WO1995009038A1 - Procede et dispositif de filtration lente d'eau non traitee - Google Patents

Procede et dispositif de filtration lente d'eau non traitee Download PDF

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Publication number
WO1995009038A1
WO1995009038A1 PCT/FI1994/000433 FI9400433W WO9509038A1 WO 1995009038 A1 WO1995009038 A1 WO 1995009038A1 FI 9400433 W FI9400433 W FI 9400433W WO 9509038 A1 WO9509038 A1 WO 9509038A1
Authority
WO
WIPO (PCT)
Prior art keywords
filter
slow
water
filtration
raw water
Prior art date
Application number
PCT/FI1994/000433
Other languages
English (en)
Inventor
Juha Huhta
Original Assignee
Paroc Oy Ab
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 Paroc Oy Ab filed Critical Paroc Oy Ab
Publication of WO1995009038A1 publication Critical patent/WO1995009038A1/fr

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/02—Aerobic processes
    • C02F3/06—Aerobic processes using submerged filters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D24/00—Filters comprising loose filtering material, i.e. filtering material without any binder between the individual particles or fibres thereof
    • B01D24/02—Filters comprising loose filtering material, i.e. filtering material without any binder between the individual particles or fibres thereof with the filter bed stationary during the filtration
    • B01D24/10—Filters comprising loose filtering material, i.e. filtering material without any binder between the individual particles or fibres thereof with the filter bed stationary during the filtration the filtering material being held in a closed container
    • B01D24/12—Downward filtration, the filtering material being supported by pervious surfaces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D24/00—Filters comprising loose filtering material, i.e. filtering material without any binder between the individual particles or fibres thereof
    • B01D24/02—Filters comprising loose filtering material, i.e. filtering material without any binder between the individual particles or fibres thereof with the filter bed stationary during the filtration
    • B01D24/20—Filters comprising loose filtering material, i.e. filtering material without any binder between the individual particles or fibres thereof with the filter bed stationary during the filtration the filtering material being provided in an open container
    • B01D24/24—Downward filtration, the container having distribution or collection headers or pervious conduits
    • 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
    • B01D29/114—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 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
    • B01D29/39—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 hollow discs side by side on, or around, one or more tubes, e.g. of the leaf type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D35/00—Filtering devices having features not specifically covered by groups B01D24/00 - B01D33/00, or for applications not specifically covered by groups B01D24/00 - B01D33/00; Auxiliary devices for filtration; Filter housing constructions
    • B01D35/30—Filter housing constructions
    • B01D35/301—Constructions of two or more housings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D36/00—Filter circuits or combinations of filters with other separating devices
    • B01D36/02—Combinations of filters of different kinds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/58—Treatment of water, waste water, or sewage by removing specified dissolved compounds
    • C02F1/62—Heavy metal compounds
    • C02F1/64—Heavy metal compounds of iron or manganese
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2201/00—Details relating to filtering apparatus
    • B01D2201/10—Filtration under gravity in large open drainage basins
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00—Technologies for wastewater treatment
    • Y02W10/10—Biological treatment of water, waste water, or sewage

Definitions

  • the present invention relates to a filtration method and apparatus for treatment of raw water based on aeration, pretreatment and slow filtration of raw water pumped from an aquifer.
  • Water treated according to the invention is as such, or in some cases after optional al alization, ready for use.
  • Slow filtration is understood to refer to such a water treatment process in which the surface loading rate in the actual filtration step is smaller than 0.5 m/h (that is, m 3 water/h per 1 m 2 of filter surface) .
  • Slow filtration can be used for the treatment of both surface water and ground water.
  • the chief goals in slow filtration of surface water include improvement of the hygienic quality of the water, removal of solids and reduction of organic matter and nutrients.
  • slow filtration of ground water chiefly aims at removing iron and manganese. Other goals could be removal of ammonia, and in some cases, reduction of organic matter, too.
  • iron and manganese contained in the ground water are oxidized by air, whereby these ion species are converted from soluble form into solid form, and hence, can be removed from the water with the help of naturally occurring microbial fauna (biological treatment) and sedimentation mechanisms (using physico-chemical treat ⁇ ments) .
  • the elevated dissolved oxygen content and redox potential of the raw water required for the function of the iron and manganese bacteria employed in the oxidation process and biofiltration are attained by aeration.
  • Multiple different known arrangements are available for accomplishing the aeration such as ejector, tray or stepped-flow aerator.
  • Aeration of raw water also reduces the carbon dioxide content of the water and removes gases such as methane and hydrogen sulfide that degrade the smell and taste of water.
  • Pretreatment of raw water conventionally comprises at least a coarse filtration step which prior to the slow filtration step is capable of removing a major portion of iron contained in water. This contributes to a longer operating interval of the slow filter prior to its clogging.
  • the pretreatment process may also include a clarification step.
  • the filter medium accu ⁇ mulates filtered sediment which acts as a growth substrate for iron and manganese bacteria.
  • the strains of iron and manganese bacteria growing on this kind of substrate precipitate iron and manganese species contained in the water.
  • solids, microbes and other matter are retained by the filter.
  • Prior-art slow filters have comprised very large basins with a surface area of 5000 m 2 , and even more, in which pure sand is used as the filter medium.
  • the filter sand should have a grain size (d 10 ) of 0.15-0.75 mm, homogeneity factor (d 60 /d 10 ) of 1.5-3.4 and iron content less than 0.1 %. Furthermore, the sand should be free of humic matter and other impurities. Availability of such pure and homogeneous iron-free sand is a major problem. In summary, a sand filter is hampered by a large land requirement, rapid clogging of the filter surface, difficult cleaning of the filter and poor availability plus high cost of filter sand.
  • the embodiment according to the invention provides a high- performance, easy-to-service slow filter characterized by appreciably reduced headroom requirement need as compared to a conventional horizontal basin filter.
  • the filter elements are advantageously manufactured from mineral fiber which is stiffened by known binding methods to a desired shape. Then, the properties of the mineral fiber layer can be advantageously utilized including its excellent filtering capacity in a direction normal to the fiber orientation and high hydraulic conductivity in a direction parallel to the fiber orientation.
  • a slow filter is attained with a headroom requirement of only a fraction of that of a conventional horizontal pool filter.
  • the filter is also immediately in full operating condition after the replacement of the vertical filter elements, because the space between the elements on the bottom of the filter will contain a sufficient seeding amount of iron- and manganese-oxidizing bacteria to restore the biofiltra- tion process.
  • the filter can be readily constructed in a closed space, whereby the detrimental effects of naturally occurring impurities and sunlight on the water contained in the filter tank are avoided.
  • Figure 1 is a schematic representation of a conventional slow filtration process
  • Figure 2 is a schematic sectional side view of a lamellar slow filter according to the invention.
  • a conventional slow filtration method comprises pumping raw water from an aquifer to a raw water aerator 1 in order to elevate the dissolved oxygen content of water to a level sufficiently high for starting the biofiltration process.
  • the aerated water is prepurified in a coarse filter 3 which may be a rock-bed filter of crushed stone, for instance.
  • a coarse filter 3 which may be a rock-bed filter of crushed stone, for instance.
  • solids will be removed from the raw water, and from ground water in particular, a major portion of iron. This results in an essential lengthening of the clogging interval of the slow filter 4 proper.
  • the coarse filtered water further passes a clarification step 5 prior to the slow filtration step proper.
  • the slow filter 4 comprises a water inlet 6, a basin 7, a sand filter layer 8 and discharge means 9 of filtered water.
  • the sediment formed on the filtration surface 10 of the filtering sand layer 8 provides a growth substrate for the bacteria employed in the biofiltration process.
  • the surface area of the sand filter must be extremely large to assure a reliable long-term operation of the filter.
  • the surface sand layer of the slow sand filter is peeled off for a depth of several tens of centimeters with the help of earth moving equipment and replaced by fresh sand. Then, exhausted bacterial populations is lost almost entirely with the removed portion of filter sand bed.
  • a slow filter 4 comprises a modular unit formed by a covered container or tank 7 into which the water to be filtered flows via a separate water inlet 6, or alternatively, through a modular coarse filter unit 3 placed above the slow filter 4.
  • the tank bottom is provided with a mineral fiber bottom layer 11 and discharge means 9 of purified water. Projecting upward from the top of the mineral fiber layer 11 are placed a number of appropriately supported, vertical filter elements 8, advantageously made from mineral fiber into the shape of a slab, pipe or other functional element. The lower parts of the filter elements 8 may be inserted into the bottom layer 11 as shown in the diagram.
  • Fiber orientation in at least the center of the filter elements 8 is made parallel to the filtering surfaces 10 of the filter elements.
  • Water level 12 is controlled to such a level that yields a desired through-flow time for the water passing through the filter.
  • the vertically aligned filter elements 8 of the slow filter 4 comprise parallel-oriented mineral fiber slabs with a standard size of, e.g., 1200 mm x 650 mm and a thickness ranging from 40 mm to 140 mm. Accordingly, filtration takes place on both sides of the mineral fiber slab.
  • the filter elements 8 may also have a trapezoidal section, whereby the element thickness can be arranged to increase either upward or downward.
  • a downward flaring thickness is advantageously employed.
  • a filter element with upward increasing thickness may be the most preferable choice.
  • An extremely advantageous embodiment is achieved by fabri ⁇ cating the filter elements 8 into essentially vertical tubes made of bonded mineral fiber. Then, the filtration can be arranged either so that both the inner and outer surfaces of the tube act as filter surfaces 10, or alter- natively, so that only the outer surface acts as the filter surface 10, while the filtered water seeps into the core of the tube flowing therefrom along the inner surface of the tube to the collecting space arranged below the bottom layer 11. In the latter case the tubular elements must either extend above the water level 12, or alternatively, have closed upper ends.
  • the coarse filter 3 may advantageously have a construction similar to that of the slow filter 4.
  • the filter elements may also in this embodiment be fabricated from mineral fiber with properties suited for coarse filtering. Both the slow and coarse filter modular units may be connected in parallel and series as required.
  • the arrangement according to the invention offers a substantial reduction in the footprint of a slow filtration plant and/or extended maintenance interval of the filter.
  • the filter tanks can be constructed entirely closed, whereby a high water quality is easy to sustain.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Organic Chemistry (AREA)
  • Biodiversity & Conservation Biology (AREA)
  • Microbiology (AREA)
  • Biological Treatment Of Waste Water (AREA)
  • Purification Treatments By Anaerobic Or Anaerobic And Aerobic Bacteria Or Animals (AREA)
  • Filtering Materials (AREA)

Abstract

L'invention concerne un procédé et un dispositif de filtre conçu de sorte que la filtration puisse s'effectuer sur des surfaces de filtre pratiquement verticales. Les éléments du filtre sont en fibre minérale. L'encombrement au sol de la station de filtration est réduit, ce qui permet d'installer le filtre dans un espace clos. On peut ainsi éviter les effets de décomposition induits par les impuretés apparaissant naturellement et les effets du soleil sur la qualité de l'eau non traitée. Par ailleurs, l'entretien du filtre est plus facile et moins fréquent.
PCT/FI1994/000433 1993-09-27 1994-09-27 Procede et dispositif de filtration lente d'eau non traitee WO1995009038A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI934241 1993-09-27
FI934241A FI96001C (fi) 1993-09-27 1993-09-27 Menetelmä ja laite raakaveden hidassuodatusta varten

Publications (1)

Publication Number Publication Date
WO1995009038A1 true WO1995009038A1 (fr) 1995-04-06

Family

ID=8538671

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI1994/000433 WO1995009038A1 (fr) 1993-09-27 1994-09-27 Procede et dispositif de filtration lente d'eau non traitee

Country Status (3)

Country Link
FI (1) FI96001C (fr)
SE (1) SE9403262D0 (fr)
WO (1) WO1995009038A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0231587A2 (fr) * 1986-01-31 1987-08-12 Schewitz, Jonathan Méthode "Batch-filtration" et les moyens de contrôle du filtre
EP0264703A1 (fr) * 1986-10-13 1988-04-27 Siemens Aktiengesellschaft Filtre à couches
WO1989001814A1 (fr) * 1987-08-27 1989-03-09 Maelkki Esko Installation de filtration

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0231587A2 (fr) * 1986-01-31 1987-08-12 Schewitz, Jonathan Méthode "Batch-filtration" et les moyens de contrôle du filtre
EP0264703A1 (fr) * 1986-10-13 1988-04-27 Siemens Aktiengesellschaft Filtre à couches
WO1989001814A1 (fr) * 1987-08-27 1989-03-09 Maelkki Esko Installation de filtration

Also Published As

Publication number Publication date
SE9403262D0 (sv) 1994-09-27
FI96001B (fi) 1996-01-15
FI934241A0 (fi) 1993-09-27
FI96001C (fi) 1996-04-25
FI934241A (fi) 1995-03-28

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