AU2009200113A1

AU2009200113A1 - Water purification

Info

Publication number: AU2009200113A1
Application number: AU2009200113A
Authority: AU
Inventors: Clement Hinchliffe; Gunter Gerhard Lempert
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-02-01
Filing date: 2009-01-12
Publication date: 2009-08-20

Description

S&F Ref: 886487 AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name and Address Clement Hinchliffe, of Applicants: of 13/125 Mona Vale Road, St Ives, New South Wales, 2075, Australia Gunter Gerhard Lempert, of PO Box 698, Windhoek, Namibia Actual Inventor(s): Clement Hinchliffe Gunter Gerhard Lempert Address for Service: Spruson & Ferguson St Martins Tower Level 35 31 Market Street Sydney NSW 2000 (CCN 3710000177) Invention Title: Water purification Associated Provisional Application Details: [33] Country: [31] Appl'n No(s): [32] Application Date: AU 2008900446 01 Feb 2008 The following statement is a full description of this invention, including the best method of performing it known to me/us: 5845c(1922770_1) Water purification Technical Field The present invention relates to a process for purifying water and to a water purification system. s Background of the Invention Many regions of Australia are suffering shortages of potable water due to lack of adequate supplies of water which are suitable for upgrading to potable standards and which are accessible to population centres. These shortages are made more severe because of unreliable rainfall and/or growing population. There is therefore an urgent io need for new water treatment processes to safely and economically purify to potable standards the available sources of lower quality waters that existing treatments cannot purify. Also, many regions of Australia are suffering shortages of potable water because available and accessible water supplies that are also suitable for treatment by traditional is potable water processes are fully committed. Additionally because of increasingly unreliable rainfall and/or expanding populations, there is an urgent need for water purification that will provide plentiful potable water from supplies that existing treatment processes cannot purify on quality or cost considerations or both. Many existing water purification systems are designed to deal with a particular 20 feedwater quality, and are incapable of generating suitably pure water from feedwaters of widely varying quality. Therefore a new process would preferably be versatile so as to be able to purify a variety of feedwaters of lower salinity to potable standards without incurring the high capital and operating costs of sea water desalination. In general, typical purification unit processes are incapable of providing absolute 25 removal of all harmful or objectionable contaminants. Consequently the safety and aesthetic acceptability of product waters from these unit processes can not be guaranteed. This can at times result in outbreaks of disease due to incomplete removal of pathogens. Reverse osmosis is a well known method for purifying water. It is commonly characterised by high energy usage and costs plus significant negative climate change 30 effects, due to the requirement to operate at high pressures in order to overcome the osmotic pressure of feedwaters containing high levels of salts, as exemplified when sea water is used to supply the desalination plant. Additionally, without extensive pre- 2 treatment membranes are readily fouled by organic and/or inorganic water contaminants, requiring cleaning with consequent downtime and reduced life of costly membranes. There is therefore a need for a water purification process that is sufficiently versatile to provide potable water from a range of different feedwaters without incurring 5 high energy operating costs of sea water desalination. Object of the Invention It is an object of the present invention to substantially overcome or at least ameliorate one or more of the above disadvantages. It is a further object to at least partially overcome at least one of the above needs. 10 Summary of the Invention Disclosed herein is a process for producing potable water, said process comprising: 1) treating secondary and/or tertiary treated sewage using a first treatment process to generate a purified liquid; and 2) treating the purified liquid using reverse osmosis to provide the potable water. is The purified liquid produced in step 1 may be a purified (or partially purified) aqueous liquid. It may be purified water. It may be purified secondary and/or tertiary treated sewage. Step 2) may comprise treating the purified liquid using reverse osmosis and disinfecting a permeate from said reverse osmosis to provide the potable water. It may comprise treating the purified liquid using reverse osmosis to produce a permeate, 20 disinfecting the permeate from said reverse osmosis to produce a disinfected permeate and remineralising the disinfected permeate to provide the potable water. Step 1) may comprise any one or more (e.g. 2, 3, 4, 5, 6, 7 or 8), optionally all, of the following: * addition of an adsorbent 25 0 preoxidation e addition of one or more coagulants and/or flocculants e physical-chemical particle separation 0 filtration * addition of one or more oxidants 30 0 removal of unreacted oxidant(s) * biofiltration * activated carbon filtration, optionally granular activated carbon filtration.

3 The step of addition of one or more oxidants should be specifically selected to provide optimal purification. It may use one of the following processes, which may be selected according to the quality of the feedwater: * Ozonation (preozonation); 5 * Addition of diamond electrode generated electrolysed water; * Advanced oxidation using either hydrogen peroxide dosage accompanied by ultraviolet radiation or ozone addition accompanied by ultraviolet radiation. Additionally any one or more (e.g. 2 or all) of the following may also be incorporated into step 1): io microfiltration * ultrafiltration * ion exchange The process may comprise more than one (optionally all) of any one of the above steps. The steps may be in any suitable order. The process may comprise at least two is purification steps for removing each contaminant or class of contaminant which could be harmful (e.g. toxic) to the human body. It may comprise at least two purification steps for removing each contaminant or class of contaminant which could be aesthetically objectionable. It may comprise at least two purification steps for removing each contaminant or class of contaminant which could be either harmful (e.g. toxic) to the 20 human body or aesthetically objectionable. In an embodiment of the invention there is provided a process for producing potable water comprising: 1) treating secondary and/or tertiary treated sewage using a first treatment process to generate a purified liquid, wherein the first treatment process comprises at least two 25 purification steps for removing each contaminant or class of contaminant which could be harmful to the human body or aesthetically objectionable; and 2) treating the purified liquid using reverse osmosis to provide the potable water. The process may comprise more than one oxidation step. It may for example comprise two or three oxidation steps. For example step 1) may comprise a pre-oxidation 30 (e.g. pre-ozonation) step prior to the addition of one or more coagulants and/or flocculants, and may comprise a further oxidation (e.g. ozonation) step following physical-chemical particle separation. The process may comprise disinfection of, e.g. addition of a disinfectant to, the permeate from the reverse osmosis of step 2. Suitable disinfectants include chlorine and chloramine. Sufficient disinfectant should be added so 4 that the water produced by the process contains residual disinfectant. This may ensure sterility of the water. The process may comprise remineralisation of the permeate from the reverse osmosis of step 2), optionally of the disinfected permeate. The secondary and/or tertiary treated sewage may be combined with an aqueous 5 liquid prior to step 1. The aqueous liquid may comprise water from a river, a well a borehole, or some other source. It may be fresh water. It may be potable water. It may be non-potable water. It may be an aqueous liquid that is returned from within the process for retreating. It may comprise more than one of the above. In another embodiment there is provided a process for producing potable water, said 10 process comprising: 1) treating secondary and/or tertiary treated sewage using a first treatment process to generate a purified aqueous liquid; and 2) treating the purified aqueous liquid using reverse osmosis to provide the potable water. 1s In another embodiment of the invention there is provided a process for producing potable water, said process comprising: * addition of one or more oxidants to secondary and/or tertiary treated sewage to produce a first intermediate liquid (this step may for example be a pre-ozonation step); 20 e addition of a coagulant and/or flocculant (e.g. ferric chloride) to the first intermediate liquid to produce a second intermediate liquid; * physical-chemical particle separation (e.g. by dissolved air flotation) from the second intermediate liquid; * filtration (e.g. multimedia filtration) of the second intermediate liquid, 25 * applying oxidation (optionally advanced oxidation) to the resulting filtrate to form a third intermediate liquid (this step may comprise addition of an oxidant such as ozone to said resulting filtrate to produce said third intermediate liquid); & removing unreacted oxidant(s) from the third intermediate liquid (e.g. by use of UV energy or addition of potassium permanganate); 30 e biofiltration of the third intermediate liquid to produce a fourth intermediate liquid; e activated carbon filtration of the fourth intermediate liquid to generate a purified liquid; 5 " treatment of the purified liquid using reverse osmosis to provide a permeate liquid; and " disinfection of the permeate liquid to provide the potable water. The process may also comprise addition of an adsorbent prior to the addition of the 5 one or more oxidants to the secondary and/or tertiary treated sewage. In preferred embodiments the process also comprises a monitoring step for monitoring a level of contamination of water between two of the treatment steps of the process so as to determine if the water meets a predetermined standard. There may be more than one such monitoring step. Monitoring may be conducted between each two 10 (i.e. each pair of) successive treatment steps of the process. Monitoring may be conducted at the end of the process. The monitoring step may monitor a level of contamination of water between two of the treatment steps of the process so as to determine if the water meets a predetermined standard. A monitoring step may be conducted between each two successive treatment steps of the process. Water may be permitted to pass to a treatment 15 step following a monitoring step only if said monitoring step indicates that the water meets the predetermined standard. Thus in some preferred embodiments, water is permitted to pass from a particular treatment step to a subsequent treatment step only if monitoring indicates that the water meets the predetermined standard. If the monitoring indicates that the water fails to meet 20 the predetermined standard, the water may be returned to the start of the first treatment process. This provides surety that the water produced by the process is of acceptable quality and/or purity. The process may comprise controlling one or more components of the system used for conducting the process. In another embodiment of the invention there is provided a process for producing 25 potable water comprising: 1) treating secondary and/or tertiary treated sewage using a first treatment process to generate a purified liquid, wherein the first treatment process comprises at least two purification steps for removing each contaminant or class of contaminant which could be harmful to the human body or aesthetically objectionable; 30 2) monitoring quality of the water following each purification step so as to determine if the water meets a predetermined standard; 3) if the monitoring indicates that the water fails to meet the predetermined standard, returning the water to the start of the first treatment process; and 4) treating the purified liquid using reverse osmosis to provide a permeate liquid; and 6 5) disinfection of the permeate liquid to provide the potable water.. In another embodiment there is provided a process for producing potable water, said process comprising: * addition of ozone to secondary and/or tertiary treated sewage to produce a first 5 intermediate liquid; e addition of ferric chloride to the first intermediate liquid to produce a second intermediate liquid; e dissolved air flotation of the second intermediate liquid; e multimedia filtration of the second intermediate liquid; io e addition of ozone to the resulting filtrate to form a third intermediate liquid; e removing unreacted oxidant(s) from the third intermediate liquid; * biofiltration of the third intermediate liquid to produce a fourth intermediate liquid; * granulated activated carbon filtration of the fourth intermediate liquid to generate a purified liquid; 15 * treatment of the purified liquid using reverse osmosis to provide a permeate; * disinfection of the permeate with chlorine or chloramine to provide a disinfected permeate; e remineralisation of the disinfected permeate to provide the potable water; * monitoring a level of contamination of water between two of the treatment steps of 20 the process so as to determine if the water meets a predetermined standard; * permitting water to pass to a treatment step following said monitoring only if said monitoring indicates that the water meets the predetermined standard; and * if the monitoring indicates that the water fails to meet the predetermined standard, returning the water to the start of the first treatment process. 25 There is also disclosed a water treatment system comprising: 1) a first treatment unit for treating secondary and/or tertiary treated sewage using a first treatment process to generate a purified liquid; and 2) a reverse osmosis unit coupled to the first treatment unit for treating the purified liquid. 30 In an embodiment there is provided a water treatment system comprising: 1) a first treatment unit for treating secondary and/or tertiary treated sewage using a first treatment process to generate a purified aqueous liquid; and 2) a reverse osmosis unit coupled to the first treatment unit for treating the purified liquid to produce potable water.

7 The system may additionally comprise a disinfection device, which may be located after the reverse osmosis unit. It may comprise a remineralisation device, which may be located after the disinfection device. It may comprise a disinfection device located after the reverse osmosis unit and a remineralisation device located after the disinfection 5 device. The first treatment unit may comprise any one or more (e.g. 2, 3, 4, 5, 6, 7 or 8), optionally all, of the following: * an adsorbent addition device * a pre-oxidation device 10 e a coagulant and/or flocculant addition device e a physical-chemical particle separation device e a filtration device e an oxidant addition device e an oxidant removal device 15 e a biofiltration device * an activated carbon filtration device Additionally any one or more of the following may also be incorporated into the first treatment unit: " a microfiltration device 20 * an ultrafiltration device e an ion exchanger The system may comprise more than one (optionally all) of any one of the above devices. The devices may be connected in series, so that the output, or at least a purified portion of the output, from any device (other than the last device) is fed to the next device 25 as an input. The system may comprise at least two purification devices for removing each contaminant or class of contaminant which could be harmful to the human body or aesthetically objectionable. In one embodiment the first treatment unit comprises: e a pre-oxidation device; 30 * a coagulant and/or flocculant addition device; e a physical-chemical particle separation device; e a filtration device, * an oxidation or advanced oxidation device; e an oxidant removal device; 8 * a biofiltration device; and * an activated carbon filtration device. In another embodiment the first treatment unit comprises: e a pre-oxidation device for treating secondary and/or tertiary treated sewage; 5 e a coagulant and/or flocculant addition device for treating output water from the pre-oxidation device; * a physical-chemical particle separation device for treating output water from the coagulant and/or flocculant addition device; e a filtration device for treating output water from the physical-chemical particle 10 separation device; e an oxidation or advanced oxidation device for treating output water from the filtration device; e an oxidant removal device for treating output water from the oxidation of advanced oxidation device; is a biofiltration device for treating output water from the oxidant removal device; and * an activated carbon filtration device for treating output water from the biofiltration device so as to produce the purified liquid. These embodiments may also comprise an adsorbent addition device for treating 20 (i.e. adding adsorbent to) the secondary and/or tertiary treated sewage prior to its passing to the pre-oxidation device. In an embodiment of the invention there is provided a water treatment system comprising: 1) a first treatment unit for treating secondary and/or tertiary treated sewage using a first 25 treatment process to generate a purified liquid, wherein the first treatment unit comprises at least two purification devices for removing each contaminant or class of contaminant which could be harmful to the human body or aesthetically objectionable; and 2) a reverse osmosis unit coupled to the first treatment unit for treating the purified 30 liquid. The system may comprise more than one oxidation device, for example two or three oxidation devices. For example, there may a pre-oxidation device (e.g. a pre-ozonation device) at the start of the first treatment unit, and a further oxidation device (e.g. oxidant addition device) following a filtration device. The system may additionally comprise a 9 disinfection device for disinfecting (optionally for adding disinfectant to) the permeate from the reverse osmosis unit. It may further comprise a remineralisation device for remineralising (i.e. adding one or more mineral salts to) the permeate from the reverse osmosis unit, optionally to the disinfected permeate. 5 The system may comprise a supplementary water inlet for combining the secondary and/or tertiary treated sewage with an aqueous liquid prior its entering the first treatment unit. In a preferred embodiment the system additionally comprises a monitoring device for monitoring a level of contamination of water between two of the purification devices 1o of the process so as to determine if the water meets a predetermined standard. There may be more than one such monitoring device. There may be monitoring devices between the treatment devices of more than one pair of treatment devices. A monitoring device may be present for monitoring a level of contamination between each two successive treatment devices of the system. There may be a monitoring device for monitoring the output from 15 the final treatment device of the system. The system may comprise an openable barrier (e.g. a valve) so that water is permitted to pass from a particular purification device to a subsequent purification device only if said monitoring device indicates that the water meets the predetermined standard. It may comprise a water diverter disposed so that, if said monitoring device indicates that the water fails to meet the predetermined standard, 20 said diverter diverts the water to the start of the first treatment unit. The system may comprise a return line for returning said water to the start of the first treatment unit. In some embodiments the openable barrier and the water diverter are combined into a single device (e.g. a three way valve), which device is capable of directing a purified output from a particular purification device either to the subsequent purification device or to the 25 start of the first treatment device, depending on whether the purified output meets the predetermined standard. The system may comprise one or more such monitoring devices. Each may be associated with one or more openable barriers, e.g. valves, as described above. The water treatment system may additionally comprise a controller for controlling 30 one or more components of the system, for example the monitoring device(s) and/or water diverter(s) and/or openable barrier(s). The controller may be capable of receiving one or more signals from the monitoring device(s) and of controlling the water diverter(s) and/or openable barrier(s) in response to said signal(s).

10 In another embodiment of the invention there is provided a water treatment system comprising: 1) a first treatment unit for treating secondary and/or tertiary treated sewage using a first treatment process to generate a purified liquid, wherein the first treatment unit 5 comprises at least two purification devices for removing each contaminant or class of contaminant which could be harmful to the human body or aesthetically objectionable; 2) a monitoring device for monitoring a level of contamination of water following each purification device so as to determine if the water meets a predetermined standard; io 3) a water diverter disposed so that, if said monitoring device indicates that the water fails to meet the predetermined standard, said diverter diverts the water to the start of the first treatment unit; 4) a reverse osmosis unit coupled to the first treatment unit for treating the purified liquid; and is 5) a disinfection device for disinfecting the treated purified liquid. In another embodiment of the invention there is provided a water treatment system for producing potable water, said system comprising: * a pre-oxidation device * a coagulant and/or flocculant addition device; 20 e a physical-chemical particle separation device; e a filtration device, e an oxidation or advanced oxidation device; * an oxidant removal device; e a biofiltration device; 25 e an activated carbon filtration device; e a reverse osmosis unit; and * a disinfection device. The system may also comprise an adsorbent addition device, which may be located prior to the pre-oxidation device. 30 In another embodiment there is provided a water treatment system for producing potable water, said system comprising: * a preozonation device; e a coagulant and/or flocculant addition device; e a dissolved air flotation (DAF) device; 11 e a multimedia filtration device; e an ozone addition device; * an oxidant removal device; e a biofiltration device; 5 e an activated carbon filtration device; e a reverse osmosis unit; e a disinfection device; and * a remineralisation device. In another embodiment there is provided a water treatment system for producing 10 potable water, said system comprising: e a preozonation device; e a coagulant and/or flocculant addition device; * a DAF device; e a multimedia filtration device; is e an ozone addition device; * an ozone removal device; * a biofiltration device; e a granular activated carbon filtration device; * a reverse osmosis unit; 20 e a disinfection device; e a remineralisation device; * at least one monitoring device for monitoring a level of contamination of water between two successive treatment devices of the system so as to determine if the water meets a predetermined standard; 25 e an openable barrier following each monitoring device, said openable barrier being disposed so that water is permitted to pass to a purification device following a monitoring device only if said monitoring device indicates that the water meets the predetermined standard; and * at least one water diverter, each being disposed so that, if said monitoring device 30 indicates that the water fails to meet the predetermined standard, said diverter diverts the water to the input of the water treatment system. In another embodiment there is provided a water treatment system for producing potable water, said system comprising: e a pre-oxidation device for treating secondary and/or tertiary treated sewage; 12 e a coagulant and/or flocculant addition device for treating output water from the pre-oxidation device; e a physical-chemical particle separation device for treating output water from the coagulant and/or flocculant addition device; 5 e a filtration device for treating output water from the physical-chemical particle separation device; e an oxidation or advanced oxidation device for treating output water from the filtration device; 0 an oxidant removal device for treating output water from the oxidation of 10 advanced oxidation device; e a biofiltration device for treating output water from the oxidant removal device; and e an activated carbon filtration device for treating output water from the biofiltration device so as to produce a purified liquid. is e a reverse osmosis unit for treating the purified liquid to generate a permeate; * a disinfection device for disinfecting the permeate to generate a disinfected permeate; e a remineralisation device for treating the disinfected permeate to generate potable water; 20 e at least one monitoring device for monitoring a level of contamination of water between two successive treatment devices of the system so as to determine if the water meets a predetermined standard; e an openable barrier following each monitoring device, said openable barrier being disposed so that water is permitted to pass to a treatment device following a 25 monitoring device only if said monitoring device indicates that the water meets the predetermined standard; and * at least one water diverter, each being disposed so that, if said monitoring device indicates that the water fails to meet the predetermined standard, said diverter diverts the water to the input of the water treatment system. 30 Brief Description of the Drawings A preferred embodiment of the present invention will now be described, by way of an example only, with reference to the accompanying drawings wherein: Figure 1 is a process schematic of a water treatment system; and 13 Figure 2 is a diagram of a water treatment process with monitoring and recycling capability. Detailed Description of Preferred Embodiments The present invention provides a process and apparatus for purifying secondary 5 and/or tertiary treated sewage. In the context of the present specification, the term "purifying" (and related terms such as "purify", "purification", "purified" etc.) refer to removal of contaminants, commonly harmful or unaesthetic contaminants, in the secondary and/or tertiary treated sewage. A "purified" liquid will therefore be a liquid from which at least one of such contaminants have been at least partially removed. It will to therefore have a lower level of at least one of such contaminants than the liquid before the purification. It may have a zero level, or a non-zero level, of each of those contaminants. In the context of the present invention, sewage is defined as "[t]he used water and added waste of a community which is carried away by drains and sewers" (http://www.sandiego.gov/mwwd/general/glossary.shtml). It commonly comprises human is excrement. The sewage is commonly aqueous sewage. Commonly the secondary and/or tertiary treated sewage will have at least some, preferably most and more preferably substantially all of the solids removed therefrom. The requirement for treatment of water for drinking purposes depends on the water quality at individual locations. In some locations the quality will be good and reverse 20 osmosis will not be required. However investigations show that in many regional and rural areas where the present process will be mostly applicable, water qualities are such that the reverse osmosis stage is essential. Production of potable water from saline water for example seawater requires high pressure to overcome the osmotic pressure of the feedwater. However use of water, such as secondary and/or tertiary treated sewage, which 25 has a lower concentration of salts and consequently a lower osmotic pressure, will require lower pressures and hence lower energy costs for treatment and reduced negative climate change impacts. In many cases, secondary and/or tertiary treated sewage which has been subsequently treated with common processes but without reverse osmosis would not be of 30 drinking water quality. Waters with dissolved solids contents in excess of 1,000 mg/L are not uncommon. Such waters are indicated by Australian Drinking Water Guidelines as "May be associated with excessive scaling, corrosion and unsatisfactory taste". On occasions waters being considered for potable purposes have had much higher dissolved solids levels.

14 For the many communities where water shortages are extremely severe, the present process would be of major benefit because it enables the utilisation of a regular and reliable source of water that is close by the community. For these distressed communities, the security and the dependability of the supply of water is unmatched by any alternative. 5 In other words, when treated water from sewage water treatment plants (SWTPs) is the only source of water available and this cannot be effectively and affordably raised to potable standards, the present process can achieve this and this cannot be achieved affordably by existing processes. Treated sewage plants are readily and constantly available close to centres of io population where large quantities of potable water are required. The water treatment system described herein may therefore be conveniently located in close proximity to such sewage plants in order to provide suitable supplies of potable water to the population in those centres. Locating the system near a treated sewage plant provides benefits of reduced costs of piping and power in transferring feed water from the treated sewage is plants to the water treatment system, as well as providing the potable water near the location where it is required. Compared to the typical membrane desalination process presently used for sea water desalination, the present process is typically: 1) 40% lower in capital cost of the required equipment 20 2) 50% lower in operating costs. 3) Substantially lower in power usage 4) Substantially lower in climate change impacts 5) Not environmentally detrimental to marine creatures or the sea bed 6) Significantly environmentally friendly because the volume of reject water is reduced 25 by 80% 7) Significantly environmentally friendly because of less usage of hazardous cleaning chemicals due to: Fewer membranes installed, lower usage of chemicals. Lower frequency of cleaning requirements 30 Any discharges of wastes from the present process may conveniently be returned to the inlet of the sewage treatment plant which provides the secondary and/or tertiary treated sewage which represents a feed stream to the present process. The water treatment system of the present invention would likely be located close to such a sewage treatment plant. This would provide convenient transfer of the secondary and/or tertiary treated 15 sewage from the sewage treatment plant to the water treatment system. It would also enable staff of the sewage treatment plant to provide the low level of supervision required for operation of the automated water treatment system. It would also be convenient to return wastes from the water treatment system to the sewage treatment plant. This would 5 have little or insignificant effect on the operation of the sewage treatment plant and on the quantity and nature of solid wastes from that plant. A preferred embodiment of the present invention is summarised in the table below. Name of Step Process Aim Adsorption (optional) Powdered Activated Remove high levels of Carbon organics Pre-ozonation Low dosage of ozone Oxidise some of organics to assist removal of some organics and destroying some pathogens Coagulation/Flocculation Addition of (typically) Increase removal of Ferric Chloride suspended solids Air Flotation (e.g. DAF) Using micro air bubbles Maximise removal of to float flocs of suspended solids suspended solids to surface of water for removal by skimming Multi Media Filtration Separating suspended Remove suspended solids solids from water by from water retaining solids in/on filter for subsequent removal by backwashing Main ozonation Applying micro bubbles Destroy pathogens and of ozone/air or organics and/or make these ozone/oxygen, vulnerable to removal by optionally together with micro-organisms in the BAC UV radiation Filter Remove unused oxidants Applying potassium Remove unused oxidants to permanganate or UV protect micro-organisms in/on 16 energy, or use of a coal the Biologically Active Filter or other carbon layer in the BAC filter Biologically Active Organisms living on the Enable micro-organisms in/on Carbon (BAG) Filter media of the filter the filter to destroy by remove organics from consuming the organic the water contaminants and/or the debris of dead organisms Granular Active Carbon Adsorb residual organics Extend the removal of (GAC) Filter and filter out debris organic and prevent debris released by the BAC from BAG Filter fouling the Filter RO Membranes and/or contaminating the water Reverse Osmosis (RO) Removing dissolved Remove dissolved solids, inorganic and organic mainly inorganic salts, materials from the water residual organic and chloramine residual in the potable water. This is a requirement by State __________________Health Departments Re-mineralisation Adding specific Minimise corrosion of the (optional - preferred) chemicals to the reticulation systems and to permeate from the RO improve the taste of the notable water A diagramatic representation of a typical water purification system according to the present invention is provided in Fig. 1. The separate elements of the system of Fig. I are described below. 5 Input water (secondary or tertiary treated wastewater): the present system may be run using secondary and/or tertiary treated effluent. This may be supplemented by one or more other aqueous streams, for example from a river, a lake, a reservoir, an aqueous industrial waste stream, or some other aqueous stream. The other aqueous streams may comprise fresh water. The input water may also comprise water recycled from later in the 17 system but which has failed to meet a predetermined standard of purity. The proportion of secondary and/or tertiary treated effluent in the total input water to the system may be between about 50 and about 100%, or about 60 to 100, 70 to 100, 80 to 100, 90 to 100, 50 to 90, 50 to 70, 60 to 90 or 80 to 90%. The input water is fed to a feed water sump which 5 contains a number of baffles in order to promote plug flow conditions. Powdered activated carbon may also be added at this stage. Pre-ozonation: The input water is fed to a pre-ozonation unit. This unit comprises a tank for holding the input water from the feed water sump. The tank is fitted with one or more ozone inlets for admitting ozone to the tank. The ozone inlets may comprise a disperser to 1o ensure that the input ozone stream is provided in small bubbles so as to facilitate their dispersal through, and/or dissolution in, the liquid in the tank. The tank may also be fitted with a stirrer or agitator for dispersing the ozone through the tank. It may also be fitted with a number of baffles in order to ensure plug flow conditions are maintained in the tank. The system may also comprise an ozone generator for generating the ozone from is oxygen, or from dry air, for example by use of UV energy or of a corona discharge. The ozone entering the tank (i.e. the ozone generated by the ozone generator, if present) may be in a mixture with one or more other gases. It may be mixed with air, or oxygen, or nitrogen or carbon dioxide or with a mixture of any two or more of these. It may have a concentration in the other gas or gases of between about 1 and about 20% on a weight or 20 volume basis, or about I to 15, 1 to 10, 1 to 5, 1 to 4, 1 to 3, 2 to 5, 3 to 5, 2 to 4, 2 to 10, 2to 20,5 to 20, l0to 20, 10to 15,5 to 15 or 5to 10%, e.g. about 1,2,3,4, 5,6,7, 8,9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20%. It may be greater than 20%. The flow of ozone into the tank may be sufficient that the quantity of any organic matter in the input water is decreased to an extent that the coagulation/flocculation unit operates efficiently. 25 The preozonation unit may serve to at least partially sterilise the input water (i.e. kill microorganisms therein) and to reduce the organic loading in the input water. This may reduce the loading of toxic, pathogenic and/or unpleasant smelling or tasting components in the input water. It may serve to improve the efficiency of coagulation and/or flocculation. It may improve the settling of suspended solids. 30 Coagulant/flocculant addition: Water exiting the preozonation tank is treated with one or more coagulants and/or flocculants, typically ferric chloride (as shown in Fig. 1) or alum and/or a polyelectrolyte. The coagulant/flocculant may be added in aqueous solution. It may be a saturated solution or may be between about 50 and about 100% saturated, or about 60 to 100, 80 to 100, 50 to 90, 50 to 70 or 70 to 90% saturated, e.g.

18 about 50, 60, 70, 80, 90, 95 or 100% saturated. A saturated solution minimises the volume of added liquid required to achieve a given amount of coagulant/flocculant addition. In some instances the coagulant/flocculant is added at low concentration. It may for example be added at a concentration of about 0.01 to about 1% w/v, or about 0.05 to 1, 0.1 to 1, 5 0.5 to 1, 0.01 to 0.5, 0.01 to 0.1, 0.01 to 0.05, 0.05 to 0.5 or 0.05 to 0.2%, e.g. about 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1% w/v. Ferric chloride and alum are well known flocculants, and are used for agglomerating colloidal materials and other suspended matter and organics from water so that the resultant particles can subsequently be removed easily by a physical separation process such as dissolved air flotation (DAF), 10 sedimentation, filtration or a combination of more than one of these. It is known that viruses in water commonly adhere to solids and colloidal particles, and so the viral loading may be reduced during flocculation and subsequent separation of flocculated matter. Other flocculants/coagulants may be used in addition or instead of ferric chloride. These include polyelectrolytes and alum. The rate of addition of ferric chloride (and/or is other flocculant/coagulant) may be sufficient to achieve the desired level of removal of suspended matter once the coagulum is removed from the water. The desired level may be greater than about 50%, or greater than about 60, 70, 80, 90 or 95%, e.g. about 50, 60, 70, 80, 90, 95, 99, 99.5, 99.9% or 100%. Coagulation/Flocculation: Following addition of a coagulant/flocculant, the water is 20 allowed time, optionally with suitable agitation, for flocculation to occur. This may for example be provided in a tank which is fitted with one or more stirrers and/or agitators, optionally with baffles and flow disruptors. These provide an output which contains flocculated matter suspended in the water. This may be regarded a physical-chemical particle separation, in that the use of chemicals (coagulants and flocculants) results in and 25 allows a physical particle separation within the water. Colloidal particles that have the same sign of charge (commonly a negative charge) in water can give rise to murkiness and/or colour in the water. Because of this equal charge sign on the particles, the repulsive forces cause these particles to remain suspended in the water and not settle out. Thus, to get them to loose their charge and to agglomerate to form bigger particles that 30 can settle out, chemicals may be added to the water. These chemicals are coagulants and flocculants. Typically, a coagulant neutralizes the charges on the particles and the flocculant then causes the colloidal particles to bind together to form bigger particles, called flocs. Commonly, the same chemical that causes coagulation also causes flocculation, but sometimes it is necessary to add different chemicals to achieve this. The 19 bigger flocs are then easily removed by sedimentation, DAF (as described elsewhere herein) and/or filtration. Thus, with particular reference to the term physical-chemical: a) "Chemical". There is a chemical reaction that takes place to neutralize the charges on the colloidal particles. For example, if ferric chloride is added to water: 5 FeC 3 +3H 2 0 -- Fe(OH) 3 + 3H+ + 3Cr; The H' then neutralises the negatively charged colloidal particles. b) "Physical". After charge-neutralisation one needs a physical process to get the neutralized particles to agglomerate and form flocs so that latter can be removed. This may be achieved by slowly agitating (e.g. stirring) the volume of water to allow the small to particles to collide with each other and form bigger particles. Latter are then removed physically, e.g. by settling, DAF or filtration or a combination thereof. Flotation (DAF): The output from the coagulation/flocculation stage is passed to a dissolved air flotation (DAF) unit or other suitable separation unit for physical separation of the coagulated/flocculated matter. In DAF the water is saturated with air under is pressure, and then released into the DAF tank. The release in pressure causes the air to come out of solution in the water in the form of small bubbles which adhere to the coagulated/flocculated matter, thereby causing it to rise to the surface. It may then be removed by skimming, allowing the clarified water to pass to the next stage. Other particle separation processes may be used in place of DAF, for example sedimentation or 20 fine bubble aeration. In fine bubble aeration, air is introduced and dispersed as fine bubbles into the water. These bubbles adhere or attach to the coagulated/flocculated matter and cause the latter to rise to the surface of the water. If sedimentation is used, the particulate matter that is formed by coagulation/flocculation is allowed to settle to the bottom of the tank. This may be a purposely designed sedimentation tank. The resulting 25 sludge is removed periodically from the bottom of the tank and the clarified water is allowed to pass to the next stage. In some cases a filtration step may be included, optionally in addition to either the DAF or sedimentation steps described above, in order to remove further coagulated/flocculated matter. Monitoring: Following the DAF, a monitoring stage monitors the quality of the water. 30 Commonly this will monitor for suspended solids (e.g. by measuring turbidity and/or by particle counting). It may additionally or alternatively measure organic matter in the water. In the event that the monitoring reveals the water to be of insufficient quality, a three way valve (or alternatively a pair of valves) operates so as to divert the water to the feed water sump until the water at the monitoring stage improves sufficiently. In some 20 embodiments the return line (labelled "plant recycle water" in Fig. 1) that takes the diverted water from the valves is connected to the feed line to the feed water sump, whereas in other embodiments it is connected directly to the feed water sump. There may be a non-return valve in the return line so as to prevent contaminated water in the line 5 returning to the purification devices in the event of a sufficient backpressure. Multimedia filtration: Solid matter remaining in the water at this stage, including residual flocculated matter, may be largely removed by a multimedia filter, e.g. a dual media filter. In a suitable filter, a coarse upper layer is used to prevent caking of the flocculant and encourage deeper bed penetration, and a finer lower layer is used to io provide efficient removal of fine solids. Typically particles of greater than about 20 microns may be removed with moderate to high efficiency (e.g. greater than about 80%, or greater than about 90% or greater than about 99%). The high surface area of the dual media filter and the dual layer structure also mean that cleaning frequency is low. Cleaning may be effected by washing with a cleaning agent (e.g. chlorine solution) and/or is by backflushing. This may be conducted with air scouring or it may be conducted without air scouring. The dual media filter may operate under gravity or may be augmented by a pressure device. Commonly the dual media filter will comprise a sand filter together with some other type of media filter. Monitoring: Following the multimedia filter, a monitoring stage monitors the quality of 20 the water. Commonly this will monitor for suspended solids (e.g. by measuring turbidity and/or by particle counting). In the event that the monitoring reveals the water to be of insufficient quality, one or more valves operate so as to divert the water to the feed water sump until the water at the monitoring stage improves sufficiently. Main ozonation: The main ozonation unit provides ozone to the water as a strong 25 oxidant in order to oxidize certain inorganic constituents, remove harmful or unpleasant smelling or tasting organics, remove colourant components and kill any remaining microorganisms, including viruses. Additionally, oxidation in the main ozonation unit predisposes organic matter to biodegradation in the biologically active carbon. The organic load entering the main ozonation unit is typically relatively low, as much of the 30 organic loading will have been removed by preozonation, coagulation/flocculation, clarification and filtration. The main ozonation unit typically is in the form of a series of tanks, or of a single tank having a series of baffles to facilitate plug flow, prevent short circuiting of the water and ensure correct reaction time as the water passes through the unit. Ozone may be fed into the unit through a number of ozone inlets, typically at least 21 one per individual tank (or per region of the tank separated by baffles). The inlets may comprise flits or other devices designed to encourage the formation of large numbers of small bubbles of ozone in the water. This increases the efficiency of ozonation of the water. As noted earlier, the ozone may be generated by an ozone generator. It may be 5 provided as a mixture with one or more other gases as described earlier. Ozone has the advantage as a means for disinfecting and removing organics that it is unstable, and any unused ozone degrades to harmless oxygen. Additionally, it is efficient, and is readily produced by an inexpensive method. Alternatives to the use of ozone as a main oxidant include addition of diamond electrode generated electrolysed water and advanced to oxidation using either hydrogen peroxide dosage catalysed by ultraviolet radiation or ozone catalysed with ultraviolet radiation. Boron doped diamond electrodes (commonly nanocrystalline electrodes) used for electrolysis of water are know to provide a mixed oxidant including active oxygen for purification of water and destruction of pollutants and microorganisms. It will be understood that any of these alternatives may be used in is addition to ozonation in some cases. An advantage of use of hydrogen peroxide in combination with UV radiation is that it has been approved by Queensland water authorities for use in purification of water to a potable standard. Unused Oxidant Removal: An oxidant removal step is inserted at the end of the main ozonation in order to remove oxidant that has not been consumed after the main 20 ozonation step. This restricts exposure of the BAC (below) to ozone or other oxidants, and prevents the destruction of microorganisms that grow on the BAC. If a separate oxidant remover is not used, a layer of coal below or before the BAC Filter Bed or the BAC may perform that function. For example a layer of anthracite of about 50 to about 100mm thickness is generally sufficient to remove all residual ozone. In the absence of 25 such a layer, residual ozone will generally be consumed in the first about 25 to about 50mm of the BAC. Replacing or regenerating the BAC may therefore be a part of routine maintenance of the system. In some embodiments, unused oxidant is removed using UV energy. This converts the residual ozone to transient, extremely reactive, oxygen species which rapidly degrade so as to leave the water free of strong oxidants. This may therefore 30 function both to remove unused oxidant and as a supplementary advanced oxidation step. The present invention may use normal oxidation and/or advanced oxidation. Normal oxidation commonly uses a single oxidant, preferably a strong oxidant (e.g. ozone). Advanced oxidation employs stronger oxidants than normal oxidation, and may involve more than one oxidant, commonly more than one strong oxidant. Frequently two 22 oxidants are used, although in certain cases three, four or more than four may be present. Advanced oxidation may involve formation of more aggressive oxidants e.g. radicals. These may be formed in situ as the more than one oxidants are added to the water, or may be preformed prior to addition to the water. Advanced oxidation results in more powerful 5 and/or more complete oxidation than normal oxidation. As an alternative to the main ozonation, oxidation, sterilizing and purifying processes may be achieved by using a Neutral Electrolysed Water Generator. This comprises electrical and electronic equipment connected to specialized electrodes, e.g. boron doped diamond coated electrodes, that are at least partially immersed in the water. 10 Application of a voltage across the electrodes results in a current flow through the water. This produces a variety of oxidizing radical species, including ozone, which perform the same functions as the ozone in the main ozonation described above. The neutral electrolysed water has significant bactericidal, virucidal and fungicidal properties. Monitoring: Following the main ozonation stage, a monitoring stage monitors the quality is of the water. Commonly this will monitor for oxidation-reduction potential (ORP) but may also monitor other water quality indicators. In the event that the monitoring reveals the water to be of insufficient quality, one or more valves operate so as to divert the water to the feed water sump until the water at the monitoring stage improves sufficiently. Biologically activated carbon (BAC): This comprises a granulated activated carbon 20 filter that houses microorganism that establish themselves naturally on and/or inside the carbon bed and proliferate naturally. Biodegradation and adsorption of mainly organic constituents take place inside the carbon bed to remove organic matter from the water. Oxidation of organic matter in the water in the main ozonation unit activates the organic matter to removal by the BAC unit, both by increasing its polarity, thereby improving its 25 adsorption efficiency on the activated carbon granules, and by rendering it more susceptible to biodegradation on the carbon. Granulated activated carbon (GAC): a two stage activated carbon filtration unit is provided as a polishing step to remove any residual organic matter, and any degradation products and/or microbial by-products from the BAC unit, that remain in the water. These 30 units operate partially by adsorption onto the surface of the activated carbon, and partially by removal of undissolved solids by filtration. The unit may be capable of removing solid matter down to about 1 micron diameter (or down to about 2, 5, 10 or 20 microns diameter, depending on the nature of the GAC unit). It may remove at least about 95% of such solids, or at least about 96, 97, 98, 99, 99.5 or 99.9% thereof.

23 Monitoring: Following the GAC filtration stage, a monitoring stage, typically for dissolved organic carbon (DOC) and/or total organic carbon (TOC), monitors the quality of the water. In the event that the monitoring reveals the water to be of insufficient quality, one or more valves operate so as to divert the water to the feed water sump until 5 the water at the monitoring stage improves sufficiently. Water that passes the monitoring at this stage is fed to a membrane feed sump which provides the feed water for the Reverse Osmosis unit. Reverse osmosis (RO): a reverse osmosis unit is used to remove dissolved salts and small organic materials that have survived the earlier separation steps. The removal efficiency 10 will not be the same for all contaminants. For any particular contaminant the efficiency may be between about 50 and about 100%, or about 60 to 100, 70 to 100, 80 to 100, 90 to 100, 95 to 100, 99 to 100, 50 to 90, 60 to 90, 90 to 99, 90 to 95 or 95 to 99%, e.g. about 50, 60, 70, 80, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 or 100%. Due to the substantial removal of contaminants in earlier separation steps, the loading of organic and inorganic is constituents, organisms and solids in the feed to the RO unit is likely to be low. Thus the osmotic pressure of the feed will be similarly low. This enables the RO unit to operate at high efficiency and with relatively low energy consumption. The pressure used in the RO unit will also depend on the salt content (TDS), the nature of the salts and the desired recovery rate. Suitable pressures are commonly about 30 to about 70 bar. The pressure 20 may be about 30 to 60, 30 to 50, 40 to 70, 50 to 70, 35 to 65, 35 to 50 or 50 to 65 bar, e.g. about 30, 35, 40, 45, 50, 55, 60, 65 or 70 bar. In some cases pressures of less than 30 bar may be used, e.g. 20-30 bar or 25-30 bar. The membranes used in reverse osmosis are well known. Suitable membranes include asymmetric membranes and thin film composite membranes. Suitable asymmetric membranes include cellulose triacetate (CA 25 membranes) and polyamide (PA-membranes). Suitable composite membranes include cross-linked fully aromatic polyamide membranes, crosslinked polymerised polyamide membranes and polyimide membranes. In thin film composite membranes, a thin film layer is supported on a porous substrate. The porous substrate may be a polysulfone. The reverse osmosis membrane may be used in hollow fibre or spiral wound configuration. 30 Monitoring: Following the reverse osmosis unit, a monitoring stage monitors the quality of the water. Commonly this will monitor for dissolved solids (e.g. by conductivity). In the event that the monitoring reveals the water to be of insufficient quality, one or more valves operate so as to divert the water to the feed water sump until the water at the monitoring stage improves sufficiently to meet the required standard.

24 Disinfection: Final disinfection of the permeate water from the RO unit may be performed, typically using chlorine, in order to terminally sterilize the water produced by the system. As the level of microbial contamination is likely to be low at this stage, the chlorination may be at a low level, and may therefore produce water that does not have a 5 strong taste, and which is therefore palatable to humans. Commonly chlorine (either as a gas or in solution) is added in line to the water, which then passes to a holding tank. The residence in the holding tank should be sufficient for the chlorine to sterilize the water to the required standard. Alternatively the chlorine may be added to the water in the holding tank, and the tank agitated to ensure that any microorganisms in the water are contacted 10 with the chlorine. The residence time in the holding tank may be at least about 20 minutes in order to allow the chlorine to properly react and efficiently kill any microorganisms present. Chloramine may be used as an alternative disinfectant to chlorine. Additionally, complementary disinfection methods, such as ozone addition and/or UV energy may be used in combination with the main disinfectant. These complementary disinfection 15 methods commonly leave no residual disinfectant in the water (other than the main disinfectant). Remineralisation: Commonly the product of a reverse osmosis process will lack mineral salts. It may therefore taste flat and unappealing. Remineralisation (i.e. adding mineral salts commonly present in drinking water at levels commonly pertaining in drinking 20 water) may be conducted in order to improve the taste of the product water and therefore its acceptance by a community. The mineral salts and their dosage levels may be selected so as to mimic those present in an existing potable water supply used by the community. The salts added at this stage may also be beneficial for humans consuming the water. Suitable added salts include lime, sodium carbonate and sodium bicarbonate. Carbon 25 dioxide may also be provided for stabilization. Additionally it is known that RO treated water can be corrosive to metals. Remineralisation may stabilize the water against this by adjusting levels e.g. of calcium and alkalinity to overcome this. The output water from the system may be tested for purity, potability and/or acceptability for the desired use. As well as testing for physical, inorganic, organic and/or 30 bacteriological constituents and/or determinants, the output water from the system may be subjected to a suitable test using exposure by an indicator fish. Thus for example, a small proportion of the output water of the system may be continuously diverted to a tank or container containing the indicator fish. An output (e.g. overflow) from the tank should be provided so as to maintain an approximately constant level of water in the tank or 25 container. The health and wellbeing of the indicator fish may then be monitored as an indication of the acceptability of the water entering the tank (i.e. of the water exiting the system). In the event that one or more of the fish becomes ill or dies, the system may be switched (either automatically or manually) to a recycle mode so as to return output water s to an early stage of the system for reprocessing. Alternatively, in the event that one or more fish becomes ill or dies, further testing on the output water may be prompted (either automatically or manually) so as to determine if the illness or death was a result of impurities in the water. The fish should be a freshwater fish. Preferably the output from the tank will be discarded due to possible contaminants added to the output water by the io fish. The system may also comprise one or more pumps. There may be for example an inlet pump for pumping the secondary and/or tertiary treated sewage into the first treatment unit. There may be one or more intermediate pumps in the system for pumping intermediate, partially purified water through the system. There may be a return pump for 15 pumping water to the start of the first treatment unit if said water fails to meet the required standard at any one of the monitoring steps. There may be a pump associated with the reverse osmosis unit for raising the pressure of the water entering the unit to a sufficient pressure for operation of the reverse osmosis unit. There may be a permeate pump for pumping the permeate from the reverse osmosis unit to disinfection and/or 20 remineralisation devices if present. Suitable pumps are well known. They may be electrically operated pumps. They may be controlled by the controller of the system (if present). Thus the process of the present invention may comprise a number of purification steps, e.g. adsorption of organics, preoxidation (e.g. preozonation), clarification, 25 flocculation/coagulation, multimedia filtration, ozonation or other main oxidation, removal of unused oxidant, biologically active filtration, carbon filtration, reverse osmosis and final disinfection. The process may also comprise monitoring a level of contamination of water between any two of these purification steps of the process so as to determine if the water meets a predetermined standard. Monitoring commonly will be for 30 the particular contaminant that should have been removed by the purification step immediately preceding the monitoring, or for an indicator for said contaminant. In some embodiments, there is monitoring after each of the purification steps of the process. In some embodiments, water is permitted to pass from a particular purification step to a subsequent purification step only if said monitoring indicates that the water meets the 26 predetermined standard. Thus if the monitoring indicates that the water is not of the required quality or purity, it will not be permitted to pass to the next treatment step (or, in the case of the final treatment step, will not be released from the treatment system). If the monitoring indicates that the water fails to meet the predetermined standard, the water 5 may be returned to the start of the first treatment process. In this case, water will circulate within the system until the water is of acceptable quality. The process may comprise controlling one or more components of the system used for conducting the process. In the event that more than one monitoring function is performed in the process, there may be a separate monitoring device for each monitoring function, or one 10 monitoring device may monitor more than one function. It should be understood that, when describing a monitoring device as being "between" two treatment devices, this is taken to mean that water flows from one of the treatment devices to the monitoring device and thence to the other of the treatment devices. It should not be taken to indicate that the monitoring device is necessarily physically located between the two treatment devices is (although this may in some cases be the case). Similarly reference to a monitoring device "following" a treatment device is taken to mean that water flows from the treatment devices to the monitoring device. It should not be taken to indicate that the monitoring device is necessarily physically located adjacent the two treatment devices (although again this may in some cases be the case). Other related terms should also be interpreted 20 in a similar fashion. A preferred embodiment of the present invention is designed as packaged plant modules. It may be sized so as to be capable of generating a desired output rate of drinking water deemed safe for human consumption at all times. The desired output rate may be at least 20m 3 /h, or multiples of this output. It will be understood that the volume 25 of output may be adjusted by resizing the components of the system in order to achieve any desired output volume. In order to achieve the required quality standard, a "multiple barrier" approach is adopted. This means that the treatment processes employed ensure that at least two (in many cases three or more) unit processes are provided for removing each crucial contaminant, which could be harmful to the human body or aesthetically 30 objectionable. Contaminants which may be harmful to the human body include pathogens and toxins. Contaminants which may be aesthetically objectionable include taste and odour components, e.g. mercaptans, disulfides, indoles, halorganics, bitter agents, salts etc. For example, complete and/or partial barriers for one of the most resistant pathogens, Cryptospiridium, include enhanced coagulation/flocculation, dissolved air flotation 27 (DAF), dual media filtration, ozonation, reverse osmosis and chlorination. Similarly, multiple barriers may be used against organic substances, viz. enhanced coagulation/flocculation, ozonation, removal of unused oxidant, biologically activated carbon (BAC), granular activated carbon (GAC) adsorption and reverse osmosis. This 5 ensures both degradation and removal of micro-pollutant and Endocrine Disrupting Compounds (if present) as well as a substantial reduction in THM (trihalomethane) formation potential. The following unit processes were included in the final plant design: powdered activated carbon (PAC) dosing, pre-oxidation and pre-ozonation, flash mixing, enhanced 1o coagulation and flocculation, dissolved air flotation, dual media rapid gravity sand filtration, ozonation, removal of unused oxidant, BAC filtration, GAC filtration, reverse osmosis (RO), disinfection and remineralisation. An important feature of the design of a preferred embodiment is the fully integrated multi-stage monitoring of water quality and the physical prevention of any water not is meeting the demanding standard at any of these monitoring points being allowed to pass to the next treatment stage or barrier. Instead, water not meeting the quality standard at any particular intermediate stage is returned back to the inlet of the plant and recycled through to the Feed Water Sump, or may be returned directly to the Feed Water Sump. It is then reprocessed through all processes preceding the particular intermediate stage until 20 water quality reaches the required standard. Only then will the water be allowed to pass to the next stage of the plant. This comprehensive monitoring and control system provides a level of quality assurance that is exceptional in potable water treatment and is unique in treatment plants of this capacity. 25 In an embodiment of the invention the process may be fully automated. It may have a minimum of 5 built-in Safety Check Accept/Reject Controls based on individual continuous monitoring. After each critical stage or barrier, a continuously operating monitor evaluates the water quality for the specific standard after completion of that treatment stage. When it is shown that the water at that point meets the standard, the 30 water is transferred to the next treatment stage. Should the water not meet the specific standard, the water is redirected back to the inlet tank of the plant. Water would continue to recirculate within the plant until all sequential monitoring checks confirm that all standards have been achieved. Water is not 28 permitted to pass any stage or barrier until the quality fully complies with the standard for that stage. Each array of membranes may have its own monitor. Should the monitor show that the quality standard is not met, the water supply to that array of the membrane unit is shut 5 off and the array is not returned to service until investigation and remediation work restores the array to full functionality. The monitoring and sequential safety back up facilities provide the highest standard of safety and quality assurance, exceeding Water Treatment Industry Acceptable Standards. Additional supervision may be provided by means of a supervisory control and 1o data acquisition (SCADA) system. These assurances may be further monitored and supervised by regular and routine sampling and laboratory testing, thereby confirming the performance of the automatic and continuous monitoring and control regimes. Fig. 2 shows a diagram of a system which incorporates monitoring and recycling is capability. System 100 of Fig. 2 shows a first treatment unit 110 comprising three separate purification stages (120, 140 and 160). Suitable treatment stages are described earlier in this specification, and may for example include a adsorbent addition, pre ozonation, coagulation/flocculation/particle separation stage, an oxidation stage, an unused oxidant removal and a biofiltration stage, although other suitable stages may be 20 present. Although Fig. 2 shows only three purification stages, there may be more or (in some instances) less than this number in suitable systems, and three have been shown merely for the purpose of illustration. System 100 also comprises a reverse osmosis stage 180, which is located downstream of first treatment unit 110. Following each purification stage, including the reverse osmosis stage, is a monitoring device (monitoring device 122 25 following purification stage 120, monitoring device 142 following purification stage 140, monitoring device 162 following purification stage 160, monitoring device 182 following purification stage 180), and following each monitoring device is a diverter valve (diverter valve 124 following monitoring device 122, diverter valve 144 following monitoring device 142, diverter valve 164 following monitoring device 162, diverter valve 184 30 following monitoring device 182), which is connected to the next purification stage by lines 126, 146, 166 and 186 respectively. Return line 200 is provided for recycling rejected water from the system to inlet line 210, and diverter valves 124, 144, 164 and 184 are connected to return line 200 by lines 128, 148, 168 and 188 respectively. Purification stages 120, 140, 160 and 180 are connected to the corresponding diverter 29 valve by lines 130, 150, 170 and 190 respectively, and these lines are fitted with monitoring devices 124, 144, 164 and 184 respectively. Each of diverter valves 124, 144, 164 and 184 is capable of either allowing water from the corresponding previous stage to pass to the subsequent stage or to return line 200. Line 186 from reverse osmosis stage 5 180 leads to disinfection stage 220 and thence to remineralisation stage 230 which connects to output line 240. Data lines 132, 152, 172 and 192 are provided to provide control signals to diverter valves 124, 144, 164 and 184 respectively. In operation, secondary and/or tertiary treated sewage enters system 100 via inlet line 210, and may be supplemented by recycled water from return line 200. It passes io initially to purification stage 120 where it undergoes a first purification process, designed to reduce the concentration of a first contaminant to a below a first threshold level. It then passes out of stage 120 through line 130, and past monitoring device 122, which measures a concentration of the first contaminant. Device 122 compares the concentration of the first contaminant to a predetermined threshold level. If the concentration is below the is threshold level, monitoring device 122 will signal diverter valve 124 to send the water through line 126 to the subsequent purification stage 140. If the concentration is above the threshold level, monitoring device 122 will signal diverter valve 124 to send the water through line 128, which leads to return line 200, recycling the rejected water to inlet line 210. 20 The purified water, which has a concentration of the first contaminant below the first threshold level then passes to purification stage 140 where it undergoes a second purification process, designed to reduce the concentration of a second contaminant (which may be the same as or different to the first contaminant) to a below a second level. It then passes out of stage 140 through line 150, and past monitoring device 142, which measures 25 a concentration of the second contaminant. Device 142 compares the concentration of the second contaminant to a predetermined threshold level. If the concentration is below the threshold level, monitoring device 142 will signal diverter valve 144 to send the water through line 146 to the subsequent purification stage 160. If the concentration is above the threshold level, monitoring device 142 will signal diverter valve 144 to send the water 30 through line 148, which leads to return line 200, recycling the rejected water to inlet line 210. The purified water, which has a concentration of the second contaminant below the second level then passes to purification stage 160 where it undergoes a third purification process, designed to reduce the concentration of a third contaminant (which may be the 30 same as or different to the first contaminant or the second contaminant) to a below a third level. It then passes out of stage 160 through line 170, and past monitoring device 162, which measures a concentration of the second contaminant. Device 162 compares the concentration of the third contaminant to a predetermined threshold level. If the s concentration is below the threshold level, monitoring device 162 will signal diverter valve 164 to send the water through line 166 to the reverse osmosis stage 180. If the concentration is above the threshold level, monitoring device 162 will signal diverter valve 164 to send the water through line 168, which leads to return line 200, recycling the rejected water to inlet line 210. 10 The purified water, which has a concentration of the third contaminant below the third level then passes to reverse osmosis stage 180 where it passes through a reverse osmosis membrane in order to reduce the concentration of salts to a below a fourth level. The permeate from the reverse osmosis membrane then passes out of reverse osmosis stage 180 through line 190, and past monitoring device 182, which measures a is concentration of salts (for example by means of conductivity). Device 182 compares the concentration of salts to a predetermined threshold level. If the concentration is below the threshold level, monitoring device 182 will signal diverter valve 184 to send the water through line 186 to disinfectant stage 220. If the concentration is above the threshold level, monitoring device 182 will signal diverter valve 184 to send the water through line 20 188, which leads to return line 200, recycling the rejected water to inlet line 210. Purified water from disinfectant stage 220 passes through remineralisation stage 230, where salts are added back to the water in order to improve its taste. The output from stage 230 passes out of system 100 through output line 240. Water Quality. 25 Typically the plant will produce, from secondary and/or tertiary treatment wastewater, potable water safe for human consumption and adhering to all applicable standards as set out by the relevant authorities and revised from time-to-time. Example 30 Raw water was processed using a water treatment system as described above with reference to Fig. 2. Input and output water test results are shown below. Raw water quality: o COD = 75 mg/l o BOD = 20 mg/l 31 o DOC = 15 mg/l (dissolved organic carbon) o TDS = 900 mg/i (total dissolved solids) o TSS = 25 mg/i (total suspended solids) o Ammonia (NH 4 -N)= 2 mg/l; 5 o Nitrate + Nitrite = 20 mg/i o Turbidity = 20 NTU o Iron = 3 mg/i as Fe o Manganese = 0,5 mg/l as Mn o Fluorine = I mg/i as F 10 o Sulphate = 50 mg/l as SO 4 o Ortho Phosphate = I mg/l as P o Total Hardness = 100 mg/l as CaCO 3 o FOG = I mg/I (fat, oil and grease) is Final water quality.- Before re-mineralisation, o COD, BOD, DOC = Not Detectable o Organo-metallic compounds = Not Detectable o No viable microorganisms present o TDS = 50 mg/l 20 o Turbidity = 0,05 NTU o Total for Iron and Manganese = 500 jig/l o FOG = Not Detectable 25

Claims

1. A process for producing potable water, said process comprising: 1) treating secondary and/or tertiary treated sewage using a first treatment process to generate a purified liquid; and 5 2) treating the purified liquid using reverse osmosis to provide the potable water.

2. The process of claim I wherein step 2) comprises treating the purified liquid using reverse osmosis and disinfecting a permeate from said reverse osmosis to provide the potable water.

3. The process of claim 1 wherein step 2) comprises treating the purified liquid 1o using reverse osmosis to produce a permeate, disinfecting the permeate from said reverse osmosis to produce a disinfected permeate and remineralising the disinfected permeate to provide the potable water.

4. The process of any one of claims I to 3 wherein step 1) comprises at least one of the following: 15 e addition of an adsorbent * addition of one or more coagulants and/or flocculants * physical-chemical particle separation 0 multi-media filtration e addition of one or more oxidants 20 e removal of unreacted oxidant(s) e biofiltration 0 activated carbon filtration 9 microfiltration * ultrafiltration 25 * ion exchange

5. The process of any one of claims I to 4 comprising at least two purification steps for removing each contaminant or class of contaminant which could be harmful to the human body.

6. The process of any one of claims I to 5 comprising at least two purification 30 steps for removing each contaminant or class of contaminant which could be aesthetically objectionable.

7. The process of any one of claims I to 6 wherein step 1) comprises: * addition of one or more oxidants to secondary and/or tertiary treated sewage to produce a first intermediate liquid; 33 * addition of a coagulant and/or flocculant to the first intermediate liquid to produce a second intermediate liquid; * physical-chemical particle separation from the second intermediate liquid; * filtration of the second intermediate liquid; 5 e addition of an oxidant to the resulting filtrate to form a third intermediate liquid; e removing unreacted oxidant(s) from the third intermediate liquid; * biofiltration of the third intermediate liquid to produce a fourth intermediate liquid; and * activated carbon filtration of the fourth intermediate liquid to generate the purified 1o liquid.

8. The process of any one of claims 1 to 7 additionally comprising a monitoring step for monitoring a level of contamination of water between two of the treatment steps of the process so as to determine if the water meets a predetermined standard.

9. The process of claim 8 wherein a monitoring step is conducted between each is two successive treatment steps of the process.

10. The process of claim 8 or claim 9 wherein water is permitted to pass to a treatment step following a monitoring step only if said monitoring step indicates that the water meets the predetermined standard.

11. The process of any one of claims 8 to 10 wherein, if said monitoring step 20 indicates that the water fails to meet the predetermined standard, the water is returned to the start of the first treatment process.

12. A water treatment system comprising: 1) a first treatment unit for treating secondary and/or tertiary treated sewage using a first treatment process to generate a purified liquid; and 25 2) a reverse osmosis unit coupled to the first treatment unit for treating the purified liquid.

13. The water treatment system of claim 12 wherein the first treatment unit comprises at least one of the following: * an adsorbent addition device 30 e a pre-oxidation device e a coagulant and/or flocculant addition device * a physical-chemical particle separation device e a filtration device * an oxidant addition device 34 * an oxidant removal device e a biofiltration device * an activated carbon filtration device * a microfiltration device s e an ultrafiltration device * an ion exchanger

14. The water treatment system of claim 12 or claim 13 comprising at least two purification devices for removing each contaminant or class of contaminant which could be harmful to the human body or aesthetically objectionable. 1o

15. The water treatment system of any one of claims 12 to 14 additionally comprising a disinfectant addition device for disinfecting a permeate from the reverse osmosis unit.

16. The water treatment system of any one of claims 12 to 15 additionally comprising a remineralisation device for adding one or more mineral salts to a permeate 15 from the reverse osmosis unit.

17. The water treatment system of any one of claims 12 to 16 wherein the first treatment unit comprises: * a pre-oxidation device 0 a coagulant and/or flocculant addition device; 20 e a physical-chemical particle separation device; * a filtration device, e an oxidation or advanced oxidation device; e an oxidant removal device; e a biofiltration device; and 25 e an activated carbon filtration device.

18. The water treatment system of any one of claims 12 to 17 additionally comprising a monitoring device for monitoring a level of contamination of water between two of the purification devices of the system so as to determine if the water meets a predetermined standard. 30

19. The water treatment system of claim 18 wherein a monitoring device is present for monitoring a level of contamination between each two successive purification devices of the system.

20. The water treatment system of claim 18 or claim 19 comprising an openable barrier following each monitoring device, said barrier being disposed so that water is 35 permitted to pass to a purification device following a monitoring device only if said monitoring device indicates that the water meets the predetermined standard.

21. The water treatment system of any one of claims 18 to 20 comprising a water diverter disposed so that, if said monitoring device indicates that the water fails to meet 5 the predetermined standard, said diverter diverts the water to the start of the first treatment unit.

22. The water treatment system of any one of claims 12 to 20 additionally comprising a controller for controlling one or more components of the system.

23. Use of a water treatment system according to any one of claims 12 to 22 for 10 the production of potable water. Dated 12 January, 2009 Clement Hinchliffe and Ginter Gerhard Lempert Patent Attorneys for the Applicant/Nominated Person SPRUSON & FERGUSON 15