Patent Publication Number: US-2020283311-A1

Title: Apparatus for disinfecting a fluid

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/815,029, filed Mar. 7, 2019, which is incorporated herein by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates to an apparatus for disinfecting a fluid such as water. 
     BACKGROUND OF THE DISCLOSURE 
     Drinking water typically requires disinfection before it can be delivered to users. For example, in the aviation industry, water stored onboard an aircraft may be disinfected prior to delivery to the crew and passengers. For example, the stored water may be pumped through a disinfection reactor before being delivered to one or more faucets. As the water flows through the reactor, it is exposed to ultraviolet (UV) light from one or more UV-light sources, and is therefore disinfected. 
     Prior art disinfection reactors have generally relied on mercury lamps to disinfect water. More recently, light-emitting diodes (LEDs) have come to replace such lamps, in part due to their lower cost and increased energy efficiency. LEDs, however, typically generate substantial amounts of heat during operation, and require cooling in order to be operated for extended periods of time. Insufficient cooling may risk the LEDs overheating, whereas operating the LEDs at a lower power to mitigate the risk of overheating may result in inadequate disinfection. 
     The present disclosure relates to improvements in a UV-LED-based disinfection apparatus. 
     SUMMARY OF THE DISCLOSURE 
     According to a first aspect of the disclosure, there is provided an apparatus for disinfecting a fluid, comprising: a housing comprising: a fluid inlet for inflow of a fluid to be disinfected; and a fluid outlet for outflow of the fluid to be disinfected; and one or more light-emitting diodes (LEDs) operable to emit ultraviolet (UV) light for disinfecting the fluid to be disinfected, wherein fluid flow path extends from the fluid inlet to the fluid outlet and is configured such that, when the fluid to be disinfected flows along the fluid flow path, the fluid to be disinfected flows sufficiently close to the one or more LEDs so as to absorb heat generated by the one or more LEDs. 
     The one or more LEDs may be mounted on one or more substrates, and the one or more substrates may define a boundary of at least a portion of the fluid flow path such that, when the fluid to be disinfected flows along the fluid flow path, the fluid to be disinfected flows in contact with the one or more substrates. The one or more substrates may comprise one or more printed circuit boards (PCBs). 
     The one or more LEDs may be mounted on one or more substrates, the apparatus may further comprise a conductive member on which are provided the one or more substrates, and the conductive member may define a boundary of at least a portion of the fluid flow path such that, when the fluid to be disinfected flows along the fluid flow path, the fluid to be disinfected flows in contact with the conductive member. 
     A distance between the one or more portions of the fluid flow path and the one or more LEDs may be configured such that, when the fluid to be disinfected flows along the fluid flow path, at least about 90% of heat generated by the one or more LEDs is absorbed by the fluid to be disinfected. 
     One or more of the following may be selected such that, when the fluid to be disinfected flows along the fluid flow path, the fluid to be disinfected is disinfected at a rate of at least about 16 mJ/cm 2  at 90% UV transmissivity of the fluid: a length of the fluid flow path; a setting of a flow regulator for controlling a rate of flow of the fluid to be disinfected; and a power output of the one or more LEDs. 
     The apparatus may further comprise one or more baffles defining one or more portions of the fluid flow path such that the fluid flow path comprises one or more first branches extending in a first direction, and one or more second branches extending in a second direction opposite the first direction. The one or more baffles may further define one or more annular spaces within the housing. The one or more annular spaces may be concentric. 
     The one or more baffles may be configured such that, when the fluid to be disinfected flows along the fluid flow path, the fluid to be disinfected flows from a near end to an opposite far end of a first one of the one or more annular spaces, and then from a far end to an opposite near end of a second one of the one or more annular spaces. 
     The one or more annular spaces may comprise a sequence of annular spaces, and the one or more baffles may be configured such that, when the fluid to be disinfected flows along the fluid flow path, the fluid to be disinfected flows sequentially from one annular space to the next annular space in the sequence of annular spaces. 
     The one or more baffles may be configured such that a direction of the fluid flow path is reversed at least once. 
     The one or more baffles may comprise one or more portions that are at least partially transparent to UV light. 
     The one or more LEDs may define one or more light beams, and: one or more first portions of the fluid flow path may not pass through the one or more light beams; and/or one or more second portions of the fluid flow path may pass through the one or more light beams. 
     One or more first portions of the fluid flow path may pass behind the one or more LEDs such that, when the fluid to be disinfected flows along the one or more first portions of the fluid flow path, the fluid to be disinfected flows sufficiently close to the one or more LEDs so as to absorb, from behind the one or more LEDs, heat generated by the one or more LEDs. 
     One or more second portions of the fluid flow path may pass in front of the one or more LEDs such that, when the fluid to be disinfected flows along the one or more second portions of the fluid flow path, the fluid to be disinfected flows sufficiently close to the one or more LEDs so as to absorb, from in front of the one or more LEDs, heat generated by the one or more LEDs. 
     The fluid flow path may be further configured such that, when the fluid to be disinfected flows along the fluid flow path, the fluid to be disinfected flows sequentially from the fluid inlet, to the one or more first portions of the fluid flow path, to one or more second portions of the fluid flow path, and to the fluid outlet. The fluid flow path may be further configured such that, when the fluid to be disinfected flows along the fluid flow path, the fluid to be disinfected flows further via the one or more annular spaces when flowing from the one or more first portions of the fluid flow path to the one or more second portions of the fluid flow path. 
     The apparatus may further comprise: a window at least partially transparent to UV light, positioned in front of the one or more LEDs; and a conductive material positioned between the one or more LEDs and the window. The conductive material may comprise a thermally conductive foam. The conductive material may be in contact with the one or more LEDs and the window. 
     The window may define a boundary of at least a portion of the fluid flow path such that, when the fluid to be disinfected flows along the fluid flow path, the fluid to be disinfected flows in contact with the window. 
     The fluid inlet may be off-axis relative to the one or more LEDs. 
     The housing may comprise a reflective surface for reflecting UV light. For example, the housing may be formed of a material reflective to UV light. 
     The apparatus may further comprise a controller configured to control the one or more LEDs. The controller may be further configured to gradually increase and/or decrease a current drawn by at least one of the one or more LEDs. 
     The one or more LEDs may comprise multiple LEDs, and the controller may be further configured to sequentially activate and/or deactivate the LEDs. 
     The controller may be further configured to activate an alarm in response to determining that a disinfection rate, or a UV transmissivity of the fluid, has dropped below a preset threshold. The controller may be further configured to determine whether the disinfection rate, or the UV transmissivity, has dropped below the preset threshold based on one or more of: a flow rate of the fluid to be disinfected; an intensity of UV light reflected from the housing; a duration that the one or more LEDs have been operated for; and a power output of the one or more LEDs. 
     The controller may comprise: circuitry; or one or more processors communicative with memory having stored thereon computer program code executable by the one or more processors. 
     The controller may be further configured to: determine an intensity of UV light having passed through a fluid flowing through the apparatus; determine whether the measured intensity is outside a threshold window; and if the measured intensity is outside the threshold window, adjust a current driving the one or more LEDs. 
     The one or more LEDs may comprise multiple groups of LEDs, each group of LEDs may comprise one or more LEDs, and the controller may be further configured to, after determining that the measured intensity is outside the threshold window and before adjusting the current: sequentially drive each group of LEDs; and for each group of LEDs, determine whether a power output of at least one of the LEDs in the group of LEDs is less than an expected power output; and if the power output of the at least one of the LEDs is less than the expected power output, then the adjusting of the current driving the one or more LEDs is based on the power output of the at least one of the LEDs, to compensate for the power output of the at least one of the LEDs; and if the power output of the at least one of the LEDs is not less than the expected power output, then the controller is further configured to adjust a UV transmissivity value of the fluid, and wherein the adjusting of the current driving the one or more LEDs is based on the adjusted UV transmissivity value, to compensate for the adjusted UV transmissivity value. 
     Determining whether the power output of the at least one of the LEDs is less than an expected power output may comprise: determining with the controller an intensity of UV light having passed through a fluid flowing through the apparatus; and determining with the controller whether the measured intensity of UV light is below an expected threshold. 
     If compensating for the adjusted UV transmissivity value or the power output of the at least one of the LEDs would require the current driving the one or more LEDs to be increased beyond a maximum driving current, then the controller may be further configured to activate an alarm. 
     The apparatus may further comprise one or more sensors for detecting an intensity of UV light that has passed through a fluid flowing through the apparatus, and/or that has been reflected from the housing. 
     The apparatus may further comprise a flow regulator for controlling a flow of the fluid to be disinfected through the apparatus. 
     The apparatus may further comprise a flow sensor for detecting a flow rate of the fluid to be disinfected through the apparatus. 
     The apparatus may not comprise any additional means for cooling the one or more LEDs. The additional means may comprise a separate fluid inlet and a separate fluid outlet for receiving a separate coolant for cooling the one or more LEDs. The additional means may comprise a heatsink. 
     The apparatus may further comprise one or more baffles defining one or more portions of the fluid flow path, and each baffle may comprise one or more apertures formed therein. The one or more baffles may comprise a sequence of baffles comprising a sequence of one or more disc-shaped baffles and one or more annulus-shaped baffles, each disc-shaped baffle may comprise one more peripherally-located apertures, and each annulus-shaped baffle may comprise a centrally-located aperture. In the sequence of baffles, the one or more disc-shaped baffles may alternate with the one or more annulus-shaped baffles. 
     In a further aspect of the disclosure, there is provided a method of disinfecting a fluid, comprising: providing an apparatus comprising: a housing comprising: a fluid inlet; and a fluid outlet; and one or more light-emitting diodes (LEDs) operable to emit ultraviolet (UV) light, wherein a fluid flow path extends from the fluid inlet to the fluid outlet and is configured such that, when a fluid flows along the fluid flow path, the fluid flows sufficiently close to the one or more LEDs so as to absorb heat generated by the one or more LEDs; flowing a fluid from the fluid inlet to the fluid outlet, via the fluid flow path; and operating the one or more LEDs. 
     In a further aspect of the disclosure, there is provided a method of operating one or more light-emitting diodes (LEDs) in a fluid disinfection apparatus, the one or more LEDs being operable to emit ultraviolet (UV) light, the method comprising: measuring an intensity of UV light having passed through a fluid flowing through the apparatus; determining whether the measured intensity is outside a threshold window; and if the measured intensity is outside the threshold window, adjusting a current driving the one or more LEDs. 
     The one or more LEDs may comprise multiple groups of LEDs, each group of LEDs may comprise one or more LEDs, and the method may further comprise, after determining that the measured intensity is outside the threshold window and before adjusting the current: sequentially driving each group of LEDs; and for each group of LEDs, determining whether a power output of at least one of the LEDs in the group of LEDs is less than an expected power output; and if the power output of the at least one of the LEDs is less than the expected power output, then the adjusting of the current driving the one or more LEDs is based on the power output of the at least one of the LEDs, to compensate for the power output of the at least one of the LEDs; and if the power output of the at least one of the LEDs is not less than the expected power output, then adjusting a UV transmissivity value of the fluid, and wherein the adjusting of the current driving the one or more LEDs is based on the adjusted UV transmissivity value, to compensate for the adjusted UV transmissivity value. 
     Determining whether the power output of the at least one of the LEDs is less than an expected power output may comprise: measuring an intensity of UV light having passed through a fluid flowing through the apparatus; and determining whether the measured intensity of UV light is below an expected threshold. 
     If compensating for the adjusted UV transmissivity value or the power output of the at least one of the LEDs would require the current driving the one or more LEDs to be increased beyond a maximum driving current, then the method may further comprise activating an alarm. 
     Throughout the disclosure, the term fluid inlet encompasses more than one fluid inlet, and the term fluid outlet encompasses more than one fluid outlet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the disclosure will now be described in detail in conjunction with the accompanying drawings of which: 
         FIG. 1  is a first cross-sectional view of an apparatus for disinfecting a fluid, according to embodiments of the disclosure; 
         FIG. 2  shows a magnified portion of the apparatus of  FIG. 1 ; 
         FIG. 3  is a second cross-sectional view of the apparatus of  FIG. 1 ; 
         FIG. 4  shows plots of current draw over time for different groups of LEDs, according to embodiments of the disclosure; 
         FIG. 5  shows plots of current draw over time, according to embodiments of the disclosure; 
         FIG. 6  is a flow diagram of a method of operating LEDs, according to embodiments of the disclosure; 
         FIG. 7  is a cross-sectional view of an apparatus for disinfecting a fluid, according to embodiments of the disclosure; and 
         FIGS. 8A and 8B  show cross-sectional and perspective views, respectively, of an apparatus for disinfecting a fluid, according to embodiments of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     The present disclosure seeks to provide an improved apparatus for disinfecting a fluid. While various embodiments of the disclosure are described below, the disclosure is not limited to these embodiments, and variations of these embodiments may well fall within the scope of the disclosure which is to be limited only by the appended claims. 
     The word “a” or “an” when used in conjunction with the term “comprising” or “including” in the claims and/or the specification may mean “one”, but it is also consistent with the meaning of “one or more”, “at least one”, and “one or more than one” unless the content clearly dictates otherwise. Similarly, the word “another” may mean at least a second or more unless the content clearly dictates otherwise. 
     The terms “coupled”, “coupling” or “connected” as used herein can have several different meanings depending on the context in which these terms are used. For example, the terms coupled, coupling, or connected can have a mechanical or electrical connotation. For example, as used herein, the terms coupled, coupling, or connected can indicate that two elements or devices are directly connected to one another or connected to one another through one or more intermediate elements or devices via an electrical element, electrical signal or a mechanical element depending on the particular context. The term “and/or” herein when used in association with a list of items means any one or more of the items comprising that list. 
     As used herein, a reference to “about” or “approximately” a number or to being “substantially” equal to a number means being within +/−10% of that number. 
     Generally, according to embodiments of the disclosure, there is described an apparatus for disinfecting a fluid. The apparatus is designed to permit a fluid that is to be disinfected, such as water that is to be used for drinking, to flow into a housing via one or more fluid inlets (“the fluid inlet”). Within the housing, the fluid flows along a fluid flow path from the fluid inlet to one or more fluid outlets (“the fluid outlet”), whereupon the fluid exits the apparatus. Within the housing are provided one or more LEDs operable to emit light having one or more wavelengths in the UV range. For example, according to some embodiments, the one or more LEDs may be operable to emit light with a wavelength in the range of 260 nm-275 nm. The LEDs and the fluid flow path are configured such that the emitted UV light intersects the fluid flow path at one or more points. Thus, as the fluid flows through the apparatus, it is subjected to the UV light and as a result undergoes disinfection. 
     Depending on the current that is being drawn, LEDs can generate substantial amounts of heat during operation, and therefore often require some form of cooling. In order to cool the LEDs during operation, the fluid flow path is configured so as to bring the fluid within relatively close proximity of the LEDs. In particular, the LEDs may be mounted on one or more printed circuit boards (PCBs) which may be disposed or otherwise in contact with a conductive plate. The conductive plate may define a portion of a boundary of the fluid flow path, such that the fluid is brought into contact with the conductive plate as the fluid flows along the fluid flow path. By coming into contact with the conductive plate, the fluid draws heat away from the LEDs (and away from the PCB on which are mounted the LEDs). In addition, the fluid flow path may be further configured such that the fluid is brought into contact with a window positioned in front of the LEDs. The window may itself be in contact with a conductive material which in turn may be in contact with the LEDs. Thus, heat may be drawn away from the LEDs by fluid flow both from behind and in front of the LEDs. Advantageously, the fluid to be disinfected acts as a coolant. There therefore may be no need for any additional cooling means. 
     In order to facilitate effective disinfection of the fluid, the fluid flow path may be deliberately extended within the housing, through the use of one or more UV-transparent baffles. For example, the direction of the fluid flow path may be reversed or altered by the baffles one or more times such that the fluid flow path is sinusoidally, circuitously, or otherwise tortuously disposed within the housing. In this manner, the fluid is exposed to the UV light for a greater period of time than if the fluid flow path simply took a more direct route from the fluid inlet to the fluid outlet. 
     Embodiments of the disclosure will now be described in more detail. 
     Turning to  FIG. 1 , there is shown a cross-sectional view of an apparatus  100  for disinfecting a fluid. Apparatus  100  comprises a generally cylindrical structure or housing  10  having a fluid inlet  12  at one end thereof and a fluid outlet  14  at an opposite end thereof. Housing  10  is formed of or otherwise comprises a UV-reflective material such as Teflon. 
     Apparatus  100  further includes an LED module  16  housing an LED array comprising multiple groups of one or more LEDs  18 . Each LED  18  is configured to emit UV light in the range of 260 nm-275 nm, although according to some embodiments other suitable UV wavelengths may be used. LEDs  18  are mounted on a first PCB  20  and are operably connected to a controller (not shown) provided on a second PCB  22 . The controller is configured to drive LEDs  18  according to one or more various control methods or algorithms, as described in further detail below. 
     LED module  16  comprises an optical window  24  provided in front of LEDs  18 . According to the present embodiment, optical window  24  comprises quartz, but other suitable materials may be used. Further housed within LED module  16  is a conductive material  26  provided between optical window  24  and LEDs  18 . Conductive material  26  comprises a foam containing a conductive paste. Conductive material  26  extends from LEDs  18  to optical window  24 , and acts to conductively couple LEDs  18  and optical window  24 , thereby facilitating the transfer of heat from LEDs  18  to optical window  24 . 
     A rear of LED module  16  is provided with a conductive member  28  against which is positioned PCB  20 . Conductive member  28  may be, for example, a stainless steel plate. Conductive member  28  and optical window  24  serve to fluidly seal LED module  16 . LED module  16  and its components are shown in more detail in  FIG. 2 . 
     Apparatus  100  further includes multiple cylindrical baffles, and in particular a first cylindrical baffle  30  and a second cylindrical baffle  32 . Baffles  30  and  32  define first and second concentric annular spaces  34  and  36 . Annular spaces  34  and  36  are disposed about a central, cylindrical chamber  38  defined by cylindrical baffle  32 . Chamber  38  is fluidly coupled to fluid outlet  14 . Baffles  30  and  32  are formed of a material, such as quartz, that is largely optically transparent to UV light. 
     Apparatus  100  further includes a flow regulator  44  for controlling a rate of flow of a fluid flowing into apparatus  100  via fluid inlet  12 , and a flow detection port  46  for detecting or sensing a rate of flow of a fluid flowing through apparatus  100 . For example, flow regulator  44  may limit a maximum flow rate of fluid through apparatus  100  to 1 gallon/minute. Apparatus  100  further includes a power and communications connector  50  for coupling PCB  22  to an external power source. 
     Baffles  30  and  32 , in combination with portions of housing  10 , define a fluid flow path extending from fluid inlet  12  to fluid outlet  14 . The fluid flow path is shown in more detail in  FIG. 3 . As can be seen from  FIG. 3 , the fluid flow path extends from fluid inlet  12  to a first, rear chamber  40  located at the rear of LED module  16 , adjacent conductive member  28 . Fluid flowing into apparatus  100  via fluid inlet  12  therefore flows into rear chamber  40 . After entering rear chamber  40 , the fluid is directed via one or more apertures formed within rear chamber  40  to first annular space  34 . The fluid flow path then extends from a near end of annular space  34  to a far end of annular space  34 . In the context of the present embodiment, a near end may be an end closest to LED module  16 , and a far end may be an end furthest from LED module  16 . 
     At the far end of annular space  34 , the fluid flow path extends into adjacently disposed second annular space  36 . The fluid flow path then extends from a far end of annular space  36  to a near end of annular space  36 , whereupon the fluid flow path passes into a second, front chamber  42  located in front of LED module  16 . Thus, fluid flowing out of rear chamber  40  flows into and along annular space  34 , then into and along annular space  36 , and then into front chamber  42 . The fluid flow path then passes into chamber  38  via one or more apertures formed within front chamber  42 , and finally out of apparatus  100  via fluid outlet  14 . Thus, baffles  30  and  32  serve to reverse multiple times a direction of the fluid flow path. 
     As can be seen from the above description and  FIG. 3 , the fluid flow path is configured such that, when the fluid to be disinfected flows along the fluid flow path, the fluid to be disinfected flows adjacent LED module  16  on two separate occasions. In particular, the fluid is brought sufficiently close to LEDs  18  and PCB  20  so as to absorb heat generated by LEDs  18  during their operation. According to some embodiments, a distance of about 1.5 mm separates PCB  20  from rear chamber  40 . 
     By virtue of the fluid flowing within rear chamber  40 , the fluid flows into contact with conductive member  28  and draws heat generated by LEDs  18  through a rear of LED module  16 , via PCB  20  and conductive member  28 . Furthermore, by virtue of the fluid flowing within front chamber  42 , the fluid flows into contact with optical window  24  and draws heat generated by LEDs  18  through a front of LED module  16 , via conductive material  26  and optical window  24 . While optical window  24  may not be particularly conductive, conductive material  26  assists in transferring heat generated by LEDs  18  to the fluid. 
     During operation of LEDs  18 , the fluid is subjected to disinfection by UV light emitted from LEDs  18 . Furthermore, by virtue of baffles  30  and  32 , a duration during which the fluid flowing through apparatus  100  is subjected to UV light may be increased when compared to when the fluid flow path takes a more direct route from fluid inlet  12  to fluid outlet  14 . Baffles  30  and  32  are substantially transparent to UV light, and therefore the fluid undergoes disinfection as it flows along annular spaces  34  and  36 . 
     In  FIG. 3 , portions of the fluid flow path that pass through rear and front chambers  40  and  42  (and therefore are associated with cooling) are shown in blue arrows, and portions of the fluid flow path that pass through first and second annular spaces  34  and  36 , and through chamber  38  (and therefore are associated with disinfection), are shown in green arrows. Fluid flowing in contact with optical window  28  provides both a cooling function as well as simultaneously undergoing disinfection. 
     According to embodiments described herein, a majority, such as about 90% or more, of heat generated by LEDs  18  may be absorbed by the fluid flowing through apparatus  100 . To adjust the cooling effect of the fluid on LEDs  18 , various parameters of apparatus  100  may be varied. For example, the total length of the fluid flow path may be adjusted, as well as the power output by LEDs  18 , the rate of flow of the fluid through apparatus  100 , and a temperature of the fluid entering apparatus  100 . 
     As mentioned above, LEDs  18  are controlled by a controller provided on PCB  22 . The controller may comprise circuitry configured to perform any of the methods described below, and/or may comprise a microprocessor or similar device that is communicative with memory on which are stored the instructions for performing any of the methods described below. 
     According to some embodiments, the controller is configured to sequentially activate and deactivate one or more groups of LEDs  18 , using for example pulse width modulation (PWM). As can be seen in  FIG. 4 , the LED array comprises groups of LEDs  18  (each group comprising one or more individual LEDs  18 ). Each group of LEDs  18  is asynchronously activated relative to the other groups of LEDs  18 . Additionally, each group of LEDs  18  is asynchronously deactivated relative to the other groups of LEDs  18 . Asynchronously activating and/or deactivating the LED groups in this fashion reduces the magnitude of current transients during activation/deactivation of the LED groups. 
     For example, as can be seen at the bottom of  FIG. 4 , the average current drawn when asynchronously activating and deactivating the LED groups is similar to the average current that is drawn when all LED groups are synchronously activated and deactivated. However, the average rate of change of current that is drawn is less when asynchronously activating and deactivating the LED groups. Reducing current transients in this fashion may reduce the effect of electromagnetic interference such as harmonic distortion. 
     Turning to  FIG. 5 , there is shown another method of controlling the LED array. According to this method, the current used to drive an LED  18  is gradually adjusted. For example, an LED  18  or multiple LEDs  18  may be first driven with 50% of a total current, then 75% of the total current, then 90% of the total current, and lastly 100% of the total current. Thus, the rate of change of current is reduced, similarly to the method described in connection with  FIG. 4 . The method of  FIG. 5  may be combined with that of  FIG. 4 . 
     The controller may be communicatively coupled to an alarm (not shown) for alerting a user when a disinfection rate of the fluid decreases below a certain threshold. The disinfection rate will depend on various factors, such as the UV transmissivity of the fluid, the power output by the LED array, and the duration the fluid is exposed to UV light within apparatus  100 , which itself may be a function of the length of the fluid flow path as well as the rate of flow of the fluid through apparatus  100 . 
     In order to determine whether the disinfection rate is too low, the controller may evaluate various factors, such as the effective power output of LEDs  18  and the rate of flow of fluid through apparatus  100 . The effective power output of an LED will naturally decay through extended use, and the controller may be configured to estimate or determine this decay by measuring an intensity of UV light reflected by housing  10 . For example, apparatus  100  may include one or more UV sensors communicative with the controller and configured to detect and output a reading of the intensity of UV light reflected by housing  10 . In combination with the rate of fluid flow through apparatus  100 , which may be determined from flow detection port  46 , the controller may determine a disinfection rate of apparatus  100 . The disinfection rate may be any value or parameter that relates to the effectiveness of disinfection by apparatus  100 . Once the disinfection rate is determined to be too low, the controller may activate an alarm. Such an alarm may notify a user that, for example, the LEDs are in need of replacing. 
     Furthermore, the controller may be configured to regulate the power output of LEDs as a function of the flow rate of the fluid as detected by flow detection port  46 . In particular, the output of flow detection port  46  may be read by the controller, and the controller may adjust the power output of LEDs as a function of the reading. For example, if flow detection port  46  detects a drop in the flow rate of the fluid, then the controller may correspondingly lower the power output of LEDs. Similarly, if flow detection port  46  detects an increase in the flow rate of the fluid (up to the maximum allowable as set by flow regulator  44 ), then the controller may correspondingly increase the power output of LEDs. 
     The disinfection rate may also depend on the UV transmissivity of the fluid, and the controller may be further configured to adjust the power output of LEDs  18  as a function of the UV transmissivity. Turning to  FIG. 6 , there is shown a flow diagram of an example method that may be performed by the controller, according to embodiments of the disclosure. 
     At block  60 , the controller drives the LEDs groups. At block  61 , the controller determines an intensity of UV light that has passed through the fluid, that has been reflected from housing  10 , and that has been detected by one or more UV sensors communicating with the controller. At block  62 , the controller determines whether the measured intensity is outside a threshold window (e.g. a range of acceptable or expected UV intensities, for a given UV transmissivity of the fluid). If the measured intensity is within the threshold window, then the process returns to block  60 . If the measured intensity is outside the threshold window, then the controller determines whether one or more of the LED groups (or one or more individual LEDs) are operating below their nominal decay rate (e.g. whether their effective power output is decaying more rapidly than expected due to extended use). 
     In order to do this, the controller may sequentially activate each LED group and determine, using the one or more UV sensors, whether the measured UV intensity of each LED group is within an acceptable range of UV intensities. If, for one or more of the LED groups, the measured intensity is outside the acceptable range of UV intensities, then the controller determines that those LED groups are decaying more rapidly than expected, and are contributing to the drop in measured intensity of UV light reflected by housing  10 . Thus, at block  68 , the controller increases a current driving the LED array in order to compensate for the faster-than-expected decay in power output of any such LED groups. At block  69 , the controller determines whether, given the current UV transmissivity, it is impossible to compensate for the faster-than-expected decay in power output, for example if compensating for the faster-than-expected decay in power output would require a current driving the LED array to be increased above an upper limit. If the controller determines that it is impossible to compensate for the faster-than-expected decay in power output, then at block  67  the controller activates an alarm to warn a user. Therefore, the controller alerts the user that, given the current UV transmissivity of the fluid, and the maximum available power output of the LED array, it is not possible to sustain a minimum required disinfection rate. 
     Returning to block  63 , if, for each LED group, the measured intensity is within the acceptable range of UV intensities, then the controller determines that the UV transmissivity of the fluid has decreased (e.g. the fluid has become more opaque to UV light). Thus, at block  64 , the controller adjusts a UV transmissivity value for the fluid, and at block  65  the controller adjusts a current driving the LED array in order to compensate for the decreased UV transmissivity. At block  66 , the controller determines whether it is impossible to compensate for the decreased UV transmissivity, for example if compensating for the decreased UV transmissivity would require a current driving the LED array to be increased above an upper limit. If the controller determines that it is impossible to compensate for the decreased UV transmissivity, then at block  67  the controller activates an alarm (assuming the UV transmissivity has dropped below a certain threshold). Therefore, the controller alerts the user that, given the current UV transmissivity of the fluid, and the maximum available power output of the LED array, it is not possible to sustain a minimum required disinfection rate. 
     According to some embodiments, LEDs  18  may be operated so as to obtain a disinfection rate of at least 16 mJ/cm 2  at 90% UV transmissivity, and according to some embodiments may be operated so as to obtain a disinfection rate of at least about 19 mJ/cm 2  at 90% UV transmissivity. 
     Turning to  FIGS. 6, 7A, and 7B , there are shown other embodiments of the disclosure, in which the baffles may be shaped differently. For example, as can be seen in  FIG. 7 , apparatus  200  does not include a rear chamber, but instead only uses a front chamber for cooling the LED array. In particular, fluid flowing into apparatus  200  via fluid inlet  12  is directed, by cylindrical baffles  30  and  32 , along a first annular space  34  according to a first direction, subsequently along a second annular space  36  according to a second direction opposite the first direction, and then into a central chamber  38  according to the first direction. As the fluid passes from annular space  36  to chamber  38 , the fluid comes into contact with LED module  16 , and may absorb heat generated by the LEDs housed within LED module  16 , for example by flowing into contact with an optical window provided in the front of LED module  16  (similarly to the embodiment of  FIG. 1 ). Baffles  30  and  32  comprise an optically transparent material so that the fluid may undergo disinfection before reaching chamber  38 . 
     A further embodiment of an apparatus  300  for disinfecting a fluid is shown in  FIGS. 8A and 8B . In this embodiment, the baffles are shaped as discs  30  and  32 . The discs include annular discs  30  comprising central apertures  31  formed therein, and discs  32  with peripheral apertures  33  formed therein. Fluid flowing from the fluid inlet to the fluid outlet passes first via central aperture  31  of a first disc  30 , subsequently through peripheral apertures  33  of a second disc  32 , subsequently through central aperture  31  of a third disc  30 , and subsequently through peripheral apertures  33  of a fourth disc  32 . Thus, the fluid effects multiples passes before exiting apparatus  300 . 
     As the skilled person will appreciate, there exists a multitude of different shapes and designs that the apparatus may embody. For example, the fluid flow path may be altered or otherwise adjusted, for instance by repositioned, omitting, or providing additional baffles. The embodiments shown and described herein represent merely some examples of how the apparatus may be designed. 
     Furthermore, in some embodiments, the fluid flow path may be configured such that the fluid is brought into direct contact with the PCB or other substrate on which the LEDs are mounted (for example by omitting the conductive member that separates the fluid from the PCB). In still other embodiments, the fluid flow path may be configured such that the fluid is brought into direct contact with the LEDs themselves (for example by omitting the optical window and the conductive material that separate the fluid from the LEDs). 
     With this in mind, while the disclosure has been described in connection with specific embodiments, it is to be understood that the disclosure is not limited to these embodiments, and that alterations, modifications, and variations of these embodiments may be carried out by the skilled person without departing from the scope of the disclosure. It is furthermore contemplated that any part of any aspect or embodiment discussed in this specification can be implemented or combined with any part of any other aspect or embodiment discussed in this specification.