AU2013337588A1

AU2013337588A1 - Process and apparatus for water treatment

Info

Publication number: AU2013337588A1
Application number: AU2013337588A
Authority: AU
Inventors: Gheorghe Emil Duta
Original assignee: Water Science Technologies Pty Ltd
Current assignee: Infinite Water Technologies Pty Ltd
Priority date: 2012-11-01
Filing date: 2013-10-28
Publication date: 2015-06-11
Anticipated expiration: 2033-10-28
Also published as: AU2013337588B2; WO2014066931A1; HK1213869A1; CN104936904B; CN104936904A

Abstract

A process for treating water comprising the step of oxygenating water for treatment with an oxygen containing gas in a conditioning module wherein said oxygenation process is catalysed by at least one metal salt dosed into said conditioning module under oxidising and p H conditions at which reactive metal radicals and hydroxyl radicals form. The oxygenation process does not require the use of hydrogen peroxide or ozone and can be conducted at ambient temperature and pressure. Apparatus (700) to conduct the process is also disclosed.

Description

WO 2014/066931 PCT/AU2013/001242 1 PROCESS AND APPARATUS FOR WATER TREATMENT This invention relates to a process and apparatus for water treatment, the water treatment including at least one catalytic oxidation step. Water scarcity is a growing world problem threatening to have an 5 economic impact greater than recent financial crises. During the 2 0 th century the world population increased four times while water consumption increased nine times. More than 70 countries experience water restrictions and scarcity. The situation is not limited to developing countries. About 97% of the water available on Earth is saline. Desalination is rapidly expanding. However, desalination 10 technologies available to treat sea water to potable water quality require large amounts of energy and the growing number of seawater desalination plants could have considerable climate change impact. While seawater desalination can provide water security for coastal cities, treatment of water for small communities and away from coastal areas 15 encounters serious difficulties. Water composition varies broadly from place to place and may greatly vary with time. This makes it difficult to achieve water feed quality needed for membrane separation and UV disinfection when used. The operation and maintenance of membrane systems is complex and not well suited for remote applications where highly skilled operators are not available. 20 One of the most challenging applications for water treatment is treatment of industrial wastewater at the source. Industrial wastewater composition typically shows large variance in speciation, possibly containing high metal concentrations and/or organics. From the same industrial plant, there are typically multiple streams of waste water of different composition requiring treatment. These 25 streams are usually mixed into a single stream directed to water treatment even though the various streams could perhaps be more efficiently treated without mixing the streams so increasing the complexity of contamination. Economically treating separate streams of wastewater in small amounts is not generally practical, with the current state of water treatment technology. As a result, 30 compliance exception licenses are often issued for discharging, into environment and municipal sewer, wastewater with contaminants exceeding established safe standards. This makes it more difficult to treat the wastewater by municipal utility WO 2014/066931 PCT/AU2013/001242 2 plants and to avoid contamination of sludge which could be processed into soil conditioner. Availability of clean raw water sources, requiring only minimal treatment for achieving potable water quality, is more and more limited. Increasingly, the water 5 to be treated for human consumption is seriously contaminated with mineral and organic material and pathogens. For example, arsenic and fluoride in excess in drinking water each are affecting more than 100 million people. Cases of serious illness and death from drinking pathogen contaminated water exceed one billion per year. Research projections show that even by achieving the Millennium 10 Development Goals, which would essentially improve the current situation of access to safe drinking water, minimum number of death from waterborne diseases will be around 30 million people, in 2020. Disinfection level and standards have been adopted for drinking water treatment of wastewater for reuse. Water turbidity is associated with disinfection 15 level on the basis that suspended solids passing through the treatment system into the treated water could harbour and protect pathogens from inactivation and destruction. Potable water should be free from dangerous bacteria and viruses. When there is high risk of human contact with treated water E. Coli count has to be less than 10 per 100 ml of water. It is thought that in such case the turbidity of 20 the water before disinfection should be less than 2 NTU in order to achieve disinfection targets. This holds true for the use of traditional technologies for water disinfection to produce high quality water. Technologies used are a combination of membrane filtration and ozone and ultraviolet radiation, potentially expensive processes. Similar treatment challenges and disinfection requirements 25 are encountered for the reuse of industrial wastewater from food production, slaughterhouses, pulp and paper mills and storm water. The last treatment stage of municipal wastewater and industrial wastewater with high organic load, where disinfection is included, is called tertiary treatment. Twin mixed media filters in series can remove a high concentration of 30 suspended solids. The arrangement in which each filter is backwashed with the feed water to that particular filter and sized to operate at constant flow rate is very economical while achieving a high degree of clarification. Such filters could produce water with turbidity of less than 4 NTU. Whilst this is a good WO 2014/066931 PCT/AU2013/001242 3 performance, the quality of the water produced is not suitable for disinfection to produce safe high quality water. One more filtration stage is needed and membrane filtration is typically the additional final stage. Microfiltration and ultra filtration membranes, achieve the level of clarification needed before disinfection. 5 Some of the shortcomings of membranes, compared to mixed media filters are higher cost, higher operating pressure and lower water efficiency due to more frequent backwash. An object of the invention is to propose an energy efficient and cost effective alternative water purification process suitable for addressing aspects of 10 water contamination and scarcity as described above. With this object in view, the present invention provides, in a first embodiment, a process for treating water comprising the step of oxygenating water for treatment with an oxygen containing gas in a conditioning module wherein said oxygenation process is catalysed by at least one metal salt dosed 15 into said conditioning module under oxidising and pH conditions at which reactive metal radicals and hydroxyl radicals form. In a second embodiment, the present invention provides an apparatus for treating water comprising a conditioning module provided with an oxygen containing gas supply means to enable oxidation of water with an oxygen 20 containing gas; and a metal salt dosing means for supplying at least one metal salt to said conditioning module to catalyse the water oxygenation process under oxidising and pH conditions at which reactive metal radicals and hydroxyl radicals form. The oxygen containing gas may include air. Oxygen may be generated by 25 a suitable oxygen generator whether adsorption or membrane based. The gas supply means is not required to deliver gas at high pressure though control over gas flowrate is advantageous. The dominant source of oxidant used in accordance with this invention is the oxygen containing gas. Such gases are typically less expensive than oxidants such as hydrogen peroxide and ozone. 30 Handling is also typically safer. The Applicant has observed that the above processes do not need to be conducted at high pressures, say more than twice atmospheric pressure. Indeed, favoured operating pressures include atmospheric pressure and do not exceed WO 2014/066931 PCT/AU2013/001242 4 0.2 MPa. Water heating apparatus is not required either. The catalytic oxygenation process described above proceeds at acceptable rate for water treatment at ambient temperature at the geographic location of the module, expected to almost always be below 502C. The process is therefore 5 advantageously carried out at ambient temperature and ambient or near ambient pressure range as above favoured. This promotes safety, energy efficiency and reduction in plant capital and operating cost. The metal catalysed oxidation processes described in this specification are therefore distinguished from prior pressurised oxidation processes. 10 The metal salt(s) may advantageously be selected from the group consisting of water soluble iron, aluminium and manganese salts. Chlorides and sulphates of these metals, for example ferric chloride, manganese chloride, aluminium chloride and aluminium sulphate, are particularly suitable not least because selected soluble metal salts, which are a source of reactive metal 15 radicals in solution under oxidising conditions, are best selected for purposes of catalysing the oxygenation reaction process. Any of these metal salts could be introduced to water in the conditioning module as single salts. Iron salts are a particularly advantageous example since, under oxidising conditions, highly reactive metal radicals - such as ferryl ions - may be produced following a 20 Fenton reaction type scheme though not exactly the same since hydrogen peroxide (and other strong oxidants) and acid pH conditions are not generally required in accordance with the invention. Reactive metal radicals such as ferryl and analogous radicals (such as manganyl) are most stable under neutral to alkaline conditions. 25 More advantageously, a plurality of metal salts selected from the above group of salts are introduced to the conditioning module in combination to optimise catalytic oxidation forming co-precipitates or flocs enabling removal of toxic elements and organic compounds from the water being treated. A non limiting example of a useful combination is a combination of any two or more of 30 ferric, manganic or aluminium chlorides. Such metal salts form acidic solutions with water so requiring pH control at the conditioning module to ensure that the favourable alkaline conditions for oxidation and co-precipitation of elements (particularly heavy metals and metalloids together with iron, manganese and WO 2014/066931 PCT/AU2013/001242 5 aluminium) are supported and maintained. Acidic conditions should or must be avoided. Catalytic oxidation reactions should proceed to sufficient extent to lower elemental and organic concentrations in water to meet potable water standards. Without wishing to be bound by theory, introduction of such metal salts promotes 5 Fenton like reactions which generate highly reactive radicals, such as hydroxyl and ferryl (where iron is involved) radicals with oxidation capability comparable with ozone. This maximises rate of oxygenation of the water in the conditioning module. The dissolved oxygen level of water is substantially increased in the 10 conditioning module. This increase in dissolved oxygen level itself enhances the catalytic oxidation reactions within the conditioning module particularly under alkaline conditions which are generally required for water treatment according to the invention. These reactions result in substantial and efficient oxygenation necessary for metal and organic removal or decontamination without requiring 15 strong oxidants to be introduced under most circumstances. Further, introducing said at least one metal salt, but more preferably two or more metal salts, assists removal of organics and other elements through oxidation (mineralisation), co-precipitation, flocculation and/or coagulation processes, these processes themselves being driven by catalytic oxidation 20 reactions. Metal salts used in the process and apparatus of the invention, as well as most efficacious combinations of metal salts to favour mineralisation, oxidation and formation of co- precipitates and flocs, may be selected for their flocculant properties. Ferric chloride is again a suitable example of a metal salt selected for both catalytic and flocculant properties. However, polymer flocculants are more 25 conveniently dosed into the conditioning module. Polymer flocculants, conveniently those with amphoteric properties such as those based on acrylic acid and acrylamide, are of particular value when water is highly alkaline with pH above about 9. In that pH range, conventional flocculants like alum and ferric chloride may be ineffective. Anionic or cationic flocculants could also be used. 30 The conditioning module performs other potential functions in addition to water oxygenation. Settling of a portion of the flocs and precipitates is likely to occur in the conditioning module which may comprise solids removal means for WO 2014/066931 PCT/AU2013/001242 6 removing such portion of flocs and co-precipitates. As a result, water for treatment undergoes a substantial degree of clarification in the conditioning module. As desired unit operations including oxidation, coagulation, precipitation, flocculation and also disinfection) within the conditioning module are pH 5 dependent, the conditioning module desirably includes pH adjustment means for dosing acid or alkali (more typical as alkaline conditions are required) as necessary to provide a target pH, typically in the alkaline range. pH correcting chemicals may advantageously include sodium hydroxide and hydrated lime. Less typically, pH correcting chemicals such as sulphuric acid and hydrochloric 10 acid may be required. All these mentioned chemicals are relatively inexpensive reagents. In addition, provision may be made, under appropriate pH conditions for disinfection, to introduce a disinfectant, such as chlorine conveniently in the form of chlorine dioxide, to prevent bacterial growth and slime formation within the process and apparatus. 15 Additional chemicals may sometimes require to be introduced to the conditioning module. Such chemicals may include common water treatment chemicals: coagulant metal salts, polymer and other flocculants, disinfectants such as sodium hypochlorite and chlorine dioxide. The range of chemicals used as well as the number of chemical dosing units used (some units may dose more 20 than one chemical in admixture with another) varies with the overall process implementation and physico-chemical speciation of the water to be treated. That is, some reagents may only be required if speciation or nature of the water to be treated requires. For example, water with low suspended solids content might not require a complex flocculant to be introduced. 25 However, the processes of oxygenation and clarification, necessary to achieve potable water standards are not completed within the conditioning module. It is expected to be necessary to subject water to further substantial oxygenation and clarification or filtration in a suitable module connected through a water transfer line. 30 To this end, the process and apparatus should include a further catalytic oxidation module and a filtration module. The catalytic oxidation and filtration modules could form separate, though interconnected, modules within the process and apparatus. More conveniently, the process and apparatus includes a single WO 2014/066931 PCT/AU2013/001242 7 module which integrates the processes of oxidation and filtration. This simplifies the process flowsheet and reduces the capital and operating cost of water treatment plant operating in accordance with the above described water treatment process. 5 A catalytic oxidation and filtration module (a term which should be understood to comprehend either a single such module incorporating functions of both catalytic oxidation and filtration or separate catalytic oxidation and filtration modules for each unit operation) comprises a bed of granular material, typically in form of a fixed bed. The granular material, which may comprise a mixture of 10 granular materials, is selected to provide catalytic oxidation and filtration functions. In effect, the granular material forms a catalytic filter. Preferred granular materials are metal oxide catalysts, for example, and especially preferred, manganese oxide catalysts, which have the function of promoting oxidation and co-precipitation of elements with the iron, aluminium and manganese salts used 15 in the conditioning module. Such metal oxides are conveniently deposited on, that is supported, by various supports which include silica sand, garnet and zeolites. Another category of catalytic granular materials is obtained by deposition of noble metals on various substrates of granules with large surface area. For example, gold or platinum may be deposited on granular carbon. Selection of granular 20 materials may depend on the catalytic efficiency needed, that is, the degree of catalytic activity and oxidation necessary to treat a water stream with particular physical and chemical properties. The particle size of the granular material should be optimised to provide surface area for promoting catalytic oxidation reactions as well as filtration 25 capability. It is important that co-precipitates formed in the oxidation and filtration module, as well as any carryover precipitates or flocs from the conditioning module are removed at this stage in the process and apparatus. Bed depth and aspect ratio (height to diameter in case of circular tanks or width, other transverse dimension) may be selected to achieve requisite degree of 30 catalytic oxidation and filtration. An oxidant, especially a strong oxidant such as hydrogen peroxide, may be introduced - if only occasionally necessary - to the catalytic oxidation and filtration module to promote catalytic advanced oxidation and precipitation of WO 2014/066931 PCT/AU2013/001242 8 particularly organics but also any elements still present within the water. Oxidation by any such oxidant is catalysed by the granular material catalyst as described above. Fenton and Fenton type reactions may be observed with a number of metal salts. If an iron salt is present, such reactions may proceed in accordance 5 with the following Fenton reaction scheme illustrating generation of reactive radicals which participate in catalytic oxidation and catalytic advanced oxidation: Fe 2 , + H 2 0 2 -> Fe 3 , + OHO + OH OHO + H 2 0 2 -> HO 2 0 + H 2 0 10 Fe 3 + HO 2 0 -> Fe 2 * + H* + 02 Fe 2 * + HO 2 0 -> Fe 3 * + H0 2 Fe 2 * + HOO-> Fe 3 + OH Some other metals may provide similar reactive radical generation. 15 Manganese is an example. For such suitable metals, the Fe can be replaced in the above scheme with Mn or M. The highly reactive hydroxyl (stronger oxidant than ozone) and ferryl or other metallic radicals particularly react, in catalytic advanced oxidation to degrade or mineralise organic material. In the case of mineralisation, organic 20 material is degraded to carbon dioxide, salts and mineral acids. Mineralisation of pathogens also results in disinfection though a disinfectant would still typically be required. Such catalytic advanced oxidation is not typically necessary for removal of metals. Such oxidant, as described above, may also be dosed - together with any 25 other required reagents (especially metal salt catalysts or pH correction chemicals) into the conditioning module, or the line interconnecting the conditioning module with the catalytic oxidation and filtration module, as required, potentially substituting disinfectant if not required. The process and apparatus requires water transfer means to convey water 30 from the conditioning module to the catalytic oxidation module. Although this could possibly occur by gravity, at least one pump is likely to be required for water transfer between the conditioning and catalytic oxidation modules. A pump should be selected which avoids shearing of flocs and co-precipitates to extent WO 2014/066931 PCT/AU2013/001242 9 interfering with the necessary filtration to meet potable water standards of these flocs/co- precipitates from the water in the catalytic oxidation and filtration module. A progressive cavity pump may be especially suitable. Water from the conditioning module is advantageously pumped at 5 controlled rate through the catalytic oxidation and filtration module. This allows more efficient catalytic oxidation and filtration. Either conditioning or catalytic oxidation and filtration modules may perform unit operations other than as above described. For example, the conditioning module may be configured to conduct water softening. 10 Raw water for treatment in the process and apparatus may be from primary sources such as groundwater or water already processed through a primary treatment for removal of large solids, oils and fats and heavy petroleum hydrocarbons for which specialized equipment known to those skilled in the art is used for these purposes. The raw water may contain high levels of heavy metals. 15 Following water treatment in both the conditioning and catalytic oxidation and filtration modules, product potable water is available for supply to users. Such water may be stored in a product water storage vessel. Each of the conditioning and catalytic oxidation and filtration modules require unit operations to be conducted in vessels, typically tanks, comprised 20 within each module. As few tanks as possible should be used to reduce costs. For many applications, it may be sufficient to have a single vessel, conveniently a tank, in each module. Some applications may require two vessels in each module. If the conditioning module comprises a plurality of vessels or tanks, one 25 tank may be subjected to aeration (with air or other gas) and a second tank to oxygenation (with oxygen or oxygen enriched gas) to enable more complex treatment schemes. The catalytic oxidation and filtration module may comprise a plurality of vessels or tanks for applications where there is a high suspended solids content 30 in the raw water (or as a result of catalytic oxidation). In such case, a first filter tank may include a filter bed only performing filtration, a second or subsequent tank also performing catalytic oxidation. Alternatively, all tanks in the catalytic oxidation and filtration module may perform both catalytic oxidation and filtration.

WO 2014/066931 PCT/AU2013/001242 10 Granular material may have different resolution (that is, particle size distribution, mean particle size) between the tanks. If two or more tanks are used, the first tank may have a filter bed having coarser resolution than granular material used in the second and any subsequent tanks. 5 A modular construction approach may be adopted for the water treatment apparatus of the invention with additional vessels being added either in series or parallel as water treatment capacity is scaled up. The Applicant's research shows that treatment of water to potable standard is possible using one or two vessels though this will depend on treatment capacity and the rate at which metal salts 10 and other reagents are dosed into the conditioning module, in particular. The fewer the vessels used for a given water treatment capacity, the more cost effective will be a water treatment plant constructed and operated in accordance with the process and apparatus of the invention. The vessels, typically tanks, may provide for recirculation either to 15 themselves or to another tank whether in the same or different module. That is, the vessels may be operated in batch or continuous mode. Tank level may be monitored and treatment processes implemented dependent on tank level, some processes being conducted only when a tank is substantially full. Tank(s) used in the conditioning module may be provided with an overflow 20 arrangement for directing water to the catalytic oxidation and filtration module. Conditioning tank(s) may be enclosed, for reasons of hygiene, though this is not mandatory as would be the case if pressurisation for pressure oxidation was required. Tank(s) used in the catalytic oxidation and filtration modules are enclosed and typically enclose a headspace above the catalytic filter bed. A 25 distributor may be included to distribute water over the surface of the catalytic filter bed to minimise prospect of channelling or voidage. The process and apparatus are not expected to be suitable for desalination operations, that is for removal of soluble salts if present) in water to be treated. Desalination involves, for example, removal of chlorides; especially sodium 30 chloride from briny water, often the only permanent water source in some remote regions. If required, desalination of water may be conducted downstream of the conditioning and catalytic oxidation and filtration modules. Membrane processes are most likely to be suitable for desalination applications.

WO 2014/066931 PCT/AU2013/001242 11 As regards desalination and other possible downstream contaminant removal processes, particularly ion exchange, such processes are likely to be made more economical and efficient by producing well clarified water, free from heavy metals and organics in the prior conditioning and catalytic oxidation and 5 filtration modules. The conditioning and filtration module should be subjected to backwashing at regular intervals to prevent clogging of the catalytic filter bed with precipitates and other contaminants. In traditional water utility plants, water for backwashing the filters is typically stored in a separate tank. Dedicated pump and plumbing are 10 also required. For pressure filtration a common solution is to use three or more filters and backwash one filter at a time by directing the water exiting the other filters in reverse through the bed of the filter to be backwashed. Such plant is made relatively compact through avoiding water storage for backwash. However, many filter units and valves are likely to be required. The process and apparatus 15 of the present invention does not require either water storage or complex filter unit/valve/pump arrangements for backwashing. Precipitates and other solids may be separated by any convenient means. It may also be convenient and cost effective to recycle backwash water to the conditioning module or even raw water storage. 20 When backwashing of the catalytic filter(s) is required, the process and apparatus conveniently switches to batch mode with raw water supply being shut off. Water from the conditioning module is then pumped through the catalytic oxidation and filtration module and returned to the conditioning module in a closed loop. When the water is of quality suitable for backwashing then 25 backwashing is performed. Backwashing water does not have to be of the same quality as final product water. Switching the plant to batch mode processing could also be useful in case of serious deterioration of raw water quality due to natural disasters causing floods or accidental contamination from human economic activities. However, in 30 this case, water exiting the catalytic oxidation module would preferably be directed to product water storage instead of directing it to that tank in the conditioning module. Although, the capacity of the plant is lower than in WO 2014/066931 PCT/AU2013/001242 12 continuous mode, the duration of individual processes is flexible and the plant could handle much higher level of water contamination than in continuous mode. Fine particles could escape from time to time from the catalytic filter bed and a fine filter may be included, if necessary, to retain such particles, preventing 5 entrainment in the potable water produced by the process and apparatus of the invention and directed to users or storage as product water. The process and apparatus of the present invention is applicable for treatment of water from primary sources such as groundwater, treatment of wastewater for reuse or safe disposal and treatment of water for remediation of 10 contaminated sites. The process is especially applicable to heavy metal contaminated water and treatment of acid mine drainage water which requires to be treated to reduce dissolved metals and acidity. The water treatment process and apparatus may be more fully understood from the following non-limiting description of a preferred embodiment of the water 15 treatment apparatus of the present invention. The description refers to the following figures: Fig. I is a process diagram of a water treatment apparatus constructed and, operated in accordance with one embodiment of the present invention; Fig. 2 is a process diagram of a water treatment apparatus constructed 20 and operated in accordance with another embodiment of the present invention; Fig. 3 is a process diagram of water treatment apparatus constructed and operated in accordance with another embodiment of the present invention. In Figs. 1, 2 and 3, there is shown a water treatment plant 700, constituent modules and components of which will now be described. Tank 10 is provided 25 with level switches to detect full condition so that the flow of incoming raw water could be stopped, preventing overflow, and a low limit for initiating fill up and receiving raw water. Another level switch might be used to detect tank empty condition and prevent the transfer pump 20 from running dry. The transfer pump 20 is controlled using a variable speed drive so that in conjunction with flow 30 transmitter 300 the water flow rate could be programmed, monitored and corrected. In line strainer 40 has the purpose of retaining large solids contained in raw water; it may be isolated for cleaning by closing manual valve 30 either when WO 2014/066931 PCT/AU2013/001242 13 clogging occurs or during routine maintenance aimed at avoiding clogging. Clogging level of strainer 40 is detected by the control system through the increase in speed of transfer pump 20 required to maintain a given flow in order to overcome obstruction of water passage by debris accumulated in the strainer 5 40. Transfer pump 20 delivers the water to vessel 120, here a tank, in the conditioning module 100 at a continuous controlled rate (though it may be noted that the process could be operated in batch mode). Water level in tank 120 is monitored by ultrasonic level transmitter 80 and maintained close to full level by 10 adjusting the speed of main pump 180 where necessary to maintain the level. This is done to maximise efficiency of the process and output of product water likely to be subject to high user demand. Tank 120 is provided with a filter breather 90 to prevent potential contamination from air entering tank 20 when the level of water decreases as 15 happens during backwash operation or batch operating mode. The dosing unit 50 doses a metal salt, such as ferric chloride into the water for treatment. Such ferric chloride solution, as dosed, will be acidic with pH about 2. More than one metal salt dosing unit may be used for dosing a combination of metal salts (especially iron, aluminium and manganese salts) into the water. A 20 plurality of dosing units and injection points for the metal salts and any other reagents may be located on the incoming raw water line 25 to introduce these metal salts. The primary role of the metal salts is to provide a source of reactive metal radicals to catalyse oxygenation of the water to increase dissolved oxygen level and drive co-precipitation and flocculation processes which facilitate removal 25 of contaminant elements and organics from the water to be treated. In some cases, such metal catalysed oxidation may directly remove contaminants from the water through an oxidation process which volatilises or mineralises the contaminant, often an organic contaminant, away from the liquid or aqueous phase. Where pathogens are mineralised, disinfectant requirements may be 30 reduced since the oxidation process itself has a disinfecting effect. As catalytic oxidation proceeds, pH tends to decrease from the moderately alkaline range where reactive metal radical and hydroxyl radicals most optimally progress oxygenation towards neutral level, partly as a result of chemical species WO 2014/066931 PCT/AU2013/001242 14 formed by the oxidation reactions and partly due to introduction of acidic metal salt solutions, for example ferric chloride solution. pH may fall from the range of 9 11 to about 7 to 8. pH decrease is a function of contamination of the water. A relatively clean water may only undergo a pH adjustment of about 0.5. A more 5 contaminated water may undergo a pH adjustment of a few pH units. As the treatment processes are highly pH dependent, pH adjustment is likely to be necessary to maintain pH at a typically alkaline level favouring co precipitation and flocculation. Conditioning tank 120 includes a dosing unit 50, of conventional type for use in water treatment plants, for adding pH correcting 10 chemicals which may most advantageously be selected from the following: sulphuric acid, hydrochloric acid, sodium hydroxide and hydrated lime, relatively inexpensive reagents. Required pH range may be achieved by suitable control unit such as a SCADA, DCS or other control unit supervising the operations of water treatment plant 700. 15 Disinfectant, such as sodium hypochlorite, may require to be added to conditioning tank 120 for local plant disinfection and also to provide a residual as is the case of drinking water to be distributed through a pipe network. Disinfectant dosing unit 70 is also of typical construction and is used for dosing sodium hypochlorite. Dosing of disinfectant may depend on pathogen concentration, e. g 20 E coli count in the water to be treated. The dosing unit 70 may dose hydrogen peroxide, where very occasionally necessary, to further promote catalytic advanced oxidation for destruction of organics through mineralisation processes caused by reaction of highly reactive hydroxyl and ferryl radicals with the organics as above described. Preferred point 25 of injection of hydrogen peroxide is just before the filter reactor for implementation of catalytic advanced oxidation. Addition of hydrogen peroxide generates Fenton reactions, as above described, to generate the hydroxyl and ferry radicals. Other reactive metallic radicals may also be generated in Fenton type reactions. Destruction of organics also has a disinfectant effect and may reduce disinfectant 30 reagent consumption. A key component of the conditioning module A is the oxygen generator 100 which supplies oxygen gas, diffused into the water through fine bubble diffuser 110, into conditioning tank 120. The oxygen generator 100 is preferably WO 2014/066931 PCT/AU2013/001242 15 of pressure swing adsorption type using a zeolite bed; it produces oxygen of purity close to 90% for use in water treatment plant 700. The dissolved oxygen level of water is therefore substantially and deliberately increased in conditioning tank 120 by oxygen diffusion. This increase 5 in dissolved oxygen level itself drives the catalytic oxidation reactions within the conditioning module. These reactions result in substantial and efficient oxygenation and co-precipitation, flocculation and/or coagulation processes for contaminant removal, as above described, these processes themselves being driven by catalytic oxidation reactions. 10 Introduction of oxygen to conditioning tank 120 also allows thorough mixing of water and reagents within that tank 120. This increases process efficiency in an energy efficient manner. Some high density particles (not necessarily generated by the catalytic oxidation reactions but rather solids present in raw water not separated by in line 15 strainer 40) may be present in the water from time to time and metal oxide and hydroxide flocs may settle in part, together with high density particles at the bottom of the tank 120. Removal of high density particles is important to avoid contamination of filtration and catalytic oxidation beds and potential jamming or damage to the motorized valves. Valve 160 is opened intermittently, if required, to 20 discharge matter settled at the bottom of tank 120. However, it is not always critical that flocculated material be removed through settling and discharge from tank 120. Retention of flocculated material may also, or even more conveniently, take place in the filtration and catalytic oxidation beds. Catalytic oxidation beds retain flocculated matter in the upper side of the bed. The suction connection for 25 the main pump 180 is located above the bottom of tank 120. The bottom side of tank 120 is shaped so that precipitated matter slides down the side walls and settles, concentrating at the bottom for discharge. Most often the bottom of tank 120 is of conical shape with internal angle of cone of 60 degrees or less. Manual valve 170 is used for isolating the tank 120, preventing water 30 leakage, if the main pump 180 has to be serviced or other components downstream from the valves 170 have to be dismantled. The main pump 180 is preferably of progressive cavity type run through a variable speed drive. This type of pump delivers smooth flow, without pulses and WO 2014/066931 PCT/AU2013/001242 16 does not shear flocs formed through coagulation-flocculation during catalytic oxidation processes. Sweeping flocs can form without addition of specific flocculent polymer. Usually the pressure rating of the pump used is less than 300 kPa. All the components in the water treatment plant 700 on the pressure side of 5 the pump have higher pressure rating. Thus, the pressure relief valve 190 is used only to protect the pump 180. The chemicals dosing unit 200 is used for dosing a flocculant polymer into water transferring from conditioning module A to catalytic oxidation and filtration module B. The flocculant polymer may be an amphoteric polymer flocculant 10 based on acrylic acid and acrylamide and available from Itochu Chemicals. Such polymer flocculant is efficient at the moderately alkaline pH (above 9) where other flocculants such as alum and ferric chloride are ineffective. Mixing and aggregation of flocs takes place in the pipes and components along the line before the catalytic filter tank 240 of catalytic oxidation and filtration module B and 15 in the headspace above the catalytic filter bed inside the catalytic filter tank 240. This catalytic filter bed is fixed and water is distributed over the surface of the bed by a suitable distributor. Tank 240 is purposefully not pressurised to degree required for pressure oxidation. The catalytic filter bed of tank 240 comprises granular material selected to 20 provide catalytic and filtration functions. In effect, the granular material forms a catalytic filter. Preferred granular materials are metal oxide catalysts which have the function of promoting oxidation and co- precipitation of elements with the iron, aluminium and manganese salts used in the conditioning module. Such metal oxides are conveniently deposited on, that is supported, by various supports 25 which include silica sand, garnet and zeolites. Manganese oxide catalyst materials including supported manganese oxide catalysts are suitable and preferred. Manganese greensand has a zeolite base or support on which manganese oxide is deposited. DM1 65 material available from Quantum Filtration Pty Ltd has manganese oxide attached to a substrate of silica sand. 30 These materials, and others, could be used alone or in combination. The granular material may be selected with reference to the required degree of catalytic oxidation in catalytic oxidation and filtration module B.

WO 2014/066931 PCT/AU2013/001242 17 The particle size of the granular material within the catalytic filter bed is optimised to provide surface area for promoting catalytic oxidation reactions as well as filtration capability. It is important that co-precipitates formed in the oxidation and filtration module B, as well as any carryover precipitates or flocs 5 from the conditioning module A are removed at this stage in the water treatment plant 700. Bed depth and aspect ratio (height to diameter in case of circular tanks or width, other transverse dimension) may be selected to achieve requisite degree of catalytic oxidation and filtration. 10 Instruments 210 and 260 are pressure indicators, pressure gauges showing total system pressure and respectively pressure downstream from catalytic oxidation and filtration module B (and catalytic filter tank 240). At the same time pressure indicator 260 will show a pressure increase with the increase in clogging level of in line fine filter 280 for polishing any small particulate material 15 remaining in the water at this stage. Pressure transmitter 220 measures total system pressure on pressure side of main pump 180. Pressure transmitter 250 measures pressure downstream from catalytic oxidation module B. The pressure difference is used to trigger backwashing of the catalytic filter tank 240 bed. 20 Backwashing may be triggered based on set time interval or initiated manually if needed. The three way motorized valves 230 are of type typically used for pressurized sand filters and mixed media filters and operating modes of the catalytic oxidation filters are the same: 1) Normal mode whereby the water enters the catalytic filter tank bed 240 25 through upper side connection, travels through the bed downwards, then is collected through pipes provided with slots at the bottom of the filter tank 240 and through a central raising pipe connected to lower side connection of filter tank, exits the filter tank 240, then is directed by valve 270 to clean water tank 290 ; 30 2) Backwash mode whereby the water enters the filter tank 240 through the lower side connection of catalytic filter tank 240 and exits through the slotted pipes at the bottom of the filter bed. Then the water travels upwards expanding the bed and entraining debris retained in the bed.

WO 2014/066931 PCT/AU2013/001242 18 Water exits through the upper side connection of the filter tank 240 and is directed to spent backwash waste tank or pond. Sludge thickening and filtration for water recovery may be further performed on spent backwash water. 5 3) Rinse mode, whereby the water travels through the catalytic filter bed within tank 240 the same way as in normal mode except that valve 270 directs the water back to tank 120 in the water conditioning module. Rinse mode is used to clear suspended solids which could settle in the lower part of the bed following the backwash and bed settling. 10 In line filter 280 is used to retain breakage which may escape from time to time form the catalytic filter tank 240 bed. Filtration resolution (particle size as measured by mean particle size) recommended when treating groundwater is five microns. For surface water one micron resolution is recommended to provide an additional barrier for 15 Cryptosporidium oocysts. Treated water is stored for use or downstream processing (such as desalination using membranes or ion exchange) in the product or clean water tank 290. This water may be used directly from tank 290 or may be re-chlorinated and pumped through a pipe network for distribution as may be the case with potable water. 20 There are two modes of operation of the water treatment plant 700 for producing water for delivery to tank 290. Continuous mode of operation is the normal mode, while batch mode could be used in special situations. In addition there are operating modes related to mixed media filter or catalytic filter backwashing. These are: water preparation for backwashing, backwashing and 25 rinse modes. When the plant operates in continuous mode, raw water is received into tank 10 and is pumped at controlled flow rate to the conditioning tank 120 of conditioning module A by transfer pump 10. Water is treated in the conditioning module A with chemicals, including metal salts and any additional chemicals as 30 above described, and oxygenated in preparation for filtration and catalytic oxidation in module B. Main pump 180 follows incoming flow so that water level in tank 120 is maintained close to full level. Main pump 180 pumps the water WO 2014/066931 PCT/AU2013/001242 19 through the catalytic filter bed, in catalytic filter tank 240, then through the valve 270, in line filter 280 and into treated water tank 290. When water treatment plant 700 operates in batch mode, and any other mode related to backwash, the supply of water from raw water tank 10 to 5 downstream modules A and B of water treatment plant 700 is interrupted until one batch of water has been treated; or backwash and rinse mode are completed. In batch mode, when tank 120 is confirmed full, pump 20 stops. Part of any additional chemicals required is dosed or injected during filling up of tank 120. Additional mixing is provided by running oxygenation generator 10 100 through bubble diffuser 110 if needed. A flocculant injection valve (not shown) has to be connected to a spare socket on top of tank 120 and any connection used in continuous mode has to be plugged. After dosage of flocculant and mixing through oxygenation, flocs are allowed to settle and sludge is discharged by temporarily opening bottom valve 160. 15 The water is then oxygenated (as above described) and disinfectant is dosed during final part of oxygenation when the water in tank 120 is thoroughly mixed. When water conditioning tank 120 is again ready for catalytic oxidation and clarification operations, main pump 180 starts and water is processed through catalytic oxidation and filtration module B in the same manner as 20 described above for continuous mode. If low tank 120 level is detected by level transmitter 80, the process stops, pump 20 starts and water is pumped to the conditioning module until tank 120 is full and the process continues with treatment of the new batch of water. For preparation of water for backwash and rinse tank 120 is filled up and 25 transfer pump 20 stops. Then the water is conditioned and clarified in a manner similar to batch mode operation. Further operation and position of valves is the same as in rinse mode and continues until the water is ready to be used for backwashing. Disinfectant dosing amount is usually higher than for batch mode. Referring to Fig. 2, the second embodiment of the apparatus operated in 30 accordance with the process and apparatus of the invention shows a water treatment plant with two tanks 120 in the conditioning module A. This arrangement allows for more complex conditioning treatment when the plant is operated in continuous mode. An important modification, when comparing with WO 2014/066931 PCT/AU2013/001242 20 the plant shown in Fig 1, is that the first tank 120A is provided with aeration (with air) instead of oxygenation (with oxygen from oxygen generator 100). Aeration means 310 could be a diaphragm air pump or blower. Aeration provides air stripping, oxidation and chemicals mixing with the water. The chemical dosing unit 5 320 may be used for dosing a second metal salt as would be the case when removing cadmium by dosing manganese chloride in addition to iron chloride or sulphate. Dosing the metal salts in the first tank 120A increases the amount of dissolved metals, in this case iron and manganese in the water. Metal salts in solution creating highly acidic solutions decrease the pH of the water so pH 10 control to maintain moderately alkaline conditions, favouring both combined oxidation (with hydroxyl and reactive metal radicals) and element co-precipitation, is required. While water treatment plant 700 is running in continuous mode, dosing sodium hydroxide in the same tank would not favour dissolution of iron and 15 manganese. Co-precipitation starts in the second tank 120B when pH increases through addition of sodium hydroxide. Some other processes might be implemented by diffusing oxygen in both tanks 120A, 120B or by diffusing another gas, other than air, in the first tank 120A. The lower part of first tank 120 is connected through a launder to upper part of the second tank 1 20 so that water 20 flows by gravity from first tank into the second tank. Water level monitoring is also set up for the second tank 120B. Arrangement of second tank 120B, provided with oxygenation, together with the catalytic oxidation module B otherwise functions in identical modes to the plant shown in Fig 1. When operating in batch mode or preparing water for backwash, 25 water is directed through the additional or first tank 120A provided with aeration until the second tank 1 20B, provided with oxygenation, is full. Referring to Fig. 3, there is shown a third embodiment in which water treatment plant 700 comprises two filter tanks 240 and 245 in the catalytic oxidation module B. This arrangement allows for more complex treatment in the 30 catalytic oxidation module B. The additional filter tank 245 is placed before catalytic filter tank 240. Such construction (which may follow modular construction principles) may be suitable for handling a large volume of suspended solids without the need to WO 2014/066931 PCT/AU2013/001242 21 use a further dedicated clarifier. In such case, the filter tank 245 could be loaded with a mixed media bed, which though of manganese oxide as above described is of coarser filtration resolution (i. e particle size distribution) than the resolution for the bed of catalytic filter 240. The mean particle size of granular material in the 5 bed of filter tank 245 is about two times larger than the size of granular material in filter tank 240. The Applicant's tests find this particle size to be optimum for operating two filter beds in series with at least the second filter tank 240 holding a catalytic oxidation filter bed. Without wishing to be bound by theory, such particle size selection may favour the physical (e.g adsorption) and chemical phenomena 10 involved in efficient catalytic oxidation and co-precipitation. The first bed located in filter tank 245 could be also of catalytic type when targeting a finer degree of removal of particular contaminants through catalytic oxidation. The water treatment plant of Fig. 3 is also configured for chemical water softening. The pH of the water could be raised in the conditioning module A. The 15 tank 120 could be run with solid particles in suspension to provide seeding for precipitation of water hardness (in the form of calcium and magnesium salts at least). As the particles grow larger, they settle to the bottom of the tank 120 and are intermittently discharged through valve 160. Suspended solids, fine particles and metal hydroxide and oxide precipitates could be filtered for removal from 20 water by the bed in filter tank 245. Until the water exits tank 245, the pH will be maintained high or moderately alkaline to promote oxygenation through activity of the highly reactive metal and hydroxyl radicals. Polymer flocculant, such as the amphoteric polymer flocculant described above, dosed through dosing unit 200 supports flocculation at high pH. After the 25 water exits filter tank 245, acid (e. g sulphuric acid) is dosed through chemical dosing unit 55 to lower pH. Metal salts for catalytic oxidation are dosed through chemical dosing unit 50 and sodium hypochlorite disinfectant is dosed through chemical dosing unit 70. Dosing sodium hypochlorite at high pH is not effective for disinfection. To keep the system clean from bacteria, chlorine dioxide may be 30 dosed intermittently into incoming raw water before tank(s) 120, 120A, 120B in the conditioning module A. When operating in continuous mode, additional pressure indicator 2.5 and pressure transmitter 225 measure the pressure WO 2014/066931 PCT/AU2013/001242 22 downstream from first filter tank 245. Thus individual pressure drop on each of the two filter tanks can be monitored. Backwash can be triggered when any of the two filter tanks 240, 245 reaches a maximum set pressure drop. If the water treatment plant 700 is 5 configured to include chemical water softening, the water is prepared first for backwashing the granular bed of filter tank 245, just in tank 120 without running it through downstream filter 280. Time has to be allowed for settling, and then the sludge is drained, through bottom valve 160, from the bottom of tank 120. Suitable water for backwashing filter 245 can be achieved although this water is 10 not required to be as clean as product water. After backwashing filter 235, this filter 235 is set in normal mode, rinsing for this filter is not needed. In preparation for backwashing the catalytic filter 240 water is treated through both filters 240 and 245. Water exiting filter 240 is directed by valve 270 back to the tank 120 in closed loop. During this sequence, the pH of water has to 15 be maintained at the same level before catalytic filter 240 as when operating the water treatment plant 700 in normal mode. When the water is suitable for backwashing catalytic filter 240 the process starts, filter 245 operating in normal mode. Adjustment of pH is not needed and acid dosing is not performed. Only dosing of disinfectant is used for this mode. 20 Batch mode operation of plant shown in Fig. 3 is the same as described above for the plant in Fig. 1 except that for the plant in Fig. 3, water has to pass through the two filter tanks 240 and 245 and then is directed to clean water tank 290 by valve 270. Experimental test work in laboratory and field, using an apparatus with two 25 filter tanks 240 and 245 in series as shown in Fig. 3, has shown consistently high performance in clarification of water from just under 100 NTU raw water to less than 0.5 NTU (lower limit of detection of the method) treated water. Simultaneously, a broad range of heavy metals were removed to low parts per billion and parts per trillion levels. Amongst the heavy metals removed were: iron, 30 manganese, molybdenum, aluminium, copper, nickel, cadmium, chromium, zinc, lead and mercury.

WO 2014/066931 PCT/AU2013/001242 23 5 The Table provides further data for some of the metals as follows: Element Raw Water Treated Water Pb (mg/L) 1.7 0.0009 Al (mg/L) 0.46 0.02 Cu (mg/L) 1.9 0,059 Fe (mg/L) 4.9 <0.01 Mn (mg/L) 0.14 <0,001 Mo (mg/L) 0.04 0,003 Ni (mg/L) 0.09 0005 Zn (mg/L) 12 0.03 10 All treated element concentrations complied with the Australian Drinking Water Guidelines though discharge to sea was also feasible. Chemical oxygen demand also fell from 62 mg/L to 35 mg/L and pH fell from 9.2 to 7.3, again acceptable levels. Removal of arsenic could be achieved through co- precipitation at the 15 same level of resolution of parts per trillion. Cost of water treatment is low compared to traditional technologies due to inherent process efficiency and low energy input needed. In addition, by structuring a modular concept of plant and processes, the physical hardware modules may vary little and may be combined in a limited number of ways. Thus, production of plants in large number benefit 20 from economy of scale, and flexibility. Customization relates more to the use of specific chemicals (which may themselves depend on raw water chemical speciation and physical properties), granular materials used for filtration and catalytic beds and control software.

WO 2014/066931 PCT/AU2013/001242 24 Modifications and variations to the water treatment process and apparatus of the present invention may be apparent to the skilled reader of this disclosure. Such modifications and variations are deemed within the scope of the present disclosure. 5

Claims

1. A process for treating water comprising the step of oxygenating water for treatment with an oxygen containing gas in a conditioning module wherein said oxygenation process is catalysed by at least one metal salt dosed into said 5 conditioning module under oxidising and pH conditions at which reactive metal radicals and hydroxyl radicals form.

2. A process as claimed in claim 1 wherein said pH conditions are alkaline conditions.

3. A process as claimed in claim 1 or 2 wherein said process is conducted at 10 ambient temperature and pressure.

4. A process as claimed in any one of the preceding claims wherein said at least one metal salt is a metal salt selected from the group consisting of water soluble iron, aluminium and manganese salts.

5. A process as claimed in claim 4 wherein a plurality of metal salts selected 15 from the group consisting of water soluble iron, aluminium and manganese salts.

6. A process as claimed in claim 4 or 5 wherein said reactive metal radicals include at least one of ferryl radicals and manganyl radicals.

7. A process as claimed in any one of the preceding claims wherein a polymer flocculant is introduced to said conditioning module. 20

8. A process as claimed in any one of the preceding claims comprising further steps of catalytic oxidation and filtration.

9. A process as claimed in claim 8 wherein said further steps are conducted within a single module. WO 2014/066931 PCT/AU2013/001242 26

10.A process as claimed in any one of the preceding claims wherein water to be treated contains heavy metals.

11.An apparatus for treating water comprising a conditioning module provided with an oxygen containing gas supply means to enable oxidation of water with an 5 oxygen containing gas; and a metal salt dosing means for supplying at least one metal salt to said conditioning module to catalyse the water oxygenation process under oxidising and pH conditions at which reactive metal radicals and hydroxyl radicals form.

12.An apparatus as claimed in claim 10 including at least one further module for 10 conducting further steps of catalytic oxidation and filtration.

13. An apparatus as claimed in claim 11 wherein said further steps of catalytic oxidation and filtration are conducted in a single integrated module.