Patent Publication Number: US-2015068977-A1

Title: Integrated membrane system for distributed water treatment

Description:
This is a Divisional application of Ser. No. 13/195,746 filed Aug. 1, 2011, which is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     Embodiments of the invention relate to water and wastewater treatment and more particularly to integrated membrane treatment systems. 
     BACKGROUND 
     There are many technologies for water/wastewater treatment with practically no limit to water quality achievable when treating a majority of the existing water/wastewater streams. Biological treatment is the most widely used technology. It utilizes metabolism of microorganisms to remove organic matter, as well as other dissolved nutrients including nitrogen and phosphorus. Biological mass (biomass) is also known to adsorb heavy metals, suspended solids, and other sorts of contaminants which do not undergo biological degradation. Biomass is separated from the treated liquid, thus allowing for discharge of treated water (effluent) and disposal of the excess of the biomass (sludge). Depending on the quality of the water for treatment (influent), two biological treatment methods are typically used separately or in combination. A first is anaerobic treatment, which does not require aeration (addition of dissolved oxygen). The other is aerobic treatment, utilizing dissolved oxygen in the biological treatment. 
     For concentrated wastewater streams, anaerobic treatment is commonly used to achieve partial degradation of the contamination. Although aerobic treatment consumes more energy than anaerobic treatment, aerobic treatment is often used to achieve a more rapid and complete removal of the organic pollutants. The activated sludge method is an example of an aerobic biological treatment for municipal wastewater containing a relatively low level of organic impurities using biomass mixed with the treated liquid. 
     Recent development in wastewater treatment technology have demonstrated integration of a filtration membrane (micro or ultra) with activated sludge or anaerobic treatment provides effective method of sludge separation and process control, achieving more efficient treatment. Such a combination is called a Membrane Bioreactor (MBR). However, the effluent produced by biological treatment and microfiltration is insufficient for significant number of uses as the effluent contains bacteria, viruses, and residual amounts of organic and inorganic contaminants. Therefore additional treatment, such as chemical disinfection, UV disinfection, ion exchange, sorption, etc. is common. Because of limitations in treatment efficiency, these technologies are often used in combination, resulting in high treatment cost. 
     Reverse Osmosis (RO) technology is another commonly used process which provides high treatment efficiency. RO membranes effectively remove suspended solids (including viruses and bacteria), often with higher efficiency and reliability than MBR. RO membranes also remove inorganic matter (including dissolved salts, thus providing softening effect). RO can also remove high molecular weight dissolved organics, which is typically a main fraction of the biological treatment effluent. 
     However, conventional implementations of both MBR and RO technologies have significant drawbacks resulting in high treatment cost. For example, MBR requires a long retention time to ensure efficient nitrogen removal. This long retention time translates into large footprint and higher capital cost. Also, conventional MBR implementations require a large number of units of mechanical equipment, including hydraulic pumps, blowers, compressors, vacuum pumps, etc. This again increases capital cost and maintenance cost, and raises reliability concerns. 
     Deficiencies in conventional RO implementations include high-energy consumption and high pretreatment cost. Another problem with treating MBR effluent by RO is bio-fouling of RO membranes. Controlling bio-fouling by disinfection is difficult due to the fact that oxidizing biocides may attack the membrane material and adversely affect membrane performance. Disinfection also typically entails a use of chemicals which require special permits and adds operational complexity 
     In view of recent trends in environmental/health regulations, as well as greater public awareness of the importance of clean water, decentralized small-scale treatment technologies are expected to become more important. Generally, when scaling the typical applications down, the cost of each volumetric unit of the treated water increases exponentially. More particularly, the operational difficulties, permitting, and concomitant costs described above have thus far limited application of these treatment technologies to large treatment plants of a size of the POTW (publicly owned treatment works). Furthermore, systems designed to overcome the constraints typical of smaller scale systems may also prove to be cost competitive for implementations at the POTW scale. 
     SUMMARY OF DESCRIPTION 
     Embodiments of the present invention integrated membrane systems which when operated independently are comparatively less efficient. The integrated systems enable efficient operation across a wide range of volumetric flows for scalability that is well-suited to a distributed treatment model. In certain embodiments, the integrated treatment systems described herein are implemented for distributed treatment within a framework of an existing sewerage system. 
     In embodiments, RO is integrated with other components of a water treatment system, such as a biological unit, or an MBR, to recover energy from the RO unit, for example from the RO concentrate (reject), to operate the other components. In one such embodiment, a single hydraulic pump is harnessed to operate the majority of the treatment system. As such, synergy between the RO and other components of the system simplify operation and maintenance of the water treatment system. 
     In embodiments, RO is integrated with other components of a water treatment system, such as a biological unit, or an MBR, to leverage the RO&#39;s ability to remove inorganic nitrogen. In certain such embodiments, removal of nitrogen by RO enables biological treatment to be performed incompletely, thereby advantageously reducing retention times. In further embodiments, reliance on the RO for nitrogen removal enables biological treatment to be performed with only partial nitrification (oxidation of ammonia to nitrate) further enabling the biological treatment to be performed with no pH control. In embodiments with no pH control, pH freely varies as a function of the wastewater influent quality and level of biological activity sustainable with no active pH control. As such, ammonia may exist in the treated water with the pH most likely dropping below 7. With no active pH control, chemical use and handling is reduced. As such, synergy between the RO and other components of the system simplify operation and maintenance of the water treatment system. 
     In embodiments, RO is integrated with a chlorine generator to convert chlorides present in the RO concentrate for an in-situ source of oxidizing biocides for disinfection purposes. In certain such embodiments, where biological treatment is performed incompletely, residual inorganic nitrogen in the RO concentrate (present because of the partial nitrification) is further utilized, along with the chlorides to derive chloramines for disinfection purposes. In further embodiments, the pressurized RO concentrate is utilized to drive service flows employing the disinfectant so that a separate metering system is not required. As such, a synergy between the RO and other components of the system reduces system complexity, chemical use, and improves membrane lifetimes. 
     In embodiments, carrier media is employed in a membrane tank to improve effectiveness of membrane scouring through mechanical agitation by the carrier media and potentially enhance removal of residual organics by the MBR. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention are illustrated by way of example, and not limitation, in the figures of the accompanying drawings in which: 
         FIG. 1  illustrates a flow path diagram for water treatment system with an energy recovery system for integrated treatment and/or filtration of an aqueous solution, in accordance with an embodiment of the present invention; 
         FIG. 2  illustrates a water treatment method which may be performed by water treatment system illustrated in  FIG. 1  to employ RO and recover energy there from for integrated treatment and/or filtration of an aqueous solution, in accordance with an embodiment of the present invention; 
         FIG. 3A  illustrates a flow path diagram for a water treatment system with an RO salt electrolysis system for integrated disinfection of the system and aqueous solution treated by the system, in accordance with an embodiment of the present invention; 
         FIG. 3B  illustrates an isometric view of a membrane filter, scouring elements, and scouring element retainer, in accordance with an embodiment of the present invention; 
         FIG. 4  illustrates a water treatment method which may be performed by water treatment system illustrated in  FIG. 3A  to convert salts recovered from an RO concentrate into oxidizing biocides for integrated disinfection of the system and the aqueous solution treated by the system, in accordance with an embodiment of the present invention; 
         FIG. 5  illustrates a flow path diagram for a water treatment system integrating treatment, membrane filtration, and RO with energy recovery and disinfection systems, in accordance with an embodiment of the present invention; 
         FIG. 6  illustrates a water treatment method which may be performed by water treatment system illustrated in  FIG. 5  to integrate treatment, membrane filtration, and RO with energy recovery and disinfection, in accordance with an embodiment of the present invention; 
         FIG. 7A  illustrates a cross-sectional side view of a water treatment and membrane filtration apparatus which may be utilized in the water treatment system illustrated in the  FIG. 5 , in accordance with embodiments of the present invention; 
         FIG. 7B  illustrates a plan view of the water treatment and membrane filtration apparatus illustrated in  FIG. 7A , in accordance with embodiments of the present invention; 
         FIG. 8  illustrates a water treatment method which may be performed by the water treatment and membrane filtration apparatus illustrated in  FIGS. 7A ,  7 B to implement the treatment and filtration operations illustrated in  FIG. 6 , in accordance with an embodiment of the present invention; and 
         FIG. 9  is a water treatment system architecture in which the integrated water treatment system illustrated in  FIG. 5  may be implemented within an existing sewer or industrial treatment system, in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Described herein are integrated membrane water treatment systems and water treatment methods which may be performed by such systems. In the following description, numerous specific details are set forth, such as exemplary treatment and filtration apparatuses to describe embodiments of the present invention. However, it will be apparent to one skilled in the art that embodiments of the present invention may be practiced without such specific details. In other instances, well-known aspects, such as specific biological treatment techniques, solids separation techniques, etc. and associated hardware, are not described in detail to avoid unnecessarily obscuring embodiments of the present invention. 
     Reference throughout this specification to “an embodiment” means that a particular system component or operative sequence described in connection with the embodiment is included in at least one embodiment of the invention. Thus, use of the phrase “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the invention. Furthermore, exemplary system components or operative sequences may be combined in any suitable manner in one or more embodiments. Also, it is to be understood that the various exemplary embodiments shown in the Figures are merely illustrative representations, are not to scale, and are not exclusive of additional hardware and/or operations which remain otherwise consistent with system operation. In the figures, reference numbers are retained where convenient for the sake of avoiding duplicative description of components shared between embodiments. 
     The terms “coupled” and “in fluid communication,” are used herein to describe structural and functional relationships between components, respectively. Two components “coupled” together are in either direct or indirect (with other intervening components between them) physical contact with each other. Two components “in fluid communication” are coupled in a manner such that a fluid from one component is capable of flowing to the other component. 
     Generally, the systems described herein are for the removal of any contaminant from any aqueous solution. Therefore, the term “water treatment” is employed herein in its broadest sense to mean removal of a contaminant, be it by solids separation, chemical, physical, biological treatment, etc. Similarly, any reference to “wastewater” is to be understood as a label for any aqueous solution having an impurity level which is to be improved, be it domestic sewage effluent, industrial effluent, or non-point source runoff, etc. Exemplary embodiments describing the treatment of any specific classes or types of wastewater are therefore merely to emphasize the broad applicability of the present invention. 
       FIG. 1  illustrates a flow path diagram for a water treatment system  100  with an energy recovery system for integrated treatment and/or filtration of an aqueous solution, in accordance with an embodiment of the present invention.  FIG. 1  is described in the context of  FIG. 2 , illustrating operations of an exemplary water treatment method  200  that may be performed by the water treatment system  100 . 
     Beginning at operation  201 , an aqueous solution having impurities of any type (i.e., “wastewater”) is received as the influent stream  101  ( FIG. 1 ) to a vessel  105 . In certain embodiments, the wastewater is preferably with a brackish salinity level to provide a source of salts which are employed as an in-situ source of biocides, as described further herein. 
     At operation  205  ( FIG. 2 ), at least one of filtration, aerobic or anaerobic biological treatment, chemical treatment (e.g., oxidation of Mn and Fe, etc. or chemical precipitation such as HF waste with CaCl 2 , etc.), or physical-chemical treatment (e.g., coagulation or flocculation) of the aqueous solution is performed within the vessel  105 . The term “filtration” is employed here, as well as throughout the remainder description, to refer to either microfiltration or ultrafiltration, as the present invention is not limited in that respect. 
     In an embodiment, processed effluent from the vessel  105  is utilized to drive one or more activities occurring in the vessel  105 . In the exemplary implementation, the processed effluent is driven downstream by a hydraulic pump  120  disposed downstream from the vessel  105 . Energy may be recovered from the hydraulic pump  120  utilized to drive one or more activities performed in the vessel  105 . In the depicted embodiment, the processed effluent is supplied into an influent side of an RO unit  110 . The RO unit is drawn in dashed line to emphasize, that the energy recovery illustrated in  FIG. 1  is not dependent on RO being performed downstream, though additional synergies are to be had for those embodiments employing an RO unit, as described elsewhere herein. 
     For embodiments herein employing RO, the RO unit  110  may be of any design known in the art with many variants being commercially available to filter via a diffusive mechanism with separation efficiency being dependent on solute concentration, pressure, and flux rate rather than size exclusion as for membrane filtration. Effluent from the RO includes a permeate stream  116  and concentrate (reject) stream  114 . The permeate stream  116 , as the product of the water treatment system  100  is provided to a downstream application, be it further purification or consumption. Although the hydraulic pump  120  is in fluid communication with both the vessel  105  and the RO unit  110 , the breaks in the effluent stream  107  denote that one or more intervening process vessels, process controls, etc. may be disposed there between. 
     As illustrated in  FIG. 1 , a motor  130  is driven with the pressurized vessel effluent at operation  230 . The hydraulically driven motor  130  may be of any design known in the art, with an exemplary system being the HydroDrive, commercially available from Hastec HydroDrives, Inc. of St. Catharines, Ontario, Canada. Depending on the embodiment, and as illustrated in  FIG. 1 , the drive side of the motor  130  is in fluid communication with either or both the RO concentrate stream  114  or an RO bypass stream  112  disposed downstream of the hydraulic pump  120  and upstream of the RO unit  110 , each of which provides a pressurized source with an associated pressure head and volumetric flow rate. 
     For embodiments where no RO is employed, at least some portion of effluent from the pump  120  is utilized to drive one or more motor  130  as coupled to either or both the compressor  140  (to provide aeration and/or pressurization gas stream  142 ) and mixer  150 . Depending on the stream employed to drive the motor  130 , the motor effluent stream  135  may be either reintroduced into the system upstream of the hydraulic pump  120  (e.g., returned vessel effluent stream  107  where RO bypass stream  112  drives the motor  130 ) or discharged to a waste drain (e.g., where the RO concentrate stream  114  drives the motor  130 ). For embodiments in which the drive side of the motor  130  is in fluid communication with the RO concentrate stream  114 , the motor  130  provides a means of recovery residual energy remaining downstream of the RO unit. For embodiments in which the drive side of the motor  130  is in fluid communication with the RO bypass stream  112 , the motor  130  provides a means to enable the hydraulic pump  120  to be a single energy source for the treatment system  100 . The hydraulic pump  120  is therefore to be sized to accommodate the additional load associated with driving the motor  130 . 
     With the motor  130  having a drive side in fluid communication with the hydraulic pump  120 , a driven side of the motor  130  is harnessed at operation  240  ( FIG. 2 ) to power one or more action performed in the vessel  105 . Although any processing action conventional in the art may be powered by the motor  130 , exemplary embodiments include one or more of mixing, aerating, or pressurizing a filtration or biological, chemical, or physical-chemical treatment with at least some portion of effluent from the vessel  105 . In one embodiment, the driven side of the motor  130  coupled to a compressor  140  having an inlet coupled to a gas source, such as ambient air, and an outlet coupled into the vessel  105  to pressurize the vessel (e.g., in the case of a filtration process occurring in the vessel  105 , as described further elsewhere herein) or aerate processes performed in the vessel with the gas (e.g., air) introduced. Typically, for such an application, the drive side of the motor  130  is to be in fluid communication with the RO bypass stream  112  for a larger pressure head and volumetric flow rate. 
     In another embodiment, the motor  130  has the driven side coupled to a mechanical mixer  150  disposed within the vessel  105 . For one such an embodiment, the vessel  105  may be operated as a CSTR with the mixer shaft  152  driven by the motor  130 . Depending on the load, the drive side of the motor  130  may be in fluid communication with either concentrate outlet of the RO unit  110  (to be driven by the concentrate stream  114 ) or in fluid communication with the RO bypass stream  112 . In further embodiments, multiple motors  130  may be driven by the pressurized vessel effluent. For example, and as further described elsewhere herein, a first motor  130  drives the mixer  150  with the RO concentrate stream  114  while a second motor  130  drives the compressor  140  with the RO bypass stream  112 . 
       FIG. 3A  illustrates a flow path diagram for a water treatment system  300  with an RO salt electrolysis system for integrated disinfection of the system and of the aqueous solution treated by the system, in accordance with an embodiment of the present invention.  FIG. 3A  is described in the context of  FIG. 4  illustrating an exemplary operation of a water treatment method  400  that may be performed by the water treatment system  300 . 
     Beginning at operation  401 , an aqueous solution having biodegradable impurities is received as the influent stream  304  ( FIG. 3A ) to a filtration vessel  305 . For the exemplary embodiment illustrated in  FIG. 3A , a porous membrane filter  306  is submerged within the filtration vessel  305  with an effluent side of the filter  306  passing through a wall of the filtration vessel  305  for solid separation in addition to biological treatment, for example in the case of an MBR. 
     In the exemplary embodiment, biological treatment at operation  404  is performed incompletely, such that nitrogen (e.g., ammonia) is not completely removed. For example, operation  404  may have a corresponding solids retention time of between 1 and 15 days whereas in conventional systems designed for complete nitrogen removal retention time is typically 20 to 40 days. In further embodiments, operation  404  is performed without pH control. As such, operation  404 , and indeed all the operations in the entire treatment system  300 , is operated at whatever steady-state pH naturally occurs (e.g., as a function of the biological treatment process performed at operation  404 ). With nitrification occurring to some extent, steady-state pH is lowered, for example to be below 7. A lower pH inhibits biological processes as well as further nitrification. Allowing pH to drop freely to a relatively low level has the advantage of avoiding caustic addition, reduced oxygen demand and therefore a lower energy consumption for aeration, and reduced bio-fouling of the membrane filter  306 . 
     Effluent from the filtration vessel  305  is driven into an influent side of the RO unit  110  by the hydraulic pump  120  disposed downstream from the filtration vessel  305 . Inorganic nitrogen (ammonia, ammonium salt, etc.) remaining after the treatment operation  404  is removed by the RO at operation  406 . RO permeate stream  116 , as the product of the water treatment system  300  is provided to a downstream application, be it further purification or consumption. For those embodiments where pH is allowed to drop freely (e.g., upon partial nitrification), scaling of the RO membrane will be advantageously reduced. Although the hydraulic pump  120  is in fluid communication with both the filtration vessel  305  and the RO unit  110 , the breaks in the effluent stream  307  denote one or more intervening process vessels, process controls, etc. may be disposed there between. 
     In an embodiment of the present invention a chlorine generator is integrated with the RO unit  110  for in-situ generation of biocides for disinfection. As further illustrated in  FIG. 3A , an electrolytic cell  365  is in fluid communication with the concentrate outlet of the RO unit  110 . The electrolytic cell  365  is to decompose by electrolysis at least some of the salts present in the RO concentrate into more reactive species which are either oxidizing biocides or can be further reacted into oxidizing biocides. The electrolytic cell  365  may be any known in the art designed for electrolysis of aqueous salt solutions, such as those commercially available for brine/seawater processing. Exemplary systems are available under the trade name SEACLOR® from Severn Trent De Nora located in Sugarland, Tex. While such systems are typically designed to generate biocides from a seawater influent or high concentration sodium chloride solution, for embodiments of the present invention the electrolytic cell  365  is integrated into the water treatment system  300  for in-situ derivation of oxidizing species from the RO concentrate stream  114  which is high in salts separated from the vessel effluent stream  307 . Chlorides concentration in the RO reject will be typically 4-5 times as high as that of the vessel effluent stream  307 , but 1-2 orders of magnitude lower concentration than sea water. 
     In the exemplary method illustrated in  FIG. 4 , chloride salts (e.g., NaCl) in the RO concentrate stream  114  are decomposed at operation  465  to produce a reactive chlorine-containing species, such as, but not limited to one or more of chlorine (Cl 2 ), hypochlorite (ClO − ), chlorine dioxide (ClO 2 ), and chloride ions (CO with byproducts including aqueous sodium hydroxide (NaOH). Depending on the other constituents in the RO concentrate stream  114 , the reactive chlorine-containing species may be further reacted with one or more constituents in the RO concentrate stream  114 . As further illustrated in  FIG. 4 , at operation  466 , nitrogen sources (e.g. ammonia (NH 3 )) in RO concentrate stream  114  react with the reactive chlorine-containing species form chloramines, such as, but not limited to, monochloramine ClNH 2 . 
     At operation  470 , the treatment system  300 , as well as the filtered effluent stream  307  itself in certain embodiments (e.g., in generation of drinking water), is disinfected by the oxidizing biocides derived from the RO and electrolysis processes. Operation  470  may be performed continuously during operation of the treatment system  300  or intermittently as a service flow method. As further illustrated in  FIG. 3A , the electrolytic cell  365  is coupled to at least one of the filtration vessel  305  and RO unit  110 . In one embodiment, a backwash apparatus  362  is coupled to both the electrolytic cell effluent stream  368  and the RO bypass stream  112 . The backwash apparatus  362  intermittently provides a liquid back-pulse  372  from an effluent side to an influent side of the membrane filter  306  to clean the membrane pores (e.g., when MBR permeation is not pressurized). The backwash apparatus  362  may be of any design in the art with many variants being commercially available for this purpose. Because the liquid back-pulse contains the oxidizing species (biocides), the membrane filter  306  is also disinfected by the liquid back-pulse with the biocide concentration determined by mixture of the electrolytic cell effluent stream  368  and the RO bypass stream  112 , both of which are pressurized by the hydraulic pump  120 . Similarly, the filtration vessel  305  may also be disinfected by a periodic supply of oxidizing species provided by the backwash apparatus  362 . In the preferred embodiment, with the liquid back-pulse being pressurized by the hydraulic pump  120 , overall system design is simplified and capital costs reduced since a separate, dedicated metering system is not required. 
     In another embodiment, the electrolytic cell  365  has an outlet coupled downstream of the filtration vessel  305  for conduction of the oxidizing species (biocide) to an inlet or outlet (not depicted) of the RO unit  110 , as driven by the pressure of the RO concentrate stream  514 . In the illustrative embodiment, an electrolytic cell effluent stream  369  is introduced into the filtered effluent stream  307  upstream of the hydraulic pump  120  (low pressure side) for injection into the RO unit  110 . RO membranes are therefore also disinfected at the operation  470  ( FIG. 4 ), either continuously or by periodic feed from the electrolytic cell  365 . For embodiments where chloramines are generated by the system  300 , negative effects of chlorination to the RO membrane(s) in the RO unit  110  may be reduced. 
     In further embodiments, the components illustrated in the treatment systems  100  and  300  are combined into a single treatment system to leverage operational synergies between the respective components.  FIG. 5  illustrates a flow path diagram for a water treatment system  500  integrating treatment, membrane filtration, and RO with energy recovery and disinfection systems, in accordance with an embodiment of the present invention.  FIG. 5  is described in the context of  FIG. 6 , illustrating operations of an exemplary water treatment method  600  that may be performed by the water treatment system  500 . 
     Beginning at operation  601 , an aqueous solution having impurities of any type (i.e., “wastewater”) is received as the influent stream  101  ( FIG. 5 ) to a solids separator  503  for pretreatment. In the exemplary embodiment of municipal wastewater treatment, upstream of the solids separator  503  is a diversion valve, allowing discharge of any non-treated wastewater into a municipal sewer  502 , for example when the treatment system  500  is taken out of service or when influent exceeds capacity of the system. This guarantees full reliability of the installation. 
     In the exemplary embodiment, the aqueous solution continuously flows by gravity into the solids separator  503 . At operation  603 , the solids separator  503  removes course particulates and/or grease etc. that may otherwise interfere with subsequent treatment processes. Any solids separator known in the art to have this functionality may be employed as the present invention is not limited in this context. The solids separator  503  is equipped with a drain connected to the municipal sewer  502  (or a retention vessel, etc.) to prevent excessive solids and grease accumulation. 
     Separator effluent stream  504  overflows to the reactor  505 . At operation  605  ( FIG. 2 ), at least one of biological, chemical (e.g., oxidation or chemical precipitation, etc.), or physical-chemical (e.g., flocculation) treatment of the aqueous solution is performed within the reactor  605  as the main treatment operation, depending on the quality of the separator effluent stream  504 , process requirements, etc. For embodiments where the separator effluent stream  504  has a high organics content the reactor  505  may operate as energy efficient anaerobic digester. For embodiments where the separator effluent stream  504  has low organics content with high solids content, the reactor  505  may operate as flocculation tank. For the illustrative embodiment of municipal wastewater treatment, the reactor  505  is a first vessel of an MBR where organics are biologically decomposed and ammonia partially oxidized. In one MBR embodiment, carrier media are disposed in the reactor  505  for support of attached biomass to prevent biomass from being washed-out. Sufficient biomass concentration may therefore be maintained without recycling during operation even if solids are drained from reactor  505  to municipal sewer  502 . Any carrier media known art for moving bed bioreactors (MBBR) may be utilized as the embodiments of the present invention are not limited in this respect. 
     Treated effluent  507  flows into the filtration vessel  305  which includes the membrane filter  306 . At operation  607 , the treated effluent  507  is polished in the filtration vessel  305 . For a municipal wastewater treatment embodiment for example, aerobic biologic treatment is performed in the filtration vessel  305 . As previously described in the context of the system  300 , biological treatment performed in the reactor  505  and/or the filtration vessel  305  may be without any pH control and with the biological treatment leaving residual nitrogen in the treated effluent  507 . The membrane filter  306  is submerged within the filtration vessel  305  with an effluent side of the filter  306  passing through a wall of the filtration vessel  305  to filter the treated effluent at operation  608 . 
     In advantageous embodiments, scouring elements  353  are also disposed within the filtration vessel  305 . The scouring elements  353  are displaceable within the filtration vessel  305 , for example by gas introduced into the filtration vessel  305 . Displacement of the scouring elements  353  is to mechanically scour an influent side of the membrane filter  306 . Additionally, any suspended biomass present in the filtration vessel  305  may also utilize the scouring elements as a support media to further enhance biological treatment and improve biomass retention. 
     In embodiments, the scouring elements  353  are inert particles freely suspendable within the filtration vessel  305  and may be, for example, plastic beads, silica slurry, or the like. The scouring elements  353  are to be too large to pass through the membrane filter  306  and indeed may be many orders of magnitude larger and sufficiently large and of a shape to avoid becoming packed into a cake by flux across the membrane filter  306  and to avoid damaging the membrane file  306  through abrasion. In the exemplary embodiment, aeration of the vessel  305  is performed in proximity to the influent side of the membrane filter, for example in any manner known in the art capable of air scouring the membrane filter  306  and this aeration provides motive force to the scouring elements  353 . Contact induced by the displacement of the scouring particles provides the mechanical scouring of the membrane filter  306 . 
     In advantageous embodiments employing the scouring elements  353 , the membrane filter  306  is surrounded by a retainer which is to retain the scouring elements  353  in proximity to the influent side of the filter  306  and thereby improve their scouring efficiency. Absent such a retainer limiting the displacement of the scouring elements to within a confined subregion of the filtration vessel  305 , the scouring elements  353  may tend to collect in locales away from the membrane filter  306  (e.g., in the relatively stagnant regions of the filtration vessel  305 ).  FIG. 3B  depicts an expanded isometric view of the membrane filter  306  with a scouring element retainer  326 . As shown, a conventional columnar membrane filter  306  includes fibers  316  which are exposed to the bulk liquid (e.g., in the filtration vessel  305 ). Surrounding the columnar filter is the cylindrically-shaped scouring element retainer  326 . The retainer  326  has a diameter larger than that of the membrane filter  306  to provide an annular region surrounding the membrane filter  306  inside of which the scouring elements  353  are to be retained. The retainer  326  may be of any material (e.g., PTFE, ceramic, stainless steel, etc.) and any structure (e.g., meshed, gridded, windowed, etc.) which allows for air/liquid exchange while still serving to confine the scouring elements  353 . The souring elements  353  are to be disposed loosely within the annular space between the membrane fibers  316  and the retainer  326  so as to be movable by an external motive force, such as the aeration and/or pressurization gas stream  142 . 
     The filtered effluent stream  307  is collected in an RO feed tank  509 , providing volume equalization and a pressure head for the hydraulic pump  120  to drive the filtered effluent stream  511  through the RO unit  110  (and one or more scale abatement systems  587  disposed there between). The RO feed tank  509  may also serve to separate gas bubbles from the MBR, reducing cavitation at the hydraulic pump  120 . Again, in the preferred embodiment the treatment system  500  relies on the single hydraulic pump  120  for operation. 
     With the permeate stream  595  provided for use at operation  685 , integration of the RO unit  110  is such that energy is recovered from the RO unit  110  at operation  650  substantially as was described for  FIGS. 1 and 2  and is applied to affect processing in any or all of the operations  605 ,  607  and  608 , as denoted by the dashed lines in  FIG. 6 . Disinfectant derived in-situ from operation of the RO unit  110  is also applied, substantially as described in the context of  FIGS. 3 and 4 , to affect processing in any or all of the operations  608  and  610 , as denoted by the dashed lines in  FIG. 6 . For example, as shown in  FIG. 5 , the electrolytic cell  365  has an effluent stream  369  coupled the RO feed tank  509  such that generated biocides (e.g., chloramines where the concentrate stream  514  includes residual inorganic nitrogen) are provided downstream of the filtration vessel  305  and upstream of the hydraulic pump  120  to introduce the biocides to an influent side of the RO unit without a separate metering system. 
     As illustrated in  FIG. 5 , pressurized RO permeate stream  514  drives a hydraulic mixer  550  (which is drawn to represent both the motor  130  and mixer  150 ), as previously described for the mixer  150  in system  100 . Mixer effluent stream  537  may then be reintroduced as a stream  538  to the solids separator  503  or discharged to the municipal sewer  502 . An RO bypass stream  512  drives a hydraulic air compressor  540  substantially as previously described for the compressor  140  in system  100  with the hydraulic air compressor  540  aerating the aerobic biological process performed in the (MBR) filtration vessel  305  via air inlet  536 . 
     Though not depicted in  FIG. 5 , air may also be similarly introduced into the reactor  505 . The air introduced by the hydraulic air compressor  540  also displaces any scouring elements disposed in the filtration vessel  305  to mechanically scour the influent side of the filter  306 . In a preferred embodiment, the filtration vessel  305  may also be intermittently pressurized above ambient conditions by the air introduced from the hydraulic air compressor  540  to drive the treated effluent  507  through the membrane filter  306 . 
       FIG. 7A  illustrates a cross-sectional side view of an exemplary water treatment and membrane filtration apparatus  700  which may be utilized in the water treatment system illustrated in the  FIG. 5 , in accordance with embodiments of the present invention.  FIG. 7B  illustrates a plan view of the water treatment and membrane filtration apparatus  700 . 
     In  FIG. 7A , the reactor  505  is defined by an inner chamber wall  733  with lines disposed therein for receiving the separator effluent stream  504  and a drain line, for example to the municipal sewer  502 . The exemplary reactor  505  is sized to provide a hydraulic retention time (HRT) of between 2 and 4 hr. The hydraulic mixer  550  is disposed on a top of the apparatus  700  with the mixing shaft  552  attached thereto. The filtration vessel  305  defined as an annular space between the inner chamber wall  733  and an outer chamber wall  734  and sized to provide an exemplary HRT 0.5-1 hr. As show in  FIG. 7B , a plurality of the membrane filter  306  are equally spaced within the annularly shaped filtration vessel. 
     As shown in  FIG. 7A , the reactor  505  includes carrier media  757  disposed therein while the filtration vessel  305  includes scouring elements  753 . Coupled to an effluent side of the membrane filter  306  are lines for conducting the filtered effluent stream  307  to the RO feed tank  509  further having line out for the filtered effluent stream  511 . 
     Air inlets  536 A and  536 B couple air from the hydraulic compressor  540  ( FIG. 5 ) into the reactor  505  and filtration vessel  305 , respectively. As further illustrated in  FIGS. 7A and 7B , a backflow prevention mechanism  762  (e.g., a plurality of check valves embedded in the inner wall  733 ) separates the reactor  505  from the filtration vessel  305  to prevent backflow of the treated effluent  507  when a pressure control device  534  (e.g., an automated air vent) causes the filtration vessel  305  to be pressurized above that of the reactor  505  via the air inlet  536 B. 
       FIG. 8  is a flow diagram illustrating a water treatment method  800  which may be performed by the water treatment and membrane filtration apparatus  700 . The method  800  should therefore be considered an exemplary sequence of operations implementing an advantageous mode of the treatment and filtration operations generally described in reference to  FIGS. 5 and 6 . 
     Method  800  begins with operation  601  where, as previously described, aqueous solution for treatment is received by the reactor  505  (inner vessel). The reactor  505  operates between low and high level sensors  752 A, for example corresponding to approximately 15% of the reactor volume. At operation  860  the reactor  505  is continuously mixed, for example via the hydraulic mixer  550 , and aerated, for example via the hydraulic air compressor  540 . At operation  862 , biomass is grown on the surface of the plastic carriers  757  as well as freely suspended in the reactor. 
     If the reactor  505  reaches the high level, then the pressure control device  534  is actuated (e.g., opened) at operation  863  to equilibrate the pressure between the reactor  505  and filtration vessel  305 , allowing for solution levels between the reactor  505  and filtration vessel  305  to equilibrate at operation  865  via the backflow prevention mechanism  762 . Screening retains biomass carriers  757  in the reactor  505 . Upon equalization of solution levels, method  800  returns to operation  266  where the pressure control device  534  actuates (e.g., closes) to allow pressure in the filtration vessel  305  to increase via air introduced through air inlet  636 B. The increased pressure drives flux across the (microfiltration) membrane filter  306  at operation  857 . The level in the filtration vessel decreases due to permeation through the membrane filter  306  with the filtered effluent stream  307  being output to the RO feed tank  509  at operation  859 . While the pressure control device  534  operates to elevate the filtration vessel pressure, the level in the reactor  505  will continue to increase due to influent stream  101 . 
     Upon the filtration vessel  305  reaching a low level located at the top of the membrane filter  306 , level sensors  752 B actuate the pressure control device  534  to reduce pressure to ambient. Solution flux through the membranes(s)  306  is thereby reduced to avoid drying out the membranes or forming a biomass cake. During all or a portion of the time while at the low level, permeate flux may be zero and utilized for the membrane back-pulse described elsewhere herein (i.e., flux reversed). 
     The RO feed tank  509  also operates between low and high level sensors  752 C. The tank is elevated by height H relative to the filtration vessel  305  to provide sufficient minimum head to the hydraulic pump  120 . When level in the RO feed tank  509  reaches the low level (e.g., insufficient MBR product), an RO feed valve downstream of the RO feed tank  509  ( FIG. 5 ) and downstream of the RO bypass,  513 A and  513 B, respectively, close at operation  872 . RO bypass return  521  recirculates the RO bypass stream  512  after driving the hydraulic air compressor  540  back to the filtered effluent (permeate) stream  511 , downstream the RO feed valve  513 A. Upon the level reaching the high level sensor (e.g., permeate flow from filtration vessel  305  exceeds capacity of the RO unit  110 ), the pressure control device  534  is actuated at operation  874  to reduce filtration vessel pressure and thereby interrupt permeate flow. When the RO feed tank level is between the level sensors, the RO feed valves  513 A and  513 B are open, allowing permeation (generating final quality permeate stream  595 ) at operation  685 . 
     As the hydraulic pump  120  drives permeation through the RO unit  110  and also supplies hydraulic power to drive the aeration, mixing, and pressurization of the filtration vessel, as well as other maintenance operations, when the RO feed is interrupted, the hydraulic pump  120  continues to recirculate RO feed quality water through the RO bypass stream  512  and back to an inlet of the hydraulic pump  120  (through the return  521 ). The pressure at the pump inlet is adjusted to be equal to the low level head of the RO feed tank, allowing both streams to feed the pump simultaneously when filtered effluent (permeate) stream  511  is available. 
     A number of service flows may also be performed either simultaneously or cyclically with the method  800 . For example, the electrolytic cell  365  generates a low-level of oxidizing species (e.g., chlorine) from the RO concentrate stream  514 , as described elsewhere herein. In the exemplary embodiment, the electrolytic cell  365  operates continuously with the retention time (and as a result the chlorine concentration) controlled by timer. Injection of the oxidizing species (biocide) may be triggered upon activating the RO feed valve. Also during the method  800 , the back-pulse as described elsewhere herein is injected into the membrane regularly when the pressure control device  534  is actuated to reduce filtration vessel pressure. The duration of the back-pulse may be controlled by timer or pressure regulated. During method  800 , excess sludge from the reactor  505  will overflow to the filtration vessel  305 . Periodically (e.g., once a day) aeration of the reactor  505  is halted, and after short settling of the scouring elements  753 , the content of the reactor will be drained, for example from the upper portion of the filtration vessel  305  and discharged into municipal sewer  502 . Other system rinses may also be performed periodically. For example, the pressurized RO concentrate stream  514  may be used for the rinses in the solids separator  503 , discharging into the municipal sewer  502 . Similarly, rinses downstream of the filtration vessel  305  may use pressurized recirculation flow via the RO bypass stream  512 . 
     Uninterrupted processing of the influent stream  101  occurs when the treatment system  500  operates normally. However, one or more of a number interlocks may be triggered in response to a system malfunction. For example, in the absence of the influent stream  101 , the level in both the reactor  505  and filtration vessel  305  will reach the respective low levels with aeration continued to maintain biomass activity. Interruption of a sufficient duration will lead to interruption of the RO unit  110 . An absence of the RO concentrate stream  514  will halt the hydraulic mixer  550 . In this case, mixing is provided by aeration only. In the event of a toxic feed, pH meter  583  will register a change in the reactor  505  and/or filtration vessel  305 , generating an alarm and/or operator response. In the event of a surge in the influent stream  101 , the high level in the reactor  505  is exceeded and a bypass valve diverts the separator effluent stream  504  to the municipal sewer  502 . In the event the filtration vessel  305  becomes clogged, hydraulic pump  120  stops, or a membrane in the RO unit  110  becomes clogged, both the filtration vessel  305  and reactor  505  reach the high level, and the bypass valve to the municipal sewer  502  is activated triggering an alarm for operator response. In the event the electrolytic cell  365  fails, membranes in the RO unit  110  will become clogged, again triggering the high levels in both the filtration vessel  305  and reactor  505  resulting in an alarm. 
       FIG. 9  is a water treatment system architecture  900  in which the integrated water treatment system  500  may be implemented within an existing POTW, in accordance with an embodiment of the present invention. As shown, the water treatment system  500  receives the influent stream  101  from one or more upstream commercial water uses  910 A,  910 B and/or household water uses  920 A,  920 B and returns a processed effluent for one or more downstream commercial water uses  940 A,  940 B or household water uses  950 A. The downstream uses may be the same as the upstream uses (e.g., a car wash) or may be downgraded (e.g., laundry upstream, car wash downstream, etc.). In the illustrative embodiment, the treatment system  500  is scaled to be completely contained within a conventional tractor trailer/shipping container  599 . As such, the treatment system  500  is capable of mobile, distributed point of use treatment which can reduce loading on the primary municipal treatment facilities and differentia water qualities based on use. At this exemplary scale, it is expected that the treatment system  500  can accommodate an average influent stream volumetric flow rate of up to 10,000 gal per day, depending on the quality of the influent stream  101 . With the treatment system  500  being a distributed treatment resource inserted into a municipal treatment framework proximate the point of use, connection to the municipal sewer  502  provides a failsafe as well as a means to dispose of separated solids, etc. in a more concentrated form. 
     The above description of illustrative embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific implementations of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. The scope of the invention is therefore to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.