FR2791971A1 - Removal of asbestos from water used when clearing asbestos from buildings in an economical process using equipment which can be moved from site to site - Google Patents

Abstract

Water for treatment is collected (10 and 10') and treated by coagulation (18), flocculation (19), settling (20), and filtration (22). The filtrate obtained can then be discharged to drain. Sludges produced are drained, then subjected to an asbestos removal treatment. Two sets of treatment equipment are arranged in parallel for alternate use and cleaning.

Description

The present invention relates to the treatment of waste water from

  asbestos removal sites. We know the problems caused by asbestos removal from buildings. Asbestos is a fibrous material which has been shown to be very highly carcinogenic, and the techniques currently used for its elimination in existing buildings must take into account its character.

dangerous to public health.

  Known asbestos removal techniques generally comprise two phases: the first consists in dismantling the finishing work and in removing the asbestos, and during the second phase, a fine cleaning of the asbestos is carried out, a compulsory prerequisite for the reconstruction, this cleaning being carried out by the wet method using high pressure cleaners equipped with rotary brushes and coupled to air + liquid filtration devices. The law and the specifications impose a rate of suspended matter in discharged water less than 45 mg / I. peak and at 30 mg / I on average, with a filter breaking capacity of five microns. Currently available filtration equipment

  in commerce has proven unsuitable for meeting these constraints.

  In addition, another problem arises which results from the quantities of water to be treated which consist, on the one hand, of cleaning water which can reach 90 m 3 / day, this water being loaded with 500 to 1000 mg / l of suspended matter, and on the other hand shower water allowing operators to decontaminate when they leave the area to be removed, which can represent a daily volume of around 20 m3 loaded with 150 mg / I of matter in suspension. It is not possible, at present, to find on the market filtration units adapted to the quantities and qualities of the waters

  to be treated on asbestos removal sites.

  The present invention has therefore set itself the objective of treating the waste water from the fine cleaning of asbestos, by the wet method, used in asbestos removal processes, with a view to reducing the rate of suspended matter in these waters, so as to comply with the regulations in force in this

  domain as well as the specifications of asbestos removal sites.

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  The subject of this invention is therefore a process for treating water resulting from asbestos removal practiced on buildings during which a fine cleaning of the asbestos is carried out, at high pressure by the wet method, the water thus used being loaded with asbestos, process being characterized in that: - all the contaminated water loaded with asbestos is centralized; - these contaminated waters are treated by decantation, flocculation and coagulation; - the water thus treated is filtered before being discharged into the sewer and, - the sludge loaded with asbestos is collected, this sludge being treated as

  as asbestos waste after draining.

  The present invention also relates to a device for implementing the method as specified above. This device is characterized in that it comprises: - at least one tank in which all the contaminated water loaded with asbestos is collected, the latter undergoing a first decantation in said tank; a separator receiving the contaminated water, having undergone the first decantation in said receiving tank, this water, before being fed into said separator, being added with a flocculant and a coagulant; - flocculation, coagulation and decantation tanks, arranged in line and supplied from said separator and, - means for filtering the purified water coming from the decantation tanks. According to a preferred embodiment of this device, two identical lines of tanks are provided, each comprising a tank for receiving and first settling contaminated water and coagulation, flocculation and settling tanks, said lines operating in parallel and being able to be stopped.

  separately, especially for cleaning.

  Preferably, the device which is the subject of the invention is produced so that it is

  mobile allowing it to be positioned in the immediate vicinity of the work areas.

  Other features and advantages of this invention will become apparent from the

  description given below with reference to the accompanying drawing, the single figure of which illustrates

  an exemplary embodiment devoid of any limiting character.

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  As can be understood, the process which is the subject of the invention lowers the suspended matter contained in the waste water from asbestos removal sites by a treatment equivalent to a treatment for the partial purification of polluted water and not by a treatment filtration as is the case in the known technique. To this end, the polluted and contaminated water is centralized and the latter is then treated by decantation, flocculation and coagulation. In the embodiment illustrated by the single figure, two identical lines of treatment tanks are used, these two lines operating in parallel. Of course, this is only an exemplary embodiment devoid of any limiting nature, the installation according to the invention may include only one

processing tank line.

  In this exemplary embodiment, the water collected from the floors of the building to be removed from the atmosphere is received in tanks such as 10, 10 ′. This water comes not only from the cleaning water but also from the operators' shower water as mentioned above. These waters undergo a first decantation in the tanks 10, 10 ′, in which the floating particles are also retained. The water to be treated is then aspirated using a pump 12 and discharged into a centrifugal separator 14 after addition of a coagulant and a flocculant carried out using metering pumps 16, 16 '. After passing through the separator 14, the waters are subjected to coagulation, flocculation and sedimentation treatments respectively in the tanks 18, 19, 20 and 18 ', 19', 20 '. After treatment in a filtration installation designated in its

  together by reference 22, the purified water is discharged to the sewer.

  The sludge which is concentrated by the centrifugal separator 14 is purged by automatic valves such as 21, 21 ′, this sludge then being collected in bag filters 23, 23 ′, with the sludge coming from the sedimentation tanks and which are collected in trays 24, 24 '. After draining, the

  filter bags are removed in order to be treated as asbestos waste.

  The advantages provided by the present invention are in particular the following: 1) Total compliance with regulations and specifications: the sampling of discharged water reveals that the treatment according to the present invention

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  makes it possible to obtain suspended solids rates which are less than half the legal threshold, which effectively makes it possible to eliminate any filtration; 2) Reduction of costs: the elimination of expensive filtration units and consuming labor and filters makes it possible to reduce the cost prices in significant proportions (around 85%). 3) Possibility of making modular and mobile treatment units, suitable for different asbestos removal sites, these units can be

  positioned in the immediate vicinity of the areas to be treated.

  4) Improvement of working conditions given the total absence

emission of asbestos fibers.

  It remains to be understood that the present invention is not limited to the embodiments described and / or mentioned above but that it

includes all variants.

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Claims (4)

  I Process for treating water resulting from asbestos removal practiced on buildings during which a fine cleaning of the asbestos is carried out, at high pressure by the wet method, the water thus used becoming charged with asbestos, this process being characterized in that : - all contaminated water loaded with asbestos is centralized; - these contaminated waters are treated by decantation, flocculation and coagulation; - the water thus treated is filtered before being discharged into the sewer and, - the sludge loaded with asbestos is collected, this sludge being treated as   as asbestos waste after draining.   2 Device for implementing the method according to claim 1 characterized in that it comprises: - at least one tank (10, 10 ') in which are collected all the contaminated water loaded with asbestos, the latter undergoing a first decantation in said tray; - A separator (14) receiving the contaminated water, having undergone the first decantation in said receiving tank, this water, before being fed into said separator, being added with a flocculant and a coagulant; - flocculation, coagulation and decantation tanks (18, 19, 20); (18 ', 19', ') arranged in line and supplied from said separator and, - means (22) for filtering the purified water coming from the settling tanks. 3 Device according to claim 2 characterized in that it comprises two identical lines of tanks each comprising a tank for receiving and first settling contaminated water and coagulation tanks, flocculation and settling, said lines operating in parallel and can be stopped   separately, especially for cleaning.   4 Device according to one of claims 2 or 3 characterized in that it is   designed is realized in a modular and mobile form.