WO1998035912A1 - The separation and reuse of nitrates in water - Google Patents

The separation and reuse of nitrates in water Download PDF

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Publication number
WO1998035912A1
WO1998035912A1 PCT/GB1998/000472 GB9800472W WO9835912A1 WO 1998035912 A1 WO1998035912 A1 WO 1998035912A1 GB 9800472 W GB9800472 W GB 9800472W WO 9835912 A1 WO9835912 A1 WO 9835912A1
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WO
WIPO (PCT)
Prior art keywords
membrane
concentrate
treatment
water
subjecting
Prior art date
Application number
PCT/GB1998/000472
Other languages
French (fr)
Inventor
Edwin William John Murrer
Original Assignee
Aw Creative Technologies Ltd.
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 Aw Creative Technologies Ltd. filed Critical Aw Creative Technologies Ltd.
Priority to AU62234/98A priority Critical patent/AU6223498A/en
Publication of WO1998035912A1 publication Critical patent/WO1998035912A1/en

Links

Classifications

    • 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
    • C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
    • 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
    • B01D61/58—Multistep 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
    • C02F1/38—Treatment of water, waste water, or sewage by centrifugal separation
    • C02F1/385—Treatment of water, waste water, or sewage by centrifugal separation by centrifuging suspensions
    • C—CHEMISTRY; METALLURGY
    • C05—FERTILISERS; MANUFACTURE THEREOF
    • C05C—NITROGENOUS FERTILISERS
    • C05C5/00—Fertilisers containing other nitrates
    • C—CHEMISTRY; METALLURGY
    • C05—FERTILISERS; MANUFACTURE THEREOF
    • C05G—MIXTURES OF FERTILISERS COVERED INDIVIDUALLY BY DIFFERENT SUBCLASSES OF CLASS C05; MIXTURES OF ONE OR MORE FERTILISERS WITH MATERIALS NOT HAVING A SPECIFIC FERTILISING ACTIVITY, e.g. PESTICIDES, SOIL-CONDITIONERS, WETTING AGENTS; FERTILISERS CHARACTERISED BY THEIR FORM
    • C05G5/00—Fertilisers characterised by their form
    • C05G5/20—Liquid fertilisers
    • C05G5/23—Solutions
    • 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
    • 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
    • B01D61/025—Reverse osmosis; Hyperfiltration
    • 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
    • B01D61/027—Nanofiltration
    • 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
    • B01D61/145—Ultrafiltration
    • 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
    • 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
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/06—Contaminated groundwater or leachate

Definitions

  • This invention relates to water treatment, and in particular to the removal of contaminants from ground water in a way that enables reuse of the contaminants.
  • salts such as nitrates must be removed. Disposal of such salts may present its own problems.
  • membrane treatment systems include membranes that are operated under relatively high pressure, e.g. by nanofiltration, hyperfiltration up to reverse osmosis, and those operated under relatively low pressure, e.g. by microfiltration or ultrafiltration.
  • Low pressure systems are economic but their use in water purification generally gives insufficient water guality.
  • one of the greatest problems for membrane treatment plants involves the disposal or treatment of nitrate-rich concentrates.
  • ground water typically contains nitrate in an amount of 50 mg/1.
  • Membrane treatment may increase the concentration by a factor of, say, 5-8, to give a concentrate containing nitrate in an amount approaching 500 mg/1.
  • the concentrate has no ready utility, and is too concentrated to be suitable for immediate disposal.
  • the present invention is based on the realisation that the economic use of membrane treatment plants can be provided with further treatment, so that the membrane concentrate is converted to a useful nitrate-containing product, in addition to purified water.
  • the concentrated product can be reused as fertiliser, thereby achieving additional advantages from an environmental viewpoint.
  • a method of treating ground water according to the present invention produces purified water and a nitrate concentrate.
  • the method comprises the steps of: subjecting the ground water to a first membrane treatment, to obtain the purified water and relatively concentrated nitrate-containing solution; subjecting the solution to a treatment whereby sparingly-soluble salts are removed; and subjecting the treated solution to a second membrane treatment, to obtain the concentrate.
  • the concentrate is treated in a further succession of steps.
  • a flocculant is added, to produce a light floe that can be removed in a further membrane treatment.
  • FIGS. 1 and 2 are each a schematic representation of apparatus that can be used in the invention.
  • each of the steps of the method of this invention may be conducted by means generally known to those skilled in the art.
  • the invention lies, not so much in the detail of any one step, but in the combination of steps. Together, they allow recovery of most of the water from the waste stream, and allow for easier disposal, e.g. to inland waters.
  • the first membrane treatment is suitably conducted under low pressure, e.g. using ultrafiltration or microfiltration.
  • the second membrane treatment is suitably under higher pressure, e.g. using nanofiltration or reverse osmosis. Examples of low and high membrane treatments are discussed in more detail in WO-A-9803252 , the content of which is incorporated herein by reference.
  • a high pressure membrane operates at a feed pressure of 5 to 20 bar.
  • a low pressure membrane may operate at a feed pressure of 0.5 to 2 bar.
  • pumps may be provided, in known manner.
  • the second step of the novel method preferably comprises the use of a centrifuge or hydrocyclone, to remove sparingly-soluble salts such as calcium carbonate. This step, i.e. the removal of hardness, is necessary in order to facilitate the third step, in a high pressure membrane .
  • a typical membrane concentrate is effectively "super" concentrated.
  • the resultant nitrate concentrate may contain, for example, 5-10% w/w nitrate. This product is suitable for reuse as a fertiliser. It may also be treated further, as described below.
  • chemical or other treatment preferably in the zone providing some reaction time, can be used to develop a light floe of the concentrate materials.
  • Known materials can be used, in known amounts. Dosing may be with or without oxygen/air.
  • the light floe can then be removed, e.g. using an ultrafiltration membrane.
  • a convenient feature is that the pressure of the concentrate leaving the second membrane treatment, in the third step described above, can be used in this further treatment. This avoids potential pump scaling problems.
  • the further membrane separator may be backwashed using permeate from that stage or from the second membrane.
  • the further membrane may also undergo chemical cleaning using its permeate. Either or each backwash may pass to a settlement vessel.
  • Fig. 1 of the accompanying drawings shows a first membrane separator 1 providing a membrane permeate 2.
  • the concentrate passes to a centrifuge or hydrocyclone 3.
  • Waste from this step passes to a settlement lagoon 4 (or any similar treatment process) .
  • the concentrate from which sparingly-soluble salts have been removed, passes to a second membrane separator 5, typically of the reverse osmosis type.
  • This provides an output of nitrate-rich concentrate at 6.
  • Fig. 2 shows, using bold arrows, the passage of concentrate to a reaction zone 10 having a softening chemical inlet 11.
  • the treated concentrate passes through a membrane separator 12, typically of the ultrafiltration type, e.g. dead end or crossflow.
  • the bold arrow leaving the separator 12 indicates the output of permeate.
  • a vessel 13 having an inlet 14 is provided for backwash.
  • the backwash line passes to the reaction zone 10 and also to a backwash settling vessel 15.
  • An outlet 16 allows settled backwash to be recycled or passed to waste/further treatment.
  • the membrane separator 12 also comprises a chemical cleaning inlet 17 and a chemical cleaning outlet 18.
  • the second membrane is a reverse osmosis unit.
  • the pressure of the concentrate leaving this unit can be utilised instead of a feed pump for an ultrafiltration unit 12.
  • the ultrafiltration backwash water may be wholly UF or RO permeate or a combination of the two.
  • the chemical cleaning solution may be UF permeate.
  • the backwash from the chemical cleaning may be settled in the same vessel as the routine backwash water.
  • Forward flush cleaning may also be provided (but is not shown) . Forward flushing may be followed by backwashing of the forward flush filtrate.

Abstract

A method of treating ground water, to obtain purified water and a nitrate concentrate, comprises the steps of: subjecting the ground water to a first membrane treatment, to obtain the purified water and relatively concentrated nitrate-containing solution; subjecting the solution to a treatment whereby sparingly-soluble salts are removed; and subjecting the treated solution to a second membrane treatment, to obtain the concentrate. The concentrate may then be treated to give a floc that can be removed in a further membrane treatment step.

Description

THE SEPARATION AND REUSE OF NITRATES IN WATER Field of the Invention
This invention relates to water treatment, and in particular to the removal of contaminants from ground water in a way that enables reuse of the contaminants. Background of the Invention
The heavy use of nitrates as fertilisers in agricultural areas leads to contamination of ground water.
In order to render the water suitable for drinking, salts such as nitrates must be removed. Disposal of such salts may present its own problems.
Various different membrane treatment systems are known. They include membranes that are operated under relatively high pressure, e.g. by nanofiltration, hyperfiltration up to reverse osmosis, and those operated under relatively low pressure, e.g. by microfiltration or ultrafiltration. Low pressure systems are economic but their use in water purification generally gives insufficient water guality. In particular, one of the greatest problems for membrane treatment plants involves the disposal or treatment of nitrate-rich concentrates.
Typically, ground water contains nitrate in an amount of 50 mg/1. Membrane treatment may increase the concentration by a factor of, say, 5-8, to give a concentrate containing nitrate in an amount approaching 500 mg/1. The concentrate has no ready utility, and is too concentrated to be suitable for immediate disposal. Summary of the Invention
The present invention is based on the realisation that the economic use of membrane treatment plants can be provided with further treatment, so that the membrane concentrate is converted to a useful nitrate-containing product, in addition to purified water. The concentrated product can be reused as fertiliser, thereby achieving additional advantages from an environmental viewpoint.
More particularly, a method of treating ground water according to the present invention produces purified water and a nitrate concentrate. The method comprises the steps of: subjecting the ground water to a first membrane treatment, to obtain the purified water and relatively concentrated nitrate-containing solution; subjecting the solution to a treatment whereby sparingly-soluble salts are removed; and subjecting the treated solution to a second membrane treatment, to obtain the concentrate. In a further aspect of the invention, the concentrate is treated in a further succession of steps. A flocculant is added, to produce a light floe that can be removed in a further membrane treatment.
Brief Description of the Drawings In the accompanying drawings, Figs. 1 and 2 are each a schematic representation of apparatus that can be used in the invention.
Description of the Invention
Each of the steps of the method of this invention may be conducted by means generally known to those skilled in the art. The invention lies, not so much in the detail of any one step, but in the combination of steps. Together, they allow recovery of most of the water from the waste stream, and allow for easier disposal, e.g. to inland waters.
The first membrane treatment is suitably conducted under low pressure, e.g. using ultrafiltration or microfiltration. The second membrane treatment is suitably under higher pressure, e.g. using nanofiltration or reverse osmosis. Examples of low and high membrane treatments are discussed in more detail in WO-A-9803252 , the content of which is incorporated herein by reference.
Typically, a high pressure membrane operates at a feed pressure of 5 to 20 bar. A low pressure membrane may operate at a feed pressure of 0.5 to 2 bar. In order to provide the appropriate pressure, pumps may be provided, in known manner. The second step of the novel method preferably comprises the use of a centrifuge or hydrocyclone, to remove sparingly-soluble salts such as calcium carbonate. This step, i.e. the removal of hardness, is necessary in order to facilitate the third step, in a high pressure membrane .
By means of the present invention, a typical membrane concentrate is effectively "super" concentrated. The resultant nitrate concentrate may contain, for example, 5-10% w/w nitrate. This product is suitable for reuse as a fertiliser. It may also be treated further, as described below.
In a further step, chemical or other treatment, preferably in the zone providing some reaction time, can be used to develop a light floe of the concentrate materials. Known materials can be used, in known amounts. Dosing may be with or without oxygen/air. The light floe can then be removed, e.g. using an ultrafiltration membrane. A convenient feature is that the pressure of the concentrate leaving the second membrane treatment, in the third step described above, can be used in this further treatment. This avoids potential pump scaling problems.
The further membrane separator may be backwashed using permeate from that stage or from the second membrane. The further membrane may also undergo chemical cleaning using its permeate. Either or each backwash may pass to a settlement vessel.
Fig. 1 of the accompanying drawings shows a first membrane separator 1 providing a membrane permeate 2. The concentrate passes to a centrifuge or hydrocyclone 3.
Waste from this step passes to a settlement lagoon 4 (or any similar treatment process) . The concentrate, from which sparingly-soluble salts have been removed, passes to a second membrane separator 5, typically of the reverse osmosis type. This provides an output of nitrate-rich concentrate at 6. Fig. 2 shows, using bold arrows, the passage of concentrate to a reaction zone 10 having a softening chemical inlet 11. The treated concentrate passes through a membrane separator 12, typically of the ultrafiltration type, e.g. dead end or crossflow. The bold arrow leaving the separator 12 indicates the output of permeate.
A vessel 13 having an inlet 14 is provided for backwash. The backwash line passes to the reaction zone 10 and also to a backwash settling vessel 15. An outlet 16 allows settled backwash to be recycled or passed to waste/further treatment. The membrane separator 12 also comprises a chemical cleaning inlet 17 and a chemical cleaning outlet 18.
By way of example, the second membrane is a reverse osmosis unit. The pressure of the concentrate leaving this unit can be utilised instead of a feed pump for an ultrafiltration unit 12. The ultrafiltration backwash water may be wholly UF or RO permeate or a combination of the two. The chemical cleaning solution may be UF permeate. The backwash from the chemical cleaning may be settled in the same vessel as the routine backwash water. Forward flush cleaning may also be provided (but is not shown) . Forward flushing may be followed by backwashing of the forward flush filtrate.

Claims

1. A method of treating water, to obtain purified water and a nitrate concentrate, which comprises the steps of: subjecting the ground water to a first membrane treatment, to obtain the purified water and relatively concentrated nitrate-containing solution; subjecting the solution to a treatment whereby sparingly-soluble salts are removed; and subjecting the treated solution to a second membrane treatment, to obtain the concentrate.
2. A method according to claim 1, wherein the first and second membrane treatments are conducted under respectively relatively low and high pressure.
3. A method according to claim 2, wherein the first membrane operates by ultrafiltration or microfiltration.
4. A method according to claim 2 or claim 3, wherein the second membrane operates by nanofiltration or reverse osmosis.
5. A method according to any preceding claim, wherein the removal of sparingly-soluble salts is conducted using a centrifuge or hydrocyclone.
6. A method according to any preceding claim, wherein the concentrate is further treated in a reaction zone, to obtain a floe that is separated in a further membrane treatment.
7. A method according to claim 6, wherein the further membrane treatment comprises ultrafiltration.
8. A method according to claim 6 or claim 7, wherein the pressure of the concentrate leaving the second membrane is used to operate the further membrane.
PCT/GB1998/000472 1997-02-14 1998-02-16 The separation and reuse of nitrates in water WO1998035912A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU62234/98A AU6223498A (en) 1997-02-14 1998-02-16 The separation and reuse of nitrates in water

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9703075.3A GB9703075D0 (en) 1997-02-14 1997-02-14 Water treatment
GB9703075.3 1997-02-14

Publications (1)

Publication Number Publication Date
WO1998035912A1 true WO1998035912A1 (en) 1998-08-20

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Family Applications (1)

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PCT/GB1998/000472 WO1998035912A1 (en) 1997-02-14 1998-02-16 The separation and reuse of nitrates in water

Country Status (3)

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AU (1) AU6223498A (en)
GB (1) GB9703075D0 (en)
WO (1) WO1998035912A1 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2393969A (en) * 2002-10-10 2004-04-14 Bosch Gmbh Robert Metal depletion in nitrate electrolytes by electrodialysis; nitrate recovery
WO2008071809A1 (en) * 2006-12-05 2008-06-19 Josep Manel Lahuerta Sabanza Refinements made to drinking water plants for regeneration of aquifers contaminated by nitrates and functioning procedure thereof
CN103359895A (en) * 2013-08-06 2013-10-23 山东建筑大学 Tandem-type removing method for oxidative pollutants in shallow groundwater

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4083781A (en) * 1976-07-12 1978-04-11 Stone & Webster Engineering Corporation Desalination process system and by-product recovery
EP0051104A1 (en) * 1980-11-03 1982-05-12 Josef van Opbergen GmbH & Co KG Process for the treatment of water containing nitrate
US4434057A (en) * 1981-02-16 1984-02-28 Hager & Elsasser Gmbh Water purification utilizing plural semipermeable membrane stages
EP0520920A1 (en) * 1991-06-26 1992-12-30 Societe De Traitements Hydrex S.N.C. Filtration module, especially for water treatment
US5490939A (en) * 1994-03-03 1996-02-13 Bayer Aktiengesellschaft Process for reconcentrating overspray from one-component coating compositions
DE19520913A1 (en) * 1995-06-08 1996-12-12 Schael Wilfried Method and device for water treatment according to the principle of reverse osmosis

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4083781A (en) * 1976-07-12 1978-04-11 Stone & Webster Engineering Corporation Desalination process system and by-product recovery
EP0051104A1 (en) * 1980-11-03 1982-05-12 Josef van Opbergen GmbH & Co KG Process for the treatment of water containing nitrate
US4434057A (en) * 1981-02-16 1984-02-28 Hager & Elsasser Gmbh Water purification utilizing plural semipermeable membrane stages
EP0520920A1 (en) * 1991-06-26 1992-12-30 Societe De Traitements Hydrex S.N.C. Filtration module, especially for water treatment
US5490939A (en) * 1994-03-03 1996-02-13 Bayer Aktiengesellschaft Process for reconcentrating overspray from one-component coating compositions
DE19520913A1 (en) * 1995-06-08 1996-12-12 Schael Wilfried Method and device for water treatment according to the principle of reverse osmosis

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2393969A (en) * 2002-10-10 2004-04-14 Bosch Gmbh Robert Metal depletion in nitrate electrolytes by electrodialysis; nitrate recovery
WO2008071809A1 (en) * 2006-12-05 2008-06-19 Josep Manel Lahuerta Sabanza Refinements made to drinking water plants for regeneration of aquifers contaminated by nitrates and functioning procedure thereof
CN103359895A (en) * 2013-08-06 2013-10-23 山东建筑大学 Tandem-type removing method for oxidative pollutants in shallow groundwater
CN103359895B (en) * 2013-08-06 2014-08-27 山东建筑大学 Tandem-type removing method for oxidative pollutants in shallow groundwater

Also Published As

Publication number Publication date
GB9703075D0 (en) 1997-04-02
AU6223498A (en) 1998-09-08

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