United States Patent
`
`[19]
`
`Schoeberl
`
`[54] APPARATUS FOR THE STERILIZATION OF
`WATER
`
`[76]
`
`Inventor: Meinolf Schoeberl, Geigelsteinstrasse
`8, Prien D-8210, Germany
`
`[21] Appl. No.:
`
`920,510
`
`[22] PCT Filed:
`
`Dec. 19, 1991
`
`[86] PCT No.:
`
`PCT/EP91/02459
`
`§ 371 Date:
`
`Oct. 1, 1992
`
`§ 102(e) Date:
`
`Oct. 1, 1992
`
`lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll
`
`USOOS439576A
`
`[11]
`
`[45]
`
`Patent Number:
`
`Date of Patent:
`
`5,439,576
`
`Aug. 8, 1995
`
`5,094,734
`5,108,563
`
`204/234
`3/1992 Torrado
`4/1992 Cook ................................... 204/149
`
`
`
`FOREIGN PATENT DOCUMENTS
`
`7/1989 European Pat. Off.
`0322478
`2644155 12/1990 France .
`2176497 12/1986 United Kingdom .
`W085/01965
`5/1985 WIPO.
`
`.
`
`Primary Examiner—John Niebling
`Assistant Examiner—Arum Phasge
`Attorney, Agent, or Firm—Townsend and Townsend
`Khourie and Crew
`
`[87] PCT Pub. No.: WO92/11209
`
`[57]
`
`ABSTRACT
`
`PCT Pub. Date: Jul. 9, 1992
`
`[30]
`
`Foreign Application Priority Data
`
`Dec. 19, 1990 [DE] Germany ........................ 40 40 694.6
`
`Int. Cl.6 .............................................. C02F 1/461
`[51]
`[52] US. Cl. .................................... 204/263; 204/269;
`204/272; 204/275; 204/290 R; 204/290 F
`[58] Field of Search ........... 204/269, 272, 275, 290 R,
`204/290 F, 149, 263
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`3,305,472 2/ 1967 Oldershaw .......................... 204/268
`4,202,738 5/ 1980 Stillman ................ 204/95
`
`5/1985 Pellegri et a].
`..
`..... 204/275
`4,519,889
`
`....... 204/95
`4,761,208
`8/1988 Gram et a1.
`
`4,997,540
`3/1991 Howlett ......
`204/271
`5,062,940 11/1991 Davies ................................. 204/228
`
`An apparatus for sterilizing water by anodic oxidation.
`A reactor contains a plurality of anodes (3) and cath-
`odes (4) arranged as parallel plates within the reactor.
`The anodes and cathodes are arranged in series within
`four modules (2). Each module includes two draw bolts
`(34, 44) extending through bores in the anodes and
`cathodes and threadably engaged to contact bolts (7) on
`either side of the module. The contact bolts provide
`high surface pressure to the anodes and cathodes so that
`high electrical currents can be conducted through the
`reactor. The anodes each consist of materials that pro-
`vide a greater overvoltage with respect to oxygen gen-
`eration than with respect to chlorine generation. Thus,
`the reactor can produce a sufficient quantity of oxidants
`to sterilize the water without adding chlorine com-
`pounds to the water.
`
`3 Claims, 6 Drawing Sheets
`
`2
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`
`3
`
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`
`Tennant Company
`Exhibit 1108
`
`Tennant Company
`Exhibit 1108
`
`

`

`US. Patent
`
`Aug. 8, 1995
`
`Sheet 1 of 6
`
`5,439,576
`
`
`
`

`

`US. Patent
`
`Aug. 8, 1995
`
`Sheet 2 of 6
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`5,439,576
`
`
`
`

`

`US. Patent
`
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`5,439,576
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`US. Patent
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`Aug. 8, 1995
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`Sheet 4 of 6
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`US. Patent
`
`Aug. 8, 1995
`
`Sheet 5 of 6
`
`5,439,576
`
`Fig°7
`
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`

`US. Patent
`
`Aug. 8, 1995
`
`Sheet 6 of 6
`
`5,439,576
`
`Fig.8
`
`1”
`
`‘
`
`15
`
`61.
`
`
`
`

`

`1
`
`5,439,576
`
`APPARATUS FOR THE STERILIZATION OF
`WATER
`
`BACKGROUND OF THE INVENTION
`
`The invention relates to an apparatus for the steriliza-
`tion of water by means of anodic oxidation comprising
`a reactor through which water flows and which has at
`least one anode and one cathode and also a power sup-
`ply means.
`Apparatus of this kind is for example known from
`DE—OS 2757 854. There the anodes and cathodes are
`formed by bars which are arranged in a grid-like man-
`ner and extend transversely through the reactor. The
`bars of the anode and of the cathode are respectively
`electrically combined with one another by a connection
`element which is connected in each case to the power
`supply. Between the bar grid of the anode and the bar
`grid of the cathode there are arranged a plurality of
`subsidiary electrode bar grids which extend parallel to
`the bars of the anode and the bars of the cathode. In this
`arrangement bar grid planes which lie behind one an-
`other in the flow direction are displaced in such a way
`that one bar of a subsequent bar grid plane is laterally
`displaced approximately into the centre of the spacing
`between two bars of a preceding bar grid plane.
`This arrangement of electrodes or subsidiary elec-
`trodes is intended to ensure that
`the liquid passes
`through a region of changing potentials with turbu-
`lence.
`A reactor is known from DE-PS 28 61 889 in which
`the electrodes are formed as bar or grid-like individual
`elements and through which water flows in cross—flow.
`In this manner, a turbulent flow is obtained in the reac-
`tor to improve of the convective material exchange at
`the electrode-phase boundary.
`These known devices bring about considerable gen-
`eration of electrolysis gases in addition to sterilization
`and these electrolysis gases adhere to the electrode
`surfaces and are intended to be carried away by the
`eddying of the flow.
`SUMMARY OF THE INVENTION
`
`It is the object of the present invention to devise an
`apparatus of the initially named kind in such a way that
`a reliable sterilizing effect is obtained with a longer life
`time of the electrodes and with a simultaneous reduc-
`tion in the formation of undesired gas bubbles and side
`reactions in the reactor.
`
`This object is satisfied in the apparatus of the inven-
`tion, in that a gap of constant gap width is provided
`between the mutually confronting surfaces of the anode
`and cathode. The gap width is dimensioned such that a
`pronounced and preferably laminar flow forms between
`the mutually confronting surfaces of the anode and
`cathode in the water flowing through the gap. The and
`in that the anode consists of a material which has an
`anode overpotential greater with respect to the genera-
`tion of oxygen than with respect to the generation of
`chlorine from chloride ions.
`
`The constant gap width over the surface of the elec—
`trodes which lie opposite to one another thereby en-
`sures the laminar flow and thus the formation of an
`essentially homogenous electrical field between the
`electrodes.
`As a result of the laminar flow between the mutually
`confronting surfaces of the anode and cathode,
`it is
`ensured that even with only low concentrations of dis-
`
`5
`
`10
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`15
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`20
`
`25
`
`30
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`35
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`4O
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`45
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`50
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`55
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`6O
`
`65
`
`2
`solved chloride ions in the water, the chloride ions are
`transported by means of electrostatic migration in the
`homogenous potential
`field uniformly to the anode
`boundary layer without being hindered in their migra-
`tory movement by turbulent flow vectors. At the same
`time it is ensured, through the choice of the anode mate-
`rial in accordance with the invention, that the undesired
`generation of molecular oxygen (and thus the undesired
`gas bubble formation on the electrode surfaces) is re—
`duced with respect to the generation of chloroxy acids,
`their salts and other oxidants which can be determined
`
`as chlorine equivalents (such as for example all oxidants
`which can be detected with DPD (Diethyl-p-phenyli-
`dene diamine, predominantly HOCl and 0C1).
`The core of the anode consists of a valve metal, such
`as for example titanium, niobium or tantalum ensuring
`that it forms a protective stable oxide layer in the elec-
`trolyte. Thus no corrosion of the anode core arises in
`regions in which the coating of the anode core has gaps.
`The efficacy of such an anode is improved because a
`plurality of layer pairs are provided which are alter-
`nately deposited. Through the special smooth surface of
`the anode, the long-term constancy of the anode activ-
`ity is
`increased—in contrast
`to customary elec-
`trolysis—because the entire active surface of the anode
`is not blocked by layers of adsorbate as a result of the
`low surface roughness.
`The modular construction of the apparatus increases
`the economy of manufacture and servicing of the appa-
`ratus. Moreover, it is in this way made possible for a
`plurality of electrode modules to be connected together
`as an electrical series circuit. In this manner, a consider-
`able enlargement of the active reactor volume and of
`the anode surface is possible, while retaining the preset
`potential and respectively pervading between the anode
`and the cathode, without
`the current which flows
`through the reactor increasing in total. As result of the
`series circuit of the modules, the necessary electrical
`power increase is obtained via an increase of the poten-
`tial applied to the reactor as a whole.
`The contacting of the electrodes extensively prevents
`resistive polarisation as a result of the high surface pres-
`sure between the boundary surfaces of the electrodes
`and the spacer elements. Thus,
`the electro-chemical
`corrosion at the boundary surfaces is almost avoided.
`This contacting is particularly reliable and effective
`under water and can be released again at any time.
`A measuring device for determining the chlorine
`equivalents of the oxidants present in the water and also
`a regulating unit, which further processes this measur-
`ing signal for the regulation of the power supply means,
`are provided in the flow direction after the reactor.
`Thus, a particularly effective automatic operation of the
`apparatus can take place.
`An apparatus of this kind is in particular suitable for
`carrying out the method of sterilizing water by means of
`anodic oxidation. The water is led through a reactor
`having at least one anode and one cathode, with the
`total electrical current density being capable of being
`changed through the determination of the concentra—
`tion of the chlorine equivalents of the oxidants and the
`comparison of this measure concentration with the de-
`sired value, namely the concentration which is neces-
`sary to kill off the germs.
`
`

`

`3
`
`5,439,576
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`4
`plates 21, 21’ are provided at their face confronting the
`inner side of the frame with grooves 24 arranged along-
`side one another and extending parallel to the axis X of
`the housing 10. A web 22, which projects into the inner
`space of the frame, can be respectively seen between the
`grooves 24.
`The grooves 24 serve for the guidance of plate-like
`
`electrodes 3, 4 which are inserted into the frame is
`which extend parallel to the side walls 23, 23' of the
`frame 20 and the plate size of which amounts preferably
`to approximately 200 mm>< 100 mm. Although only
`three electrodes are drawn in by way of example in
`FIG. 2, each groove pair 24, 24’ serves to guide an
`electrode, with the cathode 4 and anode 3 alternating
`and respectively determining a gap 25 between them
`which has the width of the associated web 22 or 22’
`(preferably about 1.3 mm,) with the respective thickness
`of the anode and cathode being about 1 mm. With this
`electrode arrangement,
`the number of cathodes is
`greater by one than that of the anodes so that a cathode
`contacts each of the side walls 23, 23’ without a gap
`being formed between this outermost cathode and the
`associated side wall 23, 23’.
`The space 26 between the outer side of the frame 2‘3
`and the inner side of the tubular housing 10 is sealed off
`relative to the inner space of the frame and is for exam—
`ple filled with foam. The sealing relative to the inner
`space of the frame 20 can, for example, take place by
`circular segment-like covers secured in the region of the
`inlet flange 11 to the end sides of the frame walls, with
`the covers which form the opening cross section for the
`water flowing through the reactor, only leaving free the
`preferably quadratic inner surface of the frame 20.
`Each housing section 10’, 10”, 10’”, 10”” has an elec»
`trode module 2’, 2”, 2’", 2”" laid out as previously de—
`scribed and arranged in a frame 20.
`A section along the line IV—IV of FIG. 2 is shown
`by FIG. 4. There, the housing 10 and also one contact
`opening 14 are shown purely sectionally. FIG. 4 shows
`the alternating arrangement of anodes 3 and cathodes 1:-
`with the gaps 25 lying between them. Each anode 3 and
`each cathode 4 has two openings of different diameter
`which are spaced apart from one another. The smaller
`opening 33 or 43 is thereby formed for the loose passage
`of a draw bolt 34 for the anode and a draw bolt 44 for
`the cathode respectively. The larger opening 45 of the
`cathode 4 permits the passage of the draw bolt 34 for
`the anode, with a radial spacing being provided be“
`tween the draw bolt 34 and the edge of the opening 45.
`In just the same way the large opening 35 of the anode
`3 permits the passage of the draw bolt 44 of the cathode
`4 while maintaining a radial spacing. The respective
`draw bolt 34 or 44 can consist of electrically conductive
`or non-conductive material.
`The contacting of the electrodes relative to one at —
`other will be explained further in connection with the
`example of the cathode 4 with reference to FIG. 5. FIG.
`5 shows the cut—out portion designated by V in FIG. I}.
`The draw bolt 44 passes through the smaller opening
`43’, 43’ of the sequential cathodes 4', 4”, with sufficient
`spacing remaining between the respective opening 43’,
`43” and the outer periphery of the draw bolt 44, that an
`axial movement of the draw bolt 44 is possible. Between
`the sequential cathodes 4’, 4”, there is provided a con-
`ductive spacer ring of a valve metal, preferably of tita-
`nium, the end surfaces of which contact the confronting
`surfaces of sequential cathodes 4’, 4”. The inner diarnew
`ter of the spacer ring 46 thereby corresponds essentially
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`20
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`25
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`3O
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`35
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`The invention will be explained in more detail in the
`following by way of an example and with reference to
`the drawing in which are shown:
`FIG. 1 illustrates a side view of a reactor of the appa--
`ratus of the invention,
`FIG. 2 illustrates a section on the line 11—11 through
`the reactor of FIG. 1,
`FIG. 3 illustrates a contact bolt, for the reactor of 10
`FIG. 1,
`FIG. 4 illustrates a section through an electrode mod—
`ule corresponding to the sectional direction IV—IV in
`FIG. 2,
`FIG. 5 illustrates a cut—out portion of an electrode
`module in accordance with V in FIG. 4,
`FIG. 6 illustrates an enlarged illustration of the anode
`assembly,
`FIG. 7 illustrates the potential behaviour of a pre—
`ferred anode material, and,
`FIG. 8 illustrates the schematic assembly of an appa-
`ratus of the invention with a regulation provided.
`In FIG. 1 there is shown a reactor 1 of an apparatus
`for sterilizing water which has a tubular housing 10
`with an inlet flange 11 and also an outlet flange 12 pro—
`vided at its axial ends.
`The housing 10 has four substantially identical hous—
`ing sections 10’, 10”, 10’”, 10””, which essentially fol~
`low one another over its axial extent. Each of these
`housing sections is provided at diametrically oppositely
`disposed locations with a first contact opening 13 and a
`second contact opening 13’ for the anode connection
`and a first contact opening 14 and also a second contact
`opening 14’ for the cathode connection The contact
`openings 13, 13’, 14, 14’ are formed as radially extending
`tubular sections which penetrate the wall of the housing
`10 and are sealingly connected in pressure-tight manner
`with the wall of the housing 10 at their outer periphery.
`The first contact opening 13, 14 and the second contact
`openings 13’, 14’ are respectively arranged alongside
`one another in the direction of the axis X of the tubular
`housing 10.
`As each housing section is provided with contact
`openings 13, 13’, 14, 14’, a housing 10 has a plurality of
`mutually diametrically oppositely disposed first and
`second contact opening pairs corresponding to the
`number of housing sections, as can be seen in FIG. 1.
`FIG. 2 represents a cross section through a reactor 1
`in accordance with the line 11—11 in FIG. 1. The tubu-
`lar cross section of the housing 10 with the two radially
`oppositely disposed first and second contact openings
`14, 14' for the cathode connection can be clearly recog-
`nized. A square frame 20, inserted into the tubular hous-
`ing 10, serves to accommodate the electrodes 3, 4 and
`consists preferably of food quality PVC. The corners of 55
`the frame 20 are chamfered off or rounded at the outer
`sides and the frame 20 is accurately fitted into the hous-
`ing 10 in such a way that the chamfered or rounded
`corners contact the inner side of the tubular housing 10.
`The upper edge and the lower edge of the frame
`thereby extend parallel to the axis 14” common to the
`contact openings 14, 14’.
`The frame 20 consists of two lateral frame walls 23,
`23’ which are respectively disposed adjacent the first
`and second contact opening for the anode connection
`and the cathode connection 13, 14; 13’, 14’. The upper
`and lower wall of the frame 20 are formed by an upper
`comb plate 21 and by a lower comb plate 21’. The comb
`
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`

`5,439,576
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`5
`to the bores 43’, 43”, so that the spacer ring 46 also does
`not hinder an axial movement of the draw bolt 44. Radi-
`ally outside of the conductive spacer ring 44, there is
`arranged an insulating intermediate ring 47, the inner
`periphery of which surrounds the outer periphery of the
`spacer ring 46. In the axial direction,
`the insulating
`intermediate ring 47 is somewhat shorter than a conduc-
`tive spacer ring, or is resilient, and its end faces contact
`confronting surfaces of the sequential cathodes 4, 4'.
`The outer periphery of the insulating intermediate ring
`27 thereby contacts the inner periphery of the large
`opening 35 of the anode 3’ disposed between the cath-
`odes 4’, 4”.
`The cathode-side draw bolt 44 is provided at its ends
`with a respective threaded section 44’, 44”. The anode-
`side draw bolt 34 also has threaded portions 34’ and 34"
`at its ends.
`The contacting of the cathodes shown in FIG. 5
`relative to one another takes place in the following
`described manner. A contact bolt 7 which is shown in
`more detail in FIG. 3 is screwed by means of an inner
`thread 70, which is provided in an axial bore 71, dis-
`posed at one end of the contact bolt 70 onto each
`threaded end 44', 44” of the cathode—side draw bolt 44.
`At the end of the contact bolt 7 provided with the inner
`thread 70, the contact bolt has a ring-like end face 72
`which enters into contact with the outer surface of the
`outermost cathode 4’” and presses the latter towards the
`spacer ring 46' disposed on the other side of this cath-
`ode. This then presses in turn against the subsequent
`cathode 4” which in turn presses against the next spacer
`ring 46 etc. The contact bolt 7’ which is screwed onto
`the thread 44’ lying at the other end of the draw bolt 44
`presses in the same manner against the cathode which is
`placed closest to it.
`If now the contact bolts 7, 7’ are tensioned relative to
`one another then a very high surface pressure arises at
`the respective parting positions between the end face 72
`of the draw bolt, the cathode 4’”, the spacer ring 46’, the
`cathode 4", the spacer ring 46, the cathode 4’ etc., and
`reduces the respective electrical
`transition resistance
`and thus permits the conduction of high electrical cur-
`rents between the contact bolts and between the cath-
`odes while minimising resistive losses. In this way, resis-
`tive polarisation is avoided at the contact surfaces and
`the associated corrosion is prevented.
`The anodes are electrically contacted relative to one
`another and with the contact bolts associated with them
`which (not shown) in a similar manner. As, however, a
`cathode is always disposed first adjacent the side walls
`23, 23’ of the frame 20, a contact bolt presses in the
`region of the anode contacting (at the top of FIG. 4)
`with its ring-like end face 72 initially against the ring-
`like end face of a conductive spacer ring 36. This in turn
`presses against the anode 3" adjacent to it etc. The
`contacting of the electrode module shown in FIG. 2 to
`the external power supply or to the next module takes
`place via the cathode contact bolts 7, 7’ and also via the
`anode—side contact bolts, which are not shown in FIG.
`4.
`
`The contact bolts 7, 7' are let out of the housing in
`sealed manner through the associated contact passages
`14, 14' for the cathode. In a similar manner, the non-
`illustrated anode—side contact bolts are led out of the
`housing through the contact passages 13, 13’.
`For sealing purposes, a contact bolt 7 has two axially
`spaced apart circumferential grooves 73, 74 into which
`a sealing ring 75, 76 is in each case inserted.
`
`6
`The sealing rings 75, 76 cooperate in a sealing manner
`with the groove 73 or 74, respectively and with the
`inner periphery of the contact passage 14, 14’; 13, 13’.
`At a remote end from the axial bore 71, the contact
`bolt 7 is provided with an axial spigot 78 while forming
`a contact surface 77, with the axial spigot being formed
`to accommodate a known cable shoe. An axially di—
`rected threaded bolt 79 joins the axial spigot 78 and is
`formed for the screwing on of a suitable nut which
`presses the non‘illustrated cable shoe of a connection
`cable against the contact surface 77.
`FIG. 6 shows the build-up of an anode. On an anode
`core, which preferably consists of a valve metal such as
`titanium, there is applied a first layer 31 of a suitable
`conductive material onto which a second layer 32 of
`another suitable conductive material is applied. A first
`layer can again be provided on this second layer and a
`second layer can again follow the first layer etc. One of
`the two layers 31, 32 consist of a titanium-mixed oxide
`and the other of the two layer consists of a platinum-
`iridium alloy. It is not important which of the two lay-
`ers is first applied to the anode core 30; the important
`feature is solely that the layers 31, 32 alternate with one
`another. A coating can be dispensed with in the region
`of the anode contacting,
`i.e. in the ring surface sur-
`rounding the smaller opening 33 (which is in contact
`with the spacer rings), which are present in order to
`improve the electrical conductivity between the anodes
`and the adjoining spacing rings), so that the spacing
`rings directly contact the core 30 of the anode formed
`of valve metal. The cathode preferably comprises (non-
`rusting) stainless steel, such as V2A-steel.
`Contrary to the customary aim in electro-synthesis of
`V reducing the anode overpotential of a particular reac-
`tion through high surface roughness, the subject of the
`application endeavours to keep the overvoltage of the
`oxygen separation as high as possible relative to the
`overpotential for chlorine separation through the pre-
`described choice of the sequentially following anode
`layers.
`FIG. 7 shows the potential behaviour of the selective
`anode with the above described construction (shown in
`broken lines). The anode potential in volts is shown on
`the ordinate and the current density in mA/cm2 is
`shown on the abscissa. The continuous curve shows the
`chlorine generation and the chain-dotted line shows the
`oxygen generation. In the entire region above the inter-
`section point of the two curves, the oxygen partial flow
`density ioz is smaller than the chlorine partial flow den-
`sity iCLz. In this way, it is ensured that on the one hand
`the oxygen generation is reduced to a desirable mini-
`mum level even at high current densities, and on the
`other hand, as a result of the high potential, oxygen
`compounds with a high oxidation potential (peroxo
`compounds of also singular oxygen) predominantly
`arise alongside the OH radical.
`Through the predescribed construction of the anode,
`it is ensured, even with low chlorine concentrations
`(under 10 mg/l), such as occur in fresh water, that for a
`relatively low electrical current one can generate an
`adequate quantity of oxidants for reliable sterilization of
`the water and these oxidants can be determined as chlo-
`rine equivalents.
`FIG. 8 shows the build-up of a regulated apparatus
`for the sterilization of water with the reactor 1, through
`which water flows from below upwardly in the direc-
`tion of the arrows W, W’. The reactor consists, in accor-
`dance with the illustration of FIG. 1, of four electrode
`
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`

`7
`modules 2', 2", 2’”, 2”” which are arranged in series in
`the flow direction. In this arrangement, the cathode-
`side of the first electrode module 2’ is connected to the
`negative output pole of a power supply means 5 via a
`minus supply line 67. For the uniform introduction of
`current into the electrode module 2’ the minus supply
`line 67 has been branched off, with each branch being
`connected to one of the contact bolts 7, 7’ shown in
`FIG. 4. The two anode-side contact bolts of the elec—
`trode module 2’ are connected via bridge line 68, 69
`with the cathode—side contact bolts of the electrode
`modules 2”. In this manner, the electrode modules 2”
`and 2’” and also 2’” and 2”” are electrically connected
`together. The two branches of a likewise branched
`positive supply line 66 are connected to the anode-side
`contact bolts of the last electrode module 2”” and con—
`nect the anodes of the last electrode module 2”” to the
`positive connection pole of the power supply means 5.
`A measuring device 60 is arranged in the discharge
`channel 15 disposed downstream of the reactor and the
`oxidants contained in the water, which can be deter-
`mined as chlorine equivalents, can be measured. The
`measuring device 60 is connected via a measurement
`line 63 with a computing unit 62 via which measure-
`ment data is delivered from the measuring device 60 to
`the computing unit 62.
`The computing unit 62 derives from the measurement
`data that is supplied to it, the concentration of the oxi-
`dants contained in the water of the discharge channel
`which are determined as chlorine equivalents. From
`this concentration, the computing unit derives the chlo—
`ride partial current density using data supplied to it by
`the power supply means 5 which represents the electri-
`cal current flowing through the reactor and in the
`knowledge of the total active electrode surface in the
`reactor. A value proportional to this chloride partial
`current density is passed on to a computing unit 61 via
`a data line 64. In the computing unit 61, this derived
`value for the partial chloride current density is com—
`pared with the corresponding value of a chloride partial
`current density of a predetermined concentration of
`free oxidants which can be determined as chlorine
`
`equivalents. The difference value resulting from this
`comparison is converted by the computing unit into a
`control signal which is supplied via a control line 65 of
`the power supply means 5.
`The power supply means 5 draws its electrical energy
`from an AC power source indicated by a wavy line. It
`converts this DC power into a DC current with the DC
`voltage lying at the DC terminals designated with +
`and —— of the power supply means 5 for the power
`supply lines 66 and 67 of the reactor 1 being automati—
`cally set in accordance with the electrical current flow
`predetermined by the regulating unit 61. A preferred
`DC voltage lies in the range from 6 to 7 volts per elec-
`tric module, so that as result of the series connection of
`the electric modules in the example of FIG. 8 approxi-
`mately 24 to 28 volts are present at the outputs of the
`power supply means 5.
`The predescribed regulating circuit makes it possible
`to set the whole apparatus in accordance with the mi—
`crobial burden of the water to a predetermined concen-
`tration of free oxidants which can be determined as
`chlorine equivalents. This setting must be carried out on
`the installation of the apparatus and can be repeated at
`large time intervals as a check. Changes of the con—
`straints relative to the electric-chemical process which
`may occur from time to time, such as for example
`
`5
`
`10
`
`15
`
`2O
`
`25
`
`30
`
`35
`
`4O
`
`45
`
`50
`
`55
`
`6O
`
`65
`
`5,439,576
`
`8
`changes of the conductivity of the water or changes of
`the efficacy of the individual electrode modules, are
`detected by the measuring and regulating device 6 as a
`result of the thereby occurring changed concentration
`of the oxidants in the discharge channel which are de—
`termined as chlorine equivalents. Thereupon the electri—
`cal current which flows through the reactor is regulated
`by the regulating means 6 in the sense of a correction of
`the chloride partial current density.
`in particular
`It has turned out to be advantageous,
`with respect to the life of the anodes, when the anode
`comprises a valve metal core with a homogenous elec—
`tro—catalytically active coating, which is predominantly
`composed of a compound of titanium and at least one
`platinum metal in oxidizing and/or non-oxidizing form.
`I claim:
`
`1. An apparatus for sterilizing water by anodic oxida—
`tion comprising:
`a reactor having at least one anode and at least one
`cathode, the reactor having a gap of constant width
`between mutually confronting surfaces of the
`anode and the cathode,
`the anode comprising a
`material that has a greater overvoltage with re—
`spect to oxygen generation and with respect
`to
`chlorine generation;
`a power supply means connected to the anode and
`the cathode in series for supplying an electric cur--
`rent between the anode and the cathode;
`a plurality of electrode modules, each electrode mod—
`ule having a plurality of anodes and cathodes alter-
`natively arranged within the module;
`anode spacer elements disposed between each anode,
`the anode spacer elements contacting a contact
`surface of each anode to electrically connect the
`anodes to each other;
`cathode spacer elements disposed between each cat1~
`ode,
`the cathode spacer elements contacting a
`contact surface of each cathode to electrically cont-
`nect the cathodes to each other; and
`means for pressing the anode and cathode spacer
`elements together under high pressure to generate
`a high specific surface pressure at the contact sur»
`faces of the anodes and the cathodes.
`2. The apparatus of claim 1 wherein the pressing
`means comprises:
`a cathode draw bolt disposed through a first coaxial
`connection bore in each cathode and anode, the
`cathode draw bolt extending through the module
`and having a threaded portion on either side of the
`module, the cathode spacer elements being annular
`rings disposed around the cathode draw bolt be»
`tween the anodes and the cathode draw bolt;
`an anode draw bolt disposed through a second coax-
`ial connection bore in each cathode and anode, the
`anode draw bolt extending through the module and
`having a threaded portion on either side of the
`module, the anode spacer elements being annular
`rings disposed around the anode draw bolt between
`the cathodes and the anode draw bolt; and
`contact bolts threadably engaged to the threaded
`portions of the anode and cathode draw bolts, the
`contact bolts being adapted to apply a tensile stress
`to the draw bolts thereby pressing the anode and
`cathode spacer elements together on either side of
`the module.
`3. The apparatus of claim 2 further comprising:
`a plurality of first annular spacer rings disposed
`around the cathode draw bolt, each first annular
`
`

`

`5,439,576
`
`9
`spacer ring separating an anode from the cathode
`spacer elements so that the anodes are insulated
`from the cathode spacer elements and the cathodes;
`and
`a plurality of second annular spacer rings disposed 5
`
`10
`around the anode draw bolt, each second annular
`spacer ring separating a cathode from the anode
`spacer elements so that the cathodes are insulated
`from the annular spacer elements and the anodes.
`*
`*
`*
`*
`*
`
`10
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`6O
`
`65
`
`