FR2789328A1 - Treatment of waste waters from fire fighting, or from vehicle washing, containing surfactants and hydrocarbons which are not treatable using existing methods - Google Patents

Abstract

Waste waters (1) containing surfactants and hydrocarbons are treated using tangential filtration and other processes. The first filter stage uses a mineral membrane of pore size 0.001 to 10 microns, and the second filter stage uses a nanofilter of 0.0001 to 0.001 microns. Filtrate from this stage can be discharged to a water course. Retentate from the filters is subject to other treatments, which may include coagulation and flocculation, precipitation of carbon by acidification or electrolytic precipitation, or biological treatment.

Description

The invention relates to a method for purifying water, in particular

  waters containing surfactants, and an installation for carrying out the process. The invention shall allow the discharge of purified water into the natural environment or recycling for subsequent uses according to the technical specifications imposed by the standard and listed in the following table: Measurement Maximum concentration Authorized concentration generally observed

PH 5.5 to 8.5 5.5 to 8.5

  Temperature <30 C <30 C MEST 100 mg / I 50 to 1000 mg / l COD 300 mg 02/1 200 to 40,000 mg 02/1 _ BOD5 100 mg 02/1 20 to 10,000 mg 02/1 Hydrocarbons 10 mg / ll 25 to 500 mg / l With: MEST total suspended solids, COD: chemical oxygen demand,

  BOD5: biological oxygen demand over 5 days.

  The invention applies more particularly but not exclusively to waters containing emulsifiers contained in the extinguishing water of a fire,

  and water from a vehicle washing center.

  Fire extinguishing water has two possible origins: water from an accidental fire (building, factory, road accident, railway accident, air accident, marine accident) and effluents from a training center at the airport.

fight against the fire.

  These aqueous effluents consist of: suspended solids, hydrocarbons, emulsifying (surfactant) and film-forming agents and

  possibly chemical agents such as baking soda.

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  Suspended solids result from the entrainment of various wastes including unburnt particles (carbon black). These materials

  suspension does not decant naturally (colloids).

  The hydrocarbons come from the fuels used, some of these hydrocarbons remain dissolved in the water of extinction because of the presence

  an emulsifier (no settling).

  The emulsifiers (surfactants) and film-forming agents are injected into the fire hose to form on the ground a foam which stifles the fire due to lack of oxygen. The discharge into the natural environment of used water used to extinguish fires poses a real problem of pollution: pollution by hydrocarbons, - pollution by suspended solids, - pollution by organic materials and in particular by agents

used emulsifiers.

  The emulsifying agent is in fact the main source of COD and its composition makes it a very little biodegradable COD (COD / BOD> 4) even in the case of

  new generation of so-called biodegradable emulsifiers.

  To date, no satisfactory fire-extinguishing water purification process has been known to meet the specifications of the

table above.

  Biological treatment alone would not achieve a compliant discharge due to the very low biodegradability of the foam concentrates and the intermittent nature of this type of treatment would be incompatible with the regularity in flow and volume.

  quality that requires such purification.

  A physico-chemical treatment alone would be insufficient to meet the standards of rejection because of the high water solubility of the surfactants which makes them very difficult to precipitate, and because of the COD treatment efficiencies.

about 40 to 60%.

  Finally, the two processes taken individually or in combination

  assume important works that are difficult to transport.

  The washing stations of light or heavy vehicles (light vehicles, trucks, airplanes, etc.), tanker truck washing stations generate water loaded with: - suspended solids,

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- hydrocarbons,

- surfactants.

  The current methods, for example those described in patent EP 0 436 or in application EP 0 567 951, use decantation methods and / or coagulation / flocculation and / or oxygenation generally not very effective on surfactants and hydrocarbons. In addition, these processes tend to be disrupted when the quality of the water to be treated changes (increase in the content of

  surfactants in case of recycling for example).

  The purpose of the invention is to solve all the problems mentioned, to allow a single installation to reject a water compliant with the standard in force and this, at least for each of the two applications mentioned, or even for other applications (for example industrial degreasing waters), this

  installation must also be easily transportable.

  This object is achieved by a water purification process, in particular water containing surfactants, for example emulsifiers contained in fire extinguishing water, water from vehicle washing centers, comprising at the beginning of chain a step of first storage of the water to be purified, characterized in that it comprises a first tangential filtration and a second tangential filtration successively under the following conditions: - the water to be treated undergoing screening before undergoing the first tangential filtration, - the first concentrate resulting from the first tangential filtration being returned to the first storage step, - the first permeate from the first tangential filtration being sent, after a second storage step, in the step of second tangential filtration, - the concentrate from the second tangential filtration being returned in the second step of stocking ge - the permeate resulting from the second tangential filtration constituting the treated water. This process may further comprise a decarbonation treatment of the first permeate resulting from the first tangential filtration and / or a treatment of

  deconcentration of the concentrate resulting from the second tangential filtration.

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  The invention also consists of a water purification plant for the implementation of a process, characterized in that it comprises: A storage stage (I) where the water to be purified is stored in a first basin where a pump sends it to the next stage, to a stage (II) of screening or filtration, * a stage (111) of first tangential filtration in a module discharging into a first storage tank a concentrate of pollution, called first retentate, the water from the screening being sent by means of a pump at the input of the module which comprises

  a recirculation loop upstream of the pump.

  A storage stage (IV) where the treated water from the previous stage and called the first permeate is sent and stored in a second storage tank, then sent by a pump into a storage tank.

The next floor.

  A stage (V) of second tangential filtration in a membrane module, a pump receiving the fluid from the second storage tank and the recirculation fluid supplying the inlet of the membrane module, the pollution concentrate from the membrane module being sent to the second storage basin, the

  permeate from the second filtration stage constituting the treated water.

  This installation may further comprise a decarbonation stage permeate from the first tangential filtration and / or a stage of

  deconcentration of the concentrate resulting from the second tangential filtration.

  This installation includes monobloc pumps to make it

transportable.

  The installation makes it possible in particular: - to carry out a thorough purification at the level of the molecule by combining two tangential filtrations, to obtain a treated water below the norms of rejection in force, to use means not very bulky so that the installation be easily transportable on a trailer in order to carry out the interventions on the site to be cleaned up,

  - not to go wrong when the amount of water to be treated is changing.

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  The invention will be better understood by means of the description which follows in

  reference to the following appended figures: FIG. 1: diagram of an installation according to the invention,

  - Figure 2: flowchart of the method according to the invention.

  The installation shown diagrammatically in FIG. 1 mainly comprises the following successive stages: At a storage stage (I) where the water to be purified is stored in a first storage basin (1). A pump (P1), possibly immersed, sends it to the next stage, o0 e A stage (II) of screening or coarse filtration in a basket-type grid filter or grid (2) for separating the solid particles from the water to be treated in order to protect the membrane of the next stage, * A stage (111) of tangential first filtration achieving a micro or ultrafiltration discharging in the storage basin (1) a pollution concentrate, called first retentate (3C) . This micro or ultrafiltration is performed on modules (3A) with a mineral membrane with a cutoff threshold of between 10 .mu.m and 0.001 .mu.m. The water resulting from the screening is sent by means of a pump (P2) to the inlet of the module (3A) which

  has a recirculation loop (3R) upstream of the pump (P2).

  By rejecting the first retentate (3C) in the storage tank, this stage makes it possible to retain and accumulate suspended solids,

  hydrocarbons and a fraction of the surfactants.

  A stage (IV) storage where the treated water from the previous stage and called first permeate (3B) is sent and stored in a second storage tank (4), then sent by a pump possibly

  immersed (P3) in the next stage.

  * A stage (V) performing a second tangential filtration in a module (5A) on manofiltration or reverse osmosis membranes of the first permeate (3B) and whose cutoff threshold is between 0.01 and 0.0001 plm . A pump (P4) receiving the fluid from the pond (4) and the recirculation fluid (5R) feeds the inlet of the membrane module (5A). The pollution concentrate (5C) from the membrane module (5A) is sent to a storage tank (4) or a specific tank (variant not shown) located in the recirculation mouth. The treated water is called second permeate (5B). This

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  Permeate is released into the natural environment as it complies with generally accepted release standards (COD below 300 mgO2 / Il, BOD less than 100 mg / l, suspended solids content below 30 mg / l, hydrocarbon content below 10 mg / l To obtain this result, it may be necessary to add the optional stages described below: The second permeate may also be recycled for

subsequent uses.

  An optional decarbonation stage (VI) is added to protect the membrane (5A) depending on the salt composition of the first permeate (3B). The decarbonation treatment is based on a first variant on the acidification of the medium with a mineral acid, making it possible to convert the carbonate ions into CO2, thus avoiding their crystallization in the following treatment. For example, but not exclusively, as in FIG. 1, the permeate (3B) is pumped by an optionally submerged pump (Ps) from the second storage tank (4) and sent to an acidification means (6) precipitating the carbonate of calcium. According to a second variant not shown, the decarbonation is replaced by an electrolytic treatment of the water generating OH- ions precipitating calcium carbonate by recovering it in a decanter, A stage (VII) of deconcentration treatment to reduce the cost the destruction of the residue: - during use of the second tangential filtration stage, the concentrate (5C) can be treated continuously or discontinuously by physicochemical treatment of coagulation-flocculation or flotation. The treatment comprises a coagulant injection system (7), a mixing system (8), a flocculant injection system (9), a flocculator (10) and finally a decanter (11). This can be done by the same pump (P5) taking the mixture of permeate (3B) and concentrates (5C) in the basin (4) and the

  distributing successively in the means (6) to (11).

  depending on the type of chemical molecule contained in the water to be treated, the means (7) to (10) can be replaced by an aerated tank acting as an aerobic biological treatment, the sludge

  The decanter is partly recirculated to the aerated pond.

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  depending on the type of chemical molecule contained in the water to be treated, the means (7) to (10) may be replaced by an ultrafiltration or nanofiltration stage on mineral membranes for deconcentrating the concentrate of the second filtration stage . It may include the return by a pump water basin (4) to the basin (1) (load of the first stage of filtration). In the latter case, the operation will be more particularly effective when the basin (1) is empty or at low level (end of concentration) and when the second stage of tangential filtration

  is in a high concentration stage.

  depending on the type of chemical molecule contained in the water to be treated, the means (7) to (10) can be replaced by a chemical treatment of oxidation with hydrogen peroxide, with ozone or with

  sodium hypochlorite (bleach).

  1 5 - the decanter (11) can be completed by a tangential microfiltration installation ensuring the absence of material in

  suspension in the return to the pelvis (4).

  The treatment of the concentrate (5C) by the means (7) to (10) makes it possible to lower the COD and thus reduce the organic charge of the second filtration stage V. This operation offers the double advantage of lowering the COD of the

  second permeate and limit the fouling of the filtration membranes.

  The ultimate objective is to obtain a higher volume concentration factor of the load of the stage V thus to limit the volume and thus the cost of destruction of the

second retentate.

  Advantageously, the means constituting the installation will be arranged

  on a transportable chassis to the site to be cleaned up.

  For this arrangement, one-piece pumps (P1) to (P5) will be used.

  do not require realignment of axes after transport.

  FIG. 2 shows a flowchart of the operating method of the installation: Between the entry of water to be treated and the outlet of treated water, the water undergoes the following steps: I first storage It is screened

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  III first tangential filtration with direct recirculation in the first storage IV second storage V second tangential filtration VI decarbonation optional from the second storage and recirculation therein VII deconcentration from the second storage and recirculation therein.

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Claims (25)

  1. Method for purifying water, in particular water containing surfactants, for example emulsifiers contained in fire-extinguishing water, water from vehicle washing centers, comprising at the beginning of the chain a step first storage of the water to be purified, characterized in that it comprises a first tangential filtration and a second tangential filtration successively under the following conditions: 0 - the water to be treated undergoing screening before undergoing the first filtration tangential, - the first concentrate (3C) from the first tangential filtration being returned to the first storage step, - the first permeate from the first tangential filtration being sent, after a second storage step, in the step of second tangential filtration, - the concentrate (5C) from the second tangential filtration being returned in the second storage step, - the pe rmeat (5B) resulting from the second tangential filtration constituting Treated water.   2. Water purification process according to claim 1, characterized in that the first tangential filtration is an ultrafiltration treatment on mineral membranes with a cutoff threshold between 10 μm and 0.001 gm.   3. A method of water purification according to one of claims 1 to 2,   characterized in that the second tangential filtration is a membrane nanofiltration treatment having a cutoff threshold between 0.001 μm and 0.0001 μm.   4. A method of water purification according to one of claims 1 to 3,   characterized in that the second filtration is an osmosis treatment   inverse on membranes with a cut-off threshold lower than 0.001 p.m.   5. A method of water purification according to one of claims 1 to 4,   characterized in that it further comprises a decarbonation treatment permeate (3B) from the first filtration tangential. 2789328   6. A method of water purification according to claim 5, characterized in that the decarbonation is based on the acidification of the medium by a mineral acid.   7. Water purification process according to claim 5, characterized in that the carbonation is based on an electrolytic treatment   precipitating calcium carbonate.   8. Water purification process according to one of claims 1 to 7,   characterized in that it further comprises a deconcentration treatment (5C) of the concentrate resulting from the second filtration tangential.   9. Process for purifying water according to claim 8, characterized in that the deconcentration is based on a coagulation treatment   flocculation of the permeate from the second filtration.   10. Process for purifying water according to claim 8, characterized in   what deconcentration is based on aerobic biological treatment.   1 1. Water purification process according to claim 8, characterized in that the deconcentration is based on a tangential filtration on membrane modules.   12. A method of water purification according to claim 8, characterized in that the deconcentration is based on a chemical oxidation treatment. 13. Water purification plant for the implementation of a process   according to one of claims 1 to 12, characterized in that   comprises: * A storage stage (I) where the water to be purified is stored in a first storage tank (1) where a pump (Pl) sends it to the next stage, * A stage (II) screening or filtration, At a stage (III) of first tangential filtration in a module (3A) discharging in a first storage tank (1) a pollution concentrate, called first retentate (3C), the water from the screening being sent by means of a pump (P2) to the input of the module (3A) which comprises a recirculation loop (3R) upstream of the pump (P2). ] A storage stage (IV) where the treated water from the previous stage and called first permeate (3B) is sent and stored in a second storage tank (4) and then sent by a pump (P3) in the next floor.   * A stage (V) of tangential second filtration in a membrane module (5A), a pump (P4) receiving the fluid from the second storage tank (4) and the recirculation fluid (5R) supplying the inlet of the module membrane (5A), the pollution concentrate (5C) from the membrane module (5A) being sent to the second storage pond (4), the permeate (5B) from the second   filtration stage constituting the treated water.   14. A water purification plant according to claim 13, characterized in that the first tangential filtration stage comprises a mineral membrane ultrafiltration module of cutoff threshold included between 10m and 0.001m.   15. Water treatment plant according to one of claims 13 to 14,   characterized in that the second tangential filtration stage comprises a membrane nanofiltration module with a threshold of   cutoff between 0.001 pm and 0.0001 rim.   16. Water treatment plant according to one of claims 13 to 14,   characterized in that the second tangential filtration stage comprises a reverse osmosis module on membranes with a threshold of cutoff less than 0.001 pm.   Water purification plant according to one of claims 13 to 16,   characterized in that it further comprises a stage of   decarbonation of the first permeate (3B).   Water treatment plant according to Claim 17, characterized in that the permeate (3B) is pumped by a pump (Ps) from the second storage tank (4) to an acidification means (6).   precipitating calcium carbonate in a decanter.   19. A water purification plant according to claim 18, characterized in that it further comprises a deconcentration stage of the second concentrate (5C).   20. Water treatment plant according to claim 19, characterized   in that it comprises a physicochemical stage of coagulation-type 12 2789328   flocculation comprising a mixing system (8), a system   flocculant injection device (9), a flocculator (10) and finally a decanter (11).   Water purification plant according to one of claims 18 to 20,   characterized in that a pump (Ps) delivers the mixture of second concentrate (5C) and first permeate (3B) contained in the second   storage tank (4) successively in the means (6) to (11).   22. Water purification plant according to claim 19, characterized in that it comprises an aerated tank acting aerobic biological treatment, sludge from the decanter being partly recirculated to the aerated basin.   23. water purification plant according to claim 19, characterized in that it comprises an ultrafiltration stage or nanofiltration on   inorganic membranes replacing the means (7) to (10).   24. Water treatment plant according to claim 19, characterized in that it comprises a recycling of the concentrate of the second stage.   (basin 4) upstream of the first floor (basin 1).   Water treatment plant according to claim 19, characterized   in that it comprises a chemical oxidation treatment stage.   26. Water treatment plant according to claim 20, characterized in that the decanter (11) may be completed by a tangential microfiltration installation ensuring the absence of suspended matter.   in the return to the second tank (4) storage.   Water purification plant according to one of claims 13 to 26,   characterized in that the means constituting it are arranged on a transportable chassis and in that the pumps (P,) to (Ps) are monobloc pumps.