process for cleaning a polluted pipe

Abstract

The invention relates to a method for cleaning at least one polluted pipe intended to convey drinking water, said method employing an aqueous composition comprising at least one anionic surfactant approved for food contact, as well as the use of such an aqueous composition to clean a polluted pipe, in particular one in a drinking water infrastructure. Figure to be published: Figure 1

Description

Title of the invention: Method for cleaning a polluted pipe

[0001] The present invention relates to the field of drinking water networks and their depollution and / or cleaning, in particular the depollution of organic contaminants such as aromatic hydrocarbons, petroleum derivatives, and / or bituminous residues.

[0002] The invention relates more particularly to a method for cleaning at least one polluted pipe, intended to convey drinking water, said method employing an aqueous composition comprising at least one anionic surfactant approved for food contact, as well as the use of such an aqueous composition to clean a polluted pipe, in particular of a drinking water infrastructure.

[0003] Contamination of drinking water pipes can have several origins. Pollution can occur during water production through the accidental introduction of an undetected chemical, or during transport through the accidental or intentional introduction of a chemical into the pipe. Examples include backflow of polluted water from a connection point during transport, injection of a chemical via a network access point, or permeation of a spilled product into the ground.

[0004] As soon as contamination is detected, one initial technique involves launching high-flow hydraulic flushing programs (speed > 1 m / s) to renew the water in the pipe and remove or dilute the pollutant. This initial technique can achieve water quality that meets the requirements of the public health code. However, the time required to restore the drinking water network is highly variable, and water usage restrictions can last from a few days to several months in the most difficult cases, particularly in the event of hydrocarbon pollution. The disadvantages of hydraulic flushing, which are proportional to the duration of the operation, are: excessive water consumption for flushing carried out over extended periods, the need to distribute bottled water to the population during the drinking water network outage, and uncertain network restoration times.Furthermore, this first technique requires that the contaminants be soluble in water.

[0005] Other techniques have also been proposed for cleaning drinking water pipes. A second technique, also known as the "Hamman process," consists of cleaning a pipe with water and pulsed air, making it possible to remove non-adherent deposits. This second technique relies on the circulation High-velocity water jets coupled with air injection into a pipe are used. Calibrated air bubbles circulate in successive pulses at regular intervals within an isolated section of the network, the pressure of which has been intentionally lowered below the operating pressure. The air pulses, calibrated according to the diameter and length of the pipes to be treated, are introduced sequentially into the section and are propelled by the water flow towards a drainage device. The turbulence created at the air / water interface dislodges loose deposits. These deposits, thus suspended, are carried towards the drainage device by the successive bubbles and the existing flow within the section. A third technique involves the use of at least one flexible scraper, and in particular the introduction and propulsion of a polyurethane foam pad into a pipe.This technique requires clearing the water pipe for access and creating an entry point to insert the flexible scraper. A fourth, well-known technique, called "icepigging," removes non-adherent deposits using a plug of ice and salt. This technique is particularly expensive.

[0006] International application WO2012 / 168645 describes a method for dynamically cleaning the drinking water supply lines of a vehicle, comprising partially filling a volume with a liquid, filling the volume not occupied by the liquid with pressurized gas, releasing the liquid through a constriction communicating with the end of said line(s) to be cleaned, the other end of which is open while maintaining pressure, so as to create an accelerated displacement of the liquid initially and of the gas and liquid mixture created subsequently, and then to generate a shock wave, once the volume is emptied, a shock wave which propagates through the mixture.

[0007] Although potentially effective, none of the aforementioned techniques can be implemented in an emergency situation, as they require advance planning and are costly. Furthermore, they can cause other disturbances to water quality because they can damage the surface of materials, particularly by dislodging corrosion elements from steel or cast iron pipes. Finally, these techniques are not suitable for decontaminating pipes containing organic compounds adhering to the internal pipe walls, and in particular organic contaminants such as aromatic hydrocarbons, petroleum derivatives, and / or bituminous residues.

[0008] Thus, the object of the present invention is to overcome the drawbacks of the aforementioned prior art and to provide a rapid method for cleaning drinking water pipes, without requiring prior planning, and which is suitable for removing all types of compounds adhering to the internal walls of a pipe, and in particular compounds poorly or not soluble in water such as organic compounds of the aromatic hydrocarbon type, petroleum derivatives, and / or bituminous residues.

[0009] The object of the invention is achieved by the process which will be described below.

[0010] The present invention thus relates first to a method for cleaning at least one polluted pipe intended to convey drinking water, said method comprising at least the following steps: - a step i) in which an aqueous composition comprising potable water is circulated through the polluted pipe, and - a step ii) of rinsing the pipeline at the end of step i), to obtain a decontaminated pipeline, said process being characterized in that the aqueous composition further comprises at least one anionic surfactant suitable for food contact.

[0011] By using an aqueous composition containing at least one anionic surfactant [step i)], the polluted pipe is cleaned efficiently, quickly, and without prior planning. Furthermore, it removes all types of compounds adhering to the pipe walls and is particularly suitable for decontaminating pipes or conduits containing compounds that are poorly or not at all soluble in water, such as organic compounds like aromatic hydrocarbons, petroleum derivatives, and / or bituminous residues. In addition, the rinsing step ii) and the use of a food-grade surfactant quickly restore the water to a safe drinking water state, making it safe for human consumption. Finally, the process is non-intrusive as it avoids the need to open up roads and cut pipes.

[0012] At the end of the process of the invention, the decontaminated pipeline can be put back into service.

[0013] In the invention, a pipe can also be called a conduit.

[0014] The polluted pipe can have a diameter D ranging from approximately 32 mm to 400 mm.

[0015] The polluted pipeline can have a length L ranging from approximately 1 m to 2000 m.

[0016] Preferably, the volume of the polluted pipe does not exceed 20 m3.

[0017] Indeed, beyond this volume, the pipe can be cleaned using the process of the invention by section (volume slice of at most 20 m3).

[0018] The pipeline (or conduit) may be a cast iron, steel, polyvinyl chloride (PVC), polyethylene such as high-density polyethylene, or cement-lined pipeline.

[0019] The polluted pipe is preferably in a drinking water infrastructure, and more particularly in a drinking water distribution network.

[0020] A drinking water distribution network consists of a network of pipes to carry water to consumers.

[0021] The process of the invention can be carried out during the renewal of pipes, during the laying of new pipes (network extensions) or connections, and / or in the event of proven or potential degradation of water quality in networks, in particular of chemical contamination (for example of organic origin).

[0022] Drinking water is understood to mean water intended for human consumption.

[0023] The pipeline in step i) is polluted. In other words, it may include one or more contaminants such as mineral and / or organic deposits, and preferably one or more organic compounds adhering to the internal walls of the pipeline.

[0024] The organic compounds can be selected from aromatic hydrocarbons such as polycyclic aromatic hydrocarbons (PAHs), petroleum derivatives, bituminous residues, greases, lubricants, and a mixture thereof.

[0025] The anionic surfactant in the aqueous composition is a food-grade surfactant. In other words, said anionic surfactant is approved for food contact.

[0026] In the invention, the term "food contact approved agent" means any agent that is likely to come into contact with food, i.e., with foodstuffs, products and beverages intended for human and animal consumption. Such agents are included in a list of constituents authorized in cleaning products for materials that come into contact with food, this list being regularly updated and available on the following website: https: / / www.legifrance.gouv.fr / loda / id / LEGIARTI000028457490 / 2014-01-01 / .

[0027] The anionic surfactant of the aqueous composition is in particular considered to be approved for food contact if it is part of the aforementioned list, part relating to the first group, constituents of the type "surfactants", part A relating to anionic surfactants.

[0028] The anionic surfactant and the aqueous composition make it possible to promote the dispersion of contaminants, and in particular of organic compounds as defined above.

[0029] The anionic surfactant preferably comprises at least one sulfonate, sulfate, and / or carboxylate function.

[0030] Examples of surfactants comprising at least one sulfonate function include alkali alkylsulfonates, alkali alkylarylsulfonates, alkali alkylaryl polyglycol ether sulfonates, alkali mono- and dialkyl-diphenyl oxide disulfonates, or sodium salts of alpha-olefin sulfonates.

[0031] Examples of surfactants comprising at least one sulfate function include alkali alkyl sulfates or alkali alkyl ethers sulfates.

[0032] By way of examples of surfactants comprising at least one car- function Examples of boxylates include sodium or potassium carboxylates.

[0033] The aqueous composition preferably comprises at least one alkali alkylarylsulfonate, such as, for example, a mono-alkylated Cw-b derivative of benzene sulfonate.

[0034] The aqueous composition of step i) comprises potable water and said anionic surfactant.

[0035] The aqueous composition preferably comprises approximately 0.0001% to 0.15% by mass, particularly preferably approximately 0.001% to 0.02% by mass, and even more particularly preferably approximately 0.004% to 0.014% by mass, of the food-grade anionic surfactant(s), relative to the total mass of the aqueous composition. This minimum concentration is sufficient to decontaminate the pipe and, in particular, to remove organic compounds adhering to the internal walls of said pipe. Furthermore, the maximum concentration facilitates step ii) of rinsing and makes it faster.

[0036] During step i), the aqueous composition comprising potable water and said anionic surfactant is circulated through the polluted pipe.

[0037] Step i) preferably includes circulating potable water in the polluted pipe, and injecting said anionic surfactant into the polluted pipe.

[0038] Thus, the injection of said anionic surfactant into the polluted pipe makes it possible to form the aqueous composition.

[0039] The introduction of potable water into the polluted pipe and the injection of said anionic surfactant into the polluted pipe are preferably simultaneous, or alternatively, as soon as potable water is circulating in the polluted pipe, said surfactant is injected while maintaining the circulation of potable water in the polluted pipe. The anionic surfactant then spreads throughout the pipe to form a homogeneous aqueous composition with the potable water.

[0040] According to one embodiment of the invention, drinking water flows through the polluted pipe during step i) with a flow rate ranging from approximately 1 m3 / h to 25 m3 / h, and preferably from approximately 5 m3 / h to 10 m3 / h.

[0041] The flow rate of potable water during step i) can be controlled using a system comprising a valve and a flow meter, said system being able to be connected to a fire hydrant of the polluted pipeline located downstream of the polluted pipeline.

[0042] The injection of the surfactant into the pipeline during step i) is preferably carried out with a flow rate of approximately 0.1 l / min to 1.5 l / min.

[0043] The steps of circulating potable water and injecting the anionic surfactant are preferably carried out in turbulent flow. This promotes the formation of a homogeneous aqueous composition in the polluted pipe. In other words, this means that a number of Reynolds number of at least 3000, and preferably at least 5000.

[0044] Step i) is preferably carried out for a sufficient time to remove organic compounds adhering to one or more internal walls of the polluted pipe.

[0045] The organic compounds may be aromatic hydrocarbons such as polycyclic aromatic hydrocarbons (PAHs), petroleum derivatives, bituminous residues, greases and / or lubricants, and preferably aromatic hydrocarbons such as polycyclic aromatic hydrocarbons (PAHs), petroleum derivatives, and / or bituminous residues.

[0046] The injection of the anionic surfactant can be carried out using an injection system comprising an injection pump, an injection lance, and a generator.

[0047] The surfactant flow rate during the injection in step i) can be controlled using the injection pump.

[0048] The injection is preferably carried out upstream of the pipe to be cleaned.

[0049] During step i), and in particular during the injection of the surfactant into the ca In the case of polluted pipes, this product can be used alone or diluted in an aqueous solution, and preferably diluted in an aqueous solution. This helps to promote the formation of a homogeneous aqueous composition during step i) within the polluted pipe.

[0050] Step i) lasts, particularly preferably, from 45 minutes to 2 hours.

[0051] Step ii) allows the pipeline to be rinsed after step i), to obtain a ca The treated water system allows for the delivery of clean drinking water. It facilitates the removal of the anionic surfactant and contaminants (e.g., the aforementioned organic compounds).

[0052] Step ii) of rinsing is preferably carried out by circulating potable water through the pipeline after step i). This involves renewing the volume of the pipeline at least 3 times, and preferably at least 4 times.

[0053] Step ii) can last from 90 minutes to 4 hours.

[0054] According to one embodiment of the invention, drinking water flows through the pipeline during step ii) with a flow rate ranging from approximately 1 m3 / h to 25 m3 / h, and preferably from approximately 5 m3 / h to 10 m3 / h.

[0055] Step ii) is particularly preferably carried out in turbulent flow. In other words, this means that a Reynolds number of at least 3000, and preferably at least 5000, is preferably applied.

[0056] The process may further include, between steps i) and ii), a step i-1) of stagnating the aqueous composition in the polluted pipe. This promotes the detachment of organic compounds adhering to the internal walls of the ca- polluted nationalization.

[0057] Step i-1) can last from 30 minutes to 4 hours, depending in particular on the volume of pipe to be cleaned.

[0058] The process may further include a step iii) of measuring, preferably in situ, the quantity of anionic surfactant in the pipeline. This step iii) makes it possible to monitor the proper execution of the process of the invention and to determine its effectiveness, and in particular the effectiveness of step i) and possibly of step i-1) if it exists.

[0059] This step iii) is preferably carried out by measuring UV absorption, preferably at a wavelength of 254 nm; or the amount of total organic carbon (TOC) in a liquid contained in the pipeline (polluted or depolluted). This liquid may be potable water circulating in the pipeline before the implementation of step i), the aqueous composition circulating during step i) and / or stagnant during step i-1), and / or potable water circulating during step ii).

[0060] The measurement of the quantity of total organic carbon in the pipeline liquid can be carried out using a portable TOC analyzer, in particular sold under the trade name "Sievers M9".

[0061] During step iii), the flow rate of the liquid in the pipeline is reduced compared to the flow rate implemented during the step in which the measurement is performed. In particular, it can be reduced by 40 to 50% compared to the flow rate implemented before step i), during step i), i-1), ii), or after step ii). This makes it easier to perform the measurement.

[0062] When step iii) is carried out after step ii) of rinsing and it reveals the presence of the surfactant and / or contaminants (e.g. organic compounds), steps i) and / or ii) may be repeated.

[0063] The process may further include a step iv) of measuring the concentration of chlorine in the liquid flowing in the pipeline.

[0064] The process may further include, prior to step i), a step i-0) of purging the contaminated pipe. This step may allow for the removal of loose deposits and promote the penetration of the anionic surfactant or the aqueous composition into the contaminated pipe during step i). The purging is preferably carried out at high velocity (i.e., preferably with a velocity greater than 1 m / s).

[0065] The second object of the invention is the use of an aqueous composition as defined in the first object of the invention to clean a polluted pipe, in particular of a drinking water infrastructure.

[0066] The polluted pipeline and drinking water infrastructure are preferably as defined in the first object of the invention.

[0067] The present invention is illustrated by the following embodiments, to which However, it is not limited. Brief description of the drawings

[0068] The attached drawing illustrates the invention.

[0069] Fig. 1 is a representative diagram of a system for cleaning a polluted pipe enabling the implementation of the process of the invention.

[0070] Example 1: Description of the process of the invention

[0071] Figure 1 shows a system for cleaning a cast iron pipe 1, enabling the implementation of the method of the invention. This pipe is isolated from other connections by closing valves.

[0072] System 1 comprises a polluted pipe 2 including a branch connection on pipe 3 upstream of the polluted pipe 2. In the process of the invention, a reservoir 4 containing said anionic surfactant alone or in aqueous solution 5 is connected to an injection pump 6, itself connected to an injection lance 7. The injection system, comprising the injection pump 6, the injection lance 7, and a generator (not shown in [Fig. 1]), allows the anionic surfactant 5 to be injected into the polluted pipe 2 at a flow rate of 0.15 L / min for a cast iron pipe 900 m long and 80 mm in diameter. Before the injection of the anionic surfactant, potable water is circulated through the polluted pipe 2 at a flow rate of 9 m³ / h. The flow rate of drinking water is controlled using a flow meter and a valve (not shown in the [Fig.l) connected to a fire hydrant 8 downstream of the contaminated pipe. Pipe 2 includes an outlet valve 9 which remains closed during the injection of the anionic surfactant and the circulation of the aqueous composition in the contaminated pipe (step i)). The injection of the anionic surfactant 5 circulates an aqueous composition comprising potable water and the anionic surfactant 5 within the contaminated pipe. The injection lasts approximately 30 minutes. The injection is then stopped, and the valve on the fire hydrant 8 is closed, allowing the aqueous composition to stagnate in the pipe for approximately 15 minutes. Then, potable water is circulated through the pipe at a flow rate of 9 m³ / h for a flushing step (step ii)). This step lasts approximately 40 minutes.One or more steps iii) of measuring the quantity of total organic carbon in the liquid circulating in the pipeline may be carried out at a fire hydrant 10 as an intermediate control post. During these measurement steps iii), the potable water flow rate is reduced to 5 m3 / h.

[0073] By way of example, Table 1 below lists the TOC values ​​according to the liquid flowing in the pipeline. The surfactant content in the aqueous composition is given as a percentage by mass, relative to the total mass of the com- aqueous position.

[0074] [Tables 1] Liquid concerned TOC measurement (mg / l) Drinking water before step i) 0.4 Aqueous composition with 0.007% anionic surfactant during step i) 4.04 Aqueous composition with 0.07% anionic surfactant during step i) 33.3 Drinking water after step ii) 0.4

[0075] Example 2: Determination of the effectiveness of the process according to the invention

[0076] The effectiveness of the process of the invention was determined on a poly-vinyl chloride (PVC) pipeline polluted with different types of hydrocarbons.

[0077] First, water is circulated through a clean PVC pipe. At T0 (T0 = 0 min), the concentration of four compounds belonging to the aromatic hydrocarbon group in the water circulating in the pipe is measured. Then, a diesel fuel-type liquid is intentionally circulated through the PVC pipe for 20 min. At T1 (T1 = 20 min), the concentration of the four compounds belonging to the aromatic hydrocarbon group in this liquid circulating in the pipe is measured. An aqueous composition is prepared comprising an anionic surfactant at 0.07% by mass (relative to the total mass of the aqueous composition). At T2 (T2 = 60 min), this aqueous composition is injected into the pipe according to step i) of the process of the invention. The composition is allowed to circulate in the pipe for approximately 30 min and then remain stagnant in the pipe for approximately 10 min.At T3 (T3 = 100 min), the concentration of 4 compounds belonging to the aromatic hydrocarbon group is measured in the aqueous composition circulating in the pipe. Then, the pipe is rinsed with water according to step ii) of the process of the invention. At T4 (T4 = 160 min), i.e., after 60 min of rinsing the cleaned pipe, the rinsing is stopped and the concentration of 4 compounds belonging to the aromatic hydrocarbon group in the water circulating in the pipe is measured.

[0078] Table 2 below lists the mass concentrations of four compounds belonging to the group of aromatic hydrocarbons found in the liquid circulating in the pipe before and after implementation of the process of the invention. C(T0) corresponds to the concentration of the species in the water circulating in the pipe before contamination. C(T1) corresponds to the concentration of the species in the liquid circulating in the pipe during contamination. C(T3) corresponds to the concentration of the species in the aqueous composition circulating in the pipe during cleaning. before rinsing. C (T4) corresponds to the concentration of species in the water circulating in the pipe after rinsing.

[0079] [Tables2] Benzene concentration (yg / L) Toluene (pg / L) Ethylbenzene (pg / L) o-xylene (pg / L) (To) <0.10 0.081 <0.10 <0.10 C (Ti) 0.57 13 8.30 15 C (T3) 0.43 10 6.90 13 C(Ti) <0.10 0.13 0.10 0.17

Claims

Demands

1. A method for cleaning at least one pipeline polluted by one or more organic compounds adhering to the internal walls of the pipeline, said polluted pipeline being intended to convey drinking water, said method comprising at least the following steps: - a step i) in which an aqueous composition comprising drinking water is circulated in the polluted pipeline, and - a step ii) of rinsing the pipeline at the end of step i), to obtain a depolluted pipeline, said method being characterized in that the aqueous composition further comprises at least one anionic surfactant suitable for food contact, and the one or more organic compounds are selected from aromatic hydrocarbons, petroleum derivatives, bituminous residues, greases, lubricants, and a mixture thereof.

2. A process according to claim 1, characterized in that the anionic surfactant comprises at least one sulfonate, sulfate, and / or carboxylate function.

3. A process according to claim 1 or 2, characterized in that the aqueous composition comprises from 0.0001 to 0.15% by mass of the anionic food contact surfactant(s), relative to the total mass of the aqueous composition.

4. A method according to any one of the preceding claims, characterized in that step i) comprises circulating potable water in the polluted pipeline, and injecting said anionic surfactant into the polluted pipeline, preferably in turbulent flow.

5. A method according to any one of the preceding claims, characterized in that step ii) of rinsing is carried out by circulating potable water in the pipeline at the end of step i), preferably in turbulent flow.

6. A method according to any one of the preceding claims, characterized in that it further comprises a step iii) of measuring the quantity of anionic surfactant in the pipeline, preferably by measuring UV absorption at a wavelength of 254 nm or the quantity of total organic carbon in a liquid contained in the pipeline.

7. A method according to any one of the preceding claims, ca- characterized in that step i) is carried out from 45 min to 2 hours to remove said organic compounds adhering to the internal walls of the polluted pipe.

8. A process according to any one of the preceding claims, characterized in that the organic compounds are polycyclic aromatic hydrocarbons.

9. A method according to any one of the preceding claims, characterized in that the method further comprises, before step i), a step i-0) of purging the polluted pipeline.

10. Use of an aqueous composition comprising potable water and at least one food-contact anionic surfactant, for cleaning a polluted pipeline, in particular a drinking water infrastructure, said pipeline being polluted by one or more organic compounds adhering to the internal walls of the pipeline, the one or more organic compounds being selected from aromatic hydrocarbons, petroleum derivatives, bituminous residues, greases, lubricants, and a mixture thereof.