Patent Publication Number: US-2018028944-A1

Title: Water processing system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of International Patent Application No. PCT/AU2015/050132, filed Mar. 25, 2015 and claims priority to Australian Patent Application No. 2016235031, filed Oct. 1, 2016, the disclosures of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a water processing system. The system has been developed primarily for use in agricultural applications, and will be described hereinafter with reference to that application. However, it will be appreciated that the system may also be used in other applications, such as in small communities, remote locations, in emergency situations, and in other circumstances, particularly where a relatively low capital cost and quickly commissionable water treatment system is required. 
     BACKGROUND 
     Known water treatment systems typically include a mixing station in which a flocculating agent is mixed with water undergoing treatment. The output from the mixing station is fed to a very large capacity settling tank, which is often formed from concrete or steel, in which floccules of contaminant from the water are allowed to settle whilst relatively clear water is removed from the top of the settling tank. 
     A disadvantage of known water treatment systems is their relatively high capital cost. Another problem is that they are not readily able to be scaled up or down in capacity if the quantity of water requiring treatment increases or declines. A further problem with known water treatment systems is that they can be very difficult to install in remote locations. 
     SUMMARY 
     Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. 
     Throughout this specification the word “intermediate bulk container” or “IBC”, will be understood to also encompass those containers referred to as a “plastic tote” or “bulky box”. Such containers are available in abundance, being commonly used to transport a large variety of materials, especially bulk quantities of liquids. 
     In a first aspect, there is provided a water treatment system comprising: 
     a mixing station comprising:
         a first reservoir for receiving water for treatment,   an agitator in the first reservoir for mixing coagulant into the water; and       

     a settlement station downstream of the mixing station for receiving water output from the mixing station, the settlement station comprising a plurality of intermediate bulk containers in which contaminants from the water output from the mixing station are allowed to settle. 
     The settlement station may comprise a first plurality of intermediate bulk containers hydraulically connected together in series. The first plurality of intermediate bulk containers may comprise three or more intermediate bulk containers. The settlement station may comprise a second plurality of intermediate bulk containers hydraulically connected together in series and in which water output from the mixing station is allowed to settle, the second plurality of intermediate bulk containers being in parallel to the first plurality of intermediate bulk containers. The second plurality of intermediate bulk containers may comprise three or more intermediate bulk containers. 
     A floccule accumulation station may be provided between the mixing station and the settlement station to receive output from the mixing station and to discharge into the settlement station. The floccule accumulation station may comprise a second reservoir and a slow speed stirrer extending into the second reservoir, the stirrer being configured to promote building of floccules. The slow speed stirrer may rotate at a speed less than that of the agitator in the first reservoir. The slow speed stirrer may rotate at between 1 and 100 revolutions per minute depending on the geometry of the stirrer and the capacity of the second reservoir. The second reservoir may be an intermediate bulk container. The floccule accumulation station may comprise two or more of the second reservoirs, each having an associated slow speed stirrer. 
     The mixing station may be detachable from the settlement station and may be mounted on a vehicle to facilitate its deployment at various sites. The vehicle may be a powered vehicle, such as a utility truck, or may be an unpowered vehicle, such as a towable trailer. The floccule accumulation station may also be detachable from the settlement station and mounted on the vehicle. The vehicle may include a power source for powering the agitator(s) and/or stirrer(s) of the water treatment system. In other embodiments, the water treatment system is transportable altogether. 
     The agitator in the first reservoir may rotate at between 1000 and 3000 revolutions per minute depending on the geometry of the agitator and the capacity of the first reservoir. 
     A water pump may be associated with the mixing station for pumping water for treatment into the first reservoir. 
     A coagulant dosing pump may be associated with the mixing station for injecting coagulant into the first reservoir. The coagulant may comprise, for example, alum, ferric chloride or aluminium chlorohydrate. 
     A filtration station may be provided at the downstream end of the system. The filtration station may comprise a granular filter, such as a sand, zeolite or diatomaceous earth filter, or a paper-type cartridge filter. 
     A disinfectant dosing pump may be provided to inject disinfectant into water output from the downstream end of the settlement station. The disinfectant may comprise, for example, chlorine, sodium hypochlorite or hydrogen peroxide and/or silver ion. A reservoir for relatively clear water may be connected to a downstream end of the settlement station for receiving output therefrom and the disinfectant may be injected into this reservoir. 
     A water pump may be provided to pump water output from the downstream end of the settlement station to a large storage reservoir. 
     In a second aspect, there is provided a water treatment system comprising: 
     a mixing station comprising:
         a first reservoir for receiving water for treatment,   an agitator in the first reservoir for mixing coagulant into the water; and       

     a settlement station downstream of the mixing station comprising at least one settling reservoir in which contaminants from the water output from the mixing station are allowed to settle, 
     wherein the mixing station is detachable from the settlement station and mounted on a vehicle to facilitate its deployment at various sites. 
     The at least one settling reservoir may comprise a first plurality of intermediate bulk containers hydraulically connected together in series, and contaminants in the water may be allowed to settle in the intermediate bulk containers in a clarifying sequence. The settlement station may comprise a second plurality of intermediate bulk containers hydraulically connected together in series, the second plurality of intermediate bulk containers being in parallel to the first plurality of intermediate bulk containers, such that contaminants in the water are allowed to settle in each branch of the intermediate bulk containers in a clarifying sequence. The first plurality of intermediate bulk containers may comprise three or more intermediate bulk containers. The second plurality of intermediate bulk containers may comprise three or more intermediate bulk containers. 
     A floccule accumulation station may be hydraulically connected to the mixing station for receiving output therefrom. The floccule accumulation station may comprise a second reservoir and a slow speed stirrer extending into the second reservoir, the stirrer being configured to promote building of floccules. The slow speed stirrer may rotate at a speed less than that of the agitator in the first reservoir. The slow speed stirrer may rotate at between 1 and 100 revolutions per minute depending on the geometry of the stirrer and the capacity of the second reservoir. The second reservoir may be an intermediate bulk container. The floccule accumulation station may comprise two or more of the second reservoirs, each having an associated slow speed stirrer. 
     The vehicle may be a powered vehicle, such as a utility truck, or may be an unpowered vehicle, such as a towable trailer. The vehicle may include a power source for powering the agitator(s) and/or stirrer(s) of the water treatment system. 
     The agitator in the first reservoir may rotate at between 1000 and 3000 revolutions per minute depending on the geometry of the agitator and the capacity of the first reservoir. 
     A water pump may be associated with the mixing station for pumping water for treatment into the first reservoir. 
     A coagulant dosing pump may be associated with the mixing station for injecting coagulant into the first reservoir. The coagulant may comprise, for example alum, ferric chloride or aluminium chlorohydrate. 
     A filtration station may be provided at the downstream end of the system. The filtration station may comprise a granular filter, such as a sand, zeolite or diatomaceous earth filter, or a paper-type cartridge filter. 
     A disinfectant dosing pump may be provided to inject disinfectant into water output from the downstream end of the settlement station. The disinfectant may comprise, for example, chlorine, sodium hypochlorite or hydrogen peroxide and or silver ion. A reservoir for relatively clear water may be connected to a downstream end of the settlement station for receiving output therefrom and the disinfectant may be injected into this reservoir. 
     A water pump may be provided to pump water output from the downstream end of the settlement station to a large storage reservoir. 
     In a third aspect, there is provided a water treatment method, comprising: 
     directing water for treatment into a mixing station; 
     mixing coagulant into the water in the mixing station; and 
     discharging the water from the mixing station to a settlement station comprising a plurality of intermediate bulk containers and allowing contaminants in the water to settle in the intermediate bulk containers. 
     The settlement station may comprise a first plurality of intermediate bulk containers hydraulically connected together in series and in which contaminants in the water are allowed to settle in a clarifying sequence. The first plurality of intermediate bulk containers may comprise three or more intermediate bulk containers. The settlement station may comprise a second plurality of intermediate bulk containers hydraulically connected together in series, the second plurality of intermediate bulk containers being in parallel to the first plurality of intermediate bulk containers, such that contaminants in the water are allowed to settle in each branch of the intermediate bulk containers in a clarifying sequence. The second plurality of intermediate bulk containers may comprise three or more intermediate bulk containers. 
     The output from the mixing station may be directed into a floccule accumulation station and slowly stirred to promote building of floccules before being discharged into the settlement station. The stirring in the floccule accumulation station may be performed at a speed less than that of the mixing in the mixing station. The stirring may include rotating a stirrer at between 1 and 100 revolutions per minute depending on the geometry of the stirrer and the capacity of the floccule accumulation station. Stirring of the water in the floccule accumulation station may be performed in an intermediate bulk container. The floccule accumulation station may comprise two or more intermediate bulk containers, with slow stirring being performed in each of the intermediate bulk containers. Residence time of the water in the floccule accumulation station may be at least 20 minutes. 
     Residence time of the water in the mixing station may be approximately 2 minutes. 
     Residence time of the water in the settlement station may be at least 1 hour. 
     The mixing station may be detachable from the settlement station and may be mounted on a vehicle to facilitate its deployment at various sites. The vehicle may be a powered vehicle, such as a utility truck, or may be an unpowered vehicle, such as a towable trailer. The floccule accumulation station may also be detachable from the settlement station and mounted on the vehicle. The vehicle may include a power source for powering the agitator(s) and/or stirrer(s). 
     The mixing may include rotating an agitator at between 1000 and 3000 revolutions per minute depending on the geometry of the agitator and the capacity of the mixing station. 
     A water pump may be associated with the mixing station for pumping water for treatment into the mixing station. 
     A coagulant dosing pump may be associated with the mixing station for injecting the coagulant into the water in the mixing station. The coagulant may comprise, for example, alum, ferric chloride or aluminium chlorohydrate. 
     Water output from the settlement station may be filtered. The filtering may be performed using, for example, a granular filter, such as a sand, zeolite or diatomaceous earth filter, or a paper-type cartridge filter. 
     Water output from the downstream end of the settlement station may be disinfected in a disinfection station. The disinfection may be performed using, for example, chlorine, sodium hypochlorite or hydrogen peroxide and or silver ion. Residence time of the water in the disinfection station may be around 20 minutes. 
     Water output from the downstream end of the settlement station may be pumped to a large storage reservoir. 
     In a fourth aspect, there is provided a water treatment method, comprising: 
     installing a first settlement station adjacent a source of water requiring treatment, the settlement station comprising at least one settling reservoir; 
     placing a transportable mixing station adjacent the settlement station; 
     hydraulically connecting the mixing station to the settlement station; 
     directing water from the source of water requiring treatment into the mixing station; 
     mixing coagulant into the water in the mixing station; 
     directing the water from mixing station into the settlement station and allowing contaminants in the water to settle therein; 
     disconnecting the mixing station from the settlement station; and 
     deploying the mixing station at another site. 
     The first settlement station may comprise a first plurality of intermediate bulk containers which may be hydraulically connected together in series, and contaminants in the water may be allowed to settle in the intermediate bulk containers in a clarifying sequence. The first settlement station may comprise a second plurality of intermediate bulk containers hydraulically connected together in series, the second plurality of intermediate bulk containers being in parallel to the first plurality of intermediate bulk containers, such that contaminants in the water are allowed to settle in each branch of the intermediate bulk containers in a clarifying sequence. The first plurality of intermediate bulk containers may comprise three or more intermediate bulk containers. The second plurality of intermediate bulk containers may comprise three or more intermediate bulk containers. 
     The output from the mixing station may be directed into a transportable floccule accumulation station and slowly stirred to promote building of floccules before being discharged into the settlement station. The stirring in the floccule accumulation station may be performed at a speed less than that of the mixing in the mixing station. The stirring may include rotating a stirrer at between 1 and 100 revolutions per minute depending on the geometry of the stirrer and the capacity of the floccule accumulation station. Stirring of the water in the floccule accumulation station may be performed in an intermediate bulk container. The floccule accumulation station may comprise two or more intermediate bulk containers, with slow stirring being performed in each of the intermediate bulk containers. Residence time of the water in the floccule accumulation station may be at least 20 minutes. 
     Residence time of the water in the settlement station may be at least 1 hour. 
     Residence time of the water in the mixing station may be approximately 20 minutes. 
     The mixing station may be mounted on a vehicle, which may be a powered vehicle, such as a utility truck, or may be an unpowered vehicle, such as a towable trailer. The vehicle may include a power source for powering the agitator(s) and/or stirrer(s). The flocculation station may also be mounted on the vehicle. 
     The mixing may include rotating an agitator at between 1000 and 3000 revolutions per minute depending on the geometry of the agitator and the capacity of the mixing station. 
     A water pump may be associated with the mixing station for pumping water for treatment into the mixing station. 
     A coagulant dosing pump may be associated with the mixing station for injecting coagulant into the water entering the mixing station. The coagulant may comprise, for example alum, ferric chloride or aluminium chlorohydrate. 
     Water output from the downstream end of the settlement station may be disinfected in a disinfection station. The water may be disinfected with any suitable disinfectant, for example, chlorine, sodium hypochlorite, hydrogen peroxide and/or silver ion. Residence time of the water in the disinfection station may be around 20 minutes 
     Water output from the downstream end of the settlement station may be pumped to a large storage reservoir. 
     A second said settlement station may be installed adjacent a second source of water requiring treatment, and the mixing station and flocculation station may be moved between the first and second settlement stations to facilitate treatment of the first and second water sources as demand requires. 
     In a fifth aspect, there is provided a water treatment system comprising: 
     at least one water treatment unit comprising:
         one or more reservoirs for receiving water undergoing treatment in the system, each of the one or more reservoirs comprising an inlet for receiving water undergoing treatment and a first outlet for discharging the water,   at least one of the one or more reservoirs having a mixer associated therewith for mixing coagulant into the water,   at least one of the one or more reservoirs having a mixer associated therewith for promoting building of floccules in the water/coagulant mixture, and   at least one of the one or more reservoirs being configured for settling of the floccules therein,   wherein at least one of the one or more reservoirs is an intermediate bulk container (IBC).       

     The mixer for mixing coagulant into the water may take any form and may, for example, comprise: a rotatable shaft and at least one paddle mounted thereon; or the inlet being oriented or otherwise configured to cause water flowing into the reservoir to promote swirling of water in the reservoir. In some embodiments, mixing of coagulant and building of floccules may take place in the same reservoir. In such embodiments, the mixer for mixing coagulant into the water may be the same mixer as the mixer for promoting building of floccules. For example, in some embodiments, the mixer for mixing coagulant into the water may be configured to cease operating when a water level in the reservoir reaches a predetermined level, such as the reservoir being full, thereby causing movement of the water/coagulant mixture in the reservoir to slow down to promote the building of floccules. In other embodiments, the mixer for mixing coagulant into the water may be configured to more gently move the water/coagulant mixture in the reservoir when a water level in the reservoir reaches a predetermined level, such as the reservoir being full, to promote the building of floccules. 
     Each of the at least one reservoir in which settlement occurs may comprise a second outlet for discharging accumulated sludge from a lower region thereof. 
     In some embodiments, mixing of coagulant, building of floccules and settlement of floccules occurs in the same reservoir of the one or more reservoirs. In other embodiments, mixing of coagulant occurs in one or more of the one or more reservoirs, building of floccules occurs in a different one or more of the one or more reservoirs, and settlement of floccules occurs in a different one or more of the one or more reservoirs. In other embodiments, both mixing of coagulant and building of floccules occurs in one of the one or more reservoirs, and settlement of floccules occurs in a different one of the one or more reservoirs. In other embodiments, mixing of coagulant occurs in one of the one or more reservoirs, and both building of floccules and settlement of floccules occurs in a different one of the one or more reservoirs. 
     In embodiments where the mixer comprises a rotatable shaft and at least one paddle mounted thereon, the rotatable shaft may be mounted substantially vertically and substantially centrally in the associated reservoir, and the at least one paddle may be a single large paddle or a plurality of smaller paddles spaced along the shaft. The rotatable shaft may extend through a substantially central opening in the top of the associated reservoir. A guide collar, which may take the form of a boss, may be fixedly connected relative to the central opening for the shaft, the guide collar having a cylindrical opening extending therethrough that has a diameter corresponding to the diameter of the shaft, wherein the shaft extends through the cylindrical opening of the guide collar and rotates within the cylindrical opening of the guide collar in use. 
     Each of the one or more reservoirs configured for settling of floccules therein may be an IBC. Each of the one or more reservoirs in which building of floccules occurs may be an IBC. Each of the one or more reservoirs in which mixing of coagulant occurs may be an IBC. 
     Prior to any conversion required for use in the system, the IBC(s) may comprise a unitary body of one-piece construction, the body comprising a contiguous base, sidewalls and top. Any IBCs that are to have a mixer (of the type comprising a rotatable shaft and at least one paddle mounted thereon) installed may have at least one opening formed in the top, the relative sizes of the opening and the at least one paddle being such as to facilitate the at least one paddle being inserted into the IBC through the at least one opening. The at least one opening may be sealed after insertion of the at least one paddle into the IBC. The at least one opening may be sealed by a removeable closure. The at least one opening may comprise two openings at diametrically spaced apart locations in the top. In some embodiments, at least one opening may be formed in the sidewalls of the IBC to facilitate the at least one paddle being inserted into the reservoir. The at least one opening in the sidewalls may be sealed after insertion of the at least one paddle. The at least one opening in the sidewalls may be permanently sealed. 
     The rotatable shaft may be rotated by a motor and associated gearbox. The motor may comprise a variable speed drive. A support structure may extend across the top of the IBC to support the motor and gearbox. The motor may be powered by an electrical power supply, such as a generator (e.g., a petrol or diesel generator) or one or more electrochemical cells (e.g., one or more lead acid batteries). The power supply may be connected to the motor via an inverter. The inverter may step a voltage provided by the power supply up or down to match voltage requirements of the motor. The motor may be a 415 Volt motor. In embodiments comprising a plurality of the water treatment units, a single power supply may serve all of the motors. In embodiments comprising a plurality of the water treatment units, a single inverter may serve all of the motors. 
     The water treatment system may comprise a plurality of the water treatment units. The plurality of water treatment units may be configured for connection in parallel to a source of water for treatment by the system. 
     The water treatment system may comprise a controller for controlling operation of the water treatment unit(s). For example, the controller may control any one or more of, or all of: the rotational speed of the mixer; the operation of valves and/or one or more pumps controlling flow of water for treatment into, out of and/or through the water treatment unit(s); and the actuation of a coagulant dosing device for dosing coagulant into the reservoir(s). 
     A water pump may be associated with the water treatment unit(s) for pumping water for treatment into the reservoir(s). 
     A coagulant dosing pump may be associated with the water treatment unit(s) for dosing coagulant into the reservoir(s). The coagulant may comprise, for example, alum, ferric chloride or aluminium chlorohydrate. 
     At least one filtration station may be provided at the downstream end of the system for filtering treated water output from the water treatment unit(s). The filtration station may comprise a granular filter, such as a sand, zeolite or diatomaceous earth filter, or a paper-type cartridge filter. A single filtration station may serve one or more said water treatment unit. 
     At least one disinfectant dosing pump may be provided to inject disinfectant into treated water output from the water treatment unit(s). The disinfectant may comprise, for example, chlorine, sodium hypochlorite or hydrogen peroxide and/or silver ion. A reservoir for relatively clear water may be provided to receive treated water output from the water treatment unit(s) and the disinfectant may be injected into this reservoir. In other embodiments, the disinfectant may be dosed in-line. 
     A water pump may be provided to pump water output from the downstream end of the system to a large storage reservoir. 
     The system may be transportable and may, for example, be assembled in a shipping container or other housing and/or mounted on a vehicle to facilitate its deployment at various sites. 
     In a sixth aspect, there is provided a water treatment system comprising: 
     at least one water treatment unit comprising:
         a reservoir for receiving water for treatment, the reservoir being an intermediate bulk container (IBC) and comprising an inlet for receiving water for treatment and a first outlet for discharging water that has been treated in the reservoir, and   a mixer associated with the reservoir for mixing coagulant into the water and thereafter for promoting building of floccules.       

     The mixer may take any form and may, for example, comprise: a rotatable shaft and at least one paddle mounted thereon; or the inlet being oriented or otherwise configured to cause water flowing into the reservoir to promote swirling of water in the reservoir. In some embodiments, the mixer may be configured to cease operating when a water level in the reservoir reaches a predetermined level, such as the reservoir being full, thereby causing movement of the water/coagulant mixture in the reservoir to slow down to promote the building of floccules. In other embodiments, the mixer may be configured to more gently move the water/coagulant mixture in the reservoir when a water level in the reservoir reaches a predetermined level, such as the reservoir being full, to promote the building of floccules. The reservoir may comprise a second outlet for discharging accumulated sludge from a lower region of the reservoir. 
     In embodiments where the mixer comprises a rotatable shaft and at least one paddle mounted thereon, the rotatable shaft may be mounted substantially vertically and substantially centrally in the reservoir, and the at least one paddle may be a single large paddle or a plurality of smaller paddles spaced along the shaft. The rotatable shaft may extend through a substantially central opening in the top of the reservoir. A guide collar, which may take the form of a boss, may be fixedly connected relative to the central opening for the shaft, the guide collar having a cylindrical opening extending therethrough that has a diameter corresponding to the diameter of the shaft, wherein the shaft extends through the cylindrical opening of the guide collar and rotates within the cylindrical opening of the guide collar in use. 
     Prior to conversion for use in the system, the IBC may comprise a unitary body of one-piece construction, the body comprising a contiguous base, sidewalls and top. The IBC may have at least one opening formed in the top, the relative sizes of the opening and the at least one paddle being such as to facilitate the at least one paddle being inserted into the reservoir through the at least one opening. The at least one opening may be sealed after insertion of the at least one paddle into the reservoir. The at least one opening may be sealed by a removeable closure. The at least one opening may comprise two openings at diametrically spaced apart locations in the top. In some embodiments, at least one opening may be formed in the sidewalls of the IBC to facilitate the at least one paddle being inserted into the reservoir. The at least one opening in the sidewalls may be sealed after insertion of the at least one paddle into the reservoir. The at least one opening in the sidewalls may be permanently sealed. 
     The rotatable shaft may be rotated by a motor and associated gearbox. The motor may comprise a variable speed drive. A support structure may extend across the top of the reservoir to support the motor and gearbox. The motor may be powered by an electrical power supply, such as a generator (e.g., a petrol or diesel generator) or one or more electrochemical cells (e.g., one or more lead acid batteries). The power supply may be connected to the motor via an inverter. The inverter may step a voltage provided by the power supply up or down to match voltage requirements of the motor. The motor may be a 415 Volt motor. In embodiments comprising a plurality of the water treatment units, a single power supply may serve all of the motors. In embodiments comprising a plurality of the water treatment units, a single inverter may serve all of the motors. 
     The water treatment system may comprise a plurality of the water treatment units. The plurality of water treatment units may be configured for connection in parallel to a source of water for treatment by the system. 
     The water treatment system may comprise a controller for controlling operation of the water treatment unit(s). For example, the controller may control any one or more of, or all of: the rotational speed of the mixer; the operation of valves and/or one or more pumps controlling flow of water for treatment into, out of and/or through the water treatment unit(s); and the actuation of a coagulant dosing device for dosing coagulant into the reservoir(s). 
     A water pump may be associated with the water treatment unit(s) for pumping water for treatment into the reservoir(s). 
     A coagulant dosing pump may be associated with the water treatment unit(s) for dosing coagulant into the reservoir(s). The coagulant may comprise, for example, alum, ferric chloride or aluminium chlorohydrate. 
     At least one filtration station may be provided at the downstream end of the system for filtering treated water decanted from the reservoir(s) via the first outlet. The filtration station may comprise a granular filter, such as a sand, zeolite or diatomaceous earth filter, or a paper-type cartridge filter. A single filtration station may serve one or more said water treatment unit. 
     At least one disinfectant dosing pump may be provided to inject disinfectant into treated water decanted from the first outlet of the reservoir(s). The disinfectant may comprise, for example, chlorine, sodium hypochlorite or hydrogen peroxide and/or silver ion. A reservoir for relatively clear water may be provided to receive treated water decanted from the first outlet of the reservoir(s) and the disinfectant may be injected into this reservoir. In other embodiments, the disinfectant may be dosed in-line. 
     A water pump may be provided to pump water output from the downstream end of the system to a large storage reservoir. 
     The system may be transportable and may, for example, be assembled in a shipping container or other housing and/or mounted on a vehicle to facilitate its deployment at various sites. 
     In another aspect, there is provided a method of water treatment corresponding to the system of the fifth or sixth aspect set out above. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       An embodiment of the presently disclosed water treatment system will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic view of a first embodiment of a water treatment system embodying principles disclosed herein; 
         FIG. 2  is a schematic view of a mobile mixing/floccule accumulation station of the water treatment system of  FIG. 1 ; 
         FIG. 3  is a schematic view of an embodiment of a water treatment unit for an alternative water treatment system embodiment; 
         FIG. 4  is a view of the water treatment unit of  FIG. 3  with part of its side cut away to allow internal components to be seen; and 
         FIG. 5  is a schematic view of an embodiment of a water treatment system including the water treatment unit of  FIGS. 3 and 4 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Referring to  FIGS. 1 and 2 , there is shown a water treatment system  10 . The system  10  comprises a hydraulic circuit including a rapid mixing station  12  at an upstream end, a floccule accumulation station  14  receiving output from the mixing station, and a settlement station  16  receiving output from the floccule accumulation station. 
     The mixing station  12  includes a first reservoir  12   a  for receiving water for treatment from a source, such as a dam, river, bore or well  200 . An agitator  12   b  is provided in the first reservoir for flash mixing coagulant into the water in the first reservoir  12   a . The agitator  12   b  is powered by a motor and is adapted to rotate at a speed of around 1400 revolutions per minute depending on the geometry of the agitator  12   b  and the capacity of the reservoir  12   a.    
     The floccule accumulation station  14  comprises a second reservoir, in the form of an IBC  14   a , for receiving output from the first reservoir  12   a  of the mixing station  12 . A slow speed stirrer  14   b  extends into the second reservoir  14   a  and is configured to promote building of floccules as the coagulant causes contaminant particles in the water to clump together. The slow speed stirrer  14   b  rotates at approximately 30 revolutions per minute depending on the geometry of the stirrer  14   b  and the capacity of the reservoir  14   a.    
     The settlement station  16  is modular and comprises a plurality of intermediate bulk containers (IBCs)  16   a  hydraulically connected together in series by conduits  16   b  extending therebetween. The conduits have a minimum internal diameter of around 100 mm. The large diameter of the conduits  16   b  together with a deliberately relatively slow flow rate through the settlement station  16  inhibits the floccules from being broken up and allows them to settle to the base of the IBCs  16   a  as sludge for removal through an outlet  16   c  at the base of each IBC  16   a.    
     A downstream most of the IBCs  16   a  has an upper outlet  16   d  for discharging the relatively clear treated water to a disinfecting station  18 , which comprises a reservoir in the form of an IBC  18   a . The outlet  16   d  is located near the top of the downstream most IBC  16   a , above the level of the conduits  16   b . A disinfectant dosing pump  18   b  is provided to inject disinfectant, such as chlorine, sodium hypochlorite or hydrogen peroxide and/or silver ion into the reservoir  18 . 
     As shown in  FIG. 2 , the mixing station  12  and floccule accumulation station  14  are detachable from the settlement station  16  and mounted on a vehicle in the form of a towable trailer  50 . For ease of understanding, the trailer  50  is not shown in the schematic diagram of  FIG. 1 . The trailer  50  includes a power supply, in the form of a petrol or diesel powered generator  52 , for powering the agitator  12   b , stirrer  14   b  and various pumps of the water treatment system  10 . In some embodiments, a water pump, such as a sump pump  54 , is carried on the trailer  50  for pumping water from the source  100  into the first reservoir  12   a  for treatment. In other embodiments, a pump may be permanently installed near the water source  100  and connected to the first reservoir  12   a  when required. A coagulant dosing pump  60  is also carried on the trailer  50  for injecting coagulant, such as alum, ferric chloride or aluminium chlorohydrate, into the first reservoir  12   a . The trailer  50  has a roof  50   a  for protecting the system components carried thereon from the weather. 
     A water pump  70  is provided to pump water from the reservoir  18  to a large storage reservoir. 
     The IBCs used in the system  10  may have a capacity of 1000 L to 1500 L. The IBCs may have a galvanised steel cage therearound, particularly in cases where the IBC is blow moulded. 
     The capacity of the mixing station  12 , floccule accumulation station  14 , settlement station  16  and disinfecting station  18  can be scaled up to treat up to around 20 m 3  of water per hour or down to treat as little as around 1 m 3  of water per hour whilst still maintaining desired residence times in the various system components. For example, scaling up or down of the settlement station  16 , which has the largest capacity of the various stations in the system  10 , can be easily accomplished by adjusting the number of IBCs  16   a . The desired residence time of the water in the rapid mixing station  12  is approximately 2 minutes. The desired residence time of the water in the floccule accumulation station is at least 20 minutes. The desired residence time of the water in the settlement station  16  is at least one hour. The desired residence time of the water in the disinfection station  18  is approximately 20 minutes. 
     An alternative embodiment of a water treatment system  100  will now be described with reference to  FIGS. 3 to 5 . The water treatment system  100  comprises one or more water treatment unit(s)  110 , a filtration station  120  and a disinfection station  130 . In embodiments comprising a plurality of water treatment units  110 , the plurality of water treatment units  110  are connected in parallel to a source of water for treatment. 
     As shown in  FIGS. 3 and 4 , the water treatment unit  110  comprises a reservoir  110   a  in the form of an IBC for receiving water for treatment. The reservoir  110   a  comprises an inlet  110   b  for receiving the water for treatment and an upper outlet  110   c , located diametrically opposite the inlet  110   b , for discharging water that has been treated in the reservoir. A mixer  110   d  comprising a rotatable shaft  110   e  with two paddles  110   f  mounted thereon is mounted in the reservoir  110   a  for mixing coagulant into water contained therein and thereafter for promoting building of floccules. 
     In some embodiments, the mixer  110   d  is configured to rotate more slowly when a water level in the reservoir  110   a  reaches a predetermined level, which may be when the reservoir is full or may be a level below the maximum capacity of the reservoir, or after mixing has been performed for a predetermined period of time. Slow rotation of the mixer  110   d  causes the water/coagulant mixture in the reservoir  110   a  to move more gently and promotes the building of floccules. In other embodiments, the mixer  110   d  is configured to cease operating when the reservoir  110   a  reaches a predetermined level, which may be when the reservoir is full or may be a level below the maximum capacity of the reservoir, or when mixing has been performed for a predetermined period of time. Ceasing of operation of the mixer  110   d  causes movement of the water/coagulant mixture in the reservoir  110   a  to slow down to promote the building of floccules. In either case, the reservoir  110   a  comprises a lower outlet  110   g  for discharging settled material/accumulated sludge from the bottom of the reservoir. 
     The rotatable shaft  110   e  is mounted substantially vertically and substantially centrally in the reservoir  110   a , and the paddles  110   f  are spaced along the shaft  110   e . The shaft  110   e  extends through a substantially central opening in the top  110   h  of the reservoir  110   a . A guide collar, in form of a boss, is fixedly connected relative to the central opening in the top  110   h , the guide collar having a cylindrical opening extending therethrough that has a diameter corresponding to the diameter of the shaft  110   e . The shaft  110   e  extends through the cylindrical opening of the guide collar and rotates within the cylindrical opening of the guide collar in use. 
     The IBCs used in the system  100  may have a capacity of 1000 L to 1500 L. The IBCs may have a galvanised steel cage therearound, particularly in cases where the IBC is blow moulded. Prior to conversion for use in the system, an IBC for forming the reservoir  110   a  will generally comprise a unitary body of one-piece construction, the body comprising a contiguous base, sidewalls and top. During conversion, the IBC has two openings  110   i  formed in the top  110   h  at diametrically spaced apart locations. The relative sizes of the openings  110   i  and the paddles  110   f  are such as to facilitate the paddles being inserted into the reservoir  110   a  through the openings  110   i . The openings  110   i  are sealed with a removable closure  110   j  after insertion of the paddles  110   f  into the reservoir. In some embodiments of the water treatment unit  110 , especially embodiments where the shaft  110   e  has three or more paddles  110   f  mounted thereon, at least one opening may be formed in the sidewalls  110   k  of the IBC to facilitate one or more paddles  110   f  being inserted into the reservoir  110   a  therethrough. In such embodiments, the opening(s) in the sidewalls  110   k  are sealed, preferably permanently, after insertion of the paddle(s) therethrough. 
     The shaft  110   e  is rotated by a 415 Volt motor  110   l  and associated gearbox  110   m . The motor  110   l  comprises a variable speed drive. A support structure, in the form of a bridge  110   n , extends across the top of the reservoir  110   a  to support the motor  110   l  and gearbox  110   m . The motor  110   l  is powered by an electrical power supply in the form of a petrol or diesel generator (not shown). The power supply is connected to the motor  110   l  via an inverter (not shown). The inverter steps a voltage provided by the power supply up or down to match voltage requirements of the motor  110   l . In embodiments of the system  100  comprising a plurality of water treatment units  110 , a single power supply and single inverter serve all of the motors. 
     A water pump  54  is associated with the water treatment unit(s)  110  for pumping water for treatment into the reservoir(s)  110   a.    
     A coagulant dosing pump  60  is associated with the water treatment unit(s)  110  for dosing coagulant into the reservoir(s)  110   a . The coagulant may comprise, for example, alum, ferric chloride or aluminium chlorohydrate. 
     Filtration station  120  is provided at the downstream end of the system  100  for filtering treated water decanted from the reservoir(s)  110   a  via the upper outlet(s)  110   c . The filtration station  120  comprises a granular filter, such as a sand, zeolite or diatomaceous earth filter, or a paper-type cartridge filter. A single filtration station  120  may serve one or more water treatment unit  110 . 
     Disinfecting station  130  is provided downstream of the filtration station  120  to receive filtered water therefrom. The disinfection station  130  comprises a disinfectant pump  130   a  for in-line dosing of disinfectant into a pipe that receives filtered water from filtration station  120 . Any suitable disinfectant may be used, such as chlorine, sodium hypochlorite, hydrogen peroxide and/or silver ion. 
     A water pump  70  is provided to pump water output from the downstream end of the system  100  to a large storage reservoir. Alternatively, water treated in the system  100  may be pumped, or flow under the influence of gravity, to a plurality of IBCs for storage. 
     The water treatment system  100  comprises a controller (not shown) for controlling operation of the water treatment unit(s)  110  and other components of the system  100 . For example, the controller controls: the motor  110   l  to control the rotational speed of the mixer  110   d ; the operation of valves controlling flow of water for treatment into, out of and/or through the water treatment unit(s)  110 ; and the actuation of the coagulant and disinfectant dosing pumps  60 ,  130   a . The controller may also control actuation of pump  54  and  70 . 
     The system  100  is transportable and may, for example, be assembled in a shipping container or other housing and/or mounted on a vehicle to facilitate its deployment. 
     It will be appreciated that the above described systems and methods provide a number of advantages over the prior art. For example, the systems  10 ,  100  are relatively inexpensive, quick and easy to install due to their modular nature and use of IBCs, which are readily available at a low cost. Accordingly, systems  10 ,  100  are well suited for use in agricultural applications for treatment of water for stock, such as on feedlots, poultry farms, in piggeries and chicken sheds, as well as in remote communities or emergency situations. The systems  10 ,  100  are also easily scalable in capacity, which can be difficult in prior art systems where large capital cost reservoirs are utilised, especially for the settlement tank(s). The transportability of the mixing  12  and floccule accumulation  14  stations of system  10 , due to their disengageability from the settlement station  16  and mounting on the trailer  50 , also advantageously allows one mixing/floccule accumulation unit  12 ,  14  to be moved between several settlement stations  16  instead of requiring each settlement station to have its own dedicated mixing  12  and floccule accumulation  14  stations as is the case in the prior art. The transportability of the entire system  100  makes it advantageous for applications where there is no need for a long term water remediation solution, as the whole system  100  can be easily redeployed or moved into storage when its remediation task is completed. 
     It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. Examples of possible variations and/or modifications include, but are not limited to:
         the floccule accumulation station  14  of system  10  comprising two or more reservoirs  14   a , each having an associated slow speed stirrer;   the settlement station  16  of system  10  comprising more than three IBCs  16   a  hydraulically connected together in series;   the settlement station  16  of system  10  comprising a second plurality of IBCs hydraulically connected together in series, the second plurality of IBCs being in parallel to the first plurality of IBCs;   the reservoir  12   a  of the mixing station  12  may be an IBC;   the vehicle  50  of system  10  being a utility truck or other powered vehicle;   a filtration station, similar to filtration station  120  of system  100 , may be provided at a downstream end of system  10 , either between the downstream end of the settlement station  16  and the disinfection station  18  or downstream of the disinfection station  18 ;   system  10  being housed in a shipping container or other housing;   instead of mixer  110   d , system  100  may comprise a mixer that comprises the inlet  110   b  being oriented or otherwise configured to cause water flowing into the reservoir  110   a  to promote swirling of water in the reservoir;   more than two paddles  110   f  may be spaced along and mounted on the shaft  110   e , or a single larger paddle  110   f  may be used instead of multiple paddles;   the power supply may alternatively comprise one or more electrochemical cells (e.g., one or more lead acid batteries);   disinfectant may be dosed in-line downstream of the settlement station  16  in system  10  and the tank of disinfecting station  18  may be omitted; and/or   the coagulant dosing pump  60  may dose coagulant in-line into a conduit/pipe through which water flows into the mixing station  12  of system  10  or through which water flows into the water treatment units(s)  110  of system  100 .