CLAIM OF PRIORITY

This application claims the benefit of U.S. Patent Application Serial No. 62/745,888, filed on October 15, 2018. The entire contents of the foregoing are hereby incorporated by reference.

TECHNICAL FIELD

This disclosure relates to backwashing of ceramic membranes.

BACKGROUND

Membrane filtration offers a barrier for removing particles from liquids, including viruses, bacteria and protozoans as well as suspended solids (clays, silts and mineral precipitates). In general, membrane filtration is a pressure-driven filtration process where one feed or input stream is split into a filtered or“permeate” stream and a concentrated or“retentate” stream. Filtration membranes can be made from polymeric materials like polysulfone, or from ceramic materials.

Generally, membrane fouling is caused by the deposition of the filtered organic and inorganic particles on the membrane. In general, membrane fouling is associated with a loss of permeability of the membrane due to accumulation of these feed solids on or within a membrane’s pores. For water filtration, automated periodic backwashing can be used to control the rate of membrane fouling within acceptable limits, however backwash results in downtime and increased operating cost, along with decreased throughput and useful membrane life.

SUMMARY

This disclosure is based, in part, on the realization that evacuation of water from ceramic pore channels within a ceramic membrane prior to backwash cleaning beneficially improves the overall water filtration process by reducing the amount of filtered water wasted during the cleaning. A backwash flush forces already -filtered water or permeate through the pores of a membrane from the outside in (e.g., in the reverse direction from normal filtration), causing the pores to be cleaned. Permeate is used for a backward flush because it is located on the clean side of the membrane filtration barrier and is free of contaminants. Backwashing decreases recovery (the factor indicating the amount of filtered water production), so it is desirable to minimize the backwash time while maintaining the flow long enough to fully flush the volume of the filtration module at least once.

In some embodiments, a method of using a ceramic filtration system which comprises a feed channel and a ceramic membrane, the method comprising supplying liquid into the ceramic filtration system via the feed channel such that the liquid passes through the ceramic membrane in a first direction to become permeate separated from the feed channel by the ceramic membrane, stopping supplying of the liquid in the first direction, removing the liquid from the feed channel while introducing gas into the feed channel, and after removing the liquid from the feed channel, forcing the permeate in a second direction opposite the first direction across the ceramic membrane and into the feed channel.

The methods may include one or more of the following features: flushing the feed channel by supplying additional liquid into the ceramic filtration system at a rate 1-2 times a rate used when supplying the liquid to become permeate and removing the additional liquid from the filtration system such that the additional liquid does not cross the membrane. The ceramic filtration system includes a pump fluidly coupled with a first valve, and forcing the permeate in a second direction opposite the first direction across the ceramic membrane includes opening a second valve to remove liquid from the feed channel. Continuing forcing the permeate in a second direction opposite the first direction across the ceramic and past an outlet valve for a predetermined period of time and then resuming supplying liquid into the ceramic filtration system via the feed channel. Stopping supplying of the liquid in the first direction comprises detecting a pressure or differential pressure within the ceramic filtration system, and subsequently forcing the permeate in the second direction when the detected pressure or differential pressure reaches a predetermined maximum. Supplying liquid into the ceramic filtration system occurs under conditions where the feed flow rate equals a permeate flow rate. Supplying liquid into the ceramic filtration system occurs under conditions where the feed flow rate is greater than a permeate flow rate. Supplying liquid into the ceramic filtration system occurs under conditions where the liquid is recirculated through the feed channel such that a rate of supplying the liquid is greater than a rate the liquid passes through the ceramic membrane. Determining feed pressure data and time since a previous cleaning procedure. The permeate is drinking water. The liquid is wastewater. The feed channel comprises a plurality of feed channels. Removing the liquid comprises removing at least_eighty percent of the liquid from the feed channel. Forcing the permeate in the second direction for less than 60 seconds at a set point of at least 100 gallons per day per square foot of membrane. The liquid is removed from the feed channel for less than 30 seconds. Removing the liquid from the feed channel while introducing gas into the feed channel comprises draining the liquid from the feed channel by gravity. Removing the liquid from the feed channel while introducing gas into the feed channel comprises pumping compressed gas into the feed channel. The compressed gas is air. The gas is air. Removing the liquid from the feed channel while introducing gas into the feed channel for a preselected time interval. The preselected time interval is up to 30 seconds. The preselected time interval is up to 15 seconds. Measuring a rate at which the liquid is removed from the feed channel, and forcing the permeate in a second direction when the measured rate reaches a threshold value. Forcing the permeate in the second direction such that a peak flow rate is reached within two seconds.

In some embodiments, a computer-readable medium comprises instructions that when executed by a processor perform a method of using a ceramic filtration system which comprises a feed channel and a ceramic membrane, comprising supplying liquid into the ceramic filtration system via the feed channel such that the liquid passes through the ceramic membrane in a first direction to become permeate separated from the feed channel by the ceramic membrane, stopping supplying of the liquid in the first direction, removing the liquid from the feed channel while introducing gas into the feed channel; and after removing the liquid from the feed channel, forcing the permeate in a second direction opposite the first direction across the ceramic membrane and into the feed channel.

In some embodiments, a system comprises a ceramic filtration system, a pump in fluid communication with the ceramic filtration system, and a computing device in communication with the pump and the ceramic filtration system, the computing device configured to direct a method of using the ceramic filtration system which comprises a feed channel and a ceramic membrane, the method comprising supplying liquid into the ceramic filtration system via the feed channel such that the liquid passes through the ceramic membrane in a first direction to become permeate separated from the feed channel by the ceramic membrane, stopping supplying of the liquid in the first direction, removing the liquid from the feed channel while introducing gas into the feed channel; and after removing the liquid from the feed channel, forcing the permeate in a second direction opposite the first direction across the ceramic membrane and into the feed channel.

Polymeric and ceramic membranes have been used to remove a wide range of contaminants from various fluids. For example, treating wastewater, surface water, ground water, seawater, and producing drinking water. Ceramic membranes have benefits relative to polymeric membranes with respect to lifetime, stability to high temperatures, ability to operate at high pressures, and resistance to a wide range of chemicals. However, they are relatively complex and expensive systems compared to polymer systems.

Ceramic membranes typically have a ceramic mass with a number of feed channels running along the membrane length. Such ceramic membranes are sometimes referred to as honeycomb designs due to the hexagonal arrangement of channels. The channels are coated with a separating layer and the feed water flows into these channels, with the treated water exiting the outside of the module.

Ceramic membranes are typically run more aggressively than polymeric membranes, leading to a more rapid deposition of foulants on the membrane surface in comparison to a polymeric membrane.

Since higher backwash pressures are more effective at removing foulants than low pressures to clean a membrane effectively it is desirable to increase the backwash ramp, e.g., reverse the flow at high pressure and flow rates. Polymeric membranes would be damaged by a sudden increase in pressure. Thus, ceramic systems that can withstand high pressures have used high pressure back pulses that hit the membrane with a pressure wave over a very short period of time at above several bars. Typical ceramic membrane systems often use compressed air as a motive force for a high initial backwash rate and high backwash flux; however, the cost of the compressed air system and associated piping is very high. The systems and methods described herein allow as effective cleaning or backwashing as does a system using compressed air as the motive force, but the cost of the system is much lower as it uses conventional plastic piping and pumps as does a polymeric membrane system.

Other advantages accrue from the lack of resistance from water flow on the feed side of the filter; the speed at which the backflow process initiates is greatly increased compared to typical water-filled systems since the back-flowing permeate need not clear the channel or push against the pressure of the channel water.

Additionally, pushing permeate through the membrane to the empty or near-empty feed side causes turbulence in the flow, which enhances the membrane cleaning. Advantageously, the overall product water wasted is reduced, without a significant increase in cleaning time. Additionally, the pressure is lowered.

The details of one or more embodiments of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a system diagram of a ceramic filtration system.

FIG. 2 is a depiction of an exemplary cross section of a ceramic filter.

FIGS. 3A-C is a schematic illustration of ceramic backwashing.

FIGS. 4A-C are schematics illustrating steps for ceramic backwashing.

FIG. 5 is a flow chart showing steps for ceramic backwashing.

FIG. 6 is a block diagram of computing devices and systems used to implement ceramic backwashing.

FIGS. 7A-C are graphs showing results of experimental testing of a ceramic backwashing filter.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

In normal forward ceramic filtration, dirty water is fed into a filtration module and filters through to the clean side of the membrane to create clean permeate. A typical backwashing method involves stopping this normal filtration mode and reversing the direction of flow to push permeate from the clean side of the membrane through to the dirty side of the membrane, thereby removing retained suspended solids on the membrane surface, and flushing them to a discharge line.

The speed at which the backwash water reaches its top backwash flow rate is slowed by water resistance in the ceramic membrane’s feed channels. This slowing of the water causes some areas of the ceramic membrane, e.g., areas that first contact the flow, to be cleaned first. Once resistance at an area of the membrane has been reduced by cleaning, the continued backwash water flow preferentially flows through these cleaned areas and much less flows through the still-remaining dirty areas of the membrane. The overall backwash is thus less effective.

In the methods and systems described herein, the entire membrane is cleaned more effectively by increasing the backwash ramp, e.g., increasing the rate of change of the speed of the backwash flow. This increase results in improved transmembrane pressure (TMP) by reduced fouling buildup, and a reduction in chemical cleaning events. TMP is the difference between the average feed pressure and the permeate pressure, or the pressure gradient of the membrane. The feed pressure is often measured at the initial point of a membrane module, although this pressure does not exactly equal the average feed pressure since the flow through a membrane causes hydraulic pressure losses.

Using this method of hydraulic cleaning, the internal feed flow channels from the ceramic membrane module configured for inside (dirty or feed side) to outside (clean or permeate side) hydraulic flow are drained so that the clean side of the membrane module remains full of permeate and the feed side of the membrane module is emptied of water. Once the feed side contains primarily atmospheric air, a backwash pump pushes clean permeate under pressure from the clean side of the membrane module back into the empty feed channels and then out of the module and to a drain. The backwash flow of water reaches the targeted rate of flow much more quickly when the feed channels of the membrane module are empty as there is no resistance to the water flow when it passes from the clean side of the membrane to the dirty feed side of the membrane due to the feed channels being evacuated.

FIG. 1 illustrates a filtration system 100 for water filtration using a ceramic filtration module 102. The system 100 includes an input of feed water from a feed water source 104 that is pumped in a first direction by a feed pump 106 to the ceramic filtration module 102. The feed water may be pumped to the top or to the bottom of the ceramic filtration module 102. The system 100 also includes a permeate storage 108 that receives the permeate once filtered through the ceramic filtration module 102, controlled, for example by a valve VI. The permeate storage 108 has an output connected to a permeate pump 110 that empties the“clean” fluid stored in the permeate storage 108 and sends it downstream for use. The permeate storage 108 also has a backwash outlet connected to a backwash pump 114 and associated valve V2. Appropriate control (e.g., by a controller 120) of the backwash pump 114 and the valves VI, V2 allows permeate in the permeate storage 108 to return to the ceramic filtration module 102. In the example shown, valve VI and valve V2 are separate valves, however in some instances the two valves may be a single valve and a single fluid line fluidly connects the ceramic filtration module 102 to the permeate storage 108. The backwash pump 114 may be placed along this single fluid line, or in some embodiments, reversal of the direction of the feed pump 106 can cause the clean fluid in the permeate storage to flow back across the membrane inside the ceramic filtration module 102.

The period during which a filtration module performs filtration is called filtration time and the period during which a module is cleaned is called cleaning time. It is desirable to maximize filtration time and minimize cleaning time as when a membrane is cleaned with backflow of permeate, the production of filtered water is discontinued and lowers production. In some embodiments, the ceramic membrane is used in dead end mode where the feed flow rate equals the permeate flow rate. In other embodiments, the ceramic membrane is used in low crossflow mode with a small amount of crossflow and the feed flow up to twice the permeate flow rate.

FIG. 2 shows a partial cross section schematic through a portion of the ceramic filtration module 102. Water enters the ceramic filtration module 102 and travels through the channels 202. When dead-end filtration takes place, all the water that enters the ceramic filtration module 102 to travel through the channels 202 and contact the membrane surface 204 is pressed through the membrane 206. Solid foulants or particles 208 will stay behind on the membrane surface 204 while water flows through according to the pore size of the membrane 206. As the particles 208 (sometimes referred to as“cake”) accumulate on the membrane surface 204, the feed water will experience a greater resistance to passing through the membrane 206 to become part of the permeate 210. When the feed water pressure (e.g., from feed water source 204 in FIG. 1) is continual, this resistance will result is a decreasing flux (e.g., decreasing flow rate of permeate per unit membrane surface area, proportional to the TMP and the membrane permeability) over time, requiring cleaning of the membrane 206. The filtration module is temporarily out of order during the cleaning process. As a result, dead-end management is a discontinuous process.

Dead-end management is used because the energy loss is less than in cross- flow filtration where the feed water is recycled, or recirculated. Here, only a small part of the feed water crosses the membrane 206 to generate permeate 210, with the majority of the water leaving the module. The feed water flow is parallel to the membrane and relatively high, resulting in high flowing forces that dislodge and carry away particles 208. Due to the recirculation, cross-flow filtration has a high energy cost.

Referring back to FIG 1, the filtration system 100 includes a drain pump 116. While the backwash pump 114 and valves VI and V2 act to remove permeate from the permeate side of the ceramic filtration module, the drain pump 116 and its associated valve V3 act to remove water from the unfiltered part of the ceramic filtration module 102 (e.g., from inside channels 202). The drain pump 116 can pump water to a drain or waste container 118. For cross-flow filtration, the drain pump 116 may feed water back to the feed water source 104 for recirculation through the filtration module 102.

The filtration system 100 also includes an air valve V4. The air valve V4 is fluidly connected to the channels 202, and allows atmospheric air to enter the channels 202. When drain pump 116 is activated and valve V3 is opened in addition to air valve V4, water can be removed from the channels 202 and air flushed down through the channels 202.

A controller 120 (shown highly schematically) regulates the actions of the filtration system 100. The controller 120 is connected to the various pumps (e.g., feed pump 106, permeate pump 110, backwash pump 114, and drain pump 116) and valves (e.g., V1-V4) as is known in the art. The controller 120 can automatically control operations of the various system components, for example, controlling speed and direction of the pumps, timing of opening and closing of the valves, etc. The controller 120 can include instructions that are updated by a user, either located at the filtration system 100 site, or remotely.

FIGS. 3A-C illustrate how the speed at which backwash fluid reaches its top flow rate affects the cleaning efficacy of a fouled membrane. In FIG. 3A, a membrane 300 (e.g., a membrane or a single channel 306 that is part of the filtration system 100 of FIG 1) is fouled and ready for cleaning, with particles 302 from the water 304 that fills the channel 306 dispersed on the inner surface of the membrane 300 and within its pores. In FIG. 3B, in a typical prior art configuration, a backwash flow 308 depicted by an arrow is directed at the membrane 300 while the channel 306 remains filled with the water 304. The backwash flow is slowed because of resistance from the water 304 in the ceramic membrane channel 306. When this occurs, areas of the ceramic membrane such as the illustrated membrane flow region 310 are cleaned first. The resistance to flow at the membrane flow region 310 thus decreases, causing the backwash flow to preferentially continue to flow through the cleaned membrane flow region 310. As the backwash flow 308 is diverted to the membrane flow region 310, the backwash flow 308 through the still-remaining dirty areas of membrane 300 is reduced. The overall backwash cleaning procedure is thus less effective.

FIG. 3C illustrates the evacuation backwash procedure. In contrast to FIG 3B, the channel 306 is emptied of water and instead contains gas 312 (e.g., atmospheric air). When the backwash flow 308 is applied to the membrane 300, it experiences reduced resistance as there is no water within the channel 306. Consequently, the backwash flow rate ramps from zero to its maximum value comparatively quickly than when water 304 is present. When this occurs, no area of the ceramic membrane is cleaned first, and the overall resistance to along the membrane 300 remains roughly constant. The backwash flow 308 is not diverted to a particular region or regions of the membrane, and the entire membrane 300 is cleaned. The overall backwash cleaning procedure is thus more effective and the filtration is more productive, meaning the same volume of water is filtered compared to in FIG 3B, but with net improvement, indicated by lower TMP. FIGS. 4A-C show an exemplary sequence for backwashing an evacuated ceramic membrane. In FIG. 4A, normal forward filtration is taking place with feed pump 106 circulating water from the feed water source 104 to the filtration module 102. Once travelling through the membrane within the filtration module 102, the now-cleaned permeate is emptied into the permeate storage 108, which is in turn emptied by the permeate pump 110 for use downstream. Valve VI is open to allow permeate to enter the permeate storage 108, while the other valves are closed.

FIG. 4B shows the next step, where the filtration module 102 is drained of water in preparation for the backwashing procedure. This procedure may be triggered according to a pressure within the filtration module 102, such as the TMP. A pressure sensor 112 may detect the pressure, and trigger the cleaning operation in the following steps when the detected pressure reaches a predetermined maximum pressure. This maximum pressure may be a differential pressure or TMP.

Valve VI permitting flow to the permeate storage 108 is closed, while air valve V4 allowing air to enter the filtration module 102 and valve V3 allowing flow to the drain 118 are opened. The drain pump 116 is activated, and the unfiltered water within the feed channels of the filtration module 102 is fed to the drain. The water removed from the feed channels can be pumped, or allowed to drain under the force of gravity, or both. Atmospheric air is permitted to flow into the filtration module 102 via the air valve VI. In some instances, gases other than air can flow into the filtration module, e.g., inert gas.

In some embodiments, the water is evacuated from the filtration module 102 using the extant drain used to remove the backwash fluid from the feed channels. Advantageously, the hardware that is already in place is used, without requiring additional equipment and cost. Depending on the configuration of the drain valve V3 and drain pump 116, the draining process can be very fast, e.g., less than 30 seconds, less than 15 seconds, less than 10 seconds.

In some instances, the feed channels of the filtration module 102 are completely emptied of water. In some instances, the feed channels of the filtration module 102 are mostly emptied of water (e.g., up to 90% or more of the volume of the module drained of water, up to 80% or more of the volume of the module drained of water, up to 70% or more of the module drained of water). The water removal can continue for a reselected time interval that is known to empty a given size of filtration module 102 to one of these amounts, e.g., 30 seconds or less, or 15 seconds or less. In some embodiments, the fluid flow travelling past valve V3 is measured and a flow rate determined (e.g., using a flow meter). The water removal continues until the flow rate reaches a threshold value, at which point the next step in the cleaning process is triggered. .

Referring to FIG. 4C, once the gas has filled or partially filled the feed channels within the filtration module 102 and the water previously within the feed channels empties or mostly emptied from therein, the backwash procedure begins. Additional water from the feed water source 104 is not introduced into the feed channels. Instead, the air valve V4 is closed, and valve V2 opened to allow the backwash pump 114 to push permeate from the permeate storage 108 back to the filtration module 102 and across the membrane to the emptied feed channels. As the resistance from water flow within the feed channels has been reduced or eliminated, the speed at which the backwash process initiates is increased as the feed channels don’t first need to be cleared of dirty water. Instead, permeate empties into the void spaces of the filtration module. The flow rate of the permeate crossing the membrane can be higher than in forward filtration mode, and selected such that a peak flow rate across the membrane is achieved very quickly, e.g., in less than 5 seconds, in less than 2 seconds, in less than 1 second. The result is more even and effective cleaning of the membrane (e.g., as shown in FIG. 3C). Additionally, pushing permeate through the membrane to the empty or near-empty feed side causes turbulence in the flow, which adds to the cleaning.

The backwash cleaning procedure generally occurs every 20-60 minutes. The backwash generally lasts between 15-60 seconds, e.g., approximately 30 seconds.

The flushing procedure adds approximately 10 additional seconds to evacuate the feed channels, substantially improving the efficiency for a short increase in the downtime.

The backwash flux typically is between 200-600 L/m2/hr. For example, the backwash flux can have a value of approximately 370L/m2/hr as the set point nominal. This backward flux is typically approximately 2-4 times the forward flux rate. Ceramic membranes particularly benefit from using the flushing procedure. Backwashing procedure for polymeric membranes involves a slow ramp up of backwash feed so as not to disrupt the more delicate membranes. Lag time is built into such systems, e.g., by sequencing the valves, so that the water direction change is prevented from abruptly slamming on and off. Ceramic membranes benefit from the pressure impact, and evacuating the channels enhances the change

FIG. 5 is a flow chart that describes a method for effectively cleaning a ceramic membrane by increasing the backwash ramp, e.g., increasing the rate of change of the speed of the backwash flow. This results in improved TMP by reduced fouling buildup, and reduced chemical cleaning events. Using this method of hydraulic cleaning, the first step 502 is stopping forward filtration in normal mode.

At step 504 is draining the internal feed flow channels from the ceramic membrane module so that the clean side of the membrane module remains full of permeate and the feed side of the membrane module emptied of water and contains primarily atmospheric air. Once this condition is attained, at step 506 a backwash pump pumps clean permeate under pressure from the clean side of the membrane module back into the empty feed channels and then out of the module and to a drain. The backwash flow of water reaches the targeted rate of flow much more quickly when the feed channels of the membrane module are empty as there is no resistance to the water flow when it passes from the clean side of the membrane to the dirty feed side of the membrane due to the feed channels being evacuated. At step 508 is flushing the feed channel by supplying additional liquid into the ceramic filtration system and, at step 510, removing the additional liquid from the filtration system such that the additional liquid does not cross the membrane. The backwash cleaning technique described above can be implemented using software included on a computer-readable medium for execution on a computer (e.g., the controller 120 of FIG. 1).

FIG. 6 shows an exemplary computer system 600, which can be used to implement the techniques described herein. For example, a portion or all of the operations of a processor (e.g., the controller 120 shown in FIG. 1) may be executed by the computer device 600 (and/or a mobile computer device). Computing device 600 is intended to represent various forms of digital computers, including, e.g., laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers, but in some instances can be various forms of mobile devices, including, e.g., personal digital assistants, cellular telephones, smartphones, and other similar computing devices. The components shown here, their connections and relationships, and their functions, are meant to be examples only, and are not meant to limit implementations of the techniques described and/or claimed in this document.

Computing device 600 includes processor 602, memory 604, storage device 606, high-speed interface 608 connecting to memory 604 and high-speed expansion ports 610, and low speed interface 612 connecting to low speed bus 614 and storage device 606. Each of components 602, 604, 606, 608, 610, and 612, are interconnected using various busses, and can be mounted on a common motherboard or in other manners as appropriate. Processor 602 can process instructions for execution within computing device 600, including instructions stored in memory 604 or on storage device 606, to display graphical data for a GUI on an external input/output device, including, e.g., display 616 coupled to high speed interface 608. In other

implementations, multiple processors and/or multiple buses can be used, as appropriate, along with multiple memories and types of memory. Also, multiple computing devices 600 can be connected, with each device providing portions of the operations (e.g., as a server bank, a group of blade servers, or a multi -processor system).

Memory 604 stores data within computing device 600. In one

implementation, memory 604 is a volatile memory unit or units. In another implementation, memory 604 is a non-volatile memory unit or units. Memory 604 also can be another form of computer-readable medium, including, e.g., a magnetic or optical disk.

Storage device 606 is capable of providing mass storage for computing device 600. In one implementation, storage device 606 can be or contain a computer- readable medium, including, e.g., a floppy disk device, a hard disk device, an optical disk device, a tape device, a flash memory or other similar solid state memory device, or an array of devices, including devices in a storage area network or other configurations. A computer program product can be tangibly embodied in a data carrier. The computer program product also can contain instructions that, when executed, perform one or more methods, including, e.g., those described above. The data carrier is a computer- or machine-readable medium, including, e.g., memory 604, storage device 606, memory on processor 602, and the like.

High-speed controller 608 manages bandwidth-intensive operations for computing device 600, while low speed controller 612 manages lower bandwidth intensive operations. Such allocation of functions is an example only. In one implementation, high-speed controller 608 is coupled to memory 604, display 616 (e.g., through a graphics processor or accelerator), and to high-speed expansion ports 610, which can accept various expansion cards (not shown). In the implementation, the low-speed controller 612 is coupled to storage device 606 and low-speed expansion port 614. The low-speed expansion port, which can include various communication ports (e.g., USB, Bluetooth®, Ethernet, wireless Ethernet), can be coupled to one or more input/output devices, including, e.g., a keyboard, a pointing device, a scanner, or a networking device including, e.g., a switch or router (e.g., through a network adapter).

Computing device 600 can be implemented in a number of different forms, as shown in the figure. For example, it can be implemented as standard server 620, or multiple times in a group of such servers. It also can be implemented as part of rack server system 624. In addition or as an alternative, it can be implemented in a personal computer (e.g., laptop computer 622). Each of such devices can contain one or more of computing device 600 and an entire system can be made up of multiple computing devices 600 communicating with each other.

Various implementations of the systems and techniques described here can be realized in digital electronic circuitry, integrated circuitry, specially designed ASICs (application specific integrated circuits), computer hardware, firmware, software, and/or combinations thereof. These various implementations can include one or more computer programs that are executable and/or interpretable on a programmable system. This includes at least one programmable processor, which can be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device. These computer programs (also known as programs, software, software applications or code) include machine instructions for a programmable processor, and can be implemented in a high-level procedural and/or object-oriented programming language, and/or in assembly/machine language. As used herein, the terms machine- readable medium and computer-readable medium refer to a computer program product, apparatus and/or device (e.g., magnetic discs, optical disks, memory, Programmable Logic Devices (PLDs)) used to provide machine instructions and/or data to a programmable processor, including a machine-readable medium that receives machine instructions.

To provide for interaction with a user, the systems and techniques described here can be implemented on a computer having a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for presenting data to the user, and a keyboard and a pointing device (e.g., a mouse or a trackball) by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well. For example, feedback provided to the user can be a form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback). Input from the user can be received in a form, including acoustic, speech, or tactile input.

The systems and techniques described here can be implemented in a computing system that includes a backend component (e.g., as a data server), or that includes a middleware component (e.g., an application server), or that includes a frontend component (e.g., a client computer having a user interface or a Web browser through which a user can interact with an implementation of the systems and techniques described here), or a combination of such backend, middleware, or frontend components. The components of the system can be interconnected by a form or medium of digital data communication (e.g., a communication network).

Examples of communication networks include a local area network (LAN), a wide area network (WAN), and the Internet.

The computing system can include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other.

EXAMPLES

The disclosure is further described in the following examples, which do not limit the scope of the disclosure described in the claims.

The following are test results showing exemplary results using the ceramic backwashing techniques described herein. The amount of cleaning using the described methods compared to traditional methods is quantified. The traditional methods include air scour, where air is injected into the base of the membrane and allowed to rise next to the membrane to remove contaminants. A series of tests showed that that air scour was more effective than regular backwash procedures.

The results show that drain down channel evacuation is just as effective as air scour methods, while saving the high energy costs associated with air scour. In the following GFD is gallons per day and square foot of membrane, a normalization of flux to membrane capability.

FIGS. 7A-7C shows graphs with results from experiments using air scour and the drain down procedure as described above, where the channels are emptied of feed water from the dirty side of the membrane before backwash fluid is forced through the membrane into the feed side.

In FIG. 7A, TMP over time of the system is shown, with backwashing with air scour used to clean the membrane. Conditions included regular forward mode operation at 60 GFD for 17.5 min. As can be seen, the TMP rises during each normal forward operation period due to contaminant build up on the membrane. The peak TMP for each normal filtration cycle also increases with time due to buildup of contaminants not fully removed during each intervening hydraulic cleaning procedure. The hydraulic cleaning procedure included a first step of 15 second backwash at 250 GFD (out the top of the module in this instance), then 15 second feed flush at 1.5 times the filtration flow rate. The feed flush can be between one and two times the filtration flow rate. A 30-second air scour followed, and then a repeated 15 second backwash and 15 second feed flush. FIG. 7B shows TMP over time of the system with results indicating a similar effect from drain down compared to air scour. Conditions again included 60 GFD for 17.5 min during normal forward operation. The new drain down backwash method using a module drain down prior to backwashing was employed after the first initial forward cycles shown. The method included the steps of stopping service at the end of each normal filtration cycle and draining down the feed channels by opening a vent and a bottom drain. Subsequently, the regular backwash with pump was performed for 30 seconds (with set point = 250 GFD), followed by a feed flush at 1.5 times filtration flow. In the graph, the first several filtration cycles are backwashing with air scour (similar to in FIG. 7A), while the drain down processes followed. The TMP rises following the drain down cleaning procedures were lower compared to the initial backwash/air scour processes, indicating improved membrane cleaning. The set point can be at least 100 GFD, e.g., 250 GFD.

FIG. 7C shows TMP over time of the system with results indicating desirable pressure decrease with drain down compared to no drain down. The three cycles on the right hand side of the graph are filtration periods following cleaning with the traditional method, e.g., no drain-down. The pressure is noticeably higher than the other cycles that were performed with the drain down step. Pressure maximum when using drain down was similar to the cycle where only air scour was used, indicating that a drain down step prior to backwash is as effective as using air scour to purge water.

A number of embodiments of the disclosure have been described.

Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. For example, some polymeric filtration systems include hardware that introduces air bubbles into the bottom of the filtration module so that they bubble up and aid in physically removing contaminants from the polymers. In some instances, polymeric systems have been retrofitted with ceramic membranes that can withstand the relatively high pressures of the backwash procedures described herein. In such instances, air bubbles can be released prior to evacuating the feed channels. Additionally and alternatively, the fluid outlet that allows air bubbles to enter the filtration module can be used as a further outlet to empty the module. Similarly, systems that include hardware for an air pressure decay test can use to evacuate the channel.

Accordingly, other embodiments are within the scope of the following claims.