[0002] The invention is concerned with a water treatment process where f!oc is formed in the water and then is removed by a separation process such as sedimentation or fiuradon. Sedimentation is used where large amounts- of water are treated . Normally the clear water from the sedimentation system is subsequently subject to filtration and also to purification by means of die addition of chlorine.

[0003] Although this- process has been used successfully for many years there is presentl an acme shortage of capacity for this process. There are serious consequences arising from such shortages. The cost of increasing such capacity requires substantia! civil engineering work which is very costly and time coBs ^' aming..

[0004] We have found daat water treatment systems can have then capacit significantly increased without normal ^■ civil engineering work and at relativel sow ^' cost

[0005] Accordin to one aspect of the invention there s provided a method of treating water contprishig .subjecting the water to electronic fluid treatment in apparatus comprising electrodes: the suriaces of which : comprise inert metals , preferably inert, mixed metal oxides, adding fiocculanis vo t e water and then passing the treated water to a separation process from which the treated water is passed oat for use.

[00061 The separation process is preferably a sedimentation process. However where there are low water flows, of the order of less than 0. 1 to 0.2 Μΐ/d (Megaiitres per day) , the separation process can be carried o t in a filter. The filter may be a sand filter, or a reverse osmosis filter or a nano-tlter and preferably is a 25 micron bag filter.

[0007] Conveniently die flocculants are added to die water prior to the- electronic fluid treatment. The water to which the fioceclants have been added are preferably passed through a mixing chamber comp i in a fioccalanon channel or a rloeeulaiion tank to ive th floeculam time to mix with the water and to coagulate and to form floe. Such time is preferably of the order of two to ten minutes, convenientl two to five minutes but also between eight and ten

100081 Polymer/organic Oocenieni operate very effectively. When placed in. water they form a "floating snake" which, is charged along the length of the. polymer chain. These -attack each other and the contaminants in the, water to coagulate and agglomerate to form floe. The coagulants form . sticky . gelatinous matter. Even particles which are not charged are embedded into the .material to form heavy ffocs. The effect of the electronic process causes the iron and ^' aluminum in fee water - particularly in silt to form into hydroxides. The iron, aluminium , hydroxides and hydrogen that are bonded to particulate or organic materials are removed from the structure of the particulate and organic material leaving them highly charged. ^' Unfortunately if these f!ocee!ants are m the water passing through the electronic system , the polymer/organic flocculants rend to break down in the electronic system . To overcome this problem the water treatment system is modified in thai the flocculants are added after the electronic process and no floecu ent i added before the electronic treatment process. [0009] The electronic fluid treatment may be carried out in apparatus wherein the electrodes preferably comprise metal coated with an men metal , preferably a mixed metal oxide, which is preferably ruthenium oxjde. As a consequence the electrodes do ^■ not dissolve in water during the electronic water treatment and therefore the electrodes have a long useful life,

[0010] Where the water being treated has high levels of iron, aluminum, manganese _* and/or organic material the water is preferably treated with ozone prior to the electronic process. This serves as a booster for floceidailon and sealing - boosting the oxidation environment which is increased due to the ultrasound and electromagnetic etrect of the electronic water treatment. The additio of ozone will increase the formation of hydroxides which precipitate out in the separation process, Preferably the ozone is added in an. amount of about I gram per ^' kilolitre of water used. j ^' OOl ] Where the pB ^; of the raw water is alkaline, the water is preferably treated before the remaining steps with sulphuric aeid or hydrochloric acid until the neutral pH of 7 or lower is achieved:. Where the pH of the taw water is neutral or acidic, it is preferably rea ed after the electronic process, and efore sed imentation, by adding lime until file desired pl L which is preferably 8.5 to 9. S is achieved,

( ^' 0012] The electronic cell may be as described and: il lustrated in

WO 2008/018837:, WO 2009/156840 and WO 01/89997, The number of cel ls required per Mega litre of water to be treated is given in the following table where the ceil cross-sectional diameter in millimetres is given as "cel l #mm ":

Obviously ihe rmmbsr o cel ls used will be rounded up from die figures mentioned iii the table,

[0013] The water .from the sedlmestation step s then -subject ι . tra fiiiration. to r move the residual, very fine Hoc that has no een properly removed in t e sedimentation step so as to bring the water into a quality for drinking. This fiiiration is preferably carried out in a filter, t may be .a ..slow _. .sand . filter or a rapid sand filter.

[0014] ^' The water is then subjected to a final purification step by being treated with chlorine. 0015] A number of examples of the water treatment process will now be described by way of example, in describing these examples reference will be made to the accompanying drawings showing three flow d iagrams of the processes as will apparent from the description;

[0016] Referring now- to Figure i there is show?-- a flow diagram of a system 10 of the invention for treating water in an amount of 500 M l/d. The system is arranged for use with alkaline water which has a pH of above 8.0 and which includes dissolved organic materials. T he raw water is treated at 1 2 with sulphuric or hydroch loric acid, The dosing is continuous in die water flow hut is adjusted incrementally with a measurement of the pi I after each dosing until the pH is at about the desired pH of H 7. This is high ly desirable because die chem ical reaction (to be described) is more, ^■ efficient where the water is . neu ral or acidic .

[QGI7j After die raw- water has been treated to be neutral or acidic, the noce iant is added t 14. The noceuiarn used in th is method is a irivaiem metal Ooeculant (a poly ammmiurn chloride type polymer) , it is preferably aiummium sulphate or ferric or ferrous sulphate. The amount of fioccuiant to be added is established by carrying out a jar test. Thi comprises putting _: the pB corrected water into a beaker and then adding fioccuiant in progressive steps to achieve a dosed concentration range of between 0.024 % to 0.0025 % m/ffl. The rate of seaJernem i. e. ho long it takes: to form a good floe and the; time the floe takes to settle is measured . From this the best percentage of the fioccuiant to dose the water can be selected , in practice we have found that the average dosage rate is between 2rag/i to 4mg/l depending on streaming current detector dosage rale indication. The water is now- assed through what is herein called a " mixing chamber" 1 6 i.e. a flocculation channel or floccu iaiion tank for a period of two to five minutes to give the fioccuiant time to mix with the water and coagulate and form Hoc . [0018] Now ozone is added at 18 to d e water in an amount of 1 gram ozone per kilolitre of water being treated.

[0019] The water is- then treated in a electronic process at 2.0 comprising a set of eieciroiiic units as described with reference to and as illustrated in Figures I to 4 of WO 2009/ 156840, The electrodes comprise thick, titanium grade 1 plate which is electroplated with ruthenium or ruthenium ox ide, which is an inert platinum group metal,

0)020] The water that has been treated in the electronic process 20 is now subjected at 22 to treatment i h brae until the desired pl-j of 8,5 to 9,5 is reached. This is desirable because at bet een pH 8,5 to hi 9, 5 altnnhburn is not soluble and will precipitate out as aluminium hydroxide, iron precipitates out at about phi S,5 and above to form ferrous hydroxide. These .hydroxides: are gelatinous and Insoluble masses. They bond n to charged, particulate material in the water and this helps floeculation, forming dense floe which increases the settling rate,

[0021] The water is now passed to a conventional sedimentation treatment plant 24, ^' The sedimentation plant 24 comprises two sedimentation tanks each of four point f ve metres diameter and thre metre to base. The size is such thai the upflow rate is lower than the settling rate of the floe, ff he settling rate is the rate of settling of the floe through the distance it must travel and is measured in metres per hour). The retention time in the settling tank is typically between thirty minutes to one hour. [0022] After sedimentation the water \$ treated through two pressure sand niters 26 and thereafter treated with chlorine to typically I pra chlorine. The water is now fit for drinking.

{0023] We have found that water as treated as described abov - prior to the sedimentation- treatment - is formed with Hoc- of high, density so that the settling rate when the water is treated in the sedimentation plant is sigmficanfly higher than die settling rate achieved in conventional p!ant. s chat the plant 10 can virtually double the amount of water treated in the same rime in the conventional water processing plant with relativel little, cms engineering work.

[0024] The. steps 1:2 to 22 described above and the provision of the floeculaei channel or tank were all retro fitted to an existing system m a three month installation period . We f und that the plant previously had a capacity of 0.S Ml/d whereas after retro fitting the apparatus of die invention the output increased to 0.9- to 1.2 l/d as above described. We found too that the settling rate was 2. m/fs as compared to 1 ,8 ni/h as occurred before retrofitting as above described,

[0025] We found that reservoir feed turbidity after retrofitting as described above was reduced to 0. 1 N ^' TU (Nephelometric Turbidity Units - ¾ measure of the ^' cloudiness of water) which was well belo any previously achieved qual ity where no electronic treatment of the f occulani water took place and which was normally above 1 NTIJ. This reduction was due to the increased settling rate and improved flocculation created by the electronic process of the floccn!ant water to enable high flow rates through the plant. g

10026] A second example of the water treatment process of the invention will now be described . The steps of the process are the same as those in the first described embodiment and hence the Row diagram is the same for the second .example.

[0027] In the second example the process is for treating water in an amount of 2.0 Mi/id. The raw water pH was in the region of pH 6.8 to pH 7. The water is dosed with floc-culent. The.. fd Occident used is alum (aluminium su lphate 16 HfO) . The dosage rate was calculated on the raw water jar test to give a dosage rate of dOvng/l to i20mg/l. Thereafter the water is passed through a mixing chamber 16 comprised by a fioceulatioa channel with a retention ime of 8 to 10 mrnufes for better floe formation and then is subject to be treated in the electronic process The treated water is then dosed with ihne to ring _, its pie to about neutral i .e, 7.2.

[0028] The sed i entation plant comprises three sedi eaiauon tanks , each of hich is twelve metres long by tour metres wide and three metres to base. The water from th electronic process after being treated with lime is then passed into the sedimentation plant. The .retention time in the sedimentation tank is one to two hours.

[0029] After sedimentation the. water was passed through lour banks of pressure sand filters to remove any unwanted material in the water this would constitute about 1 % of the floe, 90%, of the fioc having been removed in the sedimentation plant. The water is subject to a final purification step by being treated with chlorine.

[0030] The electronic process and the step prior thereto and prior to the sedimentation were all retro fitted to an existing plant. We found that the initial settling rate before retro fitting was 1 .2 m h and it was 2.3 ro/h afier retro fitting. The reservoir feed turbidirv was reduced to 0.95 NTU or slightly lower which was well below die qiiality achieved prior to retrofiiuiig which was above 5 NTU and the colour was m me region. of T i l (degrees Uazen ·· a measure of ihe colour in t e water based on rng/' of platinum chloride}.

[0031 Reference is now made to the flow diagram in Figure 2 which snows an arrangement wherein a polymer organic flocealent is used . This arrangement, differ from the above described embodiments in hai ihe fiooeulant ts added &\ 30 -after the electronic process 32, This is necessary because, as discussed above, otherwise the flocculent. would be damaged in the electronic process .

10032] br a further arrangement for treating low water flows, the sedimentation, plant is omitted. Here the water mom the electronic process plant 40 is del ivered to a. sand filter 4:2 (as shown in Figure 35 which ac ¾ as the separation plant.

[0033] We fra:ve round that by treatin the water as described above, the final water quabty Is improved, A can be seen the arangevnent can be retrofitted to an established plant with considerable improvements to the operation.

[1)034] The invention is not limited to the precise details hereinbefore described.

Far example poly aluminium chloride floccuianis of many d ifferent types and names exist and may be used. The various retention tunes mentioned above may be varied.