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WO2002004089A1 - Procede et dispositif de filtrage faisant intervenir des tubes filtrants souples - Google Patents

Procede et dispositif de filtrage faisant intervenir des tubes filtrants souples Download PDF

Info

Publication number
WO2002004089A1
WO2002004089A1 PCT/IB2001/001241 IB0101241W WO0204089A1 WO 2002004089 A1 WO2002004089 A1 WO 2002004089A1 IB 0101241 W IB0101241 W IB 0101241W WO 0204089 A1 WO0204089 A1 WO 0204089A1
Authority
WO
WIPO (PCT)
Prior art keywords
filter tube
filter
solids
liquid
feed liquid
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/IB2001/001241
Other languages
English (en)
Inventor
Visvanathan Lingamu Pillay
Chettiyappan Visvanathan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Water Research Commission
Original Assignee
Water Research Commission
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Water Research Commission filed Critical Water Research Commission
Priority to AU2001272684A priority Critical patent/AU2001272684A1/en
Publication of WO2002004089A1 publication Critical patent/WO2002004089A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/11—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with bag, cage, hose, tube, sleeve or like filtering elements
    • B01D29/13—Supported filter elements
    • B01D29/15—Supported filter elements arranged for inward flow filtration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/62—Regenerating the filter material in the filter
    • B01D29/66—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/62—Regenerating the filter material in the filter
    • B01D29/70—Regenerating the filter material in the filter by forces created by movement of the filter element

Definitions

  • THIS invention relates to an apparatus for separating solids from a feed liquid having the solids entrained therein.
  • a membrane bioreactor system of this type is free from the limitations that are imposed by a settling unit.
  • the average biomass concentration in the activated sludge, measured as mixed liquor suspended solids (MLSS) should not exceed 5 g MLSS/L and should preferably be between 3 and 4 g MLSS/L, in order to achieve safe separation of treated water from the activated sludge.
  • MLSS mixed liquor suspended solids
  • a membrane filtration unit allows an effectively complete retention of biomass in the bioreactor, regardless of the properties (such as size of floes, age, and so on) of the biomass, and ensures a high quality treated water.
  • the process enables a combination of high volumetric throughputs and high mass loadings that ensure good operational reliability and stability. Almost complete nitrification is possible as a result of the high sludge age. Sludge entrainment from the settling tank into the effluent resulting in insufficient denitrification is thus no longer possible.
  • membrane fouling and polarization still present a major problem in membrane bioreactor systems, and this often necessitates a high cross flow velocity and frequent cleaning of the membrane.
  • Various operational techniques have been devised to reduce fouling, for example, the use of air and liquid back-washing, and air agitation on the outside of the membrane.
  • a further object of the invention is to provide a membrane bioreactor system for waste-water treatment which has a long operational life and in which the problem of membrane fouling and polarization is minimised.
  • apparatus for separating solids from a feed liquid having the solids entrained therein, the apparatus comprising a collapsible tube of filter material which can be immersed in the feed liquid, an outlet line in fluid communication with the lumen of the filter tube, a porous support located inside the filter tube, to prevent the filter tube from collapsing due to a pressure differential between the inside and outside of the filter tube, and control means for cyclically reversing the pressure differential across the filter tube for back-washing purposes, wherein the circumferential extent, in cross-section, of the inside of the filter tube is greater than the circumferential extent, in cross-section, of the outside of the porous support so that, during back-washing, the material of the filter tube can inflate and separate from the porous support, whereby solid material that may have collected on the outside surface of the filter tube is dislodged as a result of this movement.
  • the porous support comprises a length of tubing having a porous side wall such as a length of pipe which may be circular in cross-section and has holes located along its length.
  • the apparatus may comprise a plurality of said filter tubes, the filter tubes being spaced from and parallel to one another.
  • each of the filter tubes is connected to an outlet manifold in fluid communication with the outlet line.
  • a first end of each of the filter tubes is connected to an inlet manifold in fluid communication with an inlet line.
  • a method of separating solids from a feed liquid having the solids entrained therein comprising the following steps: immersing a collapsible tube of filter material in the feed liquid; locating a porous support inside the filter tube to prevent the filter tube from collapsing; applying a pressure differential between the inside and outside of the filter tube; withdrawing a filtered liquid from the inside of the filter tube; and inflating the filter tube by reversing the pressure differential between the inside and outside of the filter tube to dislodge intermittently accumulated solids from the outer surface of the filter tube.
  • FIG. 1 diagrammatically illustrates a waste-water treatment installation which includes a membrane filter in accordance with an embodiment of the invention
  • Figure 2 is a detail section on ll-ll in Figure 1 ;
  • Figure 3 is a cross-sectional side view of a manifold for the membrane filter illustrated in Figure 1 ;
  • FIG. 4 is a detail section on IV-IV in Figure 3;
  • FIG. 5 diagrammatically illustrates a bioreactor which includes a membrane filter in accordance with an embodiment of the invention
  • Figure 6 is a graph in which the variation of influent and effluent ammonia and nitrate is plotted against time
  • Figure 7 is a graph in which COD removal is plotted against time, showing the COD removal at various recirculation rates.
  • Figure 8 is a graph illustrating the effect of the recirculation rate on nitrogen removal.
  • reference numeral 10 indicates a waste-water treatment installation, which comprises a pair of reactor vessels 12 and 14.
  • the total working volume of the two reactor vessels 12 and 14 is 40 litres, with the volume of the second reactor vessel 14 making up 55% of the total volume.
  • a feed pump 16 is provided for pumping raw effluent into the first reactor vessel 12 via a feed line 18.
  • feed line 18 For screening out coarse particles, there is a 750 ⁇ m circular disc screen 20 in the feed line 18.
  • Overflow from the first reactor vessel 12 flows into the second reactor vessel 14, as indicated by the line 22.
  • the first reactor vessel 12 forms an anoxic zone in which denitrification of the effluent takes place.
  • the first reactor vessel 12 is provided with an electric stirrer 24 for keeping solids in the effluent in suspension.
  • the second reactor vessel 14 forms an aerobic zone where carbon oxidation and nitrification of the effluent takes place. To this end, the second reactor vessel 14 is provided with an air diffuser 26 through which air is introduced into the liquid in the vessel 14.
  • Filtered water is withdrawn from the reactor vessel 14 via a membrane filter 28 according to the invention, which is immersed in the liquid in the reactor vessel 14.
  • the membrane filter 28 has a construction in cross-section which is illustrated in Figure 2. Thus, it comprises a series of side by side filter tubes 30 of woven filter cloth. In the lumen of each of the filter tubes 30 there is an internal support 32 which is in the form of a PVC tube having a wall which has holes drilled therein along the length of the tube. It should be understood that the internal support need not be a PVC tube, but could be any tubular porous support. Examples of porous supports are porous tubes, pipes with holes, springs, meshes, extruded or injection moulded formers etc. In the example illustrated the filter tubes 30 have a pore size of 5 ⁇ m, and a total surface area of 98 cm 2 .
  • the filter tubes could be made of any suitable flexible material including paper, a textile or another fabric of natural or man-made origin.
  • the material must be liquid permeable and have pores which can retain the solids entrained in the liquid feed.
  • the inside circumferential extent of each of the filter tubes 30 is greater than the outside circumferential extent of the porous supports 32.
  • the filter tubes 30, when fully inflated, have an inside diameter of 25 mm, whereas the porous supports 32 have an outside diameter of 20 mm. It should be understood that the exact dimensions of the filter tubes and porous supports depend on the specific application.
  • the lumens of the filter tubes 30 lead to a top manifold 34 along the upper edge of the membrane filter 28.
  • the manifold 34 is connected via a line 36 to the suction inlet of a suction pump 38, which pumps the filtered water that is withdrawn from the membrane filter 28 in reactor vessel 14 into a storage tank 40. Clarified water can be withdrawn from the tank 40 via an outlet valve 50.
  • the lumens of the filter tubes 30 further lead to a bottom manifold 42 along the lower edge of the membrane filter 28, the bottom manifold being, for purposes of back-washing, connected to the delivery outlet of a back- washing pump 44 via a line 46.
  • the bottom manifold 42 could act as an end-plate for sealing the ends of the lumens of the filter tubes 30 and the back-wash process could then be conducted by reversing the flow through the top manifold 34.
  • the manifold 52 comprises a casing 54 which is connected to an end block 56.
  • An inlet/outlet pipe 58 extends from the manifold 52, and the filter tubes 30 are connected to the end plate 56, with the lumens of the filter tubes 30 in fluid communication with the manifold 52.
  • Porous supports 32 are located within the filter tubes 32.
  • an aperture 60 is provided in the end block 56 for each filter tube 30.
  • the filter tube 30 is connected to the end block 56 by way of a tapering PVC tube 62 so that the filter tube 30 is in fluid communication with the manifold 52.
  • a recess 64 surrounds the aperture 60 and the filter tube 30 is attached to the recess 64 in the end block 56 by way of an adhesive.
  • the porous support 32 fits loosely about the tapering PVC tube 62.
  • a timer 66 is provided to control operation of the pumps 38 and 44.
  • the installation 10 is able to operate in a filtering mode and in a back-washing mode.
  • the pump 38 is switched on and the pump 44 is switched off, the pump 38 withdrawing filtered water from the reactor vessel 14 via the membrane filter 28 and pumping it to the storage tank 40.
  • the pump 38 When operating in the backwash mode, the pump 38 is switched off and the pump 44 is switched on, the pump 42 pumping filtered water from the storage tank 40 via the line 46 into the lumens of the filter tubes 30 of the membrane filter 28, via the manifold 42.
  • the timer 66 serves to switch the operation cyclically from one mode to the other, at predetermined intervals of time. It should be understood that, instead of having the timer 66 controlling the pumps, the pumps could be controlled by a controller which measures the pressure differential across the membrane filter.
  • the porous supports 32 serving to keep the lumens of the filter tubes open, i.e. to prevent the filter tubes 30 from collapsing completely. Solids which are unable to pass through the walls of the filter tubes 30 remain behind and collect on the outside surfaces of the filter tubes 30.
  • the filter tubes 30 When switching from operation in the filtering mode to operation in the back-washing mode, the filter tubes 30 inflate, causing the filter tubes 30 to expand and separate from the internal supports 32. This has the effect of dislodging solids that have collected on the outside surfaces of the filter tubes 30. Furthermore, clarified water now starts to flow in a reverse direction through the walls of the filter tubes 30, cleaning the filter tubes 30 through back-rinsing.
  • FIG. 5 there is shown a bioreactor vessel 68 which has a membrane filter 70 according to the invention immersed therein.
  • the membrane filter 70 has a construction similar to that described above with reference to Figures 1 and 4, having a top manifold 72 and a bottom manifold 74.
  • a pump 76 is provided for pumping raw liquor into the vessel 68, and a pump 78 for withdrawing clarified water from the vessel 68 via the membrane filter 70.
  • a further pump 80 is provided for pumping clarified water into the membrane filter via the manifold 74, for back-washing purposes.
  • Means may be provided for entraining air in the flow stream of clarified water pumped into the membrane filter during back-washing. It has been found that this increases the effectiveness of the back-washing procedure.
  • the volumetric loading into the system was between 0,4 and 0,9 kg COD/m 3 /d.
  • the concentration of the sludge in the system was between 4 and 6,5 g MLSS/L.
  • the pH was maintained between 7,2 and 8,2, and dissolved oxygen between 2,5 and 4,5 mg/L in the reactor vessel 14 and below 0,5 in the reactor vessel 12.
  • Measurements were taken at various values of the mixed liquor recirculation rate. Tests were done at various values of the mixed liquor recirculation rate, i.e. at values of 1 , 3, and 5.
  • Back-washing as described above was carried out at a cycle time of 120:15 (i.e. 120 minutes of filtration and 15 minutes of back-washing).
  • Table 1 sets out the quality of the raw feed water
  • Table 2 sets out the quality of the treated water extracted via the membrane filter, for the three operating conditions at which measurements were made. All the analyses were based on the average of samples taken every 24 hours. From the test results it can be seen that the COD reduction does not follow the operating condition used as shown in the graph of Figure 7.
  • the residual COD represents the soluble non-biodegradable COD of the treated effluent.
  • Nitrification was completed under the three conditions at which measurements were made, and are set out in the graph of Figure 6.
  • concentration of NH -N in the treated water was less than 1 ,0 mg/L.
  • the NO 3 -N concentration in the treated effluent changes with the mixed liquor recirculation rate.
  • the recirculation rate of 3 gives a better effluent quality, giving a concentration of less than 10mg NO 3 -N/L as shown in the graph of Figure 8. This shows that at a certain value of the recirculation rate higher percentage of nitrogen removal can be achieved from the system.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

L'invention concerne un filtre à membrane immergé destiné à recueillir un liquide exempt de solides à partir d'une suspension solide/liquide. Ledit dispositif est particulièrement adapté à un système de bioréacteur à membrane destiné au traitement de déchets. Le filtre à membrane immergé comporte une série de tubes souples constitués de matériau filtrant (30) pouvant être immergés dans un liquide à traiter. Les tubes (30) s'étendent vers un collecteur (52) relié à une conduit de sortie (58). Des supports poreux (32) sont disposés à l'intérieur des tubes filtrants (30) et empêchent les tubes filtrants (30) de se plier en raison d'une pression différentielle entre l'intérieur et l'extérieur des tubes filtrants (30). Le système de filtre à membrane immergé selon l'invention présente une durée de vie élevée durant laquelle le risque d'encrassement et de polarisation de la membrane est limité.
PCT/IB2001/001241 2000-07-12 2001-07-12 Procede et dispositif de filtrage faisant intervenir des tubes filtrants souples Ceased WO2002004089A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2001272684A AU2001272684A1 (en) 2000-07-12 2001-07-12 Filtration apparatus and process with collapsible filer tubes

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ZA2000/3493 2000-07-12
ZA200003493 2000-07-12

Publications (1)

Publication Number Publication Date
WO2002004089A1 true WO2002004089A1 (fr) 2002-01-17

Family

ID=25588822

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2001/001241 Ceased WO2002004089A1 (fr) 2000-07-12 2001-07-12 Procede et dispositif de filtrage faisant intervenir des tubes filtrants souples

Country Status (2)

Country Link
AU (1) AU2001272684A1 (fr)
WO (1) WO2002004089A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2789874A1 (es) * 2019-04-25 2020-10-26 Sist Azud S A Proceso de filtración de fluidos heterogéneos que presentan materia en suspensión

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH631352A5 (en) * 1977-11-15 1982-08-13 Chemap Ag Filter
DE3340452A1 (de) * 1983-11-09 1985-05-15 Huther & Co, 6521 Bechtheim Verfahren und vorrichtung zum abtrennen von truebstoffen aus truebfluessigkeiten
US4604201A (en) * 1977-04-28 1986-08-05 Dr. Muller AG Filter

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4604201A (en) * 1977-04-28 1986-08-05 Dr. Muller AG Filter
CH631352A5 (en) * 1977-11-15 1982-08-13 Chemap Ag Filter
DE3340452A1 (de) * 1983-11-09 1985-05-15 Huther & Co, 6521 Bechtheim Verfahren und vorrichtung zum abtrennen von truebstoffen aus truebfluessigkeiten

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2789874A1 (es) * 2019-04-25 2020-10-26 Sist Azud S A Proceso de filtración de fluidos heterogéneos que presentan materia en suspensión

Also Published As

Publication number Publication date
AU2001272684A1 (en) 2002-01-21

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