respective 20 subclaims. The present invention provides filter system with a clear water storage tank and at least one filter element, the clear water storage tank having a pressure tank, said pressure tank being in communication with the filter side of the filter -2a element via a connecting pipe, wherein the wastewater side of the filter element is surrounded by the wastewater to be treated and is subjected to pressure by a water column of the wastewater, the height of the water column and the pressure in the pressure tank being adjustable, so that it is possible to set a pressure 5 difference between the filter side and the wastewater side of the filter element. Furthermore, the present invention provides a method for operation of a filter system, having a clear water storage tank and at least one filter element, wherein the clear water storage tank has a pressure tank, said pressure tank being in 10 communication with the filter side of the filter element via a connecting pipe, wherein the wastewater side of the filter element is surrounded by the wastewater to be treated and is subjected to pressure by a water column of the wastewater, the height of the water column and the pressure in the pressure tank being adjusted such that a pressure difference is adjusted between the filter side 15 and the wastewater side of the filter element. The filter system according to the invention has a clear water storage tank and at least one filter element. The clear water storage tank has a pressure tank and the clear water storage tank is preferably the pressure tank, wherein the pressure 20 tank in in communication, via a connecting pipe, with a filter side of the filter element at which the clear water or filtrate is produced. The wastewater side of the at least one filter element is surrounded by the wastewater to be treated, the wastewater side of the filter element being subjected to pressure by a water column of the surrounding wastewater. According to the invention, the height of 25 the water column and the pressure in the pressure tank are adjustable, so that it is possible to adjust a pressure difference between the filter side and the wastewater side of the filter element. According to the invention, therefore, the pressure difference be- -3 tween the filter side and the wastewater side of the at least one filter element, and thus the thereto related permeability of the at least one filter element, are select able and adjustable through simple adjustability of the height of the pressure exerting water column of the wastewater on the one hand and on the other hand 5 through adjustment of the backpressure (over- and/or, where appropriate, under pressure with respect to the pressure on the wastewater side or with respect to the ambient pressure) on the filter side of the filter element through the adjustability of the pressure in the pressure tank, with the result that, under all operating condi tions, the adjustability of the pressure difference according to the invention makes 10 it possible to achieve a good filtering effect and/or reduced fouling and/or good cleaning action, without this requiring complex pump arrangements or similar in the water circuit of the filter system according to the invention, as is required in prior-art systems. 15 Especially simple is an embodiment of the filter system according to the invention in which the at least one filter element is height-adjustably disposed on a support in a wastewater tank. Consequently, through simple adjustment of the height of the at least one filter element on the support, it is possible to adjust the water col umn above the filter element in the wastewater tank. 20 In an especially preferred embodiment, the at least one filter element is a mem brane filter and, more especially, a plate-type membrane filter or a hollow-fibre membrane filter of the kind known to the person skilled in the art. 25 In order to achieve especially simple cleaning of any accumulated dirt residues on the wastewater side of the at least one filter element, according to a preferred em bodiment of the filter system according to the invention, the at least one filter element is adapted to be set to a backwash state through variation of the pressure difference, preferably through cyclical variation of the pressure difference, so that 30 the filter element is cleaned. Said preferred backwash state according to the inven tion is obtained when the pressure on the filter side of the filter element is greater -4 than the pressure on the wastewater side of the filter element, with the result that, particularly when a membrane filter is used as the filter element, said membrane is forced concavely outwards, so that any accumulated dirt residues can more easily be flushed away, e.g. through transverse inflow, with the wastewater or can more 5 easily be flushed away in an upward direction by air bubbles from an aeration means (see below). According to the invention, therefore, there is preferably in the backwash state substantially a reversal of the direction of flow through the filter element. Whereas, in the filter state, liquid passes from the wastewater side of the filter element to the filter side, in the backwash state filtrate or clear water passes 10 from the filter side of the filter element to the wastewater side of the filter ele ment, or increased pressure on the filter side of the filter element prevents waste water from passing through the filter element. In a preferred embodiment of the invention, the pressure tank of the clear water 15 storage tank may have a compressed-air port, preferably with a three-way valve, and the pressure tank of the clear water storage tank may preferably have a clear water outflow through which the filtered clear water or filtrate can be discharged. In order further to improve the filtering effect of the filter system according to the 20 invention, the filter system may, in a preferred embodiment, be provided with flow means, such as a pump, which effect a flow of the wastewater in the waste water tank, with the result that the wastewater to be treated flows around the at least one filter element, this being accomplished preferably in the form of a trans verse inflow into the filter element according to the invention. 25 In order further to improve the filtering effect and the cleaning effect of the filter system according to the invention, it is possible to provide an aeration means in the bottom region of the wastewater tank, preferably below the filter element, said aeration means blowing air under pressure into the wastewater. 30 -5 In a preferred embodiment of the invention, the filter element may have a pres sure-relief port, this allowing the pressure difference according to the invention to be adjusted in particularly simple manner. 5 In a particularly preferred embodiment, there is provided a plurality of filter ele ments, which, in a particularly preferred embodiment, are connected in series. Preferably, the filter system according to the invention may also comprise a de vice for automated water-minimum detection, i.e. a device for detecting the 10 wastewater level, said device permitting so-called "holiday operating mode". Fur thermore, automated detection of filter fouling may preferably be provided. The aforementioned aeration and transverse inflow into the filter elements or at least one filter element takes place in consideration of the duration of the backwash state, all the process parameters being suitably coordinated. 15 The filter system according to the invention makes it possible to guarantee reliable filter operation, the only device required outside of the water area (both wastewa ter side and clear water side) being a compressed-air generator for generating the pressure in the pressure tank according to the invention. Consequently, expensive 20 pump arrangements as in the prior art are not necessary in the filter system ac cording to the invention. In the method according to the invention for operation of the above-described filter system according to the invention, there is provided a clear water storage 25 tank and at least one filter element, wherein the clear water storage tank has a pressure tank, said pressure tank being in communication with the filter side of the filter element via a connecting pipe, wherein the wastewater side of the filter ele ment is surrounded by the wastewater to be treated and is subjected to pressure by a water column of the wastewater. According to the invention, the height of the 30 water column and the pressure in the pressure tank are adjusted such that a pres- -6 sure difference is adjusted between the filter side and the wastewater side of the filter element. In the method according to the invention, the pressure difference can be so ad 5 justed, preferably cyclically, that the filter element switches between a filter state and a backwash state, the filter element being cleaned in the backwash state. In the filter state, the filter element, or the filter side of the filter element, is under an external pressure, and wastewater is forced through the filter element owing to 10 the existing pressure difference. The thus produced filtrate or clear water is then removed via a connecting pipe and via the clear water storage tank, which is in communication with the filter side of the filter element. The dirt particles con tained in the wastewater, or the therein contained biomass, are trapped by the filter element, thereby forming over time a so-called auxiliary filter layer, which addi 15 tionally supports the filtration of dirt particles. Furthermore, said auxiliary filter layer prevents the filter pores from quickly becoming clogged. In the backwash state, the filter side of the filter element is subjected to corre sponding internal pressure. Filtered clear water or filtrate is forced through the 20 filter in the direction of the wastewater. The auxiliary filter layer, or dirt particles, which has/have built up in the course of time and which over time has/have accu mulated on the filter or filter membrane, clogging the filter pores, is/are thereby broken up and can be correspondingly removed from the wastewater side of the filter element by means of transverse inflow and/or aeration. This allows espe 25 cially simple and effective cleaning of the filter system according to the invention using the method of the invention. Preferably, between the filter state and the backwash state, there is a further pres sureless state in which the pressure difference between the wastewater side and 30 the filter side of the filter element is adjusted to 0 or to substantially 0. When use is made of a preferred membrane filter according to the invention, the filter mem- -7 brane is then relaxed, and no water (neither wastewater nor clear water or filtrate) passes through the filter layer. If the pressureless state lasts too long, however, the filter pores may become clogged by biological impurities in the wastewater. 5 In order further to improve the filtering effect and/or cleaning effect when using the method according to the invention, the wastewater may flow around the at least one filter element in a transverse flow. In order further additionally to improve the filtering effect and/or cleaning effect, 10 the wastewater may preferably be aerated by an aeration means, said aeration preferably taking place at least in the region of the at least one filter element. Preferably, the cleaning effect during backwashing may be additionally improved in that suitable reagents, which cause no damage to the biomass in the wastewater, 15 are dosed, preferably through the pressure-relief port, into the filter or filter ele ment, with the result that there is preferably in-situ cleaning of the at least one filter element. Hereinbelow, the invention is described on the basis of the description of a pre 20 ferred embodiment thereof with reference to the appended drawings, in which: Figure 1 shows a schematic view of a filter system according to a pre ferred embodiment of the invention; and 25 Figures 2a to 2c show schematically a cross-sectional view of a filter element in various states according to the present invention. Figure 1 is a schematic, partially cut-away, view of a filter system according to a 30 preferred embodiment of the invention.
-8 The filter system presented in Figure 1 has a clear water storage tank 1 and a se ries of parallel-arranged filter elements 2, with only one filter element 2 being shown in Figure 1. The filter element 2 is height-adjustably disposed on a support 5 in a wastewater tank. The corresponding arrow marker indicates the height of 5 the water level of the wastewater in the wastewater tank 6 during operation of the filter system according to the invention. The attachment of the filter element 2 or filter elements 2 to the support 5 may be in the form of clamping or in another suitable manner allowing a corresponding height adjustment in the wastewater tank 6. Corresponding attachment possibilities will be familiar to the person 10 skilled in the art and are, therefore, not described in any greater detail here. The clear water storage tank 1 has a pressure tank 3, said pressure tank 3 being in pressure communication with the filter side of the at least one filter element 2 or filter elements 2 via a connecting pipe 4. The wastewater side of the filter element 2 is completely surrounded by the wastewater to be treated and is subjected to 15 pressure by the water column which is the result of the difference of the wastewa ter level and the fill level of the water in the clear water storage tank. The height of the water column is adjustable via the height of the level of the wastewater and/or via adjustment of the height of the filter element 2 or filter elements 2 on the support 5 and the pressure in the pressure tank 3 is adjustable via a com 20 pressed-air port 7 with a three-way valve such that a pressure difference between the filter side and the wastewater side of the at least one filter element 2 is adjust able according to the invention. The resulting level of the clear water in the clear water storage tank 2 or in the pressure tank 3 of the clear water storage tank 1 is likewise indicated by a corresponding arrow marker in Figure 1. The at least one 25 filter element 2 or filter elements 2 are preferably connected in series and are preferably formed of corresponding plate-type membrane filters generally known from the prior art. The at least one filter element 2 or filter elements 2 has/have a pressure-relief port 11. In the embodiment shown in Figure 1, the arrangement of the filter elements 2 is surrounded by the clear water storage tank 1 with its pres 30 sure tank 3, it being possible, from the bottom side and from the top side, for the wastewater to flow to and from the filter elements 2, as is indicated by the corre- -9 sponding arrows in Figure 1. The flow around the filter elements 2 is accom plished in Figure 1 by transverse inflow into the filter elements 2, there being pro vided a flow means 9 which causes a corresponding flow of the wastewater in the wastewater tank 6. The flow means 9 may preferably be a simple (recirculating) 5 pump or similar. Provided in the bottom region of the wastewater tank 6 below the filter elements 2 is an aeration means 10 which can be subjected to a supply of compressed air, with the result that corresponding air bubbles can be introduced into the wastewater and are able to rise upwardly along the filter elements 2. The clear water can be removed from the clear water storage tank I via a clear water 10 outflow 8. The operating principle of the filter system according to the invention is best illus trated with reference to Figures 2a to 2c, which each schematically present differ ent operating states of an individual filter element 2 of the filter system according 15 to the invention when using the method according to the invention. Figure 2a shows the filter system according to the invention in a filter state, in which the filter membrane of the filter element 2 is convexly curved, because the pressure difference between the filter side and the wastewater side of the filter 20 element 2 results in an exertion of pressure by the water column of the around flowing wastewater, the pressure in the pressure tank of the clear water storage tank (not shown in Figure 2a) being so adjusted that it is lower than the pressure caused by the corresponding water column. Consequently, as indicated by the arrows in Figure 2a, a pressure of water is exerted by the wastewater on the mem 25 brane surface of the filter element 2, said pressure of water forcing the wastewater to and through the membrane, the filtered clear water or filtrate then being re moved on the filter side of the membrane, as indicated by the up and down arrows in Figure 2a. Formed on the membrane of the filter element 2 is an auxiliary filter layer 12 consisting of accumulated dirt particles from the wastewater. The pres 30 sure in the pressure tank 3 may be provided in the form of a partial vacuum which actively removes the clear water. Alternatively, however, it is possible to provide - 10 a positive pressure in the pressure tank 3, wherein, however, said positive pressure is lower in relation to the pressure of the water column of the wastewater in the wastewater tank 6, this resulting in the filter state shown in Figure 2a. 5 Figure 2b shows the (according to the invention) preferred pressureless state of the filter element 2 of the filter system according to the invention, in which the filter membrane of the filter element 2, disposed between the two fixed membrane carriers on the top and bottom sides of the filter element 2, is in the relaxed state, i.e. extending vertically straight in cross-section; no clear water is removed or 10 supplied, nor does any wastewater pass through the membrane of the filter ele ment 2. Figure 2c shows the filter system according to the invention in a backwash state, wherein, through corresponding adjustment of the pressure difference between the 15 filter side of the filter element 2 and the wastewater side of the filter element 2 through a corresponding increase of the pressure in the pressure tank 3 of the clear water storage tank 1 (not shown in Figure 2c) via the connecting pipe 4 and/or through adjustment of the height of the water column of the wastewater acting on the wastewater side of the filter element 2, an increased pressure (in comparison 20 with the exertion of pressure by the water column of the wastewater) is produced on the filter side of the filter element 2, with the result that clear water or filtrate passes through the membrane of the filter element 2, this being illustrated by the corresponding arrows in Figure 2c, which point in the opposite direction to the direction of the arrows in Figure 2a. As a consequence thereof, the filter mem 25 brane 2 is concavely curved, as a result of which the accumulated auxiliary filter layer 12 is also concavely curved and can correspondingly be rejected from the membrane of the filter element 2, as is likewise indicated by the arrows in Figure 2c. The removal of the particles of the auxiliary filter layer 12, or of accumulated dirt, can be effected through a transverse inflow into the filter element 2 with 30 wastewater and/or through transverse inflow with blow-air. This results in the cleaning of the filter element 2.
- 11 The phases of operation of the filter system according to the invention as shown in Figures 2a to 2c may take place cyclically in succession at certain intervals, with the result that, under all given operating conditions, it is always possible to guarantee the optimal filtering and/or cleaning effect of the filter elements 2 5 without this requiring complex pumps or other cleaning operations. In particular, it is not necessary, as is often otherwise usual in the prior art, for the filter elements 2 to be especially removed for cleaning purposes, this significantly reducing the operating costs of such a filter system according to the invention in comparison with the conventional filter systems. 10 The cleaning effect during backwashing can be additionally improved in that suitable reagents, which cause no damage to the biomass in the wastewater, are dosed, preferably through the pressure-relief port or tube 11, into the filter or filter element 2. 15 Throughout the description and claims of this specification, the word "comprise" and variations of the word, such as "comprising" and "comprises", is not intended to exclude other additives, components, integers or steps. 20 The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of 25 each claim of this application.