Patent Description:
One of the inventors herein is a co-inventor of the inventions disclosed and claimed in <CIT>; and <CIT>. These Patents relate to the preparation and use of heated aluminum oxide particles (HAOPs) and Heated Iron Oxide Particles (HIOPs) for water filtration purposes. The disclosures of these references describe these particles being deposited onto a mesh layer through which contaminated water is passed. Once the particles are no longer capable of adsorbing contaminants, the exhausted particles are removed from the membrane, such as by back flushing, and new particles are deposited.

A few published journal papers describe deposition of a thin layer of HAOPs onto either a stainless steel mesh that is self-supporting<NUM> and is too stiff to collapse or a nylon mesh that is prevented from collapsing by being glued to a solid, plastic net backing<NUM>. <NUM> "<NPL>. <NUM> "<NPL>.

Addition of coagulant or powdered activated carbon (PAC) upstream of conventional UF membrane filtration is a fairly common technology in current practice. The coagulant typically reacts with water to form particles of iron oxide or aluminum oxide, and the PAC is added as particles. In principle, enough of these particles could accumulate on the membrane to form a layer like the one that we deposit. However, in such applications, the membranes get fouled long before a substantial amount of particles accumulates (less than one-tenth of the doses used in our system), the accumulation of the particles on the membranes is gradual throughout the application cycle rather than as a pulse at the beginning, and the membranes are not collapsible.

Candle filters are made by many manufacturers and are well described generically at the website http://www. solidliquid-separation. com/pressurefilters/candle/candle. An example patent is <CIT> https://patents. com/patent/<CIT>/en?q=candle&q=filter&oq=candle+filter. These filters consist of cylindrical tubes aligned vertically in a pressurized vessel (typically pressures are <NUM>-<NUM> atmospheres [<NUM>-<NUM> psi], far greater than in our application). The flow of water is from outside to inside the tubes, and only particulate contaminants (not dissolved ones) are captured. The particulates that are removed from the water accumulate on the outside of the candles. Once the applied pressure is unable to maintain a satisfactory filtration rate, the collected particles are released by a pulse ("snap blow") of backwash water, sometimes accompanied by vibration and/or high-pressure spraying of the outside of the candles. The candles are rigid, and typically no controlled deposition of "treatment particles" is applied.

In some cases, the candles are precoated with diatomaceous earth (DE). When the system is operated in this way, the coating is sometimes referred to as a "dynamic filter" and bears some similarities to our coated mesh.

Our technology is distinct from these systems in the use of flexible, collapsible mesh as the support and the use of adsorbent solids that collect not only particles that are suspended in solution, but also dissolved contaminants. In addition, the flow in candle filtration is from outside to inside the candles (opposite to that in our system), and the DE layer is typically several millimeters thick, whereas in our system, the layer is typically <<NUM> thick, so that our approach uses much less disposable material.

Asymmetric ceramic membranes (e.g., <CIT>, Composite metal-ceramic membranes and their fabrication) typically consist of a bulk, highly porous ceramic rod within which are numerous hollow lumens. A very thin skin (a few microns thick) of a different ceramic with much smaller pores is permanently deposited around the lumens; this skin is responsible for essentially all the filtration that the unit accomplishes. This arrangement differs from our system in that the filtering material removes only solids (not dissolved contaminants) and is permanently attached.

Dynamic Membrane Bio-Reactors (DMBR) have been investigated for wastewater treatment in laboratory setting for a few decades. In these reactors, particles are added to the reactors to form a layer on a support material that can be a membrane or a mesh. In cases where the support is a mesh, in all the reports that I have seen, it is attached to a frame to form a flat sheet. An impermeable backing is secured to the same frame, with a gap between the mesh and the backing. The frame is immersed in a suspension containing the wastewater and microorganisms that consume the biodegradable constituents of the raw wastewater. Inorganic particles are added to this suspension so that when it is filtered through the mesh, the solids that accumulate on the mesh are a mixture of the microorganisms and inorganic particles. In the absence of the added particles, the microorganisms form a sludge that has high hydraulic resistance; the added particles lower the resistance to flow, increasing water flux and allowing thicker layers to develop before the layer must be washed off.

In these systems, the water purification is carried out exclusively by the microorganisms; the added particles remove a negligible amount of contaminants, and are present strictly to enhance the filterability of the sludge. The system design makes it almost impossible to remove all the added particles when they are removed from the mesh, but because those particles do not play a central role in contaminant removal and are present at a much lower concentration than the microorganisms, this feature is not problematic. In fact, the particles can be washed off the mesh, mixed with the bulk water, and reused in the next cycle.

Typical investigations of DMBRs are described by <NPL>), and by <NPL>). As noted, DMBRs have been investigated at laboratory scale for at least a few decades, and I am not aware of any DMBRs that have been installed at full-scale, so it appears that there are some drawbacks to this technology that make scale-up difficult or unattractive.

Dynamic Membranes that are not coupled to biodegradation by microbes have been investigated in a few laboratories for specialized applications. Semiat's research group has published several papers on the use of zirconium oxide layers deposited on membranes or nonwoven fabrics. The layers were tested for their ability to remove the egg protein ovalbumin (MW <NUM>,<NUM>) from water under applied pressures of several atmospheres. Although they attribute the removal of the protein to interaction with the zirconium oxides, they reported that an insignificant amount was removed unless the particles were "post-treated" after deposition with polyacrylic acid. Example publications by this group are: <NPL>), and <NPL>).

The systems described in these studies differ from ours in that the contaminants are colloidal and particulate rather than small, dissolved molecules, and so the removal mechanism is primarily filtration rather than adsorption, and the fact that a "post-treatment" of the deposited layer is needed to make it functional. Also, the membrane support was a flat sheet, not a tube, and it is not clear how the dynamic layer can be removed from the support or how effective that process is (there was no mention of this step in the publications).

Bag filters made of fabric or mesh are widely used to remove particulates from air; water treatment applications are much rarer, but they do exist. A few example patents for bag filters for air treatment are:.

An overview of bag filter applications in water treatment is available at https://www. discountfilterstore. com/bag-filters. html, which includes the following:
"The primary job of bag filters is to reduce the amount of silt, sand, dirt and other types of sediment in your water. Some bags have a micron rating small enough to filter out some particulates, but they will not clean out bacteria like e. coli or chemicals like chloramines. Their primary use is in commercial, agricultural and industrial settings. Rarely, if ever, is a bag filter recommended for residential filtration. You can remove the filter from its housing and manually remove the trapped material. The reusability is another key benefit of a bag filter.

Bag filters do not remove dissolved contaminants, or even small particles; they are never cleaned in place, but rather are taken out of their housing for cleaning; and they are never used in conjunction with an intentionally pre-deposited layer of particles to assist in the treatment.

It is therefore an object of the present invention to provide for an apparatus for effectively replacing exhausted adsorption particles in a commercial water purification system.

It is a further object of the present invention to provide for water purification systems which achieves the above object in a commercial water purification system.

It is yet another object of the present invention to provide for a water purification system which achieves the above objects and which is also continuously operable. Document <CIT> discloses a treatment module according to the preamble of claim <NUM>.

The invention achieves the above objects, and other objects and advantages which will become apparent from the description which follows, by providing a water purification system and apparatus utilizing HAOPs (Heated Aluminum Oxide Particles) deposited on an oversized mesh substrate supported on an undersized frame allowing the mesh to flutter during backwashing to release exhausted HAOPs from the mesh prior to deposition of fresh layer of HAOPs thereon. The use of Heated Iron Oxide Particles (HIOPs) is also contemplated and those terms are used interchangeably herein.

In the preferred embodiments of the invention, the system is provided with modules, having manifolds supporting a plurality of cylindrical tubes for supporting the mesh membranes. A hydraulic logic system employing a plurality of modules is also disclosed.

Water purification apparatus in accordance with the principles of the invention is generally indicated at reference numeral <NUM> in the various figures of the attached drawings wherein numbered elements in the figures correspond to like numbered elements herein.

Particle deposition. The first stage is deposition of adsorbent particles on the interior surface of the mesh tubes or other support surface. This stage is initiated by injection of an aqueous slurry of the particles either accompanied or followed by injection of clean water into the module such that the fluid enters the tube interiors. Simultaneously, permeation across the tubes is allowed; this permeation flow carries the adsorbent particles to the tube walls, where they are captured as the water flows across the wall. The step continues until essentially all the particles have been deposited in layers adjacent to the tube walls. Optionally, the injected solutions can be recirculated axially to facilitate uniform deposition of the particles along the tube walls, and the permeating water can be returned to the tube inlet to minimize loss of both the adsorbent particles and water during this step.

The slurry concentration and water inflow rate should be chosen to assure that particles do not settle appreciably as the water flows through the tube. Optimal values will depend on the particle size and density and the length and orientation of the tubes; typical values are <NUM>-<NUM> grams of solids per liter in the slurry and a liquid flow velocity of <NUM> - <NUM>/s. The portion of the incoming fluid that is recirculated can range from zero to <NUM>%. The step continues until a cake layer containing almost all the injected particles has formed on the tube walls, which typically takes <NUM> - <NUM>. Typical thicknesses of the deposited layer can range from <NUM> to <NUM>.

Feed water filtration. The second stage in the process is filtration of the feed water to remove the target contaminants. During this step, the flow enters the module and the interior of the tubes. The flow can enter either or both ends of the tubes. If it enters only one end, the opposite end can be closed (dead-end operation) or it can be open, allowing flow to exit and then be returned to the inlet (recirculating flow or crossflow). Throughout this step, the permeation line is opened by an amount that allows the desired rate of outflow from the columns. The outflow is typically expressed as a flux, representing the water flow rate (e.g., liters/hour) divided by the surface area of the tubes (e.g., square meters) to yield a value with units of volume per unit area per unit time (e.g., liters per square meter per hour, LMH). The acceptable flux depends on the identity and concentration of contaminants in the water and the thickness of the deposited layer. Typical values are <NUM> -<NUM> LMH.

Filtration continues until some user-defined limit is reached. Typically, these limits relate to the duration of the filtration step (generally, <NUM>-<NUM> hours), the concentration of contaminant in the permeate (generally, <NUM>-<NUM>% of the concentration in the feed, or a fixed value set by regulation), or the pressure loss as water passes through the particle layer and tube wall (generally, <NUM> - <NUM> bar).

Particle removal and system cleaning. Once the filtration step ends, the layer of particles and any materials that they have collected are washed out of the system. This process can include steps in which water and/or air is forced through the tube from the outside-in, to help separate the particles from the tube wall (backwashing) and/or in which the water and/or air are forced through the tubes axially, shearing more particles off the wall and carrying all the particles and contaminants out of the system (flushing). If the modules are oriented vertically, the flows can be either upward or downward (and, during backwashing, can be both). These steps can be carried out in any sequence and for any duration. Typical values are <NUM>-<NUM> seconds per step, with a complete cleaning step comprising one to <NUM> steps each of backwashing and flushing.

<FIG> shows a cylindrical treatment module with five openings for entry and exit of water - three on side of the cylinder (connecting to the "shell" side of the module) and two on the end of the cylinder (connecting to the "tube" side of the module). The module size will depend on the water flow rate to be treated; typical sizes are <NUM>-to-<NUM> in diameter and <NUM>-to-<NUM> long. It can be made of any standard plumbing material that meets the regulatory requirements (e.g., NSFcertified if the water being treated is for human consumption) and is chemically compatible with the water to be treated.

<FIG> shows the same module as <FIG>, but with the bottom cap removed to show a plate (P1) with three types of holes. The small holes (H1) are for screws that hold this plate to a second plate on the interior. The medium size holes (H2) are where the end pieces of the treatment tubes penetrate. The large holes (H3) are where steel support rods penetrate. Steel rods are shown protruding through all three of the H3 holes; metal spacers are shown around two of the rods, and the third rod is shown without a spacer.

<FIG> shows the interior of the treatment module, with one steel rod (R1) and one treatment tube core (TC) in place. The treatment tube core TC is shown in greater detail in subsequent drawings. Inside the treatment tube core TC is a rod R2 made of fiberglass or other stiff material that keeps the core straight. The core snaps into an end-piece EP1 that is shown in greater detail in subsequent drawings. The drawing shows an outer view of plate P1 and an inner view of another plate P2. A pair consisting of plates P1 and P2 is placed at each end of the module, with P1 on the outside and P2 on the inside in both cases. The plates are held together by screws that pass from holes H1 in P1 to posts PP1 in P2.

<FIG> shows the same image as <FIG>, but with plate P1 removed from the top of the module.

<FIG> shows the tube core TC and one end-piece EP1. The core is a skeletal structure with rings (Ri1) attached to longitudinal members (LM). In the fully operational system, each tube core TC resides inside a loosely-fitting mesh tube sleeve (TS) (not shown in this Figure); when water flows from outside to inside the sleeve, the tube core TC prevents the sleeve from collapsing on itself. As shown in <FIG>, the prongs on the rings hold the stiff rod R2 in place, which in turn maintains the linearity of the tube core TC. The rod R2 also serves a function of occupying space so that water entering the core flows out of the system more quickly. A typical diameter for the rod R2 is <NUM>-to-<NUM>. The core can be made any material that meets the same requirements as the module shell. It can be constructed by connecting units that are <NUM>-to-<NUM> in length and that snap or are glued together to reach the desired length. The core diameter is typically from <NUM>-to-<NUM>, with gaps between the rings of <NUM>-to-<NUM>. The prongs should be long enough so that they just touch the rod R2.

<FIG> shows a cross-section of the end piece EP1. The smooth outer surface penetrates through the end plates EP1 and EP2. The ribbed outer surface is where the tube sleeve TS is attached, and the structure in the interior provides a stop for the rod R2.

<FIG> show example alternative designs for the tube core.

<FIG> shows the interior of a similar treatment module but with self-supporting porous tubes (e.g. tubular membranes) replacing the combination of tube sleeve TS, tube core TC, and stiffening rod R2. The tubular membranes typically have outside diameters of <NUM>-to-<NUM>. of the cylinder (connecting to the "shell" side of the module) and two on the end of the cylinder (connecting to the "tube" side of the module). The module size will depend on the water flow rate to be treated; typical sizes are <NUM>-to-<NUM> in diameter and <NUM>-to-<NUM> long. It can be made of any standard plumbing material that meets the regulatory requirements (e.g., NSFcertified if the water being treated is for human consumption) and is chemically compatible with the water to be treated.

<FIG> shows the interior of a similar treatment module but with self-supporting porous tubes (e.g. tubular membranes) replacing the combination of tube sleeve TS, tube core TC, and stiffening rod R2. The tubular membranes typically have outside diameters of <NUM>-to-<NUM>.

<FIG> shows a modified end-piece (EP2) that could be used if the tube cores (TC) were permanently potted in an epoxy layer rather than being individually removable and held in place by the two pairs of end-plates. This end-piece has the advantage that the portion that is smooth on the outside can be as large as the ribbed portion, thereby allowing a larger cross-section for water flow.

<FIG> shows a mesh sleeve (MS) that has been slipped over the core and attached to the end pieces.

<FIG> shows the inside of a finished module packed with tubes.

A hydraulic system that can accomplish all the steps in the operation is shown in <FIG>. In this diagram, valves are shown as Normally Open (NO) or Normally Closed (NC) to indicate their default states. Thus, when an NO valve is energized it closes, and when an NC valve is energized it opens. The pipes that are shown penetrating the module at the top and bottom are hydraulically connected to the "tube side" of the module (i.e., to the interiors of the tubes), whereas those that are shown penetrating the sides of the module are hydraulically connected to the "shell side" (i.e., inside the shell, but outside the tubes).

The system can be operated with one or more treatment modules functioning independently (parallel mode) or with the outflow from one module serving as the feed to the next module in the sequence (series mode).

The sequence of steps applicable to Module <NUM> operating alone or in parallel with Module <NUM> is as follows; the specific components mentioned are identified by reference to <FIG>:.

If multiple modules are operated in parallel, the piping and sequence of steps for each module replicates that described above for a single module, with some components (e.g., all the valves and pumps P1 and P2) dedicated to individual modules and others (e.g., pumps P4, P5, and P6) shared among several modules. For the two-module system shown in Figure XX1, valves V5, V4, V10 and V14 in Module M2 correspond to valves V2, V3, V9 and V11 in M1, respectively.

Multiple modules can also be operated in series mode. To initiate water treatment:.

Excessive discharges of phosphorus (P) in treated sewage and urban and agricultural runoff have led to the choking of lakes, rivers, and bays with algae. In addition to their foul odor and unsightly appearance, these algae deplete the oxygen supply in the water, killing fish and other aquatic organisms, and release toxins that can force shutdowns of water treatment plants that provide water for human consumption. To avoid these impacts, phosphorus must be removed from wastewater to levels of approximately <NUM>/l or lower. Existing technologies cannot achieve this goal at reasonable cost. In the tests described here, phosphorus was removed from domestic wastewater that had been conventionally treated in a membrane bioreactor (MBR) by passing the water through a thin (<<NUM>) layer of Heated Aluminum Oxide Particles (HAOPs) in a microgranular adsorptive filtration (µGAF) reactor.

Removal of P was investigated from MBR effluent from the Brightwater Wastewater Treatment Plant (WWTP) in Woodinville, WA. The total phosphorus (TP) in these solutions was almost identical to the soluble reactive phosphorus (SRP), so only SRP was analyzed. HAOPs were synthesized as described by Kim et al. <NUM> <NPL>.

The tests were conducted using two modules, each containing six <NUM>-foot-long mesh tubes with <NUM>-mm diameters and <NUM>-µm openings. HAOPs were deposited on the inner surface of these tubes, and the modules were operated in series as described in the preceding process description. The HAOPs loading on the mesh was <NUM> Al/m<NUM>, and the water flux through the tubes in each module was <NUM> liters per square meter per hour (lmh). The experiments lasted seven (<NUM>) days, with each filtration step lasting four hours (i.e., every four hours, the upstream module was taken offline, cleaned and returned to service in the downstream position).

As shown in <FIG>, the effluent from the µGAF reactor always contained <<NUM> SRP/l, with the only significant excursion occurring when the feed concentration briefly exceeded <NUM>/l. The average feed and filtrate SRP concentrations during the entire test were <NUM> and <NUM>/l, corresponding to <NUM>% removal. Thus, µGAF treatment of domestic wastewater reliably achieved the goal of removing the vast majority of the P concentration from the wastewater and lowering the concentration in the final product to <<NUM>/l.

SRP removal from treatment of MBR effluent in a µGAF reactor at the Brightwater WWTP. HAOPs loading: <NUM> Al/m<NUM>; Flux: <NUM> lmh.

Natural organic matter (NOM) in drinking water sources is problematic for multiple reasons. Among these are that it reacts with disinfectants such as chlorine to form disinfection byproducts (DBPs) that are tightly regulated because they are suspected and/or known to be carcinogenic, and it can severely impede the performance of membranes that are used to remove pathogenic microorganisms and other contaminants. Although the conventional approach for capturing NOM - coagulation with aluminum or iron salts - can remove a portion of the NOM and mitigate membrane fouling, improving these outcomes remains a high priority in the drinking water field. Current USEPA regulations require that <NUM> to <NUM>% of the total organic carbon (TOC) be removed from drinking water sources, depending on the TOC and the alkalinity in the raw water. TOC is an indicator of the NOM concentration.

Freshwater was collected from Lake Union (LU) at Portage Bay, Seattle, WA. The pH of the water was <NUM>±<NUM>. The samples contained <NUM>-<NUM>/l TOC and had UV absorbance at <NUM> (UV<NUM>) of <NUM>-<NUM>-<NUM>. Almost all of the TOC is contributed by dissolved species, so the TOC was essentially identical to the DOC (dissolved organic carbon). The buffer capacity and ionic strength were increased by adding <NUM> each of NaHCO3 and NaCl, and the pH was adjusted to <NUM>±<NUM>. If this water were used as a drinking water source, the USEPA requirement would be that <NUM>% of the TOC be removed by treatment. HAOPs were synthesized following the method of Kim et al. <NUM> The PAC used in the study was Norit SA SUPER. All filtration tests used <NUM>-mm disk filters installed into filter cartridges. Paper filters (Whatman®, grade <NUM>) with a nominal pore size of <NUM> were used to hold the adsorbent in µGAF experiments. Polyethersulfone ultrafiltration (UF) membranes with a nominal pore size of <NUM> were used in membrane filtration experiments. For DBP formation potential (DBPFP) tests, the chlorine doses were chosen to generate residual free chlorine concentrations of <NUM>±<NUM>/l as Cl<NUM> after <NUM> hours of contact. <NUM> <NPL>.

To pretreat the water by batch adsorption, flasks containing the water were dosed with the desired type(s) and amount(s) of adsorbent and placed on a rotary shaker for two hours. The solids were then removed by filtration through paper filters, and the solutions were used in subsequent membrane filtration experiments.

For pretreatment by µGAF, a cartridge was fitted with a paper filter, and a slurry of the adsorbent(s) was injected with a syringe while gently shaking the cartridge to help distribute the adsorbent uniformly. Feed was pumped into the µGAF unit to generate a constant flux of <NUM> lmh, and the effluent from the cartridge was collected for subsequent analysis or membrane filtration.

The effective adsorbent dose in these tests was defined as the ratio of the mass of adsorbent in the µGAF layer to the volume of water treated. The NOM removal efficiency for a given effective dose was defined as the DOC concentration in a composite sample of all the treated water from the beginning of the experiment until the time when that effective dose was reached.

The membrane filtration tests were conducted in cartridges identical to those used for µGAF, but with a membrane replacing the paper filter, no pre-deposition of adsorbent, and a fixed flux of <NUM> lmh. The experimental set-up for the µGAF-membrane experiments is shown schematically in <FIG>.

The dissolved organic carbon (DOC) concentration and UV254 were used as indicators of the NOM concentration in these experiments. The NOM removal efficiencies achieved by µGAF using mixtures of the two adsorbents at a fixed effective adsorbent dose of <NUM>/l are shown in <FIG>, along with the results from batch experiments at the same dose. A substantial fraction of the NOM was removed from the water in every experiment (enough to meet the EPA requirement for drinking water). NOM removal in the µGAF experiments was greater when the adsorbent comprised a mixture of HAOPs and PAC than when either adsorbent was present alone. Furthermore, for identical mixtures of the adsorbents, µGAF pretreatment always removed more NOM than batch pretreatment did.

Next, raw water and water that had been pretreated in each system characterized in <FIG> were fed to UF membranes. The magnitude and trends in fouling in all the systems investigated are compared in <FIG> for a fixed total effective adsorbent dose of <NUM>/l. For pretreatment by <NUM>/l PAC and no HAOPs (designated 20P + <NUM> in the figure), switching from batch to µGAF pretreatment led to a detectable but small decline in overall system fouling. However, as PAC was replaced with HAOPs (i. e, moving from left to right in the figure), fouling of the membrane increased dramatically for batch pretreatment, whereas both membrane fouling and total (µGAF plus membrane) fouling decreased dramatically for µGAF pretreatment. As a result, at the other extreme (0P + <NUM>), the overall system fouling after filtration of <NUM><NUM>/m<NUM> of water was almost an order of magnitude less severe for µGAF pretreatment than for the more conventional, batch approach to pretreatment.

Two tightly regulated groups of DBPs are trihalomethanes (THMs) and haloacetic acids (HAAs). The effectiveness of µGAF at reducing the THM formation potential (THMFP) and HAA formation potential (HAAFP) of the source water was evaluated in three of the waters discussed above: those treated with HAOPs only, with PAC only, and with a <NUM>:<NUM> mixture of the two adsorbents. As summarized in Table ZZ1, the mixed adsorbents reduced the DBPFP more than either pure adsorbent did. Thus, µGAF treatment using either HAOPs alone or a mixture of HAOPs and PAC provided substantial benefits over more conventional water treatment approaches with respect to both removal of contaminants from the water and facilitating further treatment by membrane filters.

Claim 1:
A treatment module, comprising:
a tube core (TC) of a skeletal structure including longitudinal members (LM) and rings (Ri1), the rings (Ri1) being attached to the longitudinal members (LM); and
a loosely-fitting mesh tube sleeve (TS) in which the tube core (TC) resides,
wherein adsorbent particles are deposited on an interior surface of the loosely-fitting mesh tube sleeve (TS),
wherein the tube core (TC) prevents the mesh tube sleeve (TS) from collapsing when water flows from outside to inside of the mesh tube sleeve (TS), and, said treatment module being characterized in that it further comprises prongs, which are disposed on the rings (Ri1) and which hold a rod inside the tube core (TC) to keep the tube core (TC) straight.