GB2351730A - Treatment of laundry water - Google Patents

Abstract

A process for purification of waste water from domestic laundry washing involves the use of flocculents for removal of soils by floc formation and separation, prior to re-use. The flocculent system comprises a primary flocculent of multivalent cations/polyethylene imines with a polyelectrolyte as secondary flocculent. A water purification kit comprising flocculent, a washing container for carrying out a household washing process and a detergent composition comprising a polyelectrolyte secondary flocculent are also disclosed.

Description

2351730 Process and Comppsition for Water Recycle

Field of the Invention

This invention relates to products and processes to enable consumers to re-use soiled wash water for example from washing processes, in particular laundry washing processes.

BackgLo-und In many countries, domestic wash habits are labour intensive and, furthermore, require large quantities of water for washing and rinsing stages. This is particularly the case for laundry washing processes. Often, inftastructure may not allow use of automatic filling/draining machines, water may have to be collected by hand and waste-water disposal may even be problematic. Such water may be recycled in conventional ways by general waste-water treatment (sewerage) or disposal directly into waterways.

Water purification processes are well known in the art, for example in GB2004535A a water clarification process is described in which polyelectrolytes are used as a flocculent. These may be either nonionic, anionic or more preferably cationic polyelectrolytes. Coagulants such as particulate minerals may be used in addition to the polyelectrolyte to assist in coagulation. The invention is said to be useful in treating waterways e.g. river water.

GB 13 91578 also relates to compositions and methods for flocculating suspended solids. It relates in particular to the removal of particles having a particle diameter of less than 10 microns. The patent specifically relates to water intended to be used for drinking, as a municipal water supply. The patent teaches use of a pre mix of water -soluble cationic and nonionic polymers in specific ratios for good water clarification.

SU891575 describes clarifying highly muddy raw water in a two stage treatment in which coagulation with aluminium sulphate is followed by filtration and subsequent treatment with polyacrylamide. SU1085942 relates to clarification of 2 waste-water from bore holes which contain clay, petroleum products, polymers and surface active agents. The water is cleaned by treating with a mixture of polyacrylamide and a polyelectrolyte of polyethyleneamine and alkaline metal chlorides. JP06071112, JP063091 10, JP54073464, JP76042078 and JP51093550 5 also relate flocculation water purifying processes.

In FR 2466438, a process is described for purifying water used in laundrettes so that it can be disposed of without overloading sewerage water treatment plants and without adding ingredients such as surfactants and phosphates directly into rivers. Alurninium sulphate and anionic polyelectrolyte are used as the flocculents.

US 5807487 treats wastewater from laundromais. Water is first held in an equalisation tank and then transferred to a second tank for acidification to a pH of not less than 6.5. A coagulant which is preferably polyaluminium chloride is then added to effect a second pH change to not less than 5.0 for further coagulation to form treated water and sludge which are then separated.

GB 1543411 describes processes form reclaiming waste water containing synthetic detergents. First, a water-insoluble surfactantis added to form an emulsion with the synthetic detergent. The emulsion is then broken by adding a flocculating agent, or by electrochemical or ultrafiltration methods.

However, all of the processes described above relate to industrial processes and do not solve the particular problems of the consumer as set out above. SummM of the Invention in accordance with the present invention there is now provided a process for treating water from a household washing process comprising separating from the items being washed, the waste-water from the washing and/or rinsing step containing organic and/or inorganic soil and surfactant, contacting the waste-water with a flocculent system comprising (i) a primary flocculent selected from multivalent cations and polyethyleneimines or mixtures thereof and (ii) a secondary flocculent selected from anionic and nonionic polyelectrolytes or mixtures thereof so that flocs are formed, separating the flocs out of the waste-water to produce purified water, and re-using the purified water.

3 In accordance with a further aspect of the invention there is also provided a a process for treating water from a household washing process comprising separating from the items being washed, the waste-water from the washing and/or rinsing step containing organic and/or inorganic soil and surfactant, contacting the waste-water 5 with a flocculent system comprising (i) a primary flocculent selected from multivalent cations and polyethyleneimines or mixtures thereof and (ii) a secondary flocculent selected from cationic polyelectrolytes or mixtures thereof so that flocs are formed, separating the flocs out of the waste-water to produce purified water, and reusing the purified water.

Preferably the household washing process is a laundry washing process. in a preferred process according to the invention, the purified water is reused in a ftirther household washing process, such as a dishwashing, laundry or personal cleansing, preferably a laundry process step, either washing and/or rinsing. Preferably the water is reused in a washing step. Such wash and/or rinse water may be purified for recycle more than once.

The invention also includes a water purification kit for household use comprising at least one unit dosage of flocculent, a unit dosage comprising from 0.5 250g flocculent and optionally means for removing flocs from treated water.

The invention also comprises a water purification kit comprising a water purification composition for household use comprising flocculent, means for providing a unit dosage of flocculent and optionally, means for removing flocs from treated water.

In a fin-ther embodiment of the invention there is also provided a washing container for carrying out a household washing process in which waste-water from the washing and rinsing step of the washing process is purified by removal of particulate solids, the washing container comprising an inner layer and an outer layer, a first of said layers forming a continuous surface so that water for washing can be held in the washing container during the washing process and a second of said layers providing a sieve enabling flow of water through the layer whilst restraining particulate solids.

4 In accordance with a finther aspect of the invention there is also provided a detergent composition comprising the secondary flocculent.

Preferably, the secondary flocculent is Present in the detergent composition in an amount such that after washing and removal of items being washed, the amount of secondary flocculent remaining is sufficient to promote flocculation on addition of the primary flocculent. Detailed Descrilgion of the Invention Addition of the Flocculent: Water Treatment SLep After washing clothes and/or other items in an aqueous liquor containing detergent, or after adding rinse water to carry out a finse step, the waste wash or rinse water is separated from the items being washed. The washing process may be any household washing process such as personal cleaning such as bathing, dish-washing, hard surface cleaning or laundry washing. Generally the washing process will be a laundry washing process and the waste-water will be separated from the wet laundry.

The waste-water will contain particulate and/or colloidal soils which are either organic and/or inorganic, in addition to detergent ingredients. In accordance with the process of the present invention the waste-water may be separated out by removal of the items being washed such as laundry from the water so that subsequent water treatment takes place in the washing container itself, or by draining off the liquor and collecting in a treatment container.

A flocculent system is then added to the waste-water in the form of a solid, such as a powder or tablet, or in the form of a liquid such as an aqueous solution, or mixtures thereof. The primary and secondary flocculents may be added to the wastewater either simultaneously or sequentially.

The Flocculent The flocculent comprises a flocculent system comprising a primary flocculent and a secondary flocculent. The primary flocculent is selected from multivalent cations and polyethyleneimines. Examples of multivalent cations are salts, including polymeric salts, of aluminium, manganese 11 or iron 111. Preferred examples are alurniniurn salts. One preferred source of aluminiurn ions is aluminium chloride. A further preferred source or aluminium ions is aluminium sulphate. A further preferred source of aluminium ions is polymeric aluminium chloride. A further preferred source of aluminiumm is polyaluminium silicate sulphate. Mixtures comprising more than one of these aluminium sources are also suitable. Iron VI ions (ferrate ions) may be preferred because, upon dissolution in water, iron III ions and peroxide will form so that some bleaching effect is added to the water for re-use, this may be advantageous particularly where the re- use stage is a laundry washing step. However, in general, the iron compounds may not be preferred in view of discoloration due to the presence of iron Ill ions.

Use of aluminium polyvalent metal ions is preferred. Whilst anhydrous or hydrated salts may both be used, hydrated salts are preferred. In particular, aluminium sulphate and aluminium chloride have been found to be particularly beneficial as they produce flocs which are rapidly formed and which may float to the surface of the waste-water and can therefore be easily removed. In a particularly preferred aspect of the invention, hydrated salts of aluminium are used as flocculent. A1C13.6H20 and A]2(S04)3.16H20 are preferred, as these have been found to promote especially rapid floc flotation in waste-water from household washing processes, particularly laundry liquors. In one embodiment of the invention, it may be preferred that the primary flocculent comprises mixtures of aluminium sulphate and aluminium chloride. The hydrated salts are particularly preferred. Mixtures of the aluminium sulphate and chloride salts comprising 5 - 60%, preferably 15 - 35%, more preferably 20 - 30% aluminium sulphate and 40 - 95% by weight, preferably 65 - 85%, more preferably 70 - 8(r/o aluminium chloride may be particularly preferred. Where the primary flocculent comprises a polyethyleneimine, suitable materials tend to have molecular weights which are less high than the molecular weights of the polyclectrolytes mentioned below, for example no greater than 5 x 1 06, preferably no greater than 1. 5x 1 06 and most preferably no greater than IX106.

Suitable secondary flocculents are organic polyelectrolytes. In accordance with one aspect of the invention, cationic polymers, preferably having a high molecular weight are preferred. However, in accordance with a flirther preferred 6 embodiment of the invention anionic and/or nonionic polyelectrolytes are preferred as the secondary flocculent.

Many suitable synthetic cationic polymeric materials are available and these are generally high molecular weight polyamides or polyamines. Particularly preferred are derivatives of polyacrylamide. Preferred molecular weights (M,,,) based on viscosity measurements are in the range I W to 10'. Preferably the molecular weight will be above 4xW, most preferably above 5xlO". Molecular weights around 6x 10" or higher are particularly preferred.

The cationic polyelectrolytes are polymers preferably having a degree of cationicity (percentage of the number of side groups which are reacted to provide a cationic group) greater than 20%, more preferably greater than 30%, and even more preferably greater than 40% or even above 60%. Particularly preferred materials have a molecular weight above 4 X I C and a cationicity greater than 40%. Suitable materials may be made by copolyrnerisation of acrylamide and quaternary (r) ammonium polyacrylamides. Examples of suitable polymers include Zetag 89, 0 Praestol 611 BC, Calfloc 1552, 1506 and 1508, and PolyminakKP97 (tradenames).

Nonionic and anionic polymers are also known in the art as flocculents, and in a highly preferred aspect of the invention, the secondary flocculent comprises a nonionic and/or anionic flocculent. Suitable anionic or nonionic polyelectrolytes are generally water-soluble high molecular weight acrylamide polymers. These may be polymers of methacrylarnide but are preferably polymers of acrylamide. Other monomers may be copolyrnerised with the (meth) acrylamide to impart anionic properties. Preferred polymers, such as polyacrylamides, have a high molecular weight, for example, above I million and often 2 to 30 million, and normally having intrinsic viscosity (in dl/g), above 5 and generally above 8. For very high molecular weights which may also be suitable, the intrinsic viscosity may even be above 10 and typically 12 to 16 or higher. Preferred polymers may have solution viscosities (as measured in a Fann viscometer at 25"C, based on a 1% solution in deionised water, and at a shear rate of 5.11 sec-1 of at least 350 cps, preferably at least 500, or even at 7 least 1000 cps. The molecular weight is preferably greater than 2 x 10' and preferably no greater than 20 x 106.

Suitable anionic polyelectrolytes may have a degree of anionicity (percentage of the number of side groups which are reacted to provide an anionic group) greater than 5%, or even greater than 10%, and even greater than 20%. Particularly preferred examples include the anionic and nonionic polyacrylamides, such as MagnaflocTm range from Allied Colloids. Such flocculants preferably have high molecular weights such as Magnafloc 155 and/or Magnafloc 351 or ultra high molecular weights such as Magnafloc; 919.

In a preferred aspect of the invention, a pH-modifier which is an acid source may be added to the waste-water prior to, or simultaneously with the primary flocculent. Since the multivalent cations react initially with anions such as phosphate, silicate and carbonate present in the waste water, the addition of an acid source enables reduced levels of primary flocculent to be used and therefore may be preferred. The acid source is preferably added to the waste water in an amount to generate an acidic pH of from about 2.5 to 7. Suitable acid sources are for example any acid, but carboxylic acids are particularly preferred such as, for example, di or polycarboxylic acids. Suitable examples comprise malic acid, citric acid, tartaric acid, maleic acid, glutaric acid, adipic acid, succinic acid and mixtures thereof.

Polymeric carboxylic acids include for example polyacrylic acids and their copolymers.

In accordance with a particularly preferred embodiment of the invention, in particular where the the secondary flocculent comprises an anionic or nonionic polyelectrolyte, a pH modifier which is an alkali source is also added to the waste- water. Suitable alkali source pH modifiers are described in more detail below. However, it is particularly preferred that the alkali source should be a buffering agent and carbonate salts such as sodiumOTpotassium carbonate are particularly preferred. Preferably at least the primary flocculent is delivered to the waste-water prior to delivery of the alkali source. This may be achieved for example by dosing the alkali source after dosing the flocculent system or after dosing the primary flocculent alone.

8 However, preferably it is dosed simultaneously with the primary flocculent and more preferably also simultaneously with the secondary flocculent, and the form of the primary flocculent and of the alkali source are selected so that the primary flocculent wfll be released into the waste-water more quickly than the alkali source.

For example, the primary flocculent may be added as a solution which is immediately delivered to the waste water. However, more preferably the flocculent is dosed in a powder/granular form. This may be achieved by dosing the primary flocculent as a smaller particle size than the alkali source, for example the geometric mean particle size of the allWi source particles may be at least 25Lrn larger than the geometric mean particle size of the primary flocculent particles, or even at least 50Lrn or even at least 75Lrri greater than the particle size of the primary flocculent. Alternatively, the alkali source may be provided in a slow release form such that it is coated or encapsulated with a water-soluble or disintegratable coating which delays the release of the alkali source.

As used herein, the phrase "geometric mean particle diameter" means the geometric mass median diameter of a set of discrete particles as measured by any standard mass-based particle size measurement technique, preferably by dry sieving.

A suitable sieving method is in accordance with ISO 3118 (1976). A suitable device is a Ro-Tap testing sieve shaker Model B using 8 inch sieves of selected sizes. As used herein, the phrase "geometric standard deviation" or "span" of a particle size distribution means the geometric breadth of the best-fitted log-normal function to the above-mentioned particle size data which can be accomplished by the ratio of the diameter of the 84.13 percentile divided by the diameter of the 5Y' percentile of the cumulative distribution (D84.13/D50); See Gotoh et al, Powder Technology Handbook, pp. 6-11, Marcel Dekker 1997.

After completion of flocculation and dissolution of the allwi-source, the preferred pH of the resulting floc-containing waste water is from 4.0 to 7.0, preferably 4.5 to 6.5.

9 An additional benefit may arise on addition of the alkali-source as effervescence may result due to reaction with polyvalent metal ions or other acid source present in the waste water. This may be desirable to promote floc flotation.

When cationic polyelectrolyte is used, the water produced after removal of the flocs may comprise high levels of polyvalent metal ions. The addition of an alkali source may also be useful in this respect as it may promote precipitation and therefore removal of these high concentrations of polyvalent metal ions. In such cases, as an alternative to the direct addition of an alkali source, such undesirably high ion concentrations may be removed by passing treated water through a bed comprising a solid support and alkali source such as a bed of sand comprising carbonate salts, or by passing treated water through a cation or mixed bed ion exchange resin bed.

In one preferred aspect of the invention, it may be preferred that the primary flocculent and the secondary flocculent are added to the waste-water simultaneously.

Alternatively, the primary flocculent may be added prior to addition of the secondary flocculent. Again this may be achieved by dosing both components simultaneously, but selecting the respective forms of the primary and secondary flocculents such that the primary flocculent is delivered to the waste-water prior to delivery of the secondary flocculent.

As a further preferred alternative, the secondary flocculent may be a component of the washing detergent which is present throughout the washing process, so that in the recycle step, flocculation occurs with addition of only primary flocculent and optional other ingredients such as pH modifier and/or effervescence system, or with the addition of these components and only low levels of secondary flocculent, after separation of the items being washed. Tbus, the present invention also encompasses processes in which a detergent composition comprising secondary flocculent is used in a domestic washing process and after separation of the items being washed, the primary flocculent is added to the waste-water to produce flocs which are then separated from the waste water, so that the water can be reused.

Preferably the flocculent system is dosed to the waste-water with stirring, or after addition of flocculent to the waste-water, the mixture will be stirred either mechanically or more usually by hand, preferably the stirring will be vigorous as this promotes rapid distribution of the flocculent through the waste water, thereby promoting efficient floc formation. Where flocculents are added sequentially, preferably there will be a stirring step after the addition of each component of the flocculent. Such mixtures have been found to produce particularly effective floc formation; rapidly formed, high strength flocs, even when using low quantities of flocculent for the amount of soil present in the wash liquor.

The amount of flocculent required depends to some extent upon the level of soil in the waste-water for purification. Generally, the total flocculent required will be from 0.05, or from 0. 1 or even from 0.5 g/Ito 20g/l or below I OgIl or even below 5 g/I water to be purified.

If the primary flocculent comprises polyvalent metal salts, these are generally used in amounts of from 0.005 to 10 g/I water to be purified, preferably in amounts of from 0. 1 to 10 g/l. A standard waste-water volume for treatment may be from 2 to or may be from 3 to 70 or 4 to 40 litres. However, when washes are carried out in a machine, slightly higher volumes of waste-water may need to be treated such as to 100 litres, more generally around 20 to 70 litres and more generally around 25 to 40 litres.

Therefore, for such waste-water treatments, especially when machines are used, the preferred dosage for the salt of polyvalent cation is generally an amount of from 40-100 g, preferably 50-120g, more preferably 60-100g.

Preferably, when the waste-water is from a hand wash step, the preferred flocculent levels will be from 0.5 to 20g/l generally above 2g1l or even above 3g/I or even above 5gA.

The secondary flocculent which may be cationic or anionic or nonionic is preferably dosed to the waste-water in amounts of from 0.00 1 -1 g/I water to be purified. More particularly, such polymeric materials are present in amounts of from 0.0 1 to 2.0 g/l or even 0. 1 - 0.8 g/l. Generally such polymeric materials are added in solution for example, as a 0. 1 to 10% by weight by solution or even a I - 10% by weight solution in water. Thus, for a standard waste-water volume to be treated, often around 30 litres, generally from 10-200ml or 10 to 100m] of a 1% solution of a polymeric flocculent component will be used, preferably from 20-50 ml, for stronger concentrations proportionally equivalent lower volumes or higher volumes of lower concentrated solutions may be used.

In addition to the flocculent components mentioned above, floc building aids may also be added to the waste-water. Suitable as floc building aids are for example, clays and/or talc, and/or synthetic zeolites, natural zeolites, celluloses especially long fibre celluloses and mixtures thereof Other optional additional ingredients in the water treatment step are dye fixation polymers which may be used to collect any dye remaining in the waste-water, for removal, pfl-modifiers, deodorants, perfinnes, antimicrobial agents, bleaching agents, dyes, suds suppressors. Dye fixation polymers in particular may be co-precipitated or trapped as part of the flocs formed during the floc formation.

The flocs formed in the process of the present invention are preferably strong so that they are not broken up substantially on separating out the flocs from the waste-water. Preferably, in addition, the flocs formed comprise a high proportion of large flocs, such as at least 60%, more preferably at least 80% of flocs having a diameter greater than 250 microns, preferably greater than 400 microns, more preferably greater than 750 and even above 1000 microns. 'Me flocs will generally not have a floc diameter greater than 5000 microns, or may be up to a maximum of 2000 microns. It is particularly preferred for the flocs formed to have floc size such that at least 70% by weight of the flocs has a floc size between 1200 and 1900 microns. These measurements are based on the proportion of flocs which pass through or stay on sieve sizes as defined, when the waste-water containing flocs is poured through a sieve. Such large flocs are particularly preferred as they enable rapid separation of the purified water.

Sgparation out of FIggs 12 The flocs formed are then separated out from the waste-water by any convenient method which is described in more detail below.

If it is desired to ensure that the flocs formed will float for ease of removal, the flocculent components may be added to the waste-water for purification in addition to a gas-producing means. Such a gas-producing means may be provided by simply bubbling gas into the waste-water as the flocs form. Alternatively, an effervescence system may be provided by a gas-producing reaction such as a carbon dioxide-producing reaction of, for example, acid and alkali in situ in the waste water. These acid and alkali reactants may be added to the waste water, for example with the flocculent system or may be components already present in the waste water. In particular, where the primary flocculent is provided by multivalent metal ions, these may provide the acid source. Alternatively, acid sources may be added to the waste water, such as a carboxylic acid, for example, di or polycarboxylic acids. Suitable examples comprise malic acid, citric acid, tartaric acid, maleic acid, glutaric acid, adipic acid, succinic acid and mixtures thereof, and an alkali source such as a carbonate, bicarbonate or sesqui-carbonate salt or mixtures thereof. Generally alkali metal salts of the carbonates are used. These components may be added in any relative proportions to produce gas, generally they wfl] be provided in substantially stoichiometric proportions. The effervescence system may also be used to ensure the appropriate pH of the purified water produced for re-use.

Re-Use of the Purified Water - After separation out of the flocs the water remaining is purified water which can be re-used. In a preferred aspect of the invention the water is re-used in a finiher laundry washing or rinsing step. Depending upon the re-use purpose of the purified water, the pH of the purified water may be modified. Preferably the flocculents are selected so that the purified water will have the desired pH for re-use, but a pH modifier may be added to produce the desired pH for any particular re-use purpose. For example, for a rinse step, in particular if it is intended to use a fabric conditioner, it is desirable for the purified water to have an acid pH, below 7 and generally from 2-7 or from 2 to 6. However, should the pH be too high or too low any acid or alkali, 13 respectively, may be added prior to addition of the fabric conditioner, in an amount such that the desired pH results.

For re-use as rinse water, to which fabric conditioner will be added, it is particularly preferred that the concentration of sulphate ions in the rinse water should not be so high that precipitation of the fabric conditioner occurs. 7lis can be avoided for example by use of lower levels of aluminium sulphate as the primary flocculent. Preferred primary flocculent may therefore be non-sulphate multivalent cations such as aluminium chloride or even mixtures of the aluminium sulphate and chloride salts, for example comprising from 5 - 60%, preferably from 15 - 35%, more preferably from 20 - 30% aluminium sulphate and from 40 - 95% by weight, preferably 65 - 85%, more preferably 70 - 80% aluminium chloride are particularly preferred. Such mixtures have been found to be preferred compared to the use of sulphate salts alone as the use of sulphate salts alone tends to reduce the ability of fabric softeners to dissolve in the water. Alternatively, sulphate ions may be removed prior to addition of the fabric conditioner for example using an ion exchange resin.

An additional benefit of the present invention may be the carry over into the purified water of useftd ingredients for the re-use. For example the surfactant concentration may be reduced by a factor of around 5 to 20, generally around 10, and the proportion of surfactant carried over into the re-use water will be beneficial where the re-use step is a washing step. Furthermore, perfumes and/or dyes from a laundry detergent may be carried over into the purified water. This results in water for re-use which is desirable for a laundry rinsing step, having an attractive colourand/or fiuce for use in a rinse step. Thus in a further preferred aspect of the invention, the water purification process is used in combination with a laundry detergent comprising a flugrance which is judged to have a stronger odour than 3,7 dimethyl-2,6, octadiene- I -nitrile (geranyl nitrile). This assessment is made by a panel of five trained perfumers and a comparison is made between a 201/G by weight solution of the fragrance in diethyl phthalate compared with a 20% by weight solution of geranyl nitrile. The comparison should be carried out using smelling 14 strips. Using such a perfume provides fragrance carry-over for re-use in the purified water, e.g. in a laundry rinse step.

In a further preferred embodiment, perfumes and/or dyes may be added with the flocculent to produce attractive fi-agrance and/or colour, suitable for use as a rinse water. Where the purified water is to be re-used in a laundry washing step, it is desirable for the water to have a pH which is greater than 7. Again, either the flocculent is selected so that this automatically results or a pH modifier may be added prior to re-using the purifed water. Any alkali may be added to achieve the desired alkaline pH.

In particular, for re-use for washing steps, it has been found that efficiency of the detergents may be adversely affected by the presence of high electrolyte concentrations due to the addition of polyvalent metal salts as flocculents. It was - found that this could be overcome by the use of an ion-exchange filter or by the addition, preferably to the purified water prior to the addition of laundry detergent, of chelant for the metal ions, optionally with pH-modifier to ensure the appropriate neub-al to alkaline pH for laundry detergent maximum performance.

Suitable chelants include builders such as the water soluble and/or insoluble builders described below, but are preferably heavy metal ion sequestrants. Watersoluble builders and heavy metal sequestrants are preferred, particularly the latter.

These may be added to the purified water in amounts to provide a concentration of at least a few ppm as even very low concentrations may be effective. For example, from 0.005 to 10 g/l may be added. HeM metal ion Muestrant Heavy metal ion sequestrant are particularly preferred chelants for use in the present invention. By heavy metal ion sequestrant it is meant herein components which act to sequester (chelate) heavy metal ions. These components may also have calcium and magnesium chelation capacity, but preferentially they show selectivity to binding heavy metal ions such as iron, manganese and copper, or any other metal ion which has been added as a flocculent.

Suitable heavy metal ion sequestrants for use herein include organic phosphonates, such as the amino alkylene poly (alkylene phosphonates), alkali metal ethane 1 -hydroxy disphosphonates and nitrilo trimethylene phosphonates. Examples include diethylene triamine penta (methylene phosphonate), ethylene diarnine tri (methylene phosphonate) hexamethylene diamine tetra (methylene phosphonate) and hydroxy-ethylene 1, 1 diphosphonate, 1, 1 hydroxyethane diphosphonic acid and 1, 1 hydroxyethane dimethylene phosphonic acid.

Preferred suitable heavy metal ion sequestrants for use herein include nitrilotriacetic acid and polyaminocarboxylic acids such as ethylenediaminotetracetic acid, ethylenediamine disuccinic acid, ethylenediamine diglutaric acid, 2 hydroxypropylenediamine disuccinic acid or any salts thereof.

Other suitable heavy metal ion sequestrants for use herein are iminodiacetic acid derivatives such as 2-hydroxyethyl diacetic acid or glyceryl imino diacetic acid, described in EP-A-317,542 and EP-A-399,133. The iminodiacetic acid-N-2 hydroxypropyl sulfanic acid- and aspartic acid N-carboxymethyl N-2- hydroxypropyl 3-sulfonic acid sequestrants described in EP-A-516,102 are also suitable herein. Tle P-alanine-N,N'-diacetic acid, aspartic acid-N,N'-diacetic acid, aspartic acid-N monoacetic acid and iminodisuccinic acid sequestrants described in EP-A- 509,382 are also suitable. EP-A-476,257 describes suitable amino based sequestrants. EP-A 510,331 describes suitable sequestrants derived from collagen, keratin or casein. EP A-528,859 describes a suitable alkyl iminodiacetic: acid sequestrant. Dipicolinic acid and 2-phosphonobutane-1,2,4-tricarboxylic acid are alos suitable. Glycinamide-NN disuccinic acid (GADS), ethylenediamine-N-M-diglutaric acid (EDDG) and 2 hydroxypropylenediaminc-N-N'-lisuccinic acid (HPDDS) are also suitable.

Especially preferred are diethylenetriamine pentacetic: acid, ethylenediaminc-N,N'-disuccinic acid (EDDS) and 1, 1 hydroxyethane diphosphonic acid or the alkali metal, alkaline earth metal, ammonium, or substituted ammonium salts thereof, or mixtures thereof Water-Purification ComMsition 16 The present invention includes a water-purification kit for household use suitable for purifying water for re-use, the kit comprising at least one unit dosage of flocculent, a unit dosage comprising 0.03 250g flocculent, preferably from 0.05 to I OOg flocculent. As described above, preferably the flocculent comprises a primary flocculent and a secondary flocculent, so that a preferred kit comprises primary and secondary flocculant, preferably in the form of separate unit dosages to be used in the process described above, either simultaneously or sequentially. In a particularly preferred kit according to the invention, the flocculant is therefore provided in two separate unit dosages comprising a first unit dosage comprising primary flocculent in an amount of from 10 - 200g where the primary flocculent comprises polyvalent, metal ions or 0.03 - 5g where the primary flocculent comprises PEI, and a second unit dosage comprising secondary flocculent in an amount of from 0.01 to 20g, preferably 0.01 to 10g, most preferably 0.01 to 5g.

The unit dosages may contain other materials such as binders, fillers, processing aids, solvents and/or disintegrants. The unit dosages may also contain an effervescence system as described above and this may serve the dual function of producing gas to enhance flotation of the flocs formed and in addition, act as a disintegrant for the unit dosage form to ensure rapid release of the flocculent to the waste-water. Other suitable disintegrants are those conventionally used in the pharmaceutical and tablet art, such as in EP 711828A, EP 488484A and EP 522766A.

The water purification kit may also contain a unit dosage pH-modifier and/or chelant as described above, where it is desired to re-use the purified water in a laundry washing step.

The present invention also comprises a water purification kit comprising the water purification composition and in addition a means for removing flocs formed, such as one or more filters or high surface area implements for collecting and removing flocs from the treated waste-water.

Separation out of Flocs 17 The floes formed in the process of the present invention may be separated out from the waste-water by any convenient method. For example, especially where the floes float, they may be removed from the surface of the waste-water by skimming off the floes, or removal for example using an implement such as a ladle or spoon.

Alternatively, where the floes sink or float, the clear water may be removed e.g. by syphoning, or pouring/decanting from either above or below the floes until the floes would start to be carried over. At this point the floc-containing water may be treated as waste. Alternatively, the floes may be removed by stirring a high surface area implement in the floc-containing waste-water, such as a brush which entraps the floes and can then be removed. Such a brush may be designed such that the charge or other surface properties e.g. tackiness, on the brush attracts the floes. Such a brush can then be dried and the dried floes easily removed. Alternatively, the floes may be removed by a filtration process, either by draining the floc-containing water through a filter placed either at the exit point for water of the treatment container or for example, by providing a sealable, removable lid or fi-ame, comprising a filter, over the washing container so that water can be poured through the filter out of the washing container, or the filter which may be a IiC, as described may be positioned at the entrance of a container into which the cleaned water is being passed for storage or immediate re-use. A filter may even be pulled through the floc-containing water to entrap the formed floes. Suitable filters include any filters comprising an appropriate mesh size. Ilie mesh size should not be so small that very slow filtration is effected and the filter becomes blocked by the floes. Equally, the filter should not have a mesh size which is so great that large amounts of the floes pass through the mesh. Suitable materials include paper, textiles, metal, polymeric materials including foam materials (polyurethane foam of standard pore sizes have been found to be particularly useful), or mineral materials such as porous stone beads. 'me preferred filters are at least partially flexible so that a filter can be fitted with ease, for example, into a washing machine or other treatment container.

Filters may be reusable and can be cleaned between filtrations, for example, floes may be removed from reusable filters, such as metal or plastic sieves or textile 18 filters or brushes, relatively easily, by brushing or scraping or other physical removal methods after drying. Alternatively, the filter may be disposable so that a new filter is used after one or a number of filtrations.

in accordance with a further aspect of the invention there is also provided a washing container for carrying out a household washing process in which wastewater from the washing and/or rinsing step of the washing process is purified by removal of particulate solids, the washing container comprising an inner layer and an outer layer, a first of said layers forming a continuous surface so that water for washing can be held in the washing container during the washing process and a second of said layers providing a sieve enabling flow of water through said layer whilst restraining particulate solids.

Where the washing container comprises a disposable filter, such a filter will be easily removed and replaced, for example a roll of filter material may be provided to the base of the washing container or a separate filter container, which can be unwound to expose a new portion of filter material as required between filtz-ations. Drawing An example of a preferred embodiment of the invention, is given in Figure I which illustrates a cross-sectional view through a container according to the invention. In this embodiment of the invention, the inner layer provides the sieve.

The inner layer I fits snugly inside the outer layer 2 and the sieve 3 is provided in the innerlayer.

Figure 2 shows an expanded cross-section from A-A of Figure I - It can be seen that sieve 3 is provided in inner layer I and that in accordance with a preferred aspect of the invention, a removable closure 4 is provided so that in use in the washing process, the washing or rinsing water does not contact sieve 3. Removable seal 4 can be removed at the end of the washing process by pulling release means 5. The removable seal is made of a resilient material which fits snugly but which can be deformed or flexed so that the sieve 3 can be exposed for a filtering step in which water flows through the sieve and solid particulates are restrained on the sieve.

19 Figure 3 shows a cross sectional view of an alternative embodiment for use at A-A, in which the sieve 3 is provided in the inner layer I and removable seal 4 is provided over the sieve which can be removed using release means 5. The embodiment shown in figure 2 is preferred as it will be obvious to a person skilled in the art that release means 3 which is fitted over upwardly extending lugs 6 will prevent water contacting sieve 3 below the upper level of projecting rim 6, so that incomplete filtration occurs. However, this remaining water can be discarded along with the particulate solids so that such an embodiment is therefore still useful.

In the embodiments of the invention illustrated in Figures I to 3, at the end of the washing process, removable seal 4 is removed exposing sieve 3 through the waste water and inner layer I is lifted out of the outer layer 2 and held so that water can flow through sieve 3 and enter container 2, whilst particulate solids are restrained on sieve I The purified water from which the particulate solids have been removed is then suitable for e-use in outer layer, 2.

A further embodiment of the invention is illustrated in Figure 5. In this embodiment, the outer layer provides sieve 3 and the inner layer 9 has a port with closure 8 which ensures that the inner layer provides a continuous surface so that water for washing can be held in the washing container during the washing process but, on opening the port by removing closure 8, water for purification can flow through sieve 3 entrapping particulate solids on sieve 3.

Form the above embodiments it can be seen that the sieve does not need to extend across the entire inner or outer surface, although such an embodiment is also within the ambit of the present invention.

Exit Port 8 may be provided by any removable seal such as a bung or tightly fitting lid, or a segmented diaphragra which can be opened and closed.

Generally, the sieve extends only across a portion of the inner or outer surface. However, in figure 6, it can be seen that the sieve itself comprises the whole outer layer.

The sieve is generally formed from polymeric materials such as polyethylene or polypropylene, alternatively it may be formed from any suitable material which enables water to flow through the sieve whilst restraining particulate solids. The mesh size of the sieve should be sufficiently small to entrap solids whilst not impeding flow of water and should not be so large that the particulate solids for filtration flow through the sieve. Generally, the mesh size of the sieve will be from 10 to 300 Lrn, preferably from 100 to 250 pm. Alternative materials for forming this sieve are metal or any other material. Where the sieve itself is made from flexible material, strengthening can be achieved by incorporating the mesh into a solid support, for example as shown in Figure 4 where the rim I I and spokes 12 are formed from any rigid material such as a polymeric material and the sieve 13 may comprise for example nylon or any other flexible mesh material.

It will be seen that the water container embodiment of the invention in all its aspects is highly suitable for use with the water purification process of the invention, whereby the particulate solids will be flocs produced by the addition to the waste water of the flocculent system and optional other additives.

Examples

ExMple 1.

Soiled laundry was washed in 30 litres of water with a standard dose of a commercially available phosphate-based laundry detergent composition, providing a concentration of laundry detergent in the wash water of 2500ppm.

After the washing process was completed, and the detergent suds had disappeared, the soil content in the water was 4g/l, determined by drying a sample in a drying oven at 120T. Into the 30 litres of waste-water, were added 70g of a Mixture Of A'2(SO4)3'16H20 and AIC13.61120, the mixture comprising these components in a weight ratio 30:70. After gentle stirring for 10 seconds, 30ml of a (ILVA) 1 wt % solution of Polymin"K097 (trade name of BASF) were added with gentle stirring for 90 seconds. Large flocs were formed. The waste-water containing the flocs was then drained from the water container through a polyurethane foam disc which captures the flocs and allows rapid permeation of the clear water through the foam for collection and re-use. The pH of the resulting purified water was approximately 4, resulting in a liquid suitable for re-use as a rinsing liquid, with an 21 attractive clear appearance. 'Re water was re-used in a laundry rinsing step to which a commercially available fabric softening composition was incorporated at the manufacturers recommended dosage.

Example 2

A commercially available phosphate-based laundry detergent composition was dissolved in 5 litres of water, providing a concentration of laundry detergent in the wash water of 560Oppm. Into this a model soil, comprising a blend of typical soils that might be found on dirty clothes, was dosed at a concentration equivalent to 250Opprn to give a solution of waste-water.

Into these 5 litres of waste-water, were added a flocculent system comprising 22.5g aluminium chloride hexahydrate, 7.5g aluminium sulphate hexadecahydrate (aluminium chloride and aluminium sulphate in a weight ratio of 3:1),andO. 375g Magnaflocrm 155. 1 1.5g sodium carbonate were also added. All of these additives were added simultaneously in a granular form. After vigorous stirring large flocs were formed. Effervescence could be noted and the flocs produced gathered at the surface of the water. 71e waste water prior to addition of the flocculent system appeared cloudy. The waste-water containing the flocs was then drained, through a 150gm filter which captures the flocs and allows rapid permeation of the clear water through the filter for collection and re-use. 'Re pH of the resulting purified water was approximately 6, resulting in a liquid suitable for re-use in a washing step of a household washing process, with an attractive clear appearance.

Example 3

In 5 litres of water a standard dose of a phosphate-based laundry detergent composition was dissolved having the following approximate composition:

Sodium alkyl benzene sulphonate 20 vnO/o Sodium tripolyphosphate 30 v^ Sodium carbonate 15 wt% Sodium sulphate 15 wt% Sodium Silicate 10 wto/o Sodium perborate (mono and tetra 22 hydrate) 2.5 wt% Suds supressor 1 wt% Magnafloc: 155 1.6 wt% Perfume, water and miscellaneous to 100 wto/o, providing a concentration of laundry detergent in the wash water of 250Oppm. Into this a model soil was dispersed at a level of 2.5g/1 or 2500 ppm, to give the wastewater. Into the 5 litres of waste-water, were added the primary flocculent, comprising 11.25g aluminium chloride hexahydrate and 3.75g aluminium sulphate hexadecahydrate (aluminium chloride and aluminium sulphate in a weight ratio of 3: 1). 5.5g sodium carbonate were also added. All of these additives were added simultaneously in a granular form. After vigorous stirring large flocs were formed. Effervescence could be noted and the flocs produced gathered at the surface of the water. The clear water can then separated from the flocs for example by syphoning off clear water from below the flocs or by filtering through a sieve, and collected for re-use. Alternatively the solution can be drained, through a polyurethane foam disc which captures the flocs and allows rapid permeation of the clear water through the foam for collection and re-use. In this example the flocs were separated from the clear water by filtering through a 150gm filter. The resulting purified water was suitable for re-use in a washing step or rinsing step of a household washing process, with an attractive clear appearance.

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Claims (28)

1. I A process for treating water from a household washing process comprising separating from the items being washed the waste-water from the washing and/or rinsing step containing organic and/or inorganic soil and synthetic detergents, contacting the waste-water with a flocculent system comprising a primary flocculent selected from multivalent cations and polyethylene imines, or mixtures thereof and a secondary flocculent selected from anionic and nonionic polyelectrolytes and mixtures thereof so that flocs are formed, separating the flocs out of the waste-water to produce purified water, and re-using the purified water.
2. 2. A process for treating water from a household washing process comprising separating from the items being washed, the waste-water from the washing and/or rinsing step containing organic and/or inorganic soil and synthetic detergents, contacting the wastc-water with a flocculent system comprising a primary flocculent selected from polyvalent cations and polyethyleneamines or mixtures thereof and a secondary flocculent selected from cationic polyelectrolytes and mixtures thereof, and re-using the purified water.
3. 3. A process according to claim I or claim 2 in which a pH-modifier which is an alkali-source is also added to the waste-water.
4. 4. A process according to claim 3 in which the pH-modifier is a carbonate salt or any other buffering salt.
5. 5. A process according to claim 3 or claim 4 in which at least the primary flocculent is delivered to the waste-water prior to delivery of the alkali-source.
6. 6. A process according to claim 5 in which the primary flocculent and the secondary flocculent and the alkali-source are dosed in to the wastewater simultaneously and the alkali-source is in a slower dissolving form than the primary flocculent.

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7. 7. A process according to any preceding claim in which a pH-modifier which is an acid source is delivered to the waste-water in addition to the flocculent system.
8. 8. A process according to claim 7 in which the acid-source is delivered to the waste-water prior to or simultaneously with the delivery of the primary flocculent.
9. 9. A process according to claim 8 in which in a first contacting step the waste water is contacted with the primary flocculent and is stirred, so that floc formation begins and in a second contacting step, the waste-water is contacted with the secondary flocculent.
10. 10. A process according to any preceding claim in which the household washing process is a laundry washing process.
11. 11. A process according to any preceding claim in which the flocculent system is such as to generate floating flocs. 15
12. 12. A process according to any preceding claim in which comprises providing an effervescence system in the waste water which producestreleases a gas.
13. 13. A process according to any preceding claim in which the primary flocculent and the secondary flocculent are contacted with the waste-water sequentially.
14. 14. A process according to any preceding claim in which the purified water is re20 used in a further laundry process step, either washing or rinsing.
15. 15. A process according to any preceding claim in which, prior to re-use a chelant is added to the purified water, to chelate the metal ions of the flocculent.
16. 16. A process according to any of claims I to 15 in which the flocs are separated out of the waste-water by lifting a filter or sieve through the floc- containing water.
17. 17. A water purification composition for household use comprising flocculent, said flocculent comprising a primary flocculent selected from polyvalent metal cations and/or polyethyleneimines and a secondary flocculent comprising anionic, nonionic or cationic polyelectrolytes or mixtures thereof.
18. 18, A water purification kit for domestic use comprising at least one unit dosage or means for providing at least one unit dosage comprising 0.03-250g flocculent.
19. 19. A water purification kit according to claim 18 comprising a first unit dosage comprising a primary flocculent selected from polyvalent metal ions or polyethyleneimines or mixtures thereof, and a second unit dosage comprising a secondary flocculent selected from anionic, nonionic or cationic polyelectrolytes or mixtures thereof
20. 20. A water purification kit according to claim 18 or claim 19 comprising primary flocculent and secondary flocculent comprising anionic and/or nonionic flocculent and additionally comprising an alkali-source.
21. 21. A water purification kit according to any of claims 18 to 20 in which the form of the primary flocculent and alUi-source will dissolve in the waste- water for treatment more slowly than the primary flocculent.
22. 22. A water purification kit according to any of claims 18 to 21 in which the primary and secondary flocculents, and alkali source are all in granular form, the alkali-source being provided in a form with a slower overall rate of dissolution than the primary flocculent.
23. 23. A washing container for carrying out a household washing process in which waste-waterfirom the washing and/or rinsing step of the washing process is purified by removal of particulate solids, the washing container comprising an inner layer (1) and an outer layer (2), a first of said layers forming a continuous surface so that water for washing can be held in the washing container during the washing process and a second of said layers providing a sieve (3) enabling flow of water through the later whilst restaining particulate solids.
24. 24. A washing container according to claim 23 in which the inner layer provides the sieve.
25. 25. A washing container according to claim 23 or claim 24 in which a removable seal is also provided, in use in the washing process, the removable seal substantially preventing contact of the water with the sieve, and at the end of the washing process.
26. 26 26. A washing container according to claim 23 or claim 25 in which the outer layer provides the sieve and the inner layer comprises a closeable outlet port which is closed during the washing process and is opened to enable flow of water through the outer layer.
27. 27. A detergent composition comprising a secondary flocculent which is a polyelectrolyte in an amount sufficient to promote flocculation after the washing step is completed.
28. 28. A detergent composition according to claim 27 in which the secondary flocculent comprises a high molecular weight polyacrylamide.