primary coagulants suitable for use herein include water - soluble inorganic salts and mixtures thereof . in highly preferred embodiments , the composition herein comprises an inorganic metal salt selected from the group consisting of iron sulphate , iron chloride , manganese sulphate , manganese chloride , copper sulphate , copper chloride , aluminium s ,. ilphate , aluminium chloride , poly - variations thereof , and combinations thereof . the inorganic metal salt of the composition of the present invention is selected on the basis that it can act as a coagulant and can interact with charged water - soluble impurities in such a manner so as to neutralise the charge of said water - soluble impurity to form a water - insoluble impurity , usually to form a water - insoluble salt of said impurity , which precipitates out of solution . the inorganic salt of the composition of the invention can also lower the turbidity of the water by increasing the particle size of the water - insoluble impurities possibly causing sedimentation or facilitating the removal of these water - insoluble impurities by filtration or other water - insoluble matter removal techniques such as flotation or decanting . the inorganic salts selected herein , can also co - precipitate heavy metal ions out of water , and can also lower the total organic content present in the water by coagulating or adsorption of this organic content onto the water - insoluble impurities which have been formed in the water . preferably the inorganic metal salt of the composition of the invention is a multivalent , preferably a di - or tri - valent , inorganic metal salt such as , aluminium iii sulphate , iron ii ( ferrous ) sulphate or iron iii ( ferric ) sulphate . a most preferred inorganic metal salt for use herein is iron iii sulphate . the term “ inorganic metal salt ” includes all poly - variations thereof such as polyaluminum chloride and polyferric material , but does not include compounds comprising methyl or ethyl groups . the inorganic metal salt is preferably free of carbon atoms . the term “ inorganic metal salts which are free of carbon atoms ” includes sources of inorganic metal salts which comprise minor amounts of carbon impurity such as often found in naturally occurring inorganic metal salt sources . for example , preferred inorganic metal salts of the composition of the invention comprise ( by weight of said salt ) less than 5 %, more preferably less than 3 %, more preferably less than 1 %, even more preferably less than 0 . 1 %, even more preferably less than 0 . 01 % carbon atoms . particularly preferred are those inorganic metal salts which are a source of acid , such as aluminium iii sulphate or iron sulphate . this is especially true when the composition herein also comprises a source of carbonate such as sodium carbonate , since the acid source , and carbonate source , may react together to form a gas . this process is known as effervescence and helps to disperse the composition herein , especially when the composition herein is in the form of a tablet . the composition herein preferably comprises ( by weight ) from 1 %, or preferably from 5 %, or preferably from 10 %, or preferably from 15 %, or preferably aom 20 %, or preferably from 25 %, and preferably to 50 %, or preferably to 40 %, or preferably to 30 % inorganic salt selected from the group consisting of iron sulphate , iron chloride , manganese sulphate , manganese chloride , copper sulphate , copper chloride , aluminium sulphate , aluminium chloride , poly - variations thereof , and combinations thereof . the water purification composition herein preferably comprises a coagulant aid ( sometimes referred to herein as ‘ first polymeric material ’). highly preferred are polymeric materials which comprises an amine group and which are therefore cationic in nature . the first polymeric material is selected on the basis that it can aid the coagulation and flocculation process and in particular can in conjunction with the primary coagulant aid particle adherence and the aggregation of water - insoluble particles into larger water - insoluble aggregated complexes known as flocs . the first polymeric material may also adsorb or coagulate oils , fats and other organic or inorganic matter , and may sequester heavy metal ions . the term “ amine group ” is defined herein as including primary amine groups , secondary amine groups , tertiary amine groups , quaternary amine groups such as quaternary ammonium groups , but the term “ amine group ” does not include amide groups . said amine group can be the group linking the monomeric units of the backbone of the polymeric material , or may be present as a side group of the polymeric material , for example as an amine side group of a polysaccharide . preferably the amine group is present as a side group . preferably , the polymeric material is substantially water - insoluble . “ substantially water - insoluble ” is defined herein as having at least 10 % by dry total weight of undissolved material present as determined by the following method : 1 g material is added to 1 litre of distilled water at a ph of between 6 . 0 and 8 . 0 , at 20 ° c . and stirred vigorously for 24 hours . the water is then filtered through a 3 micrometer filter , and the undissolved material which is collected by the filter step is dried at 80 ° c . until constant weight , typically for 24 to 48 hours . the weight of this undissolved material is then determined and the % dry weight of this undissolved material can be calculated . the amine group of the first polymeric material is preferably a least partly protonated when the first polymeric material comes into contact with water , typically this protonation reaction occurs at a ph of below 9 . 0 , and preferably at a ph of from 3 to 8 . thus , preferably the first polymeric material is cationic when in a solution of water at a ph of below 9 . alternatively , the amine group of the first polymeric material may already be in a charged state , for example a substituted or protonated state . the amine group of the first polymeric material may be a cationic quaternary ammonium group . the first polymeric material preferably comprises a polysaccharide comprising an amine group . the first polymeric material may comprise a cationic starch , for example , cationic starch obtained from potato starch , waxy maize starch , corn starch , wheat starch and rice starch . more preferably , the first polymeric material comprises a polysaccharide which comprises an amine group which is bound directly to the monomer saccharide backbone unit of said polysaccharide . more preferably the first polymeric material comprises a polymer of glucosamine where all the monomer saccharide backbone units are connected in a linear conformation via beta - 1 - 4 - glycosidic bonds . more preferably , the first polymeric material comprises a modified chitin , such as chitosan , modified chitosan , or salts thereof . most preferably the first polymeric material comprises chitosan or modified chitosan . the first polymeric material may be an impurity of chitin , and therefore , chitin may be a preferred source of first polymeric material for use herein . chitosan suitable for use herein is typically derived from the chitin of crustacea such as crabs , lobsters and shrimps . chitosan derived from the chitin of fungi can also be used herein . the chitosan for use herein is typically found in the shells of crustacea and can be extracted by any technique known in the art , for example by using the extraction techniques described in u . s . pat . no . 3 , 533 , 940 , u . s . pat . no . 3 , 862 , 122 , u . s . pat . no . 3 , 922 , 260 and u . s . pat . no . 4 , 195 , 175 . the first polymeric material for use herein typically has an amine modification degree of at least 0 . 1 , more preferably at least 0 . 2 , or preferably at least 0 . 3 , or preferably at least 0 . 4 , or preferably at least 0 . 5 , or preferably at least 0 . 6 , or preferably at least 0 . 7 , or preferably at least 0 . 8 , or preferably at least 0 . 9 , or preferably at least 1 . 0 . said modification degree is an indication of the amount of amine groups present in the polymeric material and is defined as the number ratio of the number of amine groups present in the polymeric material per monomer unit of the polymeric material . preferably , the first polymeric material has a weight average molecular weight of at least 10000 , or preferably at least 25000 , or preferably at feast 50000 , or preferably at least 75000 , or preferably at least 100000 . the composition herein preferably comprises ( by weight ) from 0 . 1 %, or preferably from 0 . 5 %, or preferably from 1 %, or preferably from 1 . 5 %, or preferably from 2 %, or preferably from 2 . 5 %, and preferably to 50 %, or preferably to 40 %, or preferably to 30 %, or preferably to 20 %, or preferably to 10 %, or preferably to 5 %, or preferably to 4 % first polymeric material . the composition also herein comprises a bridging flocculant ( sometimes referred to herein as the second polymeric material ). preferably the second polymeric material is substantially water - soluble at in - use concentrations and has a weight average molecular weight of at least about 100 , 000 , preferably at least about 2000000 . the second polymeric material is selected on the basis that it can act as flocculent and cause the aggregation of water - insoluble particles into larger water - insoluble aggregated complexes known as flocs . it is believed that the ability of the second polymeric material to act as a flocculent , is due to the combination of its high molecular weight , structure , and water - solubility properties . the second polymeric material is usually of greater molecular weight than the first polymeric material and preferably does not comprise an amine group . preferably the second polymeric material comprises an amide group . more preferably the second polymeric material is a polyacrylamide . the second polymeric material is preferably not a cationic polyacrylamide , and preferably , the second polymeric material is not cationic . preferably , the second polymeric material for use herein is nonionic or anionic , preferably anionic , more preferably the second polymeric material contains at least 0 . 02 , or preferably at least 0 . 05 , or preferably at least 0 . 1 anionic groups per monomer unit . the second polymeric material for use herein is typically a polyacrylamide , especially preferred are anionic or nonionic polyacrylamides . typical anionic and nonionic polyacrylamides for use herein are those from the magnafloc range supplied by ciba . of these polyacrylamides , especially preferred are those known under the trade name as magnafloc lt20 , magnafloc lt25 , magnafloc lt25s , magnafloc lt26 , magnafloc lt28 , magnafloc 351 and magnafloc 919 . it is preferred that a low amount of substantially water - soluble organic content is present in the composition herein . the term “ low amount of substantially water - soluble content ” can be determined by the following method : 500 mg of said composition is added to 1 litre of deionised water which comprises no detectable amounts of substantially water - soluble organic content , to form a solution . said solution is left with occasional stirring for 30 minutes and is then filtered through whatman gf / c paper having an average pore size of 1 . 2 micrometers to obtain purified water . the level of total organic content ( toc ) of said purified water is determined using the iso method 8245 : 1999 . a composition comprising “ a substantially low amount of water - soluble content ” is defined as a composition which gives a toc of said purified water of less than 10 ppm , preferably less than 7 ppm , more preferably less than 4 ppm when determined using this method . it is also preferred that a low amount of substantially water - soluble organic content is obtained on use of the composition either in - vivo or on model surface water . for this purpose , 620 mg of the composition is added to 1 litre of in - vivo or model surface water respectively and the test repeated . preferably , the toc of the water after treatment is less than 10 ppm , more preferably less than 7 ppm , and especially less than 4 ppm . preferably , the second polymeric material does not comprise a polysaccharide and more preferably the second polymeric material does not comprise a carboxymethyl cellulose or derivative thereof . preferably , the weight average molecular weight of the second polymeric material is at least 2500000 , or preferably at least 3000000 , or preferably at least 5000000 , or preferably at least 7500000 , or preferably at least 10000000 , or preferably at least 15000000 . preferably , the composition herein comprises ( by weight ) from 0 . 1 %, or preferably from 0 . 2 %, or preferably from 0 . 5 %, or preferably from 1 %, and preferably to 30 %, or preferably to 20 %, or preferably to 10 %, or preferably to 5 %, or preferably to 3 % second polymeric material . the composition herein comprises a uicrobiocidal disinfectant ( sometimes referred to herein as the disinfecting agent ). the disinfecting agent may comprise any compound which disinfects or sanitises water . the disinfecting agent may be inorganic such as silver salts , colloidal silver , nanosilver , ozone , chlorine dioxide , chlorine , sodium hypochlorite or chloramine . the disinfecting agent may also be organic such as a quaternary ammonium compound . preferred disinfecting agents include inorganic chlorine based disinfectants , wherein the chlorine is in a formal oxidation state that is not minus one , preferably above minus one . preferred sources of chlorine comprise hypochlorites ( especially calcium hypochlorite ) and organic sources of chlorine such as isocyanurates . other suitable disinfecting agents comprise iodine and sources of iodine such as polyiodide resins . as previously discussed , the disinfecting agent is preferably used in a controlled , delayed , sustained or slow release form . means for providing such controlled , delayed , sustained or slow release ( hereafter ‘ means for providing delayed release ’) can include blending or coating the disinfecting agent with , for example , a poorly water - soluble or hydrophobic material , or providing a coating of sufficient thickness that the kinetics of dissolution of the coating provide delayed release . poorly water - soluble or hydrophobic materials include waxes , paraffins , silicas , zeolites , clays , polymeric resins , celluloses , cross - linked polymers , insoluble salts such as calcium carbonate , etc . the coating material can be applied by agglomeration in , for example , pan , rotary drum and vertical blenders , or by spray atomization . other means for providing delayed release include mechanical means for altering the physical properties of the disinfecting agent , for example , compaction , granulation means for altering the particle size distribution of the disinfecting agent , etc . highly preferred herein from the viewpoint of achieving optimum flocculation and disinfectancy performance in water contaminated with high levels of organic impurities is a particulate disinfecting agent , preferably calcium hypochlorite , having a particle size distribution such that at least about 50 %, preferably at least about 75 %, more preferably at least about 90 % by weight is retained on a 210 μm ( tyler 65 mesh ) screen , preferably on a 425 μm ( 35 mesh ) screen , more preferably on a 600 μm ( 28 mesh ) screen , yet more preferably on a 710 μm ( 24 mesh ) screen , even more preferably on a 850 μm ( 20 mesh ) screen , and especially on a 1000 μm ( 16 mesh ) screen . in order to minimise random sampling variance in the final unit dose composition , it is also preferred that the particulate disinfecting agent has a particle size distribution such that at least about 50 %, preferably at least about 75 % by weight thereof passes through a 2000 μm ( 9 mesh ) screen and more preferably through a 1400 μm ( 12 mesh ) screen . the composition herein preferably comprises ( by weight ) from 0 . 01 %, or preferably from 0 . 1 %, or preferably from 0 . 2 %, or preferably from 0 . 5 %, or preferably from 0 . 7 %, or preferably from 1 . 0 %, or preferably from 1 . 2 %, or preferably from 1 . 5 %, and preferably to 20 %, or preferably to 10 %, or preferably to 5 %, or preferably to 4 %, or preferably to 2 . 5 % disinfecting agent . the oxidant systems suitable for use herein have been described in detail above . highly preferred are the autocatalytic oxidants such as the manganates and especially potassium permanganate . such systems are autocatalytic in the sense that the product of the reaction with soluble manganese , colloidal manganese dioxide , itself acts to catalyse the oxidation reaction , thereby enabling rapid oxidation within the timeframe of the coagulation / flocculation reaction . preferably the compositions herein comprise from about 0 . 001 % to about 0 . 15 %, preferably from about 0 . 01 % to about 0 . 1 %, more preferably from about 0 . 02 % to about 0 . 06 % by weight of the autocatalytic oxidant , oxidation catalyst or mixture thereof . in order to minimise random sampling variance in the final unit dose composition , it is preferred that the autocatalytic oxidant or catalyst be in particulate form with a minimum number of particles per unit dose of about 100 , the number of particles preferably being greater than about 150 and more preferably greater than about 200 . preferably the individual particles have an average weight of less than about 20 μg , more preferably less than about 10 μg . the composition herein preferably comprises a water - insoluble silicate selected from clays , zeolites and mixtures thereof . highly preferred silicates for use herein are clays . the clay acts as a seed particle onto which water - insoluble impurities can aggregate to form flocs . the presence of clay in the composition improves the rate of floc formation and allows the formation of larger flocs compared to when clay is absent from the composition herein . the clay may also act as a swelling agent , and if the composition herein is in the form of a tablet , the clay improves the rate at which the tablet disintegrates on contact with water by swelling upon contact with water so that the components of the tablet are pushed apart by the swollen clay particles . the clay can also act as a desiccant within the tablet . the clay may also act as a cationic exchange agent to remove metal ions from the water and the clay can also remove colour , heavy metals and some organic material from water by adsorption . the clay is preferably a smectite clay , preferably a dioctahedral smectite clay such as montmorillonite clay or a trioctahedral smectite clay such as hectorite clay . those clays found in bentonite clay deposits are also preferred . particularly preferred clays for use herein include laponite clay , hectorite , montmorillonite , nontronite , saponite , volkonsite , sauconite , beidellite , allevarlite , illite , halloysite and attapulgite . in compositions containing calcium hypochlorite , the free moisture content of the clay should be carefully controlled to provide acceptable disinfectant stability . preferably the free moisture content should be less than about 4 %, more preferably less than about 3 %, especially less than about 2 . 5 % and more especially less than about 1 . 5 % by weight . free moisture content is determined on a 2 g sample of the test material following the procedure as described hereinabove . highly preferred for use herein from the viewpoint of providing optimum disinfectant stability are pre - dried clays which in their dessicated form have the potential to scavenge or pick up moisture . such clays can be described in terms of their so - called ‘ water - capacity ’, defined herein as the equilibrium weight percentage of moisture picked up by a small sample ( e . g . 10 mg ) of the dessicated material from air at 80 % relative humidity and 20 ° c . as measured by dynamic vapour sorption techniques . for example , if 10 mg of the dessicated clay picks up 2 mg moisture , the dessicated clay has a water capacity of 20 %. preferred for use herein are dessicated clays having a water capacity of at least about 10 %, preferably at least about 15 %, and more preferably at least about 18 %. the composition herein preferably comprises ( by weight ) from 1 %, or preferably from 5 %, or preferably from 10 %, or preferably from 15 %, or preferably from 20 %, or preferably from 25 %, and preferably to 80 %, or preferably to 50 %, or preferably to 35 % clay . aluminosilicates may be used herein in place of , or in addition to , clay . the aluminosilicate can act as a cationic exchange agent to remove metal ions from water , and can also act as a seed particle to enhance floc formation and as dessicant for enhancing disinfectant stability . preferred aluminosilicates for use herein include zeolite a , zeolite x , zeolite y , zeolite p and zeolite beta . preferably the free moisture content of the aluminosilcate should be less than about 4 %, more preferably less than about 3 %, especially less than about 2 . 5 % and more especially less than about 1 . 5 % by weight . highly preferred for use herein from the viewpoint of providing optimum disinfectant stability are pre - dried aluminosilicates which in their dessicated form have the potential to scavenge or pick up moisture . such dessicated aluminosilicates can also be described in terms of their so - called ‘ water - capacity ’, as defined hereinabove . preferred for use herein are dessicated aluminsilicates having a water capacity of at least about 10 %, preferably at least about 15 %, and more preferably at least about 18 %. the composition herein preferably comprises ( by weight ) from 1 %, or preferably from 5 %, or preferably from 10 %, or preferably from 15 %, or preferably from 20 %, or preferably from 25 %, and preferably to 80 %, or preferably to 50 %, or preferably to 35 % aluminosilicate . the composition herein may comprise a third polymeric material . said third polymeric material does not contain an amine group and is substantially water insoluble . the term “ substantially water insoluble ” is defined hereinbefore . thus , the third polymeric material is different to , and is not , the first polymeric material or the second polymeric material . the third polymeric material is selected on the basis that it can act as a seed particle to enhance floc formation . the third polymeric material can be used in place of , or in addition to , clay or zeolite . preferably the free moisture content of the third polymeric material should be less than about 4 %, more preferably less than about 3 %, especially less than about 2 . 5 % and more especially less than about 1 . 5 % by weight . preferably the third polymeric material comprises cellulose , more preferably the third polymeric . material is an unmodified cellulose . most preferably the third polymeric material comprises powdered cellulose . the composition herein preferably comprises ( by weight ) from 1 %, or preferably from 5 %, or preferably from 10 %, or preferably from 15 %, or preferably from 20 %, or preferably from 25 %, and preferably to 80 %, or preferably to 50 %, or preferably to 35 % third polymeric material . the composition herein may comprise an alkali agent . the alkali agent can be any compound which gives alkalinity when contacted to water . the alkali agent for use herein is not a polymeric material . the composition herein preferably comprises an amount of alkali agent such that when the composition herein is contacted to water to form a solution , said solution has a ph of from 5 to 8 , preferably from 6 to 7 . preferred alkali agents are selected from the group consisting of sodium carbonate , sodium bicarbonate , sodium hydroxide , sodium oxide , calcium carbonate , calcium bicarbonate , calcium hydroxide , calcium oxide , potassium carbonate , potassium bicarbonate , potassium hydroxide , potassium oxide and combinations thereof . particular alkali agents which are a source of carbonate when contacted to water , for example sodium carbonate or sodium bicarbonate may be preferred for used herein . if the composition herein comprises a source of acid , for example an inorganic salt of the composition of the present invention such as iron sulphate , said alkali agent which is a source of carbonate can interact with said acid source in the presence of water to produce a gas . this process is known as effervescence , and improves the rate at which the composition disperses , especially when the composition herein is in the form of a tablet . highly preferred herein , especially in compositions containing calcium hypochorite as disinfecting agent , are alkalis which can also act as moisture sinks , especially anhydrous sodium carbonate . the composition herein typically comprises ( by weight ) from 1 % to 50 %, preferable from 10 %, or preferably from 15 %, or preferably from 20 %, or preferably from 25 %, and preferably to 45 %, or preferably to 40 %, or preferably to 35 % alkali agent . the composition herein is preferably in a solid unit dose form , most preferably in a tablet or powder form . the composition herein is preferably packaged so that it is protected from environmental conditions such as moisture . preferably the composition herein is packaged in a water impermeable material such as polypropylene or typical laminates . an example of one such laminate is a laminate supplied by akerlund & amp ; raus , comprising layers of coated paper ( outer ), ldpe , aluminium foil and an inner layer surlyn ( an ethylene / methacrylate co - polymer )— an fda approved food packaging . the composition herein can be used to purify water using a method comprising the steps of ( a ) contacting the composition herein to water to obtain partially purified water comprising solid matter ; and ( b ) removing at least part of said solid matter from said partially purified water by ; ( i ) filtration ; or ( ii ) decanting ; or ( iii ) sedimentation ; or ( iv ) flotation ; or ( v ) a combination thereof , to obtain purified water . the composition herein can be in the form of a tablet or solid powder which is added to water , typically to form partially purified water comprising solid matter such as flocs . this solid matter can be removed or separated from the remaining part of the partially purified water by any technique , typically by filtration but decanting , sedimentation and flotation may also be used . by filtration it is meant passing the partially purified water through a filter . filtration can occur by pouring means , for example by pouring said partially purified water through a filter to remove at least part of the solid matter from said partially purified water . filtration can also occur by centripetal force means , for example by total enclosing the partially purified water by a filter and spinning said partially purified water and said filter so that said partially purified water passes through said filter and at least part of said solid matter is separated from said partially purified water . filtration can also occur by plunging means , for example by plunging or moving a filter through said partially purified water so that at least part of said solid matter is separated from said partially purified water . filters typically used include cloth filters , non - woven and paper filters and polishing filters , such as filters comprising activated carbon , glass fibre , zeolite , ion exchange media , or a combination thereof , which remove residual water - impurities , e . g . organic matter , heavy metal ions and residual disinfectant from the water . filters suitable for use may be impregnated with silver or other biostatic components so that bacteria cannot grow on said filter and the filter can be reused several times without contaminating the water being filtered . sand filters can also be used , and more than one filter may be used in combination herein . preferably , from 10 mg , or preferably from 50 mg , or preferably from 75 mg , or preferably from 100 mg , or preferably from 150 mg , or preferably from 200 mg , or preferably from 250 mg , or preferably from 300 mg , and preferably to 2000 mg , or preferably to 1000 mg , or preferably to 750 mg of composition herein is added to 1 litre of water . the amount of composition herein which is added to the water depends on the impurity of said water . for example , less composition is needed to adequately purify water which is not very impure compared to the amount of composition herein which is needed to purify very impure water . the following compositions are in accord with the present invention . all percentages are by weight of composition . in the examples , the iron iii sulphate contains as supplied about 0 . 075 % of soluble manganese and the aluminium sulphate less than about 0 . 01 % of soluble manganese . 500 mg of the compositions a to k from example 1 were added in powder or tablet from to 1 litre of water , respectively . the water was then agitated or stirred briefly . the water was left to stand for 5 minutes , after which said water was stirred or agitated for a further minute and then left to stand for another 20 minutes . during this time , water - insoluble flocs formed in the water . the was then poured through a tightly woven cloth filter to remove said water - insoluble flocs , and the remaining part of the water was collected . this remaining part of the water is purified water . 500 mg of the compositions a , c , d , f , g , i , j and k were added in powder or tablet from to 1 litre of water , respectively . the water was then agitated or stirred briefly . the water was left to stand for 10 minutes , after which said water was stirred or agitated for a further minute and then left to stand for another 20 minutes . during this time , water - insoluble flocs formed in the water . the was then poured through a tightly woven cloth filter to remove said water - insoluble flocs , and the remaining part of the water was collected . 1 mg calcium hypochlorite was then added to the collected water , and the collected water was agitated or stirred briefly . this collected water is purified water . the following are further compositions according to the invention . all percentages are by weight of composition . in the above , the calcium hypochlorite was added in granular form comprising particles of about 1212 μm median particle size with less than 25 % by weight larger than 1400 μm , less than 0 . 5 % by weight larger than 2000 μm and less than 3 % by weight smaller than 150 μm . the free moisture content of the compositions was in the range from 1 % to 4 %. the hectorite clay , montmorillonite clay and zeolite x were all predried to a free moisture content below 1 . 5 % by weight and had a water capacity in excess of 18 %. the compositions have a t max of at least about 8 minutes and a t 80 of less than about 30 seconds . 6 . 2 g of compositions l to v were added in powder form from unit dose polypropylene sachets to 10 litres of drinking water contaminated with heavy metals , organic material , cysts and high levels of manganese . the water was then agitated or stirred briefly . the water was left to stand for 5 minutes , after which said water was stirred or agitated for a further minute , left to stand for a further five minutes , after which said water was stirred or agitated for a further minute and then left to stand for another 5 minutes . during this time , water - insoluble flocs formed in the water . the liquid was then filtered through a cotton cloth or non - woven filter to remove said water - insoluble flocs , and the filtrate was collected . the filtrate was left for a further 15 minutes and is purified water . the water is free of color (≦ 15 pcu ) both initially and on standing for periods of a week or more . all documents cited in the detailed description of the invention are , in relevant part , incorporated herein by reference ; the citation of any document is not to be construed as an admission that it is prior art with respect to the present invention . while particular embodiments of the present invention have been illustrated and described , it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention . it is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention .