Patent Publication Number: US-2017355620-A1

Title: Method of filtering waste water

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority from Australian Provisional Patent Application No 2014903912 filed on 1 Oct. 2014, the contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     This disclosure relates, generally, to a filtration system and, more particularly but not necessarily exclusively, to a method of filtering waste water and to a filtration system for use in the treatment of waste water. 
     BACKGROUND 
     Large scale waste water treatment plants run trickling systems, aerated, continuous processes and/or mechanical mixing with daily backwashing to optimise performance of granular filters used in the treatment plant. Such systems are voluminous and are expensive to run. As such, they are not appropriate for smaller scale plants such as those which may be used in domestic applications or small industry applications. 
     In other waste water treatment applications, once the treated water has passed through the granular filter, it undergoes further purification treatment by additional components of the system. Waste water which has been inadequately treated in the granular filter or which carries contaminants out of the granular filter places an increased load on those additional components resulting in overall poorer purification results. 
     Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application. 
     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. 
     In a first aspect, there is provided a method of filtering waste water using a filter of the type comprising a receptacle defining a chamber and a granular filtering medium contained in the chamber of the receptacle, the method including 
     injecting waste water to be treated at a first flow rate into the chamber of the receptacle to cause the waste water to be driven into contact with the filtering medium; 
     retaining the waste water in the chamber in contact with the filtering medium for a specified dwell time; and 
     discharging water from the chamber at a second flow rate which is lower than the first flow rate. 
     The method may include injecting the waste water at a first flow rate in the range of about 20 L/min to 50 L/min. The method may include selecting the first flow rate to be about 40 L/min. It will be appreciated that the first flow rate could be in any range from about 20 L/min-30 L/min, 30 L/min-40 L/min and 40 L/min-50 L/min. 
     The method may include selecting the specified dwell time to be in the range from about 5 minutes to about 60 minutes. The method may include selecting the specified dwell time to be about 30 minutes. It will be appreciated that the specified dwell time may fall within any of a desired number of ranges of about 5-10 minutes, 10-15 minutes, 15-20 minutes, 20-25 minutes, 25-30 minutes, 30-35 minutes, 35-40 minutes, 40-45 minutes, 45-50 minutes, 50-55 minutes and 55-60 minutes depending on the batch process in use. 
     The method may include discharging the water from the chamber of the receptacle at a second flow rate of about 1 L/min-10 L/min. The method may include selecting the second flow rate to be about 2 L/min. It will be appreciated that the second flow rate could be in any range from about 1 L/min-3 L/min, 3 L/min-5 L/min, 5 L/min-7 L/min and 7 L/min-10 L/min. 
     Further, the method may include discharging the water in a pulsed manner with a specified duty cycle. The term “duty cycle” is to be understood as the time during which a discharge pump being used to discharge the water is operative relative to the time the discharge pump is inoperative during the discharging process. 
     The duty cycle may have a range of about 4:1 to about 1:4 and, more particularly, may be at least one of an approximately 2:1 duty cycle, an approximately 1:1 duty cycle and any duty cycle in between. 
     The receptacle may define an opening via which the waste water is injected into the chamber of the receptacle and the method may include injecting the waste water and discharging the water through the same opening. 
     The method may include imparting turbulence to the waste water as it is injected into the filtering medium contained in the chamber of the receptacle. The creation of turbulence breaks down boundary layers and improves contact between the waste water and the filtering medium. 
     The method may include subjecting the water discharged from the filter to further treatment, including at least partial sterilisation, downstream of the filter and storing treated water, the method further including using a quantity of the stored, treated water to flush components used at least in the further treatment of the waste water. The further treatment may involve particle filtration followed by at least partial sterilisation and the method may include using a pulse of treated water to flush a particle filtration module and a sterilisation module used in the further treatment of the water. 
     In a second aspect, there is provided a method of filtering waste water using a filter of the type comprising a receptacle defining a chamber and a granular filtering medium contained in the chamber of the receptacle, the method including 
     injecting waste water to be treated into the chamber of the receptacle to cause the waste water to be driven into contact with the filtering medium; 
     retaining the waste water in the chamber in contact with the filtering medium for a specified dwell time; and 
     discharging water from the chamber in a pulsed manner with a specified duty cycle. 
     In a third aspect, there is provided a filtration system which includes 
     a filter comprising a receptacle defining a chamber and a granular filtering medium contained in the chamber of the receptacle, the receptacle further defining an opening; 
     an injection pump in communication with the opening for injecting waste water to be treated into the chamber of the receptacle, the injection pump being configured to pump the water into the chamber of the receptacle at a first flow rate; and 
     a discharge pump also in communication with the opening for discharging water from the chamber of the receptacle, the discharge pump being configured to discharge the water from the chamber of the receptacle at a second flow rate which is lower than the first flow rate of the injection pump. 
     The system may include a controller for controlling operation of at least the discharge pump to cause the discharge pump to discharge the water from the receptacle in a pulsed manner with a specified duty cycle. 
     The system may include a turbulence enhancing mechanism arranged downstream of the opening of the receptacle to impart turbulence to the waste water as it is injected into the chamber of the receptacle. 
     Further, the system may include an isolation valve arranged upstream of the opening to inhibit back flow of water discharged via the discharge pump into the injection pump or any components arranged upstream of the injection pump. 
     The system may include additional purification components arranged downstream of the filter and a storage unit for storing further treated water output from the additional purification components, the system further including a feedback mechanism for feeding a quantity of water stored in the storage unit to flush at least the additional purification components. The additional purification components may comprise a particle filtration module arranged downstream of the filter and a sterilisation module arranged downstream of the particle filtration module, the feedback mechanism flushing at least those modules. 
     The feedback mechanism may be configured to use a pulse of treated water stored in the storage unit to flush the particle filtration module and the sterilisation module. 
     In a fourth aspect, there is provided a filtration system which includes 
     a filter comprising a receptacle defining a chamber and a granular filtering medium contained in the chamber of the receptacle and the receptacle further defining an opening; 
     an injection pump in communication with the opening for injecting waste water to be treated into the chamber of the receptacle; 
     a discharge pump also in communication with the opening for discharging water from the chamber of the receptacle; and 
     a controller for controlling operation of at least the discharge pump to cause the discharge pump to discharge water from the receptacle in a pulsed manner with a specified duty cycle. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Embodiments of the disclosure are now described by way of example with reference to the accompanying drawings in which:— 
         FIG. 1  shows a schematic block diagram of an embodiment of a filtration system; 
         FIG. 2  shows a flow chart of an embodiment of a method of filtering waste water; 
         FIG. 3  shows a perspective view of an embodiment of a filter for use with the system of  FIG. 1 ; 
         FIG. 4  shows a plan view of the filter of  FIG. 3 ; and 
         FIG. 5  shows a sectional side view of the filter of  FIG. 3  taken along line V-V in  FIG. 4  of the drawings. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Referring initially to  FIG. 1  of the drawings, an embodiment of a filtration system is illustrated and is designated generally by the reference numeral  10 . The system  10  is intended particularly for use in the treatment of waste water. The term “waste water” is to be understood as covering both grey water and sewage. While the system  10  is intended particularly for use in the treatment of grey water, the system  10  can also treat waste water which includes sewage. 
     The system  10  comprises a filter  12  arranged downstream of a primary treatment processing module  14 . The primary treatment processing module  14  is a bubble separator for removing surfactants from the waste water as described, for example, in greater detail in our co-pending International Patent Application No. PCT/AU2015/050513 dated 1 Sep. 2015 and entitled “Apparatus for treating water”. The disclosure of the &#39;513 application deals with an improvement to the Applicant&#39;s system as described in International Patent Publication No. WO/2011/160185 filed on 24 Jun. 2011 and entitled “A process and apparatus for purifying water”. 
     As described in WO/2011/160185, the bubble separator separates bubbles and entrained contaminants from aerated waste water. The disclosure of PCT/AU2015/050513 describes an improvement in effecting separation of the surfactants from the waste water. To the extent permitted by the applicable national law, both applications are incorporated herein by reference in their entirety. 
     As shown in greater detail in  FIGS. 3-5  of the drawings, the filter  12  comprises a receptacle  16  defining a chamber  18 . The filter  12  is a carbon contact filter, also known as a “carbon contact column”. The chamber  18  of the receptacle  16  therefore contains a granular filtering medium in the form of activated carbon  20 . 
     An opening  22  is defined in a base or floor  24  of the receptacle  16  of the filter  12 . Waste water to be treated in the filter  12  is injected into the chamber  18  of the receptacle  16  via the opening  22 . The opening  22  is also used to discharge filtered, or treated, water from the chamber  18  of the receptacle  16  for further processing, as will be described in greater detail below. 
     The filtration system  10  includes an injection pump  26  connected to an outlet  28  of the primary treatment processing module  14 . The injection pump  26  pumps waste water treated in the primary treatment processing module  14  via an isolation, or one-way, valve  30  via the opening  22  into the chamber  18  of the receptacle  16  of the filter  12  to come into contact with the activated carbon  20  of the filter  12 . 
     The injection pump  26  is configured to pump the water into the chamber  18  of the receptacle  16  at a first flow rate. This first flow rate is typically in a range from about 20 L/min to about 50 L/min and, depending on the capacity of the primary treatment processing module  14  and other factors, is about 40 L/min. The filtration system  10  is a batch process system so that, while one batch of waste water is being treated in the primary treatment processing module  14 , a preceding batch is being filtered in the filter  12 . Thus, the rate at which the treated waste water is charged from the module  14  into the filter  12  depends on, amongst other factors, the capacity of the primary treatment processing module  14 . 
     The filtration system  10  further includes a discharge pump  32  in communication with the opening  22  of the receptacle  16  of the filter  12  via a valve  34 . The discharge pump  32  effects discharge of filtered, or treated, water from the chamber  18  of the receptacle  16 . 
     The discharge pump  32  is configured to discharge the treated water from the chamber  18  of the receptacle  16  at a second flow rate which is lower than the first flow rate of the injection pump  26 . This second flow rate of the discharge pump  32  is, typically, in a range from about 1 L/min to about 10 L/min and, in an embodiment, is about 2 L/min. 
     Further, the discharge pump  32  is configured to operate in a pulsed manner discharging the treated water from the chamber  18  of the receptacle  16  in pulses with a specified duty cycle. The duty cycle has a range of about 4:1 to about 1:4 and, more particularly, is, for example, about a 2:1 or about a 1:1 duty cycle or any duty cycle between these two values. 
     Thus, the system  10  includes a controller  36  which controls, inter-alia, operation of the discharge pump  32  to cause it to operate in the pulsed manner. It is noted that the controller  36  further controls operation of the injection pump  26 , the valves  30  and  34 , a further valve or pump  38  which controls ingress of waste water into the primary treatment processing module  14  and also controls a feedback mechanism  40 , as will be described in greater detail below. 
     The filter  12  further includes a turbulence enhancing mechanism  42  ( FIG. 5 ) arranged in the chamber  18  of the receptacle  16 , downstream of the opening  22  of the receptacle  16 . The filter  12  also includes a disruptor mechanism, in the form of a series of spaces baffles  44 , arranged across the chamber  18  of the receptacle  16 . The turbulence enhancing mechanism  42  serves to impart turbulence to the water as it is injected by means of the injection pump  26  into the chamber  18  of the receptacle  16  to improve contact between the water and the activated carbon  20 . The turbulence enhancing mechanism  42  also assists in inhibiting the formation of “channels” in the activated carbon  20 , particularly as the filtered water is being discharged from the chamber  18  of the receptacle  16  under the action of the discharge pump  32 . 
     The turbulence enhancing mechanism  42  comprises a porting arrangement in the form of a T-piece. A stem  43  of the porting arrangement is in communication with the opening  22  of the receptacle  16 . A cross-piece  45  of the porting arrangement defines a pair of oppositely directed ports  47 . It will be appreciated that, in other embodiments, the ports  47  of the porting arrangement could face towards each other, parallel to each other (whether facing the same way or in opposite directions) or pointing at different elevations. 
     Each port  47  is semi-occluded both to encourage turbulent flow of the waste water as it is injected into the chamber  18  of the receptacle  16  but also to inhibit the escape of activated carbon  20  through the opening  22  of the receptacle  12  when filtered water is discharged through the opening  22  of the receptacle  12 . In an embodiment, each port  47  is semi-occluded by having radially extending vanes (not shown) mounted in the port  47 . 
     The baffles  44  also serve to impart turbulence to the injected water to enhance contact between the water and the activated carbon  20  and to inhibit the formation of channels in the activated carbon  20 . Such channels can reduce the degree of contact between the water to be filtered and the activated carbon and are therefore undesirable. 
     The turbulence enhancing mechanism  42  and the baffles  44  are described in greater detail in our co-pending International Patent Application entitled “A filtration system”, claiming priority from Australian Provisional Patent Application No. 2014903913 dated 1 Oct. 2014, and filed on the same day as the present application. The contents of the co-pending International Patent Application referenced in this paragraph are incorporated herein by reference in its entirety, to the extent permitted by the applicable national law. 
     The filtration system  10  includes additional, or secondary, purification components arranged downstream of the filter  12 . These secondary purification components include a particle filtration module  46 , in the form of a pleated filter, and a sterilisation module  48 , in the form of an ultraviolet light unit (UV unit), arranged downstream of the particle filtration module  46 . 
     The filtration system  10  also includes a storage unit, in the form of a storage tank,  50  into which treated water output from the UV unit of the sterilisation module  48  is charged for subsequent re-use. 
     The feedback mechanism  40  of the system  10  comprises a pump  52  connected to an outlet  54  of the storage tank  50  and a three way valve  56  interposed between the particle filtration module  46  and the sterilisation module  48 . 
     The feedback mechanism  40  is used for flushing the particle filtration module  46  and the sterilisation module  48 . A pulse of stored, treated water is, periodically, extracted from the storage tank  50  via the pump  52  under the action of the controller  36  to be fed into the particle filtration module  46  and the sterilisation module  48  via the valve  56  to flush the modules  46  and  48 . A portion of the pulse of water may be driven through the particle filtration module  46  and used also to flush the discharge pump  32  as well as any lines between the opening  22  of the receptacle  16  of the filter  12  and the storage tank  50 . 
     It is to be noted that the water output from the primary treatment processing module  14  contains quantities of biologically active material such as bacteria. These bacteria interact with the activated carbon  20  in the receptacle  16  further to purify the water in the carbon filter  12 . The bacteria are aerobic bacteria and, as such, do not generate unpleasant odours. However, if the activated carbon  20  of the filter  12  dries out or the bacteria consume all the oxygen in the filter  12 , the bacteria begin to convert to anaerobic bacteria resulting in malodorous conditions. This affects the carbon filter  12  as well as components downstream of the carbon filter  12 . It can also adversely affect subsequent batches of water injected into the carbon filter  12 . 
     By ensuring that the activated carbon  20  of the filter  12  is consistently aerated and maintained in a moist condition, the likelihood of malodorous conditions occurring is reduced. Further, the periodic flushing of components downstream of the filter  12  using a pulse of water from the storage tank  50  further reduces the chances of malodorous conditions arising. 
     It is to be noted that the isolation valve  30  effectively separates the system  10  into two parts being, firstly, a zone of biologically active water  58  and, secondly, a zone of substantially purified water  60 . 
     Referring now to  FIG. 2  of the drawings, a flow chart of an embodiment of a method of filtering waste water is shown in greater detail and is designated generally by reference numeral  62 . At step  64 , treatment of the waste water commences by charging a batch of waste water into the bubble separator of the primary treatment processing module  14  via the inlet valve or pump  38  under the action of the controller  36 . 
     Processing of the waste water in the module  14  involves aerating the waste water using a venturi (not shown) prior to injecting the water into the bubble separator. In the bubble separator, surfactants are separated from the water. The water from which the surfactants have been separated is drawn from the module  14  through the outlet  28  via the injection pump  26  under the action of the controller  36 , through the isolation valve  30  and into the chamber  18  of the receptacle  16  of the filter  12  as shown at step  66 . 
     As described above, the water is injected into the carbon filter  12  at a flow rate of about 40 L/min. This encourages turbulent flow in the water as it is injected into the filter  12  to enhance contact with the activated carbon  20  of the filter  12 . The turbulent flow is further enhanced due to the use of the turbulence enhancing mechanism  42  and the baffles  44 . 
     The activated carbon  20 , when moist, has a tendency to clump and contract so that a gap  68  ( FIG. 5 ) forms at the top of the activated carbon  20 . When the water is injected into the chamber  18  of the receptacle  16 , if the baffles  44  were omitted, there may be a tendency for the body of activated carbon  22  to remain adhering together to move as one body, in a piston-like manner. Thus, the entire body of activated carbon  20  could be displaced in the direction of arrow  70  to close the gap  68  under the effect of the injected water with the water collecting below the carbon and reducing the contact area between the water and the carbon  20 . The baffles  44  serve to obviate this problem by inhibiting clumping of the body of activated carbon  20 . 
     Once the water has been injected into the chamber  18  of the receptacle  16 , the valves  30  and  34  are both closed under the action of the controller  36  effectively closing the opening  22  of the receptacle  16 . As shown at step  72 , the water is retained within the carbon  20  for a predetermined dwell time. 
     The dwell time is selected based on numerous factors including the size of the batch of water being treated, the extent of contamination of the water and, hence, the time to be spent in the primary treatment processing module  14 , or the like. The dwell time is selected to be in the range from about 5 minutes to about 60 minutes and, in an embodiment, is about 30 minutes. 
     After expiry of the dwell time period, the controller  36  opens the valve  34  to begin discharge of the filtered water from the filter  12  as shown at step  74  in  FIG. 2 . The controller  36  controls the discharge pump  32  to discharge the filtered water from the receptacle  16  of the filter  12  in a pulsed manner. The pump  32  extracts water from the receptacle at a rate of approximately 2 L/min. with the specified duty cycle. 
     The benefit of pulsing the water as it is extracted is that greater contact time with the activated carbon  20  occurs. Also, there is less likelihood of the draining water forming channels in the body of activated carbon  20 . As indicated above, if channels were to form in the activated carbon  20 , contact between the water to be treated and the activated carbon  20  may be reduced resulting in a reduced filtering efficiency of the filter  12 . 
     Further, causing the water to be discharged in a pulsed, slow manner from the filter  12  facilitates retaining the activated carbon  20  in a moist condition and reduces the likelihood of it drying out completely. This minimises the risk of aerobic bacteria converting to anaerobic bacteria with the consequential malodorous conditions arising. 
     After completion of discharge, the controller  36  determines whether or not the chamber  18  of the receptacle  16  is empty as shown at  76 . If the controller  36  determines that the chamber  18  is empty, it causes a further batch of treated water from the primary treatment processing module  14  to be charged into the filter  12  for filtering by the filter  12  as shown at  78 . If the controller  36  determines that the chamber  18  is not empty, it commences or continues with the discharge procedure as shown at  80 . 
     A batch of water output from the filter  12  is fed through the pleated filter of the particle filtration module  46  where additional filtering of particles entrained in the water occurs. The water output from the module  46  is then fed through the valve  56  into the sterilisation module  48  as shown at step  82 . In the sterilisation module  48 , the water is exposed to ultraviolet light via the UV unit of the module  48  to undergo at least partial sterilisation. 
     Treated water is charged from the sterilisation module  48  into the storage tank  50  as shown at  84 . 
     Another advantage of pulsing water out of the carbon filter  12  is that the UV unit of the sterilisation module  48  can be retained in an energised state. The lifespan of such a UV unit is reduced by continuously cycling it on and off. Further, retaining the UV unit energised also reduces the lifespan of the UV unit since it is likely to overheat. Pulsing water from the carbon filter  12  through the UV unit keeps the unit cool while maintaining it energised. This has the overall effect of extending the lifespan of the UV unit of the sterilisation module  48  and reduces maintenance costs of the system  10 . 
     In addition, the aerobic biological activity within the carbon filter  12  increases its performance generally and maintaining the activated carbon  20  in a moist condition extends the lifespan of the carbon filter  12 . The applicant has found that the lifespan of the carbon filter can be extended by between 10 and 50 times if the activated carbon  20  of the filter  12  is exposed to biological activity and retained in a moist condition. 
     It will be appreciated that the filtration system  10  is intended to be used in a domestic dwelling or small premises where maintenance of the system should be kept as low as possible. Ideally, the system  10  should operate in an almost “set-and-forget” manner. By extending the operating life of the carbon filter  12 , the pleated filter of the particle filtration module  46  and the UV unit of the sterilisation module  48 , the need for maintenance of the system  10  is significantly reduced. This, therefore, benefits an operator of the system  10  in that the operator need pay less attention to maintaining the system than would otherwise be the case. 
     It is a further advantage of the disclosure that a method of operating a filter  12  and filtration system  10  are provided which improves the filtering efficiency of the filter  12  and the system  10  thereby improving the overall purification of waste water treated in the system  10 . The likelihood of malodorous conditions arising are also greatly reduced and the risk of contaminating subsequent batches of water to be treated is also significantly reduced. 
     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.