FR2499544A1 - Reclamation of domestic waste water - by treatment with oxidising agent or alkali and cation exchange - Google Patents

Abstract

Method of recycling waste water from small habitation units (e.g. mobile homes, aircraft, space vehicles, ships, or houses in desert areas) comprises (a) treating with an oxidising agent or alkali and an adsorbent in a decanter, (b) pumping the treated water through a filter, (c) treating with a cation exchanger, opt. followed by active carbon, and (d) storing the regenerated water, which must contain less than 10 ppm organic C, in a tank. Step (a) can be effected with H2O2, NaOCl, Ca(OCl)2, NaOH, KOH or soda-lime in the presence of a carbon, clay or molecular sieve adsorbent. Step (b) is pref. effected on a tangential filter. The process permits at least 50% (esp. at least 90%) recovery of water from personal-, linen- and dish-washing operations.

Description

WASTEWATER RECYCLING PROCESS
The present invention relates to a process for recycling water making it possible to obtain regenerated water containing less than 10 ppm of organic carbon.

 Whether in habitable land vehicles such as caravans, camper vans or in air vehicles such as airplanes, aerospace devices or in habitable boats such as sailboats or other motor boats, weight and opportunity problems Access to reusable water arises acutely.

 Similarly, in some arid areas for example, there is the problem of available water for fixed dwellings. Most of the water consumed by humans is used in flushing toilets, for personal washing, for laundry or for washing dishes. Only a small part of the order of around 5 to 10% is used for cooking or drinking.

 It was therefore interesting and many attempts have been made to do so, to try to regenerate the water for washing, washing and washing up which represents more than half of the waste water in order to recycle it for the same uses without the Organoleptic quality or bacterial or microbial pollution problems arise acutely.

 Numerous means have been proposed in an attempt to resolve this problem, all of which have some drawback making them either too expensive or too complex and difficult to implement in a limited space.

 A process has now been found for recycling wastewater from small housing units, characterized in that the wastewater to be purified first undergoes chemical and physicochemical treatment allowing water of bacteriological and physico quality to be obtained. suitable chemical in a decanting storage tank then pumped and sent to a filter before undergoing, on all or part, a treatment on cation exchange material possibly followed by a treatment on activated carbon then are stored in a tank, the regenerated water containing less than 10 ppm organic carbon.

 By recycling process is essentially meant a process which makes it possible to recover a large part, at least 50% but preferably 75% and more preferably at least 90% of the waste water used. Wastewater mainly comprises washing water, either from people, clothes or washing up water. Washing water for people and clothes mainly contains soaps, washing powders, solids such as grains of sand, dust and grease. Dishwashing water mainly contains detergents and food residues: fats - sugars - vegetable foods - salts.

All types of proteins - carbohydrates and fats can be present. The various impurities are present either in the form of solids in suspension or not depending on their size and density, or in solution, or in colloidal form.

 The process is particularly suitable for the treatment of wastewater from small residential units and allows the treatment of quantities varying from a few tens to a few hundred liters per day.

 .I1 is therefore not a process allowing the replacement of heavy installations such as treatment plants whose 3 treatment volumes are measured in m3 / h and not in liters.

 However, under certain specific conditions, it would be possible to envisage increasing the volumes treated by the method according to the invention: there is, in fact, no technical impossibility but only economic consequences to be considered.

 The method according to the invention consists of a first step in treating the waste water in the storage container whose specially studied shape allows the settling of the solid materials present and the sludge. This storage container is advantageously equipped with a coarse filtration system for the waste water which arrives, like a grid, to retain the largest waste which could clog the pipes.

 A device is also optionally provided to allow agitation of the wastewater during the chemical treatment. This device can consist of manual or electrical agitation by propeller or any type of agitation. One can also use the pump which will send the used water in the following devices to, by means of a bypass, to set in motion the water of the settling tank.

 It is finally possible in the case of mobile vehicles not to provide any particular device, the stirring of the water being automatically carried out by the movement of the vehicle in which the device is placed.

 The chemical treatment which will make it possible to obtain water of bacteriological and physicochemical quality making it suitable for domestic washing uses consists of either an oxidizing treatment or an alkalizing treatment.

 It is indeed important that the reused water is not at the origin of contagion and is not the cause of dermal effects of bacteriological or viral origin or due to physico-chemical properties for example too much astringency by excess of acidity or basicity.

 A physicochemical treatment can also be validly carried out which will make it possible for example to deflocculate the waste water or to complete the chemical treatment.

 This chemical treatment will be carried out either in the form of an oxidizing treatment, or in the form of an alkalizing treatment.

 The oxidation treatment is advantageously obtained by adding hydrogen peroxide. It is preferable to use hydrogen peroxide at 110 volumes.

 An amount between 1 cm3 and 10 cm3 may be suitable for a volume of 100 liters of wastewater to be treated.

 One can also use sodium hypochlorite or calcium hypochlorite. Sodium hypochlorite, for example in the form of bleach or bleach extract, depending on the chlorometric strength of the solution used, is very suitable.

 Particular interest has been found in using calcium hypochlorite. This may be, in fact in the form of a tablet or a dose previously determined and conditioned.

 It is also possible to envisage treatment by using a mixture of the reagents indicated above.

 An amount of calcium or sodium hypochlorite of between 1 and 10 g and preferably between 1 and 5 g per liter of waste water to be treated is suitable.

 Advantageously, calcium hypochlorite is used having a chlorometric degree greater than 100.

 Another advantage of the use of calcium hypochlorite lies in the fact that during the oxidation of wastewater a calcium precipitate is formed which improves the filterability of the treated water by chemical transformation of the soluble or colloidal salts d fatty acids coming either from soaps and detergents, or from fatty foods in insoluble salts easily precipitable and eliminable.

 The oxidation treatment has a duration which varies according to the mass and pollution of the product to be treated, according to the amount of oxidizing material used and also according to the temperature of the water to be treated and the stirring carried out.

 A minimum duration of approximately 5 to 10 minutes is however necessary to obtain good oxidation. A longer duration, of the order of an hour, is entirely suitable and makes it possible to lead to residual organic carbon levels of less than 10 ppm.

 Another kind of chemical treatment also makes it possible to obtain the bacteriological quality sought for purified water: it is an alkaline treatment. This treatment must allow the wastewater to have a pH greater than it and preferably greater than 12.

A treatment time of around 10 minutes is a minimum. A treatment duration of 30 min to 1 hour is preferred.

 -This treatment can be carried out by adding, with stirring, sodium hydroxide or potassium hydroxide tablets or in concentrated solution or lime or soda lime in tablets or powder.

 Amounts of these pure alkaline agents of between 0.2 and 5 grams per liter of water and preferably from 0.8 to 1.5 9 / l generally make it possible to obtain a pH of the wastewater greater than 12.

 It goes without saying that if the waste water has a very acid pH #, it will be necessary to use more alkaline agent.

 Such oxidative or alkaline treatments make it possible to obtain, with a suitable duration, waters whose qualities comply with the standards prescribed by institutes and other official bodies.

 The physicochemical treatment which may take place at the same time or after the chemical treatment is essentially intended to complete the bactericidal treatment.

Other functions can be attributed to it, such as the absorption and adsorption of certain compounds from wastewater and colloidal matter.

 Such a treatment can be carried out by adding and mixing absorbent and adsorbent pulverulent products. Such products are well known. Mention may be made, among other things, of active charcoals, pulverized charcoals, natural clays or molecular sieves.

 Activated carbon will preferably be used having a particle size between 0.1 and 5 mm and more preferably between 0.5 and 2.5 mm. This activated carbon preferably has a large specific surface, advantageously greater than 1000 m2 / g. Good results are obtained with coals having a specific surface of 1500 m2tg and an apparent density of 0.3 to 0.5. This activated carbon is also most often presented in cartridges provided with a water inlet and outlet. Pulverized charcoal or other absorbent or adsorbent material may be suitable.

 Amounts per liter of waste water to be treated from 0.1 to 5 g and preferably from 0.5 to 1 g are suitable. It goes without saying that larger quantities can be introduced, but this will not significantly improve the quality of the water.

 A minimum contact time, of the order of a few minutes is necessary, as well as good agitation. It may be noted that this physico-chemical treatment, unlike the chemical treatment, can be carried out later during the treatment process, for example by passing the treated and filtered water over a layer of absorbent material.

 The waste water which has been oxidized or alkalized and has possibly undergone the physico-chemical treatment, after decantation, is then taken up by pumping to undergo the following treatments. Any type of pump driven either by electrical energy, or by human energy as a hand or foot pump, can be suitable: neither large flow nor high pressure is required. Flow rates of the order of 10 to 50 l / h are suitable as well as pressures of the order of 0.2 to 0.5 bar.

 The pumped water is sent to a filtration system. Any known filtration system suitable for the treatment chosen may be suitable, for example filtration on paper, on nonwoven, on sintered material, on porous metal, on synthetic or natural fabric.

 However, it is advantageous to implement a filtration system such that the risks of clogging are very reduced or even zero.

 It has been found that good results are obtained using a tangential filter allowing a filtrate flow rate of 5 to 40 ljh and a concentrate flow rate of 5 to 20 l / h, the concentrate being returned to the storage container.

 The fact of being able to use in the tangential filter a filtering medium which may be pre-clogged to a predetermined particle size makes it possible to obtain a totally purified filtrate of particles having a diameter greater than a predetermined dimension.

 It is known that in a tangential filter the fluid to be purified arrives tangentially to the filtering surface and at constant speed.

The fluid; purified crosses the filter surface perpendicularly and only a predetermined part of the fluid to be purified, here called a concentrate whose concentration of impurities has been increased, is eliminated or possibly recycled if the filtration rate is not considered sufficient, the filtration rate being the rate by volume of filtrate relative to the water to be filtered.

 The flow of oxidized or alkalized and filtered water, in whole or in part, then undergoes a treatment on cation exchange material.

 It may be beneficial, in fact, to maintain a hydrometric titer of the water high enough to send only part of the flow of treated water.

 Preferably cationic resins with high exchange capacity (2 to 5 meq / l) are used. These well known resins which are widely used in the trade are, for example, polyacrylic resins with free carboxylic groups.

 These resins are most often used in cartridges with a water inlet and outlet.

 The flow of water, filtered and passed through cationic resin can optionally then pass over activated carbon.

 A variant of the process in the case where the wastewater is itself highly salted or else in the case where a significant proportion of saltwater coming, for example directly from the sea or salty water is added, implies some changes in the order and the nature of the treatments.

 The possibility of adding a certain proportion of salt water to the waste water can be interesting in the case of boats located at sea. However, it is not advisable to exceed a certain proportion which can be evaluated at 10 to 20%, because there is a risk of saturating the ionic resins used very quickly.

 If, however, spare cartridges are available, it is possible to greatly exceed the rates indicated above.

 The salted waste water which has been oxidized or alkalized and filtered as indicated previously, first undergoes a treatment on activated carbon followed by a treatment on cationic resin as indicated above. A final treatment with anionic resin is necessary to remove the anions which remain in the purified water.

The suitable anionic resins are anionic resins with high exchange capacity: 1 to 5 meqll and preferably
1.5 to 3 meq./l. These commonly used products are easily found commercially. They are generally polyacrylic resins with free polyamine groups. They are generally used in the form of cartridges having a water inlet and outlet.

 Another variant, as we have indicated above, consists in carrying out only the chemical treatment in the waste water storage tank and in providing, after filtration and passage through cationic resin, a passage over absorbent and adsorbent material such as activated carbon.

 The purified water leaving either the treatment with activated carbon or the treatment with anionic resin in the variant studied above is then conveyed to a storage tank.

 The water regenerated by the process according to the invention does not contain more than 10 mg / liter of organic matter expressed as organic carbon. They do not contain insolubles. Their hardness can be lower than 5 French degrees and one can be brought to improve the quality of the water to be placed for example in the storage tank, a small quantity of calcium carbonate which will make it possible to raise the degree of hardness of the water at a more common rate on the order of 10 to 15 for example.

 It is not within the scope of the invention to add after the oxidative treatment of the waste water slaked lime which will make it possible to flocculate the colloidal particles. It goes without saying that this additional treatment will only be applied in particularly difficult cases.

 The apparatus enabling the method according to the invention to be implemented will be adapted to the intended use both with regard to its dimensions and of the arrangement chosen. However, an indication will be given here of the type of equipment to be used.

 The plastic or metal waste water storage tank can have a capacity which varies according to the intended use from 20 1 to 200 1. However these figures are not critical and correspond only to capacities advantageously used in boats or habitable vehicles.

 This tank has at its upper part a coarse grid to stop larger particles. At the bottom, it has a conical or pyramidal area terminated by a valve to eliminate sludge and solids that have settled. Lateral tubing located at the bottom of the tank allows the wastewater to be drawn off. A device placed at the top of the tank allows on the one hand the possible passage of agitation and on the other hand the addition of the oxidizing or alkaline agent.

 A side inlet located at the top allows the recycling of waste water concentrated in impurities coming from the tangential filter or other.

 A pump draws the wastewater from the tank and sends it to the filter.

 As mentioned above, any filtration system may be suitable, but it is advantageous to avoid clogging problems to use a tangential filter or a candle type filter allowing a certain self-cleaning. Such a filter is essentially composed of an upstream chamber provided with a fluid inlet and a downstream chamber provided with a fluid outlet. The two chambers are separated by a filter system of conical, cylindrical or pyramidal shape.

The base of this filtering system is provided with an outlet allowing either the elimination, or the recycling of the quantity of water concentrated in impurities which did not pass through the filtering system and which entrained said impurities, preventing clogging. of the filter system.

 The filtering system consists of a porous layer of either a textile, non-woven, paper, sintered metal or other type.

 A preliminary precolmatae of the filtering system makes it possible to determine, the size of the particles for which the crossing of the filter is tolerated. Generally this particle size is between 1 and 3 microns.

 The filtrate is then sent to cationic resins and possibly activated carbon. These materials can be placed in independent cartridges. It is also possible to design a single cartridge subdivided into compartments each comprising the material necessary for the planned treatment.

 The water which has successively passed through the various cartridges or the various compartments is then sent to a storage tank for later use.

 In the case of prolonged storage, it may be advantageous to add a small amount of bactericidal agent.

 Such a device can allow a number of recycling of wastewater. This number depends on the quantity of waste water that passes each time and on the capacity of the cartridges of activated carbon and ionic resins.

 It goes without saying that if you want high quality purified water the number of passages will be more limited, because the activated carbon and ionic resins gradually saturate and gradually lose their effectiveness.

 It will be necessary for the proper functioning of the device to keep it constantly full of water.

 A simple change of the activated carbon cartridges and ion exchange resins as well as the emptying of the sludge located in the settling tank allow to restore the device for a new use.

 It will be advantageous for reasons of space of the device to provide cartridges of small dimensions, of a few liters for example, which will however allow to consider a dozen recycling in good conditions.

 Among the numerous advantages of such a device, the simplicity of the operation will be noted: it suffices to add the oxidizing or basifying agent to the full waste water tank, to stir for a few minutes and then to start the circulation pump.

 If a tangential or self-cleaning filter is used, there will be no clogging and the filter can therefore be used for a long time. The use of cartridges or other removable devices of the exchange resins and of the activated carbon will allow easily after a certain period of operation their replacement or their regeneration. The operating time will obviously depend on the quantity of purified water produced, but it can be estimated that, depending on the dimensions of the cartridges, it will be possible to produce one or more cubic meters of purified water without change.

 Periodic emptying of the bottom of the storage tank will remove sludge and other solids that have settled.

 This installation can operate without the use of electrical energy if a hand pump is provided for example, to agitate and circulate the water in the circuit.

 The following examples are given by way of illustration.

EXAMPLE 1
There is a cylindrical tank (1) of 100 liters of polyethylene capacity provided at its lower part with a cone terminated by a drain valve. This tank is equipped with manual agitation. The upper part of the tank has an inlet provided with a screen for waste water, another inlet for introducing the oxidizing agent and a third inlet connected to the lower part of the tangential filter allowing the recycling of the concentrates.

 At the upper part of the cone there is a feed which allows the decanted wastewater to be taken off by means of an electric pump (2) allowing a flow rate of 0.2 to 2 liters / minute. The discharge pressure is 0.3 bar.

 This tank is filled with a mixture comprising 20 parts of washing-up water and 80 parts of washing water. Dishwashing water from a restaurant has the following chemical composition: carbon of mineral origin 155 ppm, carbon of organic origin 735 ppm, or total carbon: 890 ppm.

 Matter in solution 358 mg / liter and pH 9. These waters have a cloudy appearance.

 The wash water has a pH of 7.5, a rate of matter in solution of 44 mg / liter, a rate of carbon of mineral origin of 150 ppm, a rate of carbon of organic origin of 352 ppm, i.e. total carbon level of 502 ppm. These waters have a cloudy appearance.

 50 g of calcium hypochlorite having a chlorometric degree of 1150 are added to the full tank, in the form of a powder.

The mixture is stirred manually for 30 seconds. Leave to stand for about an hour.

 The sampled water is sent at a flow rate of 0.3 liters / minute on a tangential filter (3) of 0.06 m2 of filtering surface, the filtering medium being a nonwoven made of polyester fibers pre-coated with 5 microns. The flow rate of the filtrate can vary according to the flow rate of the pump between 0.2 and 0.4 liters / minute, the flow rate of the concentrate being of the same order.

 The concentrate is returned to the storage tank (1).

The filtrate is sent to a cartridge (4) containing 2 liters of cationic resin of polyacrylic type sold under the trade name of DUOLITE C 20 H. The water leaving this cartridge then enters another cartridge (5) containing 2 liters activated carbon with a specific surface of 1,500 m2tg and a particle size between 0.5 and 2.5 mm: (sold under the trade name of BKA by BAYER).

 The water leaving this cartridge is sent to a tank (6) having a capacity of 100 liters of polyethylene. The waste water tank of -100 1 is purified after 4 hours of operation for the flow rate of 0.4 1 / mon.

 Samples are taken from the tank (6) and analyzes are carried out on a Beckmann type infrared carbon metering device.

The following results are obtained
- organic carbon: 10 mg / l
which is at the limit of sensitivity of the measurements
- hardness between 5 and 15 degrees French
- insoluble part = O (not measurable)
The water is therefore reusable for washing operations such as dishes or showers.

EXAMPLE 2
The procedure is as indicated in Example 1 but with waste water which contains 900 mg / l of organic carbon. 1 g / l of pure sodium hydroxide tablet is introduced into the storage container with stirring, which brings the pH of the wastewater to 12.5. Next, 1 g / l of activated carbon (commercial brand CK SS) and 0.1 g / l of solid calcium hypochlorite are introduced.

 The decanted wastewater is filtered and then 65% of the treated wastewater, after filtration is sent on cationic resin as indicated in Example 1. The remaining 35% of the treated and filtered wastewater is directly directed to the storage container.

 It is found that the recycled water has a pH of 7.5, has a hardness of 15 and that it is not possible to detect any trace of organic carbon.

Claims (6)

10 / Process for recycling wastewater from small units  residential characterized in that the waste water to be purified  first undergo treatment with an oxidizing or alkaline agent  and physicochemical to obtain quality water  bacteriological and physico-chemical suitable in a tank  storage settling tank then pumped and sent on a filter  before undergoing, on all or part, a treatment on material  cation exchanger possibly followed by treatment on  activated carbon then are stored in a tank, the water  regenerated containing less than 10 ppm organic carbon. 20 / A method according to claim 1 characterized in that, if the  wastewater contains a significant proportion of salt, this water  worn after filtration are additionally treated with resin  anionic. 30 / A method according to claim 1 characterized in that the  physico-chemical treatment consists of adding materials to  high absorbency and adsorbency like coals,  natural clays or molecular sieves and decanting  compounds that precipitate.  401 Method according to claim 1 characterized in that the  oxidizing treatment is obtained by adding water with stirring  oxygenated or sodium hypochlorite or sodium hypochlorite  calcium.  501 Method according to claim 1 characterized in that the  alkaline treatment is obtained by adding with stirring the  soda or potash or soda lime.  60 / A method according to claim 1 characterized in that the filter  used is a tangential filter, the overall recovery rate  committed water being at least 90% purified water. 70 / A method according to claim 1 characterized in that the  treatment on cation exchange materials can be followed  of an anionic resin treatment. 80 / A method according to claim 1 characterized in that the water  wastewater mainly includes wash water and  of dishes to which a proportion can be added  notable salt water coming directly from the sea or waters  saumatres.  9 / A method according to claims 1 to 8 characterized in that it  allows the recycling of waste water from boats or  habitable vehicles.