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WO1997029997A1 - Method and plant for purification of contaminated water - Google Patents

Method and plant for purification of contaminated water Download PDF

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Publication number
WO1997029997A1
WO1997029997A1 PCT/DK1997/000061 DK9700061W WO9729997A1 WO 1997029997 A1 WO1997029997 A1 WO 1997029997A1 DK 9700061 W DK9700061 W DK 9700061W WO 9729997 A1 WO9729997 A1 WO 9729997A1
Authority
WO
WIPO (PCT)
Prior art keywords
water
ozone
basin
purification
nozzles
Prior art date
Application number
PCT/DK1997/000061
Other languages
Danish (da)
French (fr)
Inventor
Povl Kaas
Original Assignee
Aqua System A/S
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 Aqua System A/S filed Critical Aqua System A/S
Priority to AU17188/97A priority Critical patent/AU1718897A/en
Priority to PCT/DK1997/000061 priority patent/WO1997029997A1/en
Publication of WO1997029997A1 publication Critical patent/WO1997029997A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/04—Filters with filtering elements which move during the filtering operation with filtering bands or the like supported on cylinders which are impervious for filtering
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/44—Regenerating the filter material in the filter
    • B01D33/46—Regenerating the filter material in the filter by scrapers, brushes nozzles or the like acting on the cake-side of the filtering element
    • B01D33/461—Regenerating the filter material in the filter by scrapers, brushes nozzles or the like acting on the cake-side of the filtering element brushes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/44—Regenerating the filter material in the filter
    • B01D33/46—Regenerating the filter material in the filter by scrapers, brushes nozzles or the like acting on the cake-side of the filtering element
    • B01D33/463—Regenerating the filter material in the filter by scrapers, brushes nozzles or the like acting on the cake-side of the filtering element nozzles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/44—Regenerating the filter material in the filter
    • B01D33/48—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps
    • B01D33/50—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps with backwash arms, shoes or nozzles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/58—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/70—Filters with filtering elements which move during the filtering operation having feed or discharge devices
    • B01D33/74—Filters with filtering elements which move during the filtering operation having feed or discharge devices for discharging filtrate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/80—Accessories
    • B01D33/804—Accessories integrally combined with devices for controlling the filtration
    • B01D33/807—Accessories integrally combined with devices for controlling the filtration by level measuring
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/04—Feed pretreatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B01D61/147—Microfiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
    • B03D1/00—Flotation
    • B03D1/02—Froth-flotation processes
    • 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
    • C02F1/30—Treatment of water, waste water, or sewage by irradiation
    • C02F1/32—Treatment of water, waste water, or sewage by irradiation with ultraviolet light
    • 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
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
    • 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
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/78—Treatment of water, waste water, or sewage by oxidation with ozone
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2201/00—Details relating to filtering apparatus
    • B01D2201/38—Preventing rewetting of the filter cake on the filter media
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/04—Specific process operations in the feed stream; Feed pretreatment
    • 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
    • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
    • 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
    • C02F1/24—Treatment of water, waste water, or sewage by flotation
    • 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
    • C02F1/42—Treatment of water, waste water, or sewage by ion-exchange
    • 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
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • 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
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
    • C02F1/56—Macromolecular compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/16—Nitrogen compounds, e.g. ammonia
    • C02F2101/163—Nitrates

Definitions

  • the invention concerns a method for purification of contamina- ted water from especially oxidizable impurities.
  • Contaminated water is led out in great amounts as sewage from, for example, households and industries. It is required that the impurities of the sewage is removed to an excessively ex ⁇ tend, before the water is released to the recipient.
  • This pu ⁇ rification takes place, for example, in the municipal plant, where a number of processes is being used to remove and neu- tralize the impurities of the sewage.
  • a common part of the purification process is that the impurities are brought to flocculate in great basins with chemicals, which are added to the water. The created floes are precipitated as sludge, which is removed by means of, e.g. scrapers.
  • the impurities can consist of organic substances, pesticides, tensides, organic and chemical solvents and colour residues.
  • water which is contaminated with such sub ⁇ stances, can be purified by means of ozone, which usually in the form of bubbles rising through the water, exposes the sub ⁇ stances to heavy oxidation. Thereby the substances are preci ⁇ pitated as particles which can be removed by means of a filter or similar device.
  • the conventional ozone purification plants thus known have, however, a disproportionately large expenditure of ozone in relation to the purification effect obtained, and the reaction time is very long causing the necessity to use very large and expensive reaction basins. Further, the additional ozone is led out to the environment endangering person, who might be in the surroundings.
  • the object of the invention is to provide a method of the pri ⁇ or cited type, which with less use of ozone and more effi ⁇ cient than previously known, can purify the contaminated water.
  • a second object of the invention is to provide a method of the prior cited type, being adapted in such a way that the additi- onal ozone is not released to the surroundings.
  • a third object of the invention is to provide a method of the prior cited type, by means of which suspended and dissolved impurities in the sewage are brought to flocculate without addition of chemicals.
  • the new and unique by means of which this is obtained accor ⁇ ding to the invention, is that the contaminated water is led into a purification basin, where there at a first set lead-
  • a third object of the invention is to provide a method of the prior cited type, by means of which suspended and dissolved impurities in the sewage are brought to flocculate without addition of chemicals.
  • the new and unique by means of which this is obtained accor- ding to the invention, is that the contaminated water is led into a purification basin, where there at a first set lead- in's, which in reciprocal distance are dispersed between two of the opposite sides of the basin and preferably are situated near the bottom of the basin, ozone is suppplied in the form of small, fine bubbles, and that there at a second set of le ⁇ ad-in's at distance from the first set of lead-in's, and equ ⁇ ally preferably near the bottom of the basin, ozone is sup- plied in the form of bubbles, which are substantially larger than the first mentioned fine bubbles.
  • the small, fine bubbles have in combination a exceedingly large tangent surface with the water and the ozone is therefo ⁇ re quickly and efficiently brought to process large amounts of impurities.
  • the reaction products are almost momentarily for- ming a shell around each of the fine bubbles, which at the same time loose buoyancy, due to the reduced contents of ozone in the bubbles as the ozone, to a larger or smaller degree, is used for the reaction.
  • the fine bubbles with their shell of reaction products will therefore not change level substantially, while they are pushed across the bottom of the basin by new fine bubbles, which in a continuous stream are led into the basin.
  • the fine bubbles are colliding with the rising large bubbles, whereby each one of the large bubbles is catch ⁇ ing an amount of fine bubbles.
  • the bubbles merge, and the shell around the many fine bubbles are now settling as a whole shell around the large bubbles.
  • the ozone content of the large bubbles will to a greater or smaller extend be used for a continuous reac ⁇ tion with the substances not finished to react in the surroun ⁇ ding shell, and for the reaction with fresh impurities in the water.
  • the invention also concerns a plant for purification of conta ⁇ minated water for especially oxidizable impurities, and which comprises a purification basin for the contaminated water, an ozone source for, when in operation, providing the plant with ozone for purifying the water, a reaction container, which, when in operation, partly is supplied with water from a water source to a predetermined level in the container by means of a first pressure pump, partly is supplied with ozone under pres ⁇ sure from the ozone source via a gas conduit by means of a second pressure pump, which preferable is a sparkfree membrane pump, a first set of nozzles, which preferably at the bottom are place in the basin between two of the opposite sides of this basin, and which via at least a first water conduit are connected to the water in the reaction container, a second set of nozzles, which preferably at the bottom are placed in the basin at a distance from the first set of nozzles, and which are connected to at least one other water conduit, which is connected to as well the ozone source
  • the water which is added to the reaction container can with advantage be the contaminated water.
  • the whole water stream can be brought to pass the reaction container, where then an initial purification process will take place, and at the same time the water will be enriched with ozone.
  • greater water volumes are to be purified, it will, howe ⁇ ver, for practical reasons be much more expedient to let only part of the contaminated water run through the reaction container.
  • the water in the reaction container will have to absorb as much ozone as possible, and the pressure in the container must be relatively high, e.g. 10 bar. At such high pressures there is a risk that the ozone will explode, and as pressure pump for pumping the ozone from the ozone source to the reaction container, a membrane pump of sparkfree plastic can therefore expediently be used.
  • the ozone is led into the reaction container via the suction side zone, whereby it can be ensured at its optimum that the inflow of the ozone into the reaction container takes place in a wet atmosphere.
  • a second advantage which is obtained by means of this method consists of the fact that the ozone quickly is suspended in the form of fine bubbles in the water and/or is dissoluted in the water.
  • the level of the water surface is indirectly registered by means of a pressure difference gauge, which continuously measures the difference in pressure between the top and the bottom of the reaction container.
  • the measured difference in pressure is a measure for the height of the wa ⁇ ter column.
  • the pressure difference gauge is then adjusted, by deviations from a given set value, which represents the prede ⁇ termined height of the water column, to give a signal to the first pressure pump to pu p more or less water into the reac ⁇ tion container in dependence of the present value of the signal.
  • the sewage volume can vary with the time, and the same applies to the degree of contamination.
  • the purification process can ⁇ not go at its optimum, if there during the changing conditions all the time is send the same amount of ozon enriched water through a set of nozzles. According to the invention there is therefore in the water conduits for each of the two sets of nozzles inserted a valve for regulating the pressure and/or volume of the water which is added.
  • an leak of ozone can endanger the per ⁇ sons in the surroundings of the plant.
  • the purification basin is covered with a bellshaped cover for collection of additional ozone from the purification pro- cess.
  • the collected ozone is, mixed with the existing air in the bassin, led past a cooler for drying of the air mixture, which then is sent past at least one UV lamp, whereby the ozone is converted into oxygen.
  • the air mixture which now has a large contents of oxygen, is now streaming through a gas conduit to an oxygen membrane, which only allows oxygen mo ⁇ e- culars to pass.
  • the oxygen deriving from this process is fi ⁇ nally used in an ozone generator for the production of new ozone for the process. With this arrangement the nessecity of having do leak additional ozone to the surroundings will be eliminated. At the same time the process is cost saving, since the additional ozone expediently can be used again in a closed cycle.
  • Fie. l diagrammatically shows a plant according to the inven ⁇ tion to purify contaminated water
  • Fig. 2 schematically shows in principle an embodiment of the purification process according to the invention.
  • the main components in the purification plant shown in fig. 1 is a ozone generator 1, a reaction container 2 and a purifica ⁇ tion basin 3.
  • the contaminated water, which is to be purified, is in the case shown led into a main stream 4 to the purifica ⁇ tion basin 3 and in a secondary stream 5, which is drawn with a dotted line, to the reaction container 2.
  • the contaminated water can derive from many different sources.
  • the fish industry or other foodstuffs factories with sewage which typically has a large contents of organic substances.
  • the purification process can advantageously be a part of a larger process, where, in one or more previous steps solidstate substances as e.g. gravel and sand is removed, and in the succeeding steps for example nitrite will be removed.
  • the plant operates with ozone as the sole purification mean.
  • the osone is produced in the ozone generator 1 by oxygen co ⁇ ming from an oxygen membrane 6, which only allows the contents of oxygen moleculars of the air to pass.
  • the ozone generator can, for example, be of the type, which uses a high voltage area to influence a current of dry oxygen or air with electri ⁇ cal discharges, whereby a part of the oxygen moleculars are decomposed to free atoms.
  • Oxygen atoms connecting with present oxygen moleculars forms the' ozone.
  • the formed ozone is pumped by a membrane pump 7, consisting of a sparksafe type of plastic, into the reaction container under a high pressure, e.g. 10 bar.
  • the secondary stream 5 of contaminated water is pumped by a pressure pump 8 into the reaction container 2 via an ejector 9 under equally high pressure.
  • the ejector will in this process suck in ozone, which thereby quickly and efficiently will be suspended in the form of fine bubbles in the water and/or be dissolved in the water.
  • the ozone enriched water will via a water conduit 10 with a regulation valve 11 be led into the purification basin 3 via a first set of nozzles 12.
  • the amount of ozone pumped into the reaction container must be at a level, in relation to the wa ⁇ ter volume pumped in at the same time, that the water is su ⁇ persaturated with ozone under a high pressure.
  • the water in the reaction container is therefore filled with an enormous amount of very small, fine bubbles, which in the following will be referred to as microbubbles. Due to the presence of the microbubbles a float will sink to the bottom in the water. It is, however, with reasonable limits, necessary to be able to fix the height of the water surface in the reaction contai ⁇ ner. If the water surface is rising above a certain height, the ejector will be flooded, and not able to function as pre ⁇ supposed. If the container is emptied, there will via the wa ⁇ ter conduit 10, the regulation valve 11 and the nozzles 12 stream ozone directly into the purification basin 3, so that the aimed purification process is prohibited.
  • the plant according to the invention comprises therefore a pressure difference gauge 13, which via cables 14 and 15 mea ⁇ sures the pressure in the top and at the bottom, respectively, of the reaction container, and registers the difference in pressure.
  • the difference in pressure represents the height of the water column, and the pressure difference gauge is there- fore adjusted with a set value, which is equal to a predeter ⁇ mined height. If the registered difference pressure at a given moment deviates from this set value, the pressure difference gauge will via a cable 16 send a signal to the pressure pump 8 to increase or decrease the water volume, until the registered deviation from the set value is zero, and the water surface therefore will be at the predetermined level in the reaction container 2.
  • the first set of nozzles 12 are, as shown, placed in the wall of the purification basin and near the bottom. At some distan ⁇ ce from this set of nozzles there is likewise at the bottom placed a second set of nozzles 17, which are supplied with ozone enriched water via a water conduit 18, in which there is inserted a pressure pump 19, an ejector 20 and a regulation valve 21.
  • the ozone generator 1 is via a cable 22 connected to the suc ⁇ tion side of the ejector 20, whereby the water in the cable 18 is enriched with ozone.
  • the water is streaming in the water conduit 18 in this case in a cicuit from the purifi ⁇ cation basin with purified water and back again to the purifi- cation basin with ozone enriched water.
  • the water supplied by the second set of nozzles can, however, come from a different source.
  • the special mode of operation is explained in fig. 2, which in principle shows the process in the purification basin 3.
  • Ozone enriched water is pressed under high pressure, e.g. 10 bar, via the water conduit 10 and the first set of nozzles 12 into the contaminated water in the purification basin 3 near the bottom 25 of the basin. Further, ozone enriched water is pressed under somewhat lower pressure, e.g. 3 bar, via the water conduit 18 and the second set of nozzles 17 at the bot ⁇ tom 25 in a distance from the first set of nozzles 12, into the contaminated water in the purification basin 3. Pressure, ozonebearing and nozzle construction are adjusted in such a way that there at the first set of nozzles arise fine bubbles or microbubbles 23 and at the second set of nozzles large bubbles or macrobubbles 24.
  • microbubbles which are in an enormous amount and to a substantial degree already have been formed in the reaction container 2, have, if combined, an enormous surface, and their aggressive ozone content begin immediately to react with the surrounding impurities in the water.
  • Fig. 2 is very simplified and shows only one single microbubble in its various develop ⁇ ment stages, during which there succeedingly is formed a shell of reaction products around the bubble.
  • the ozone content is completely or partly used in the proces and will therefore not, as could be expected, rise in the water, but are instead being displaced to the right ⁇ in the figure) by the succeeding microbubbles, which continuously stream in through the nozzles 12.
  • the macrobubbles 24 from the nozzles 17 run equally through a number of development stages, while they as shown rises from the bottom to the water surface. In this process they encoun ⁇ ter a lot of microbubbles and merge.
  • the shells of the micro- bubbles will form a new shell around the ascending macro- bubbles, and the remaining ozone content will at the same time process non-processed substances in the shell and not yet pro ⁇ Switchd impurities in the water.
  • the content of ozone in the macrobubbles will therefore gradu ⁇ ally be reduced, as the shell increases. At the surface the bubbles will burst and the shells will collapse to floes 26, while the remaining ozone in the bubbles is released.
  • the floes 26 are removed by means of a belt filter for microfiltration 27 of the type described in the applicants' Danish Patent Application No. 0145/96, to which is referred as a reference.
  • the microbubbles 23 are so fine, that they are not visible to the naked eye but are manifested as a milky white fog in the water.
  • the water is milky white and therefore filled with microbubbles.
  • the milky fog has disappeared, which signify that the contents of ozone in the bubbles is used in the reactions processes and/or that the microbubbles have merged.
  • the purification process will normally not use the supplied amount of ozone to the fullest extend.
  • the additional ozone will therefore accumulate under a bellshaped cover 29, cove ⁇ ring the purification basin 23.
  • the accumulated ozone is, mixed with air, led from the bellshaped cover and by a cooler 30, which cools off and consequently dries the air mixture.
  • the dried air mixture is then led past a number of UV lamps, which by radiation decomposes the ozone to oxygen.
  • the dry, oxygen enriched air mixture is finally led, via a gas conduit 30, to the oxygen membrane 6, which detains all other gasses but oxygen, which, as previously described, is used as raw material in the ozone generator 1 for the production of ozone for the purification process.
  • the additional ozone is thus being recycled in the plant and is reused repeatedly economic expedient instead of being rele- ased into the invironment where the ozone could be harmful to persons in the surroundings.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Water Supply & Treatment (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Nanotechnology (AREA)
  • Treatment Of Water By Oxidation Or Reduction (AREA)

Abstract

A method and a plant serving the purpose of purifying water with ozone from especially oxidizable impurities. The plant comprises a purification basin (3) for the contaminated water, an ozone source (1) for, when in operation, supplying the plant with ozone for purification of the water, a reaction container (2), which, when in operation, partly is supplied with water from a water source to a predetermined level in the container by means of a first pressure pump (8), partly is supplied with ozone under pressure from the ozone source via a gas conduit with a second pressure pump (7), which preferably is a spark-free membrane pump. At the bottom of the basin is placed a first set of nozzles (12) which via at least one first water conduit (10) is connected to the water in the reaction container. A second set of nozzles (17) which, at the bottom are placed in the basin at a distance from the first set of nozzles, are connected to at least one second water conduit (18) which is connected to the ozone source as well as to a water source and has a third pressure pump (19) for, when in operation, driving the water through the conduit with a pressure which is smaller than the pressure in the reaction container. The plant can with less use of ozone efficiently purify the water from impurities. The additional ozone is recycled in an economic expedient way instead of being released into the environment and endangering the surroundings. Suspended and dissolved impurities in the waste water can be brought to flocculate without addition of chemicals.

Description

Method and plant for purification of contaminated water.
The invention concerns a method for purification of contamina- ted water from especially oxidizable impurities.
Contaminated water is led out in great amounts as sewage from, for example, households and industries. It is required that the impurities of the sewage is removed to an excessively ex¬ tend, before the water is released to the recipient. This pu¬ rification takes place, for example, in the municipal plant, where a number of processes is being used to remove and neu- tralize the impurities of the sewage. A common part of the purification process is that the impurities are brought to flocculate in great basins with chemicals, which are added to the water. The created floes are precipitated as sludge, which is removed by means of, e.g. scrapers.
The impurities can consist of organic substances, pesticides, tensides, organic and chemical solvents and colour residues. It is known that water, which is contaminated with such sub¬ stances, can be purified by means of ozone, which usually in the form of bubbles rising through the water, exposes the sub¬ stances to heavy oxidation. Thereby the substances are preci¬ pitated as particles which can be removed by means of a filter or similar device. The conventional ozone purification plants thus known have, however, a disproportionately large expenditure of ozone in relation to the purification effect obtained, and the reaction time is very long causing the necessity to use very large and expensive reaction basins. Further, the additional ozone is led out to the environment endangering person, who might be in the surroundings.
The object of the invention is to provide a method of the pri¬ or cited type, which with less use of ozone and more effi¬ cient than previously known, can purify the contaminated water.
A second object of the invention is to provide a method of the prior cited type, being adapted in such a way that the additi- onal ozone is not released to the surroundings.
A third object of the invention is to provide a method of the prior cited type, by means of which suspended and dissolved impurities in the sewage are brought to flocculate without addition of chemicals. The new and unique by means of which this is obtained accor¬ ding to the invention, is that the contaminated water is led into a purification basin, where there at a first set lead- A third object of the invention is to provide a method of the prior cited type, by means of which suspended and dissolved impurities in the sewage are brought to flocculate without addition of chemicals.
The new and unique by means of which this is obtained accor- ding to the invention, is that the contaminated water is led into a purification basin, where there at a first set lead- in's, which in reciprocal distance are dispersed between two of the opposite sides of the basin and preferably are situated near the bottom of the basin, ozone is suppplied in the form of small, fine bubbles, and that there at a second set of le¬ ad-in's at distance from the first set of lead-in's, and equ¬ ally preferably near the bottom of the basin, ozone is sup- plied in the form of bubbles, which are substantially larger than the first mentioned fine bubbles.
The small, fine bubbles have in combination a exceedingly large tangent surface with the water and the ozone is therefo¬ re quickly and efficiently brought to process large amounts of impurities. The reaction products are almost momentarily for- ming a shell around each of the fine bubbles, which at the same time loose buoyancy, due to the reduced contents of ozone in the bubbles as the ozone, to a larger or smaller degree, is used for the reaction.
The fine bubbles with their shell of reaction products will therefore not change level substantially, while they are pushed across the bottom of the basin by new fine bubbles, which in a continuous stream are led into the basin. During this process the fine bubbles are colliding with the rising large bubbles, whereby each one of the large bubbles is catch¬ ing an amount of fine bubbles. The bubbles merge, and the shell around the many fine bubbles are now settling as a whole shell around the large bubbles. During the continuous rising through the water, the ozone content of the large bubbles will to a greater or smaller extend be used for a continuous reac¬ tion with the substances not finished to react in the surroun¬ ding shell, and for the reaction with fresh impurities in the water. When the bubbles have reached the surface, they will break, whereby the remaining ozone is set free, while the shells are collapsing and form floes which easily can be remo¬ ved by means of, e.g. a belt filter for micro filtration. As it can be seen, these floes are thus created without use of those chemicals which normally are used to flocculation in the conventional plants.
The finest bubbles, and thereby the most efficient purificati¬ on of the contaminated water, are obtained, when they are cre¬ ated through an overpressure to drive water, which is supersa¬ turated with ozone, into the contaminated water through nozzles which are placed in the basin. The invention also concerns a plant for purification of conta¬ minated water for especially oxidizable impurities, and which comprises a purification basin for the contaminated water, an ozone source for, when in operation, providing the plant with ozone for purifying the water, a reaction container, which, when in operation, partly is supplied with water from a water source to a predetermined level in the container by means of a first pressure pump, partly is supplied with ozone under pres¬ sure from the ozone source via a gas conduit by means of a second pressure pump, which preferable is a sparkfree membrane pump, a first set of nozzles, which preferably at the bottom are place in the basin between two of the opposite sides of this basin, and which via at least a first water conduit are connected to the water in the reaction container, a second set of nozzles, which preferably at the bottom are placed in the basin at a distance from the first set of nozzles, and which are connected to at least one other water conduit, which is connected to as well the ozone source as to a water source and having a third pressure pump to drive the water, when in ope¬ ration, through the pipe with a pressure which preferably is smaller than the pressure in the reaction container. This plant is suitable to perform the procedure according the invention.
The water which is added to the reaction container, can with advantage be the contaminated water. In some cases the whole water stream can be brought to pass the reaction container, where then an initial purification process will take place, and at the same time the water will be enriched with ozone. When greater water volumes are to be purified, it will, howe¬ ver, for practical reasons be much more expedient to let only part of the contaminated water run through the reaction container.
In order to obtain optimum effect, the water in the reaction container will have to absorb as much ozone as possible, and the pressure in the container must be relatively high, e.g. 10 bar. At such high pressures there is a risk that the ozone will explode, and as pressure pump for pumping the ozone from the ozone source to the reaction container, a membrane pump of sparkfree plastic can therefore expediently be used.
The injection into a container will normally be connected with a danger of explosion, but this danger can be eliminated by having the water stream into the reaction container via an ejector which fills the space above the water surface with a fog of water and steam. An explosion cannot occure in such a wet atmosphere.
By an expedient embodiment the ozone is led into the reaction container via the suction side zone, whereby it can be ensured at its optimum that the inflow of the ozone into the reaction container takes place in a wet atmosphere. A second advantage which is obtained by means of this method, consists of the fact that the ozone quickly is suspended in the form of fine bubbles in the water and/or is dissoluted in the water.
By inserting an ejector in the second water conduit, which is connected to the second set of nozzles, and connecting the ozone source to the suction side of this ejector, the same advantages can be obtained as described above regarding the explosion security and quick and efficient suspension and/or dissolution of the ozone in the water, which is driven into the basin via the second set of nozzles.
When the water in the reaction container is supersaturated with ozone under high pressure and by that means is filled with enormous amounts of small fine bubbles, there is no lon- ger buoyancy in the water. A float will sink to the bottom. The level of the water surface can, consequently, not as usual be registered by means of a floa .
Such a registration is, however, of great importance to the secure and efficient function of the plant. Thus, the ejector will be stifled if the water rises so much that it will be flooded. If the reaction container, on the other hand, is emp¬ tied for water, the ozone will stream directly into the basin. The plant cannot operate securely and efficiently under these circumstances.
According to the invention the level of the water surface is indirectly registered by means of a pressure difference gauge, which continuously measures the difference in pressure between the top and the bottom of the reaction container. The measured difference in pressure is a measure for the height of the wa¬ ter column. The pressure difference gauge is then adjusted, by deviations from a given set value, which represents the prede¬ termined height of the water column, to give a signal to the first pressure pump to pu p more or less water into the reac¬ tion container in dependence of the present value of the signal.
The sewage volume can vary with the time, and the same applies to the degree of contamination. The purification process can¬ not go at its optimum, if there during the changing conditions all the time is send the same amount of ozon enriched water through a set of nozzles. According to the invention there is therefore in the water conduits for each of the two sets of nozzles inserted a valve for regulating the pressure and/or volume of the water which is added.
As earlier mentioned, an leak of ozone can endanger the per¬ sons in the surroundings of the plant. According to the inven¬ tion the purification basin is covered with a bellshaped cover for collection of additional ozone from the purification pro- cess. The collected ozone is, mixed with the existing air in the bassin, led past a cooler for drying of the air mixture, which then is sent past at least one UV lamp, whereby the ozone is converted into oxygen. The air mixture, which now has a large contents of oxygen, is now streaming through a gas conduit to an oxygen membrane, which only allows oxygen moϊe- culars to pass. The oxygen deriving from this process, is fi¬ nally used in an ozone generator for the production of new ozone for the process. With this arrangement the nessecity of having do leak additional ozone to the surroundings will be eliminated. At the same time the process is cost saving, since the additional ozone expediently can be used again in a closed cycle.
The invention will be explained more fully by the following description of embodiment, which just serves as example, with reference to the drawing, where
Fie. l diagrammatically shows a plant according to the inven¬ tion to purify contaminated water, and
Fig. 2 schematically shows in principle an embodiment of the purification process according to the invention. The main components in the purification plant shown in fig. 1 is a ozone generator 1, a reaction container 2 and a purifica¬ tion basin 3. The contaminated water, which is to be purified, is in the case shown led into a main stream 4 to the purifica¬ tion basin 3 and in a secondary stream 5, which is drawn with a dotted line, to the reaction container 2.
The contaminated water can derive from many different sources. For example, the fish industry or other foodstuffs factories with sewage, which typically has a large contents of organic substances. The purification process can advantageously be a part of a larger process, where, in one or more previous steps solidstate substances as e.g. gravel and sand is removed, and in the succeeding steps for example nitrite will be removed. The plant operates with ozone as the sole purification mean. The osone is produced in the ozone generator 1 by oxygen co¬ ming from an oxygen membrane 6, which only allows the contents of oxygen moleculars of the air to pass. The ozone generator can, for example, be of the type, which uses a high voltage area to influence a current of dry oxygen or air with electri¬ cal discharges, whereby a part of the oxygen moleculars are decomposed to free atoms.
Oxygen atoms connecting with present oxygen moleculars forms the' ozone. The formed ozone is pumped by a membrane pump 7, consisting of a sparksafe type of plastic, into the reaction container under a high pressure, e.g. 10 bar.
The secondary stream 5 of contaminated water is pumped by a pressure pump 8 into the reaction container 2 via an ejector 9 under equally high pressure. The ejector will in this process suck in ozone, which thereby quickly and efficiently will be suspended in the form of fine bubbles in the water and/or be dissolved in the water. The ozone enriched water will via a water conduit 10 with a regulation valve 11 be led into the purification basin 3 via a first set of nozzles 12.
According to the invention the amount of ozone pumped into the reaction container must be at a level, in relation to the wa¬ ter volume pumped in at the same time, that the water is su¬ persaturated with ozone under a high pressure. The water in the reaction container is therefore filled with an enormous amount of very small, fine bubbles, which in the following will be referred to as microbubbles. Due to the presence of the microbubbles a float will sink to the bottom in the water. It is, however, with reasonable limits, necessary to be able to fix the height of the water surface in the reaction contai¬ ner. If the water surface is rising above a certain height, the ejector will be flooded, and not able to function as pre¬ supposed. If the container is emptied, there will via the wa¬ ter conduit 10, the regulation valve 11 and the nozzles 12 stream ozone directly into the purification basin 3, so that the aimed purification process is prohibited.
The plant according to the invention comprises therefore a pressure difference gauge 13, which via cables 14 and 15 mea¬ sures the pressure in the top and at the bottom, respectively, of the reaction container, and registers the difference in pressure. The difference in pressure represents the height of the water column, and the pressure difference gauge is there- fore adjusted with a set value, which is equal to a predeter¬ mined height. If the registered difference pressure at a given moment deviates from this set value, the pressure difference gauge will via a cable 16 send a signal to the pressure pump 8 to increase or decrease the water volume, until the registered deviation from the set value is zero, and the water surface therefore will be at the predetermined level in the reaction container 2.
The first set of nozzles 12 are, as shown, placed in the wall of the purification basin and near the bottom. At some distan¬ ce from this set of nozzles there is likewise at the bottom placed a second set of nozzles 17, which are supplied with ozone enriched water via a water conduit 18, in which there is inserted a pressure pump 19, an ejector 20 and a regulation valve 21.
The ozone generator 1 is via a cable 22 connected to the suc¬ tion side of the ejector 20, whereby the water in the cable 18 is enriched with ozone. As shown, the water is streaming in the water conduit 18 in this case in a cicuit from the purifi¬ cation basin with purified water and back again to the purifi- cation basin with ozone enriched water. In other cases the water supplied by the second set of nozzles can, however, come from a different source. The special mode of operation is explained in fig. 2, which in principle shows the process in the purification basin 3.
Ozone enriched water is pressed under high pressure, e.g. 10 bar, via the water conduit 10 and the first set of nozzles 12 into the contaminated water in the purification basin 3 near the bottom 25 of the basin. Further, ozone enriched water is pressed under somewhat lower pressure, e.g. 3 bar, via the water conduit 18 and the second set of nozzles 17 at the bot¬ tom 25 in a distance from the first set of nozzles 12, into the contaminated water in the purification basin 3. Pressure, ozonebearing and nozzle construction are adjusted in such a way that there at the first set of nozzles arise fine bubbles or microbubbles 23 and at the second set of nozzles large bubbles or macrobubbles 24.
The microbubbles, which are in an enormous amount and to a substantial degree already have been formed in the reaction container 2, have, if combined, an enormous surface, and their aggressive ozone content begin immediately to react with the surrounding impurities in the water. Fig. 2 is very simplified and shows only one single microbubble in its various develop¬ ment stages, during which there succeedingly is formed a shell of reaction products around the bubble. At the same time the ozone content is completely or partly used in the proces and will therefore not, as could be expected, rise in the water, but are instead being displaced to the right {in the figure) by the succeeding microbubbles, which continuously stream in through the nozzles 12.
The macrobubbles 24 from the nozzles 17 run equally through a number of development stages, while they as shown rises from the bottom to the water surface. In this process they encoun¬ ter a lot of microbubbles and merge. The shells of the micro- bubbles will form a new shell around the ascending macro- bubbles, and the remaining ozone content will at the same time process non-processed substances in the shell and not yet pro¬ cessed impurities in the water.
The content of ozone in the macrobubbles will therefore gradu¬ ally be reduced, as the shell increases. At the surface the bubbles will burst and the shells will collapse to floes 26, while the remaining ozone in the bubbles is released.
As shown in fig. 1 the floes 26 are removed by means of a belt filter for microfiltration 27 of the type described in the applicants' Danish Patent Application No. 0145/96, to which is referred as a reference.
The microbubbles 23 are so fine, that they are not visible to the naked eye but are manifested as a milky white fog in the water. To the left of the dotted line of the purification ba¬ sin 3 in fig. 1 the water is milky white and therefore filled with microbubbles. To the right of the line 28 the milky fog has disappeared, which signify that the contents of ozone in the bubbles is used in the reactions processes and/or that the microbubbles have merged.
The purification process will normally not use the supplied amount of ozone to the fullest extend. The additional ozone will therefore accumulate under a bellshaped cover 29, cove¬ ring the purification basin 23. The accumulated ozone is, mixed with air, led from the bellshaped cover and by a cooler 30, which cools off and consequently dries the air mixture. The dried air mixture is then led past a number of UV lamps, which by radiation decomposes the ozone to oxygen. The dry, oxygen enriched air mixture is finally led, via a gas conduit 30, to the oxygen membrane 6, which detains all other gasses but oxygen, which, as previously described, is used as raw material in the ozone generator 1 for the production of ozone for the purification process.
The additional ozone is thus being recycled in the plant and is reused repeatedly economic expedient instead of being rele- ased into the invironment where the ozone could be harmful to persons in the surroundings.

Claims

Claims
l. Method fo purification of contaminated water from espe¬ cially oxidizable impurities using ozone, c h a r a c t e r ! z e d in, that the contaminated water is placed in a purification basin, that the contaminated water, at a first set of lead-in's, which in reciprocal distance are dispersed between two of the opposite sides of the basin and preferable near the bottom of the basin, is supplied with ozone in the form of small, fine bubbles, that the contaminated water at the second set of lead-in's at distance from the first set of lead-in's, and equally preferably near the bottom of the basin is supplied with ozone in the form of bubbles, which are substantially lar ger than the first mentioned fine bubbles.
2 . Method according to claim l , c h a r a c t e r i z e d in, that at least the small ozone bubbles are added to the conta¬ minated water in the waterbasm, which is supersaturated with ozone, and which is driven through nozzles being placed at the respective lead-in's.
3. Plant for, ozone-purification of contaminated water for especially oxidizable impurities, c h a r a c t e r i z e d in that it comprises
- a purification basin for the contaminated water,
- an ozone source for, when in operation, supplying ozone to the plant for purification of the water,
- a reaction container, which, when in operation, partly is supplied with water from a water source up to a predetermi ned level in the container by means of a first pressure pump, partly is supplied with ozone under pressure from the ozone source via a gas conduit with a second pressure pump, which preferably is a sparkfree membrane pump,
- a first set of nozzles, which preferably are placed in the basin between the two opposite side of this latter, and which via at least one first water conduit is connected to the water in the reaction container, - a second set of nozzles, which preferably at the bottom are placed in the basin at distance from the first set of nozzles, being connected to at least one second water condu it, which is connected as well to the ozone source as to a water source and having a third pressure pump for, when in operation, driving the water through the conduit with a pressure, which preferably is smaller than the pressure in the reaction container.
4. A plant according to claim 1, c h a r a c t e r i z e d in that the water source, when in operation for supplying the reaction container with water, is the contaminated water or a part of this. 0
5. A plant according to claim 3 or 4, c h a r a c t e r i z e d in that the water is supplied to the reaction container via at least one ejector or similar device, which has been placed at a distance above the surface of the water.
6. A plant according to claim 3, 4 or 5, c h a r a c t e r i 5 z e d in that there in the second water conduit, which is con¬ nected to the second set of nozzles, is inserted at least one ejector or similar device, which at the sucking side is con¬ nected to the ozone source.
7. A plant according to each of the claims 3 - 6, c h a r a c t e r i z e d in that it comprises a pressure difference gauge for measuring the pressure difference between the top and the 0 bottom of the reaction container and for, in dependence of the measured pressure difference, signal for regulation of the first pressure pump, which serves, when in operation, the pu- pose of pumping water from a water source to the reaction container.
8. A plant according to each of the claims 3 - 7, c h a r a c 25 t e r i z e d in that there in the first and/or the second water conduit for supply of water to the first and the second set of nozzles, respectively, in the purification basin, or in both of these water conduits, a valve for regulation of the pressure and/or volume of the supplied water has been inserted.
9. A plant according to each of the cliams 3 - 8, c h a r a c
30 t e r i z e d in that the purification basin is covered with a bellformed cover for collecting the additional ozone from the purification process, and that the top of the bell is connec¬ ted to the ozone source via a cooler for drying of the passing gasses, at least one UV lamp for decomposing ozone to oxygen and a gas conduit with an inserted oxygen membrane.
35 10. A plant according to each of the claims 3 9, c h a r a c t e r i z e d in that a belt filter for microfiltration has been placed in the purification basin, when in operation, to remove solids from the water.
PCT/DK1997/000061 1996-02-12 1997-02-11 Method and plant for purification of contaminated water WO1997029997A1 (en)

Priority Applications (2)

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AU17188/97A AU1718897A (en) 1996-02-12 1997-02-11 Method and plant for purification of contamined water
PCT/DK1997/000061 WO1997029997A1 (en) 1996-02-12 1997-02-11 Method and plant for purification of contaminated water

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DK14596 1996-02-12
DK0145/96 1996-02-12
PCT/DK1997/000061 WO1997029997A1 (en) 1996-02-12 1997-02-11 Method and plant for purification of contaminated water

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Cited By (7)

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Publication number Priority date Publication date Assignee Title
US6649052B2 (en) * 2000-01-04 2003-11-18 Iei Co., Ltd. Ozone oxidizing apparatus
US7431847B2 (en) 2002-11-20 2008-10-07 Povl Kaas Method and apparatus for purifying water by photo-chemical oxidation
US7481937B2 (en) * 2005-01-19 2009-01-27 Heavy Industry Technology Solutions, Llc Methods and systems for treating wastewater using ozone activated flotation
US20110031187A1 (en) * 2007-08-30 2011-02-10 Jong Seob Shim Water treatment system and method using high pressure advanced oxidation process with unreacted ozone reusing
WO2015160243A1 (en) * 2014-04-14 2015-10-22 Nijhuis Water Technology B.V. Assembly of a flocculation device, an ozone introduction device and a separator device and method for operating such an assembly
CN107915309A (en) * 2017-11-30 2018-04-17 安徽工业大学 A kind of method that fine catalyst efficiently separates simultaneously automatic cycle during catalytic oxidation treatment sewage
CN107930235A (en) * 2017-11-30 2018-04-20 安徽工业大学 Fine catalyst efficiently separates the device of simultaneously automatic cycle during a kind of catalytic oxidation treatment sewage

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6649052B2 (en) * 2000-01-04 2003-11-18 Iei Co., Ltd. Ozone oxidizing apparatus
US7431847B2 (en) 2002-11-20 2008-10-07 Povl Kaas Method and apparatus for purifying water by photo-chemical oxidation
US7481937B2 (en) * 2005-01-19 2009-01-27 Heavy Industry Technology Solutions, Llc Methods and systems for treating wastewater using ozone activated flotation
US20110031187A1 (en) * 2007-08-30 2011-02-10 Jong Seob Shim Water treatment system and method using high pressure advanced oxidation process with unreacted ozone reusing
US8926842B2 (en) * 2007-08-30 2015-01-06 Jong Seob Shim Water treatment system and method using high pressure advanced oxidation process with unreacted ozone reusing
WO2015160243A1 (en) * 2014-04-14 2015-10-22 Nijhuis Water Technology B.V. Assembly of a flocculation device, an ozone introduction device and a separator device and method for operating such an assembly
CN107915309A (en) * 2017-11-30 2018-04-17 安徽工业大学 A kind of method that fine catalyst efficiently separates simultaneously automatic cycle during catalytic oxidation treatment sewage
CN107930235A (en) * 2017-11-30 2018-04-20 安徽工业大学 Fine catalyst efficiently separates the device of simultaneously automatic cycle during a kind of catalytic oxidation treatment sewage
CN107930235B (en) * 2017-11-30 2019-10-29 安徽工业大学 Fine catalyst efficiently separates and the device of automatic cycle during a kind of catalytic oxidation treatment sewage
CN107915309B (en) * 2017-11-30 2020-07-31 安徽工业大学 Method for efficiently separating and automatically circulating powder catalyst in sewage catalytic oxidation treatment process

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