FIELD OF THE INVENTION

The present invention relates to water treatment process, and in particular to water treatment processes which involve the use of ion-exchange resins. The invention relates to a process for regenerating ion-exchange resin used in such processes, and especially, magnetic ion-exchange resins. For convenience, the invention will be described with reference to the treatment of raw water to produce potable water for distribution and consumption, however it is to be understood that the invention may also be used in other industrial applications, such as in processes for the treatment of sewage and effluent from industrial processes.

BACKGROUND OF THE INVENTION

The processes used in water treatment depend largely on the nature of the raw water. Water supplies which feed industrial plants for the production of potable water for distribution and consumption often contain unacceptably high levels of dissolved, dispersed or suspended organic compounds and materials. Most organic compounds, and materials found in raw water supplies are natural organic matter (NOM). A fraction of the NOM in the raw water supply is represented by dissolved organic compounds which present particular difficulties. These organic compounds referred to as dissolved organic carbon (DOC) are one of the main causes of water discolouration. DOC often includes compounds such as humic and fulvic acids which are water soluble at certain water pH levels. Humic and fulvic acids are not discrete organic compounds but mixtures of organic compounds formed by the degradation of plant residues.

The removal of DOC, from water especially humic and fulvic acids, is necessary in order to provide high quality water suitable for distribution and consumption. A majority of the compounds and materials which constitute DOC are soluble and not readily separable from the water. The DOC present in raw water renders conventional treatment difficult and expensive.

The production of safe potable water from a raw water supply often requires treatment of the raw water to make it aesthetically acceptable, as well as safe to drink. The removal of suspended matter and DOC is an important aspect of this treatment. Two approaches are commonly used for the removal of suspended matter and DOC. One involves coagulation and the other membrane filtration.

In a process involving coagulation, a coagulant is applied to destabilise and combine with suspended matter and DOC so that they coalesce and form a floe, which can then be physically removed by flotation, sedimentation, filtration or a combination thereof. Coagulants such as alum (aluminium sulphate), various iron salts and synthetic polymers are commonly used in such processes for water treatment. However, many raw water sources have high levels of DOC present, which react with the coagulant and therefore require a higher coagulant dose than would be required for removal of suspended matter alone. The bulk of the floe formed may then be removed by sedimentation or flotation and the water containing the remainder of the floe passed through a filter for final clarification. However, even after such treatment, the treated water may contain as much as 30-70% of the initial DOC.

In a membrane filtration process the water is filtered through a membrane. There are four commonly available membrane processes currently in use for water treatment. Microfiltration (MF) and Ultrafiltration (UF) are two processes generally used to remove turbidity and solid particles from water. However where the water contains high levels of DOC, the DOC tends to foul these membranes during water treatment processes. This results in a reduction of the flux across the membrane, a reduction of the life of the membrane and an increase in operating costs. Two other membrane processes, Nanofiltration (NF) and Reverse Osmosis (RO) are typically used to remove low molecular weight compounds from water, including DOC. They are also used in desalination of seawater and brackish waters (e.g. demineralisation). These membrane systems are designed to handle water which contains high levels of DOC and have much higher capital and operating costs than MF and UF for the production of potable water.

Ion-exchange resins can also be used to remove DOC present in raw water. Ion-exchange techniques conventionally involve passing water through a packed bed or column of ion- exchange resin. The target species (e.g. DOC) are removed by being adsorbed onto the ion-exchange resin. Ion-exchange resins can be used to remove up to 90% of the DOC in raw water.

Ion-exchange resins may also be used in conjunction with other methods of water purification including those mentioned previously. Sufficient resin may be added to remove a percentage of the DOC such that the cost of any subsequent treatment used to meet water quality objectives is minimised. For example, the use of ion-exchange resin for the removal of DOC may reduce the amount of coagulant required to achieve acceptable product water quality. The use of ion-exchange resin may also significantly reduce the capital and operating costs of membrane filtration.

In order to further minimise costs in water processing, ion-exchange resins are preferably recyclable and regenerable. Recyclable resins can be used multiple times without regeneration and continue to be effective in adsorbing DOC. Regenerable resins are capable of being treated to remove adsorbed DOC, and as such, these regenerated resins can be reintroduced into the treatment process.

Ion-exchange resins which incorporate dispersed magnetic particles (magnetic ion- exchange resins) readily agglomerate due to the magnetic attractive forces between them. This property renders them particularly useful as recyclable resins as the agglomerated particles tend to settle quickly and are therefore more readily removable from the water. A particularly useful magnetic ion-exchange resin for the treatment of raw water is described in WO96/07675, the entire contents of which is incorporated herein by reference. The resin disclosed in this document has magnetic particles dispersed throughout the polymeric beads such that even when they become worn through repeated use, they retain their magnetic character. Ion exchange beads of the type disclosed in this document are available from Orica Australia Pty. Ltd. under the trademark, MIEX®.

WO 96/07615, the entire contents of which is incorporated herein by reference, describes a process which removes DOC from water using an ion-exchange resin which can be recycled and regenerated. This process is particularly useful in the treatment of raw water with magnetic ion-exchange resin of the type described in WO96/07675.

The preferred ion-exchange resins disclosed in WO96/07675 are magnetic ion-exchange resins which have, throughout their structure, cationic functional groups which provide suitable sites for the adsorption of DOC. These cationic functional groups possess negatively charged counter-ions which are capable of exchanging with the negatively charged DOC. Accordingly, the negatively charged DOC is removed from the raw water through exchange with the resin's negative counter ion. As a result of this process DOC becomes bound to the magnetic ion-exchange resin and the function of the ion-exchange resin is reduced. Such resins are referred to herein as used, spent or loaded resins. When producing potable water for distribution and consumption it is particularly important to be able to regenerate the loaded resin in an efficient and cost-effective manner.

WO 96/07615 discloses a process for regenerating magnetic ion-exchange resin by contacting it with brine (which is substantially a NaCl solution). The brine solution in such a process is generally referred to as the "regenerant". Regeneration is afforded through exchange of the chloride ion for a DOC ion from the loaded resin. The byproduct from regeneration is referred to as the "spent regenerant" and is primarily a mixture of the removed DOC and brine. Generally, the spent regenerant from a regeneration process is discharged into the ocean or may be used as land fill.

The regeneration process disclosed in WO 96/07615 involves passing brine through a packed column of loaded resin. The regeneration can also be affected by a mixing or agitation process. In practice, these regeneration processes are performed in a batch manner. For example, loaded MIEX® resin is removed from the treatment process from the bottom of the settler and generally transferred to one of two regeneration vessels. When one vessel is filled the stream of resin from the settler is directed to the second regeneration vessel while the one that has been filled undergoes regeneration. The regeneration is performed either in: (i) a mixing tank where a mechanical agitator mixes the regenerant solution with the resin (agitated tank regeneration), or (ii) a tank where the regenerant solution is passed through a stationary bed of resin with the ion exchange occurring while the regenerant is in contact with the resin (column regeneration or plug flow regeneration).

These batch methods of regeneration are generally efficient at regenerating resin yet the amount of loaded resin which can be regenerated at any one time is limited by the size of the plant equipment (e.g. the regeneration vessels). A problem is that the large footprint of the additional equipment required for resin regeneration can restrict or prohibit the use of ion-exchange resins. The treatment plant may be restricted to regeneration vessels of certain sizes or the loaded resin may need to be processed off site. The space required may compromise the overall effectiveness of an ion-exchange based water treatment plant.

Accordingly, there is a need for alternative ion-exchange regeneration processes, to assist in addressing some of the shortcomings of the currently available regeneration processes.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a process for regenerating ion-exchange resin loaded with DOC which process comprises contacting the ion-exchange resin with an aqueous chloride salt solution in a continuous countercurrent system.

Accordingly, one aspect of the present invention provides a process for the continuous regeneration of ion-exchange resin loaded with dissolved organic carbon ("DOC"), the process comprising:

(a) providing a plurality of sequentially connected cells including a first cell and a last cell and optionally one or more intermediate cells; (b) providing resin loaded with DOC; (c) providing a regenerant comprising an aqueous chloride salt solution; (d) contacting said resin with the regenerant by moving said resin in a continuous flow sequentially from the first cell, through any optionally present intermediate cell(s) to the last cell, whilst simultaneously providing a flow of said regenerant sequentially from the last cell, through any optionally present intermediate cell(s), to the first cell.

In a further aspect of the invention the above mentioned processes may further comprise the step (e) whereby the regenerated resin is rinsed with a rinsing solution.

Preferably the resin loaded with DOC is regenerated and then subsequently rinsed by using a continuous countercurrent decantation system.

In a further aspect the present invention provides an industrial scale process for the removal of DOC from water containing DOC, said process comprising:

(i) contacting the water with ion-exchange resin to enable adsorption of DOC on the resin; (ii) separating at least a portion of the resin loaded with DOC from the water; (iii) regenerating at least some of the separated resin by the process steps of (a) to (d) as mentioned above; and (iv) returning the regenerated resin back to step (i).

In yet a further aspect the present invention provides an industrial scale process for the removal of DOC from water containing DOC, said process comprising:

(i) contacting the water with ion-exchange resin to enable adsorption of DOC on the resin; (ii) separating at least a portion of the resin loaded with DOC from the water; (iii) regenerating at least some of the separated resin and returning any remainder to step (i), the process of regenerating the separated resin comprising: (a) providing a plurality of sequentially connected cells including a first cell and a last cell and optionally one or more intermediate cells, where the cells are in fluid communication by conduits; (b) providing resin loaded with DOC; (c) providing a regenerant comprising an aqueous chloride salt solution; (d) moving the regenerant sequentially from the last cell through any optionally present intermediate cell(s) to the first cell via the conduits whilst moving the resin in a continuous flow sequentially from the first cell, through any optionally present intermediate cell(s) to the last cell by moving the resin into a conduit ahead of the next cell in the sequence so that the resin moves with the regenerant into said next cell; (e) rinsing the regenerated resin with water by providing a plurality of sequentially connected cells including a first cell and a last cell and optionally one or more intermediate cells and moving the regenerated resin in a continuous flow sequentially from the first cell, through any optionally present intermediate cell(s) to the last cell whilst providing a flow of water sequentially from the last cell through any optionally present intermediate cell(s) to the first cell to thereby provide a flow of resin which is opposite to the flow of the rinsing solution such that the water contacts the resin and rinses the resin; (iv) returning the regenerated rinsed resin back to step (i).

Preferably the conduits are pipes for transporting resins. Preferably the cells are in fluid communication by pipes physically connected to cells.

The above processes may further include additional steps associated with ion-exchange processes for water treatment, as would be understood by a person skilled in the art.

DESCRIPTION OF THE INVENTION

The expressions "regenerating ion-exchange resin" or "regenerating resin", as used herein refers to a process in which the ion-exchange capacity of a loaded (also referred to as spent or used) ion-exchange resin is returned to a level whereby it is rendered suitable for use in subsequent ion-exchange processes. The ion-exchange resins used in the removal of DOC have cationic groups which provide suitable sites for the adsorption of the DOC. These cationic groups have associated anions which exchange with the DOC during the ion- exchange process. The regeneration process of the present invention involves the displacement (or exchange) of the adsorbed DOC with chloride ions. It is not necessary for all ion-exchange sites in a resin to be regenerated for an ion-exchange resin to be considered "regenerated" for the purpose of the present invention. It is sufficient that the regeneration process has occurred to an extent that the ion-exchange resin is useful in subsequent ion-exchange processes in a water treatment plant. Preferably more than 80% of the ion-exchange sites previously taken up by the DOC or other compounds are regenerated, more preferably greater than 90% and most preferably greater than 98%.

The water treatment plant may be a plant for producing potable water for distribution and consumption, or may be a plant for the treatment of sewage, or industrial waste water containing DOC. An industrial water treatment plant may be associated with food processing, pharmaceutical production, electronic component manufacture, membrane plant rejects (usually derived from nanofiltration or reverse osmosis processing), hospital applications and the like. While the present invention is useful in any large scale water treatment facility, it is particularly preferred for use in the treatment of a water source to produce potable water for distribution and consumption.

The loaded ion-exchange resin (which has DOC attached to it) is regenerated through contact with an aqueous chloride salt solution (hereinafter referred to as the "regenerant") which allows the chloride ions to exchange with the DOC adsorbed on the resin. The preferred chloride salt is NaCl. Accordingly, the most preferred regenerant is brine (substantially a NaCl solution). Preferably the regeneration of the present invention is carried out with an aqueous chloride salt solution in which the chloride salt concentration is more than 1.5M, or more preferably 2M or greater.

The process of the invention provides for the "continuous" regeneration of loaded ion- exchange resin. By "continuous" it is meant that the process can be operated to provide a continuous output of regenerated resin. Such a process does not require batchwise operation but can be operated with batches of loaded resin if so desired.

The resin may move in a continuous flow from one cell into the next cell. As part of the flow individual resin particles may move about a cell for a length of time before being moved into the next cell in the sequence. There is an overall continuous flow of resin through the cells of the system.

In relation to the present invention the term "continuous countercurrent system", which is abbreviated herein as "CC system" for convenience, refers to a continuous process for regenerating ion-exchange resins where there is a flow of resin and regenerant, and that the direction of flow of the resin is counter or opposite to the direction of flow of the regenerant. The flow may be in the form of a regular sequence of pulses or a constant flow. Continuous countercurrent systems which are well known for ore extraction in the mining industry are readily adapted for use in the present invention.

The use of a continuous countercurrent system in the context of the present invention results in the resin being contacted with increasing concentrations of regenerant as the resin passes through the regeneration process and this is thought to provide for a more effective regeneration of a given quantity of resin over time.

The CC systems of the present invention include a plurality of cells connected in fluid communication in a sequential series. By "sequential" it is meant that the first cell (cell 1) is connected to the next cell (cell 2) which in turn is connected with the next cell (cell 3) and so on until the last cell. Preferably, the CC system includes 2 or more cells, and more preferably three or more cells, and most preferably more than four cells, for instance 5 or 6 cells. Accordingly, for a system which includes only 2 cells the first cell (cell 1) is connected in sequence to the last cell (cell 2). In such a system there are no "intermediate" cells. It will be understood that the number of cells required depends on many factors including cell volume size, concentration of regenerant, regenerant and resin flow rates, resin and regenerant mixing efficiency, underflow pump efficiency (e.g. transfer concentration of resin), amount of DOC to be removed from the resin, regenerant concentration coming out of the CC system, and the available footprint. It will be appreciated that the smaller number of cells the smaller the overall footprint, however the use of more cells may lead to a lessening of the required flow rate and therefore reduce waste volumes.

Preferably, the plurality of cells are positioned in a cascading arrangement, that is, the cells are arranged at increasing elevations allowing gravity flow of the regenerant between the cells. This alleviates the need for overflow pumping, however depending upon the required flow rate of the regenerant, overflow pumps like simple centrifugal pumps can be installed.

The countercurrent flow of the resin and regenerant ensures that the resin is contacted with increasingly higher concentrations of regenerant as it flows through the system.

In an embodiment of the process, the resin passes sequentially from one cell to the next adjacently positioned cell in the series and comes into contact with the regenerant which is flowing through the cells in the reverse sequence. Initial contact between the regenerant and the resin may occur outside of the cell such as in conduits such as channels or pipes connecting adjacent cells along the sequential series. The cells provide a convenient processing area in which the loaded resin may contact (or continue to contact) increasing concentrations of the regenerant and also facilitate the separation of the resin from the regenerant. The cells may take the form of columns, tanks (including mixing and/or settling tanks), auger screw segments as well as segments of a segmented carousel or conveyor. The cells may be fitted with an agitator, like for instance, a mechanical or gas bubbling agitation device.

One embodiment makes use of a conveyor whereby resin is transported along the conveyor, which is optionally compartmentalised to provide a plurality of cells. The magnetic properties of the resin (like for instance, when using MIEX®) may hold the resin in a relatively fixed position on the conveyor whilst being subjected to a flow of regenerant moving along the conveyor in the opposite (or counter) direction to the movement of the conveyor. Where the conveyor includes compartments, the compartments should permit the regenerant to pass sequentially from one compartment to the adjacent compartment. This can be done by including apertures in the walls defining the compartments.

A further embodiment makes use of an auger screw-type conveyor which may be arranged in a horizontal or inclined position. In such conveyor systems resin would move relative to the screw threads and the regions (the segments) between adjacent thread could be thought of as cells. In order to facilitate a countercurrent process the regenerant could be pumped or allowed to flow (by gravity) in an opposite direction to the flow of the resin.

Still a further embodiment consists of a plurality of cells which are arranged as a segmented carousel. In such a system the loaded resin may be feed into the segments of a rotating carousel, as the segments pass under a fixed delivery point. As the segments rotate about the central axis, the contents of the segments would be subjected to flows of regenerant of increasing concentration located at fixed positions about the central axis. The regenerated resin may be collected at a collection point when the rotational movement of the segment reaches the collection point, before again being filled with loaded resin for regeneration.

Yet a further embodiment consists of a plurality of cells on a vibrating screen. The flat screen would be tilted from the horizontal to allow for the progression of the resin from the raised end down the screen to the lower end as the screen vibrates. The screen could be in the form of a fine mesh capable of restraining the resin but allowing liquid to pass therethrough. As the resin moves down the screen it could pass through two or more regenerating regions. Each regenerating region would include a flow of regenerant provided by, for example, downward spray heads located across the width of the screen. As the resin moves down the screen it would be subjected to flows of regenerant of increasing concentrations. Drain or collection tanks may be positioned beneath the screen to collect the regenerant after contact with the resin. The regenerant from each collection tank may then be pumped (using the aforementioned pumping devices) and used as lower concentrated regenerant flow in the earlier regenerating region. In this manner the regenerated resin may be collected at the end of the screen for subsequent rinsing. Alternatively, the screen may also include rinsing regions located after the regeneration region. The rinsing regions may be set up in an analogous fashion to the regenerant flow set up already mentioned. The cleanest rinse solution (usually water) would be used at the lowest end of the screen and is collected and pumped up after use as the rinse solution in the adjacent up stream rinse region.

In a preferred embodiment the plurality of cells are a plurality of settling tanks which are sequentially in fluid communication and positioned in a cascading arrangement. In this system the loaded resin is added at the lower end ("the first cell") and the regenerant at the higher end ("the last cell"). This preferred system is herein referred to as a "continuous countercurrent decantation" system or "CCD" system as the separation of the resin and regenerant at each successive stage through the intermediate cell(s) is via decantation of the regenerant from the settled resin. The upward flow of the resin is countercurrent to the downward flow of regenerant which, due to arrangement of the tanks, is facilitated by gravity. The countercurrent flow of the resin in this preferred embodiment is carried out by the use of pumps. The loaded resin can be transferred directly from the water treatment facility to a settling tank for regeneration.

Typically the transportation of resin in this process which may involve the use of channels, pipes, pumps, belts, overflow and collection systems and other transport means will invariably also transport excess quantities of raw water with the loaded resin. The resin can then be separated from the regenerant and transferred to the next adjacent settling tank. It will be appreciated that pumping will transfer a mixture of resins and excess regenerant at each successive stage, yet the concentration of excess regenerant will systematically decrease along the sequential cell series. As aforementioned this transfer is achieved by pumps, preferably underflow pumps, which are either attached to the bottom of the settler or strategically positioned within the settler. Preferred underflow pumps are those which are capable of efficiently transferring a regular flow of resin from one cell to an adjacent cell along the series, and do not damage the resin to any great extent. In relation to magnetic ion-exchange resins, the preferred underflow pumps which are connected to the bottom of the settler are peristaltic or low shear pumps. Preferred underflow pumps which are inserted within the settler are peristaltic or airlift pumps. Airlift pumps are positioned to draw the regenerant/resin mixture up from the bottom of the settler and transfer to the next cell in the sequence of cells. Peristaltic pumps may be designed in the same way, alternatively they may draw the resin/regenerant mixture down through the bottom of the settler and pump it to the next cell. A low shear pump could also be designed for this mode of operation. In order to maximise the resin flow rate, it is preferred that the settlers have conical shaped bottoms. If the settler bottom is completely flat the resin may tend to sit in areas where the pump cannot efficiently draw the resin and therefore may lead to inefficient transfer by decreasing underflow pumping efficiency. It will be appreciated by those in the art that not all resins are amendable to being pumped. One of the reasons for this is that many resins require significant periods of time in which to settle. In the embodiments of the present invention which rely on pumping to transport the resin, magnetic ion-exchange resins are preferred due to their ability to readily agglomerate which effects easy settling and efficient pumpability.

In relation to the preferred embodiment, the mixing between the regenerant and the resin is performed in conduit pipes between settling tanks. This has been found to facilitate efficient mixing due to the flow turbulence in the pipeline. Accordingly, in the preferred CCD system, the transfer of resin (including quantities of regenerant) from one settler (cell) to another along the sequential series of settlers (cells) is achieved by pumping the resin from one settler into apipe ahead of the adjacent settler, the pipe having therein a flow of regenerant which is moving into the adjacent settler. The flow of the regenerant not only facilitates efficient mixing but also directs the resin to the adjacent settler.

In the aforementioned CCD system, separation of the resin and regenerant between successive cell takes advantage of the special qualities of resins which are able to quickly settle (e.g. due to magnetic characteristics, shape, weight, or other property). However, other separation techniques can be applied with equally good effect. For example, mixing of the regenerant and resin in a CC system can be facilitated in a series of mixing tanks as previously mentioned. A continuous flow of resin and regenerant into a tank along a series will ultimately lead to overflow. The overflow of this mixture will include both the regenerant and resin. In order to separate these components prior to the transferral of the resin to the next adjacent mixing tank, separation devices can be positioned between successive mixing tanks in the series. The overflow can be directed to spill into the separation devices. Examples of suitable separation devices include magnetic drum separators, hydrocyclones, centrifuges, multiple-compartment washing-tray thickeners, vibrating screens, baleen filters, belt-filters, and other types of standard filters may potentially be used for this purpose. Mixtures of such separation devices may also be used between settlers.

An advantage of the present process which utilises CC systems is that such systems have a smaller footprint compared to the batch processes (for the same throughput). Accordingly, the regeneration CC systems of the present invention can be readily incorporated into existing water treatment facilities which utilise ion-exchange resins. For example, it may be used in conjunction with membrane filtration techniques where ion-exchange resins are incorporated to improve the effectiveness of the membranes, increase the flux across membranes and reduce operating costs. For new installations it may be used where existing membrane filtration techniques are replaced with ion-exchange techniques. If membrane filtration techniques are still required, the present invention can be used where ion-exchange processes are incorporated to significantly reduce the size and hence capital and operating cost of a membrane filtration plant. The reduction in capital and operating costs may enable consideration to be given to the installation of membrane filtration rather than coagulation sedimentation plants thereby substantially reducing the size of the plant and enabling the production of potable water without the addition of chemicals other than for disinfection purposes. Examples of water treatment processes involving ion-exchange are disclosed in WO96/07615, and the present regeneration process can be readily incorporated into these processes.

Another advantage of the present process is that it does not require the plant operator to maintain a large reserve or inventory of resin. Batchwise resin regeneration systems require a large inventory of resin for use as spent resin is removed and stored for subsequent regeneration processing. The present invention differs from such processes as it involves a continuous regeneration system.

Accordingly, the invention also provides an industrial scale process for the removal of DOC from water containing DOC, said process comprising:

(i) contacting the water with ion exchange resin to enable adsorption of DOC on the resin; (ii) separating at least a portion of the resin loaded with DOC from the water; and (iii) regenerating at least some of the separated resin, wherein the resin is regenerated by contacting the resin with an aqueous chloride salt solution in a continuous countercurrent system.

Many processes rely on ion-exchange to produce high quality water on an industrial scale. These include, but are not limited to, softening (e.g. transforming Ca and Mg salts into sodium salts), demineralisation (removing compounds such as Ca(HCO3)2, Mg(HCO3)2, CaSO4, MgSO4 etc.), nitrate, chromate and uranium removal. These waters can then be used in a wide range of applications such as boiler feedwater, potable water or as high quality process water for the pharmaceutical manufacture, electronic component manufacture and the chemical industry. In order to use conventional ion-exchange (e.g. passing water through column of resin) it is necessary that the water being treated is relatively free of particulate matter in order to prevent plugging of the ion-exchange bed. Pretreatment using sedimentation, coagulation and filtration may be necessary.

At the present time there is very little use of ion-exchange in processes for producing potable water for distribution and consumption, due mainly to the inherent problems in treating such large volumes of water with conventional ion-exchange resin. However, the magnetic ion-exchange resin disclosed in WO96/07675 has proved particularly successful in the treatment of such large volumes of water.

In processes involving such an ion-exchange resin the raw water is generally fed into a continuously stirred tank (contactor) which has a nominal residence time usually of between about 5 and 60 minutes. The magnetic ion-exchange resin is added either directly into this tank or into the raw water in the pipeline feeding this tank. It is in this tank that the majority of the ion-exchange process occurs. Prior to treatment with the ion-exchange resin the water will generally have been screened to remove large particles to protect pumps involved in pumping the water to the treatment plant. It is also possible that the water will have been subjected to one or more pretreatment steps, such as coagulation, flocculation and subsequent clarification.

From the contactor, the resin and water (resin suspension) is generally passed to a separating stage (settler) where the resin can be recovered and regenerated and/or returned. Depending on the density of the resin it may be possible to recover it using gravity sedimentation. As mentioned earlier, magnetic ion-exchange resins have a strong tendency to agglomerate to form large and fast settling particles, when shear is removed (as occurs in the settler). The agglomerated resin particles settle rapidly and are collected on the bottom of the settler where they may be transferred (eg. by pumping) back to the head of the treatment plant for reuse in the process. At least some (and generally a small portion) of the flow which is returned back to the head of the plant can be subjected to the regeneration process of the present invention. To keep the resin concentration at the required level, fresh, regenerated resin is added to the contactor to make up for the resin not being returned. The present invention allows for this process to be done in a continuous manner. This ensures the performance of the process is maintained.

Accordingly, in a further aspect the present invention provides an industrial scale process for the removal of DOC from water containing DOC, said process comprising:

(i) contacting the water with ion-exchange resin to enable adsorption of DOC on the resin; (ii) separating at least a portion of the resin loaded with DOC from the water; (iii) regenerating at least some of the separated resin, wherein the resin is regenerated by contacting the resin with an aqueous chloride salt solution in a continuous countercurrent system; and (iv) returning the regenerated resin back to step (i).

The resin, after it has been regenerated, may be bound with excess amounts of regenerant. Accordingly, before being returned back into the head of the plant the regenerated resin may be subjected to a rinsing step by contacting the regenerated resin with a rinsing solution. Preferably the rinsing solution is water. In order to maintain a totally continuous process this rinsing step may also be performed in a CC system. Such systems would be analogous to the CC systems already disclosed whereby the regenerant is simply replaced with rinse water. Such rinsing CC systems may be integrated with the regeneration CC systems of the present invention by way of an additional series of cells. After the rinsing step the resin is said to be "fresh regenerated resin" and may be sent to a "fresh" resin tank before it is added back into the water treatment process.

Optionally one or more resin storage tanks can be fitted after the last cell of the CC regeneration system and before the cell of the CC rinsing system. This tank or tanks can contain regenerant solution in which the resin may rest or be stored before being fed into the CC rinsing system. This may provide additional benefits.

Firstly, the storage of the regenerated resin in a storage tank containing the regenerant may facilitate more efficient regeneration. For instance, it is believed that storing the resin in this way allows for the slow diffusion of excess DOC from deep within the resin, and may provide a 10% more effective deeper cleansing (regenerating) of the resin.

Secondly, having such a storage tank would provide a convenient location for the operator to store the inventory of resin when the system is shut down for routine maintenance. The resin could be collected in the storage tank(s) by shutting down the return step from the tank(s) to the rinsing system. The resin is stored in a regenerant solution, such as brine, and this can alleviate the problems associated with the build up of microbial deposits which can occur when storing resins in fresh water. To restart the system the rinsing and return part of the process can be turned back on whilst not operating the collection and regeneration part of the system or operating it at a reduced flow rate.

The process will require an inflow of regenerant, typically brine, and will produce an waste stream of spent regenerant containing a less concentrated solution of the regenerant, DOC and other compounds separated from the resin. If the process is used in combination with a rinsing process to rinse excess regenerant from the regenerated resin before the resin is re-used, then the process will also require an inflow of a rinse solution, typically water, and produce a waste stream of the rinse solution containing regenerant.

It will be appreciated that when brine is used as a regenerant and a water is used as the rinse solution, then the rinse solution waste stream will take the form of a dilute aqueous solution of the regenerant salt. Although it may be sent to drain, the used rinse water could alternatively be concentrated up and re-used as a regenerant. Procedures for concentrating such a solution would be well understood by those skilled in the art and may include evaporation techniques as well as techniques which utilise nanofiltration or reverse osmosis.

Likewise, the spent regenerant waste stream could be cleaned up to remove DOC and the non-regenerant salts. This waste stream could also be concentrated by using the techniques mentioned above. With water-treatment processes involving the use of MIEX® resin, pre-treatment is not usually required to remove solids and turbidity from the water, although the raw water may be screened to remove large particulate matter before it is introduced into a water treatment process. However, after separation of the ion-exchange resin from the water it is usual to subject the water to further processing before it is suitable for distribution and consumption.

The water may be subjected to a coagulation / flocculation step followed by clarification. This may be done in a gravity settler. The water may also be subjected to one or more of the filtration steps described above, as well as disinfection. The disinfectant may be added at any stage during the water treatment process. Usually however, disinfectants are added during or at the end of the treatment process such that there is residual disinfectant present in the water supplied to the consumer. This is known as secondary disinfection and most commonly involves the use of chlorine, chloramines and chlorine dioxide. However, in order to achieve disinfection of water, ozone, potassium permanganate, peroxone, UV radiation and combinations of the above, can also be used as primary disinfectants.

The water treatment process may also be used in conjunction with other unit processes such as ozonisation and treatment using granular activated carbon (GAC). These optional features may be incorporated at any suitable stage during the water treatment process, as would be appreciated by a person skilled in the art.

The regeneration processes of the present invention may be utilised in the above described treatment processes or similar water treatment processes, where an ion-exchange process is incorporated prior to or instead of coagulant addition. Typically, coagulants such as alum (aluminium sulphate), iron salts and synthetic polymers are used following the ion- exchange step. The removal of DOC by ion-exchange results in a substantial reduction in the quantity of coagulant required. In addition, the removal of DOC reduces the requirement for subsequent chemical additions and improves the efficiency and/or rate of coagulation, sedimentation and disinfection. This has a beneficial impact on the water quality produced and the size of most facilities required within the water treatment plant including sludge handling facilities. Since most plants have equipment for regenerating the ion-exchange resin by contact with brine, the process of the present invention can be conveniently incorporated without significant change in the overall structure or size of the water treatment plant, and in fact may free up space which has been used for batch processes with larger footprints.

The regeneration process of the present invention can be conveniently adapted for use in continuous ion-exchange water treatment processes making the whole water treatment process and resin regeneration effectively continuous.

The continuous ion-exchange water treatment process differs significantly from conventional ion-exchange process. In conventional ion-exchange columns, the water quality produced deteriorates as the ion-exchange capacity is progressively exhausted. The leakage of undesired ions eventually reaches the point where the product water is not potable. The column must then be taken-off line and the resin regenerated. In contrast the continuous process differs in that the overall ion-exchange capacity is continuously maintained. This leads to the production of water with consistent quality as well as the DOC being controlled at predetermined levels. The ability to maintain the quality of water in such processes is increased with the incorporation of the CC regeneration system of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic diagram of a CCD system, incorporating settlers, which can be used in the process of the present invention. Fig. 2 is a schematic diagram of a CCD system, incorporating settlers, which can be used to rinse the regenerated resin which has been subjected to the process of the present invention. Fig. 3 is a schematic diagram of a CC system, incorporating magnetic drum separators, which can be used in the process of the present invention. Fig. 4 is a schematic diagram of a CC system, incorporating belt filters, which can be used in the process of the present invention. Fig. 5 is a graph of chloride level (mg/L) vs settler number which shows the chloride level in settler tanks in a CCD system where the upflow of brine is twice the downflow of rinse water. Fig. 6 is a graph of chloride level (mg/L) vs settler number which shows the chloride level in settler tanks in a CCD system where the upflow of brine is the same as the downflow of rinse water. Fig. 7 is a graph of chloride level (mg/L) vs settler number which shows the chloride level in settler tanks in a CCD system where the upflow of brine and MIEX® resin is twice the downflow of rinse water.

The invention will now be further described by reference to the accompanying drawings which depict non-limiting embodiments of the invention.

The CCD system depicted in Fig. 1 consists of six settler tanks (2, 4, 6, 8, 10, 12) which are conical in configuration, The tanks are in fluid communication with each other by an arrangement of conduit pipes. Resin conduit pipes 30, 32, 34, 36 and 38 transport resin (and some regenerant) respectively from tanks 2 to 4 to 6 to 10 to 12. Regenerant conduit pipes 37, 35, 33, 31 and 24 transports regenerant respectively from tanks 12 to 10 to 8 to 6 to 4 to 2. Regenerant conduit pipe 39 carries the most concentrated regenerant which is added to tank 12.

The CCD system is connected to a buffer storage tank 14 (fitted with a mechanical stirrer 16) and a thickening settler container 18. Loaded resin removed from a water treatment process for regeneration is transferred to the buffer storage tank 14. The resin will usually contain amounts of raw water left over from the water treatment process. The buffer storage tank 14 provides some storage capacity at the head of the process and can act to concentrate the resin, with the excess water passing back to the contactors. It allows initial resin in flow rates to be adjustable, which means that the CC regeneration system does not have to match the water treatment process all the time. This provides flexibility in the system and can allow the system to be shut down for quick repairs/maintenance.

The resin mixture is transferred from tank 14 to the thickening settler container 18 by gravity through conduit pipe 20, to increase the resin concentration before being subjected to the CCD regeneration system. As the resin settles to the bottom of the thickening settler container 18 it is transferred by underflow pump 40 through resin conduit pipe 22 into the downward flow of regenerant transported by regenerant conduit pipe 24 between settler tanks 2 and 4. The regenerant together with the added resin flows into tank 2. It is advantageous to added the resin into the regenerant by pipe 24 as it facilitates mixing of the resin in the regenerant.

The regenerant overflow is decanted from the top of settler tank 2 into a spent regenerant storage container 26, through conduit pipe 28, while the resin settles to the bottom of settler tank 2 and is pumped through resin conduit pipe 30 into the regenerant conduit pipe 31 between settler tanks 4 and 6, so the resin and regenerant mixes and flows into tank 4. The process continues with the resin pumped up through the tanks 6, 8 and 10 to settler tank 12.

The resin is pumped from settler tanks 2, 4, 6, 8, 10 and to 12 by the use of continuously operating underflow pump(s) 42, 44, 46, 48 and 50 associated with pipes 30, 32, 34, 36 and 38. As the resin is moved into successive tanks 2, 4, 6, 8, 10 and 12, it comes into contact with more concentrated regenerant solution.

The concentrated regenerant 58 enters the system by regenerant pipe 39, and flows downward through successive settler tanks. The regenerated resin 55 is pumped from tank 12 by the continuously operating underflow pump 52 through the regenerated resin outflow pipe 56.

The regenerated resin can be rinsed to remove excess regenerant by subjecting it to a CCD system as depicted in Fig. 2. This CCD rinsing system is analogous to the CCD regeneration system depicted in Fig. 1. The CCD rinsing system may be in fluid communication with the earlier described regeneration CCD system with the outflow pipe 56 being connected to the resin in flow pipe 74. However, it is preferred that there is an intermediate regenerated resin storage tank (not shown) into which the regenerated resin 55 may be stored in concentrated regenerant before being collected and passed into the resin in flow pipe 74.

The rinsing CCD system of Fig. 2 consists of six settler tanks having a conical configuration (60, 62, 64, 66, 68, 70). The tanks are in fluid communication with each other by an arrangement of conduit pipes. Resin conduit pipes 80, 61, 63, 65 and 67 transport resin (and some rinsing water) respectively from tanks 60 to 62 to 64 to 66 to 68 to 70. Rinse water conduit pipes 85, 83, 81, 82 and 76 transports rinse water respectively from tanks 70 to 68 to 66 to 64 to 62 to 60. The regenerated resin (and some concentrated regenerant) 72 is transferred into the rinsing system via resin inflow conduit pipe 74. Resin passes from pipe 74 into the rinse water conduit pipe 76 between settler tanks 60 and 62. Mixing of the resin and rinsing water is facilitated in the pipe 76 and the flow of the water sweeps the resin and water into settler tank 60. The rinse water overflow is directed into a waste rinse water container 78, from the top of settler tank 60 via conduit pipe 79, while the resin settles to the bottom of settler tank 60 and is subsequently transferred via conduit pipe 80 which flows into the rinse water flow conduit pipe 82 between settler tanks 62 and 64. The process is continued with the resin moved up through tanks 64, 66, 68 and 70 and can be collected as rinsed resin 84 ("fresh regenerated resin"). This resin can be recycled back into the water treatment process for subsequent DOC removal. The resin is pumped from settler tanks 60, 62, 64, 66, 68 and to 70 by the use of continuously operating underflow pump(s) 88, 90, 92, 94 and 96 associated with pipes 80, 61, 63, 65 and 67. As the resin is moved into successive tanks 60, 62, 64, 66, 68 and 70, it comes into contact with fresher rinsing water.

A flow of rinsed resin 84 exits the system from settler tank 70 via resin conduit pipe 86. The fresh rinse water 100 enters the system via pipe 87, and flows downward through successive settler tanks. The rinsed resin 84 is pumped from tank 70 by the continuously operating underflow pump 98 through pipe 86.

Fig. 3 depicts a combined CC regeneration/rinsing system incorporating magnetic drum separators for use with magnetic ion-exchange resin. The CC system consists of six mixing tanks (110, 112, 114, 116, 118, 120) fitted with mechanical agitators (122, 124, 126, 128, 130, 132), six rotating magnetic drum separators (134, 136, 138, 140, 142, 144), and four holding tanks (146, 148, 150, 152) positioned in a cascading arrangement.

After the loaded resin 154 has been removed from the water treatment process for regeneration it is transferred to mixing tank 110 via conduit pipe 156 where it comes into contact with regenerant. The overflow from mixing tank 110 (resin and regenerant) spills onto magnetic drum separator 134. The resin is magnetically affixed to the drum and transported with the drum as it rotates. The resin is then separated from the drum when the resin is on the side of the drum closer to a mixing tank 112. This can be achieved by scrapping or washing off the bound resin or otherwise by causing the resin to fall.

The magnetic separator can operate by having an outer non-magnetisable shell and an inner magnet which is moved within the shell in a manner so that it is sufficiently close to one side of the shell so that the resin is picked up on the outside of the shell and is moved with the magnet as the magnet moves within the shell. When the magnetic reaches the other side of the shell it is moved away from the shell so that the resin falls away from the shell.

The resin passes in the direction of the arrow into mixing tank 112. The regenerant is not collected by the drum and drops, by gravity into a waste collection container 158.

In mixing tank 112 the resin is contacted again with regenerant and mixed. The overflow of mixing tank 112 (resin and regenerant) spills onto magnetic drum separator 136 where the resin is picked up by the drum and transported to mixing tank 114. The regenerant is not collected by the drum and drops, by gravity into holding tank 146 where it is collected and transferred to mixing tank 110 via pump 160 through conduit pipe 161.

In a situation where the resin is washed off the magnetic drums, the washing solution used to separate the resin from the drum may be sourced from an appropriate holding tank. For example, the washing solution to separate resin adhered to magnetic drum separator 136 may be sourced from holding tank 148. For magnetic drum separator 134, the washing solution may be sourced from 146.

In mixing tank 114 the resin is contacted again with regenerant and mixed. The overflow of mixing tank 114 (resin and regenerant) spills onto magnetic drum separator 138 where the resin is picked up by the drum and transported to mixing tank 116. The regenerant is not collected by the drum and drops, by gravity, to holding tank 148 where it is transferred (pumped) to mixing tank 112 via pump 164 through conduit pipe 166. The regenerant 162 is directly added to mixing tank 114 via pipe 163 and is moved respectively from mixing tank 114, 112 to 110 (countercurrent to the resin). The resin flows downward by gravity and the flow is assisted by the magnetic drum separators and the agitation of the mixing tanks. The resin flows sequentially from mixing tank 110, 112 to 114 where it comes into contact with a more concentrated regenerant solution in each successive mixing tank.

In mixing tank 116 the resin undergoes a rinsing process to remove excess regenerant, where it is contacted with rinsing water and mixed. The overflow of mixing tank 116 (resin and rinsing water) spills onto magnetic drum separator 140 where the resin is picked up by the drum and transported to mixing tank 118. The rinsing water is not collected by the drum and drops, by gravity, to waste collection container 168. In mixing tank 118 the resin is contacted again with rinsing water and mixed. The overflow of mixing tank 118 (resin and rinsing water) spills onto magnetic drum separator 142 where the resin is picked up by the drum transported to mixing tank 120. The rinsing water is not collected by the drum and drops, by gravity, to holding tank 150 where it is transferred (pumped) to mixing tank 116 via pump 170 through conduit pipe 172. In mixing tank 120 the resin is contacted again with rinsing water and mixed. The overflow of mixing tank 120 (resin and rinsing water) spills onto magnetic drum separator 144 where the resin is picked up by the drum and transported from the system as fresh regenerated resin into a fresh resin tank 174. The rinsing water is not collected by the drum and drops, by gravity, to holding tank 152 where it is transferred (pumped) to mixing tank 118 by pump 176 through conduit pipe 178. The rinsing water 180 which is directly added to mixing tank 120 via pipe 181 and flows sequentially from mixing tank 120, 118 to mixing tank 116 (countercurrent to the resin). The flow of resin is facilitated by gravity and assisted by the magnetic drum separators and the agitation of the mixing tanks. The resin flows sequentially from mixing tank 116, 118 to mixing tank 120 where it comes into contact with fresher rinse water in each successive mixing tank. The resin which has been rinsed ("fresh regenerated resin") can be recycled back into the water treatment process for subsequent DOC removal. All of pumps 160, 164, 170 and 176 are continuously operating pumps.

Fig. 4 depicts a combined CCD regeneration/rinsing system incorporating belt filters. The CC system consists of six mixing tanks 190, 192, 194, 196, 198, 200 equipped with mechanical agitators 202, 204, 206, 208, 210, 212, six belt filters (214, 216, 218, 220, 222, 224) and four holding tanks (226, 228, 230, 232) positioned in a cascading arrangement. After the loaded resin 234 has been removed from the water treatment process for regeneration it is transferred to mixing tank 190 where it comes into contact with regenerant. The overflow from mixing tank 190 (resin and regenerant) spills onto belt filter 214 where the resin is transported into mixing tank 192. The regenerant filters through the belt of belt filter 214 to waste collection container 236.

In mixing tank 192 the resin is contacted again with regenerant and mixed. The overflow from mixing tank 192 (resin and regenerant) spills onto belt filter 216 where the resin is transported into mixing tank 194. The regenerant filters through the belt of belt filter 216 into holding tank 226 where it is transferred (pumped) to mixing tank 190 pump 238 through conduit pipe 240.

In mixing tank 194 the resin is contacted again with regenerant and mixed. The overflow from mixing tank 194 (resin and regenerant) spills onto belt filter 218 where the resin is transported into mixing tank 196. The regenerant is filtered through the belt of 218 into holding tank 228 where it is transferred (pumped) to mixing tank 192 by pump 242 through conduit pipe 244.

The regenerant 246 is directly added to mixing tank 194 via pipe 247 and flows sequentially from mixing tank 194 to 192 to 190 (countercurrent to the resin) by pumps 242 and 238 and the associated conduit pipes 244 and 240 in the direction shown by the arrow heads. The resin flows by gravity and is assisted by the belt filter drive and the agitation of mixing tanks. The resin flows from mixing tank 190 to 192 to 194 where it comes into contact with more concentrated regenerant solution in each successive mixing tank.

In mixing tanks 196, 198 and 200 the resin undergoes a rinsing process to remove excess regenerant by contacting the resin with rinsing water. The overflow of mixing tank 196 (resin and rinsing water) spills onto belt filter 220 where the resin is transported to mixing tank 198. The rinsing water filters through the belt of belt filter 220 to rinse water waste collection container 248.

In mixing tank 198 the resin is contacted again with rinsing water and mixed. The overflow from mixing tank 198 (resin and rinsing water) spills onto belt filter 222 where the resin is transferred into mixing tank 200. The rinse water filters through the belt of belt filter 222 to holding tank 230 where it is transferred (pumped) to mixing tank 196 by pump 250 through conduit pipe 252.

In mixing tank 200 the resin is contacted again with rinsing water and mixed. The overflow from mixing tank 200 (resin and rinsing water) spills onto belt filter 224 where the resin (fresh regenerated resin, 254) is collected for return to a water treatment process. The rinsing water filters through the belt of belt filter 224 to holding tank 232 where it is transferred (pumped) to mixing tank 198 by pump 256 through conduit pipe 258. The rinsing water 260 is directly added to mixing tank 200 via pipe 261 and flows sequentially from mixing tank 200 to 198 to 196 (countercurrent to the resin), by continuously operating pumps 256 and 250 and the associated conduit pipes 258 and 252.

The resin flows by gravity and is assisted by the belt filter drive and the agitation of the mixing tanks. The resin flows from mixing tank 196 to 198 to 200 where it comes into contact with fresher rinse water in each successive mixing tank.

The following examples are provided to assist in the further understanding of the invention. Particular materials, and conditions employed are intended to be illustrative of the invention and not included to limit the scope thereof.

EXAMPLES 1. Determination of the brine concentration within a CCD system

A test was conducted to determine how the brine concentration changes within a CCD system when the upflow of brine is twice the rate of the downflow of raw (rinse) water. A CCD system was prepared to simulate a CCD rinsing system.

The equipment used in the test was six settler tanks linked in series by conduits and each fitted with an airlift pump at the bottom. Also used was an air compressor, three 2L jugs, a 100OmL measuring cylinder, a 25OmL measuring cylinder, pressure gauge, stopwatch, mercury manometer, mechanical agitator, 25kg of swimming pool salt (typically 99.5% NaCl, 1.6% moisture, 0.02% water insolubles, 100mg/kg Mg, 700 mg/kg Ca, mean particle size 2.7mm), peristaltic pump, a 200 Litre tank for preparing the brine solution, 7 sample bottles, digital scale (capacity of 30kg) and water (treated potable tap water from Melbourne, Victoria, Australia).

The conduits and pumps were arranged similar to the CCD system shown in figure 2. The overflow from the top settler (Settler 6) (equivalent to tank 70) passed into the next settler (Settler 5), (equivalent to tank 68) and so on in sequence down to the bottom settler (Settler l)(equivalent to tank 60). The end flow from the overflow conduit of the bottom settler emptied into a drain. A rinse water feed was connected to the top settler so in use rinse water would pass in sequence down the settlers via the linking overflow conduits.

The airlift pumps were used to move liquid upward from the bottom settler in sequence to the top settler. The airlift pump from the bottom settler (Settler 1) was connected to the overflow conduit linking the next two settlers (Settlers 2 and 3). The pumped solution would thus mix with the liquid flowing into the next settler (Settler 2). A similar arrangement was used for the other airlift pumps, but with the end flow from airlift pump of the top settler (Settler 6) passing into a drain. This arrangement simulated a CCD rinsing system.

The 200 litre tank was filled up with 150 Litres of water and 17.9kg of swimming pool salt (measured using the digital scale) was added to the tank to provide the equivalent of 12Og of salt per 1 Litre of water. A mechanical agitator was used inside the tank to assist in dissolving the salt and forming the brine solution.

A peristaltic pump was used to pump the brine solution into the overflow conduit between the bottom settler and the next settler. This arrangement meant the brine would first pass via the overflow into the bottom settler before being pumped in sequence up into the top settler and out the end flow. The peristaltic pump was calibrated by timing the flow of solution using the 100OmL cylinder and stop watch to achieve 600mL/min.

The air compressor was monitored by a manometer to ensure the system was operating at a pressure of 25kPa. The system was allowed to ran for a few minutes to obtain a constant pressure. The system was charged with water via the top Settler (Settler 6) at 300mL/min (half the flow rate of the brine solution). The flow rate was measured using a 100OmL measuring cylinder and stopwatch.

The system was allowed to run for 3 hours. This allowed the brine solution to replace the water that previously occupied the settlers. While the system was still running the small plastic bottles were used to take samples from the overflow of the Settlers 1 (bottom), 3, 4, 5 and 6 (top). Samples were also taken from the brine-mixing tank and outflow from the airlift pump of Settler 6. The chloride concentration of the samples was determined. The final flow rates of solution at the pump and raw water were measured with a cylinder and stopwatch.

RESULTS Initial raw water flow rate: 340mL/min Final raw water flow rate: 200mL/min Initial flow rate of brine solution at peristaltic pump: 600mL/min Final flow rate of brine solution at peristaltic pump: 580mL/min

Table 1. Chloride concentrations from Example 1.

The results were plotted and are depicted in the graph at figure 5. The test indicated that there was a steady decrease in the chloride concentration from Settlers 3 up to and out of Settler 6. The steady-state decrease in the chloride concentration is depicted by the section in figure 5 outlined by the cross-hairs with a gradient of 7,000.

2. Determination of the brine concentration within a CCD system A test was conducted to determine how the brine concentration changes within a CCD system when the upflow of brine is the same as the downflow of raw (rinse) water. The CCD system was prepared to simulate a CCD rinsing system.

The equipment and apparatus of Example 1 was used except the rinse water flow rate was substantially the same as the brine flow rate. The rinse water flow rate was recorded every 30 minutes.

RESULTS Initial raw water flow rate: 640niL/min Final raw water flow rate: 660mL/min Initial flow rate of brine solution at peristaltic pump: 600mL/min Final flow rate of brine solution at peristaltic pump: 610mL/min

Table 2. Chloride concentrations from Example 2.

These results were plotted and are depicted in the graph at figure 6. The test indicated that there was a steady decrease in the chloride concentration from Settlers 3 up to and out of Settler 6. The steady-state decrease in the chloride concentration is depicted by the section in figure 6 outlined by the cross-hairs with a gradient of 9,000. Table 3. Half hour interval measurements for flow rate of incoming raw water.

3. Determination of the brine concentration within a CCD system with MIEX® resin

A test was conducted to determine how the brine concentration changes when a mixture of MIEX resin and brine solution is used to simulate rinsing a regenerated resin mixture in a CCD system when the upflow of resin and brine is approximately twice the downflow of rinse water.

The equipment of Example 1 was used together with 35 - 50L MIEX® Resin and a sifter having very fine pores.

The method of Example 1 was followed, except the brine mixing tank was initially filled with approximately 35-50L of resin and water (at double the volume of resin). Salt was then added to give a salt concentration of 120g/L of water. The mechanical agitator was also used to ensure the resin was in suspension with the brine solution in the mixing tank during pumping.

At the overflow of the bottom settler (Settler 1) and at the airlift pump of the top settler (Settler 6), the solution was collected and resin therein allowed to settle. The excess water was drained and a fine sifter was used to collect any unsettled resin. Samples were taken after 2 and 3 hours of operation

RESULTS Initial raw water flow rate: 640mL/min Final raw water flow rate: 660mL/min Initial flow rate of brine solution at peristaltic pump: 600mL/min Final flow rate of brine solution at peristaltic pump: 600mL/min

Table 4. Chloride concentrations from Example 3

These results were plotted and are depicted in the graph at figure 7. The test indicated that there was a steady decrease in the chloride concentration from Settlers 1 up to an out of Settler 6. The steady-state decrease of the chloride concentration is observed with a gradient of 6,000. Table 5. Half hour interval measurements for flow rate of incoming raw water.

Those of ordinary skill in the art will appreciate that methods, materials (including pumping systems, regenerants, etc) and reactors other than those specifically described herein can be employed or adapted without undue experimentation to the practice of this invention. All such variants in methods, materials and reactors that are known in the art and can be so adapted or employed are encompassed by this invention.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.