Abstract:
The water treatment system and method incorporating the use of a hydrodynamic separator to remove most of the total suspended solids (TSS) in source water being treated to thereby lighten the load on membrane filtration in the water treatment system and lower energy costs.

Description:
INCORPORATION BY REFERENCE 
       [0001]    The following co-pending and commonly assigned applications, the disclosures of each being totally incorporated herein by reference, are mentioned: 
         [0002]    U.S. Published Application No. 2009/0050538, entitled, “Serpentine Structures for Continuous Flow Particle Separations”, by Lean et al.; 
         [0003]    U.S. Published Application No. 2008/0128331, entitled, “Particle Separation and Concentration System”, by Lean et al.; 
         [0004]    U.S. Published Application No. 2008/0230458, entitled, “Vortex Structure for High Throughput Continuous Flow Separation”, by Lean et al.; 
         [0005]    U.S. Published Application No. 2009/0114601, entitled, “Device and Method for Dynamic Processing in Water Purification”, by Lean et al.; 
         [0006]    U.S. Published Application No. 2009/0114607, entitled, “Fluidic Device and Method for Separation of Neutrally Buoyant Particles”, by Lean et al.; 
         [0007]    U.S. Published Application No. 2010/140092, entitled, “Flow De-Ionization Using Independently Controlled Voltages”, by Armin R. Volkel et al.; 
         [0008]    U.S. patent application Ser. No. 12/484,071, filed Jun. 12, 2009, entitled, “Method and Apparatus for Continuous Flow Membrane-Less Algae Dewatering”, by Lean et al.; 
         [0009]    U.S. Published Application No. 2009/0283455, entitled, “Fluidic Structures for Membraneless Particle Separation”, by Lean et al.; 
         [0010]    U.S. Published Application No. 2009/0283452, entitled “Method and Apparatus for Splitting Fluid Flow in a Membraneless Particle Separation System”, by Lean et al.; 
         [0011]    U.S. patent application Ser. No. 12/615,663, filed Nov. 10, 2009, entitled, “Desalination Using Supercritical Water and Spiral Separation”, by Lean et al.; 
         [0012]    U.S. Published Application No. 2010/0072142, entitled, “Method and System for Seeding with Mature Floc to Accelerate Aggregation in a Water Treatment Process”, by Lean et al.; 
         [0013]    U.S. patent application Ser. No. 12/484,038, filed Jun. 12, 2009, entitled, “Stand-Alone Integrated Water Treatment System for Distributed Water Supply to Small Communities”, by Lean et al.; 
         [0014]    U.S. patent application Ser. No. 12/484,005, filed Jun. 12, 2009, entitled, “Spiral Mixer for Floc Conditioning”, by Lean et al.; 
         [0015]    U.S. patent application Ser. No. 12/484,058, filed Jun. 12, 2009, entitled, “Platform Technology for Industrial Separations”, by Lean et al.; 
         [0016]    U.S. patent application No. [Atty. Dkt. No. 20100591-US-NP], filed ______, entitled, “Electrocoagulation System”, by Volkel et al.; 
         [0017]    U.S. patent application No. [Atty. Dkt. No. 20100997-US-NP], filed ______, entitled, “All-Electric Coagulant Generation System”, by Volkel et al.; and 
         [0018]    U.S. patent application No. [Atty. Dkt. No. 20100218-US-NP], filed ______, entitled, “System and Apparatus for Seawater Organics Removal”, by Meng H. Lean et al. 
     
    
     BACKGROUND 
       [0019]    A variety of systems for processing water have been developed. Such processes often are of a multi-stage filtration design and include sequential processing steps for coagulation, flocculation, and sedimentation. 
         [0020]    Sources of water to be processed include surface water, ground water, wastewater, brackish water, sea water, among others. One specific conventional source water treatment is based on an activated sludge process (ASP), which filters, performs solids removal and pre-treats the source water to remove from the source water containments, solids, etc. in the form of sludge. Thereafter, an aeration zone or bath is provided which permits the injections of air into the bath to aerate the treated source water. Following aeration the treated source water is provided a settler tank for additional separation and sludge removal. Thereafter, additional filtration and disinfection steps are used to produce effluent water. The ASP system is, however, quite time consuming, and requires large areas of land, and produces large amounts of sludge. 
         [0021]    Another water treatment process includes the use of membrane bioreactors (MBR). In these systems, the initial steps of solid removal and pre-treatment, as well as providing the water to an aeration zone or bath may be similar to the steps discussed above. However, in the MBR process in place of settler tanks and further filtration and/or disinfection, the MBR process employs specialized membranes which are used to operate on source water having 5-12,000 mg/l total suspended solids (TSS). The MBR process employs ultra-filtration (UF) and micro-filtration (MF) membranes. Membrane core sizes are in the range of 0.003 to 0.01 μm. The MBR technology commonly will submerge the membranes into the bioreactor. The submerged configuration relies on coarse bubble aeration to produce mixing and limit fouling. Aeration maintains solids in suspension, scours the membrane surface and provides oxygen to the biomass, leading to better degradability and cell synthesis. 
         [0022]    MBR filtration performance decreases with filtration time, due to the deposition of soluble and particulate materials onto and into the membrane. Membrane fouling results from interaction between the membrane material and the components of the activated sludge, which includes but is not limited to biological floc formed by living or dead microorganisms along with soluble and colloidal compounds. 
         [0023]    Membrane fouling is a serious problem affecting the system performance; as it leads to significant increase in hydraulic resistance, manifested as permeate flux decline or trans-membrane pressure (TMP) increase. Therefore, frequent membrane cleaning and replacement is required. 
         [0024]    Presently, air-induced cross-flow obtained in submerged MBR is used to remove or at least reduce the fouling layer on the membrane surface. Other anti-fouling strategies that can be applied to MBR applications include intermittent permeation, where the filtration is stopped at a regular time interval before being resumed. In this way, particles deposited on the membrane surface tend to diffuse back to the reactor. Membrane backwashing is used where permeation water is pumped back to the membrane and flows through the pores to feed the channel dislodging internal and external particles. Still a further anti-fouling strategy is air backwashing, where pressurized air on the permeate side of the membrane build up and release a significant pressure within a very short time period. In this situation, the membrane modules need to be in a pressurized vessel coupled to a vent system. Air is not intended to go through the membrane, as if it did, the air would dry the membrane and a re-wet step would be necessary. 
         [0025]    Thus MBR based processes involve high capital costs due to the expensive membranes, and high operation and maintenance costs due to increased energy for the aeration, trans-membrane pressure, and frequent back-flushing and/or other cleaning of the membranes to maintain their usefulness. Particularly, avoiding membrane fouling and clogging due to organics require the frequent maintenance such as the mentioned backwash. Maintaining the integrity of the membranes is important as compromised membrane integrity produces a sludge of TSS in the final water product. 
         [0026]    With attention to the mentioned high capital expenditures of MBR systems, membrane replacement costs are much higher for 5-12,000 mg/l TSS capable membranes, as compared to conventional membranes designed for less than 100 mg/l TSS. 
         [0027]    Yet another source water processing technology is known as a moving bed bioreactor (MBBR). The MBBR technology is employed in advanced high-rate source water treatment processes utilizing free-floating bio-film carrier elements in aerobic, anaerobic and anoxic reactors. The carrier elements are effectively hybrids between attached and suspended growth treatment processes, which require significantly less footprint area and natural resources to build and operate compared to other available treatment alternatives. 
         [0028]    The bio-film carrier elements provide a very large effective bio-film surface area. The biomass is trapped inside the carrier elements, and the carrier elements are kept within the reactor by an outlet sieve. The movement of these carrier elements is driven by a coarse bubble air distribution system based on a rotary displacement air blower in aerobic systems, and a mixer in anoxic and anaerobic systems. While utilizing the MBBR technology, the filling fraction of carriers in the reactor may be varied to suit the specific loadings of the source water. Treatment plants can also be designed with a number of configurations of MBBR&#39;s and combination processes to target specific contaminants. 
         [0029]    It would be desirable to use a source water treatment process that either does not need high cost membranes such as used in MBR systems, called MBR-Lite, or if such membranes are used, to extend their operation time between backwash and lower the associated maintenance costs. Still further, it would be beneficial in MBBR systems, to extend the life of the carriers and/or lower maintenance requirements by reducing the stress on the carriers. 
       BRIEF DESCRIPTION 
       [0030]    The water treatment system and method incorporates the use of a hydrodynamic separator to remove most of the total suspended solids (TSS) in source water being treated to thereby lighten the load on membrane filtration in the water treatment system and lower energy costs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]      FIG. 1  is an illustration of a source water treatment system incorporating a membrane bioreactor used in the existing art; 
           [0032]      FIG. 2  illustrates a plurality of membrane filtration modules; 
           [0033]      FIG. 3  illustrates a membrane bioreactor water treatment system incorporating a hydrodynamic separator; 
           [0034]      FIG. 4  illustrates another membrane bioreactor water treatment system incorporating a hydrodynamic separator; 
           [0035]      FIG. 5  illustrates another membrane bioreactor water treatment system incorporating a hydrodynamic separator; 
           [0036]      FIG. 6  illustrates an MBR-Lite configuration for a membrane bioreactor water treatment system incorporating a hydrodynamic separator, wherein the filtering membrane module is submerged; 
           [0037]      FIG. 7  depicts a further illustration of an MBR-Lite configuration for a membrane bioreactor water treatment system incorporating a hydrodynamic separator, wherein the filtering membranes are pressurized; 
           [0038]      FIG. 8  depicts a more detailed view of a membrane of the membrane modules of the present application; 
           [0039]      FIG. 9  depicts a moving bed bioreactor (MBBR) water treatment system integrating a hydrodynamic separator with ultra-filters; 
           [0040]      FIG. 10  illustrates a portion of a moving bed bioreactor water treatment system, wherein a hydrodynamic separator is incorporated into the MBBR aeration basin, zone or bath; 
           [0041]      FIG. 11  shows construction of a hydrodynamic separator unit designed for MBR-lite; 
           [0042]      FIG. 12  provides a comparative analysis of the size between a conventional secondary clarifier plus ultra-filters, and a hydrodynamic separator plus ultra-filters used in water processing systems; 
           [0043]      FIG. 13  illustrates one embodiment of a single hydrodynamic separator which may be used in the concepts of the present application; 
           [0044]      FIG. 14  depicts a tower of hydrodynamic separators such as shown in  FIG. 13 ; 
           [0045]      FIG. 15  depicts a tower of hydrodynamic separators which may be used in connection with the concepts of the present application; 
           [0046]      FIG. 16  depicts an alternative embodiment of a hydrodynamic separator tower which may be used in the present application; and 
           [0047]      FIG. 17  depicts a further embodiment of a hydrodynamic tower that may be used within the concepts of the present application. 
       
    
    
     DETAILED DESCRIPTION 
       [0048]      FIG. 1  illustrates a membrane bioreactor (MBR) source water treatment process system  100 . The source water may, as mentioned, be water from a number of different locations and may contain algae and/or active sludge bacteria floc, among other elements. Source water containing active sludge biological floc should behave very similarly to algae-laden water, both having similar specific gravity. Such floc is often formed on filamentous bacteria, and floc size will decrease with increasing sludge age. Active sludge bacteria floc also posses the same risk of biofilm accumulation as that of water carrying algae, and range in size between 10-200 microns. Biological floc can be found in concentrations of 500-10000 mg/l (TSS). Granular sludge up to 1 mm can be formed under certain conditions and selected bacteria strains. 
         [0049]    In system  100 , source water  102  is supplied through a grid or screen  104 . A solid removal module  106  processes the source water  102  in a known manner to remove larger solid particles, and then passes the treated source water to a pretreatment system or module  108 . Such pretreatment systems are well known in the art and are used to perform initial separation of particles from the source water. Such separation is at least in part is accomplished by having particles settle and concentrate into the form of sludge  110  at the bottom of pretreatment system  108 . The resulting sludge  110  is taken out via line  112 . The pretreated source water  102  is then passed to an aeration zone (also called basin or bath)  114  to which air bubbles  116  are supplied by air generator  118  via an air input line  120 . Aeration of the source water  102  is undertaken in a known manner, and the activated source water  102  is then passed to MBR module or system  122 . On the left-hand side of the MBR module  122  is sludge  124  that has been filtered out by membranes  126  and which is passed out of MBR module via line  128 . The treated clarified source water  102  is then passed out via line  130  for either further processing or an intended end use. It is noted line  128  also provides sludge back to an input of the aeration zone  114  to assist in the aeration process. 
         [0050]    Membranes  126  of MBR module  122  are in one embodiment hollow fiber membranes, designed to operate with source water having 5-12,000 mg/l TSS.  FIG. 2  depicts a plurality of membrane modules  200 . Such membranes have a high capital expenditure and membrane replacement cost compared to other conventional filters and/or membranes such as membranes designed to operate with source water having less than 100 mg/l TSS. Therefore, the cost of operating the system as shown in  FIG. 1  is increased due to employment of such high cost high maintenance membranes. 
         [0051]    In one embodiment, by use of the hydrodynamic separator, algae and/or TSS which is greater than 6 μm is separated from the source water effluent and diverted into algae/TSS waste stream with 95% efficiency. In some water treatment situations 50% water recovery is “good enough” to make a water treatment system useful since solids are recycled. 
         [0052]    To address issues related to existing MBR based water treatment systems.  FIG. 3  illustrates a MBR-lite processing system  300 , where a hydrodynamic separator  302  is incorporated into system  300  after pretreatment system  108  to receive the source water  102  output from pretreatment system  108 . Hydrodynamic separator  302  includes a waste outlet  304  that moves sludge that has been removed by the hydrodynamic separator  302  to line  112 . The acted upon source water  102  is then sent to aeration zone  114 , via source water outlet  306  and is processed therein in a manner similar to that described in connection with  FIG. 1 . 
         [0053]    From the aeration zone or bath  114  source water  102  is then passed to a filtering module  308  which includes at least one and commonly multiple filtering elements  310  such as membranes. As seen in this figure the filtering elements filter out sludge  312 , which is provided to line  128 . 
         [0054]    It is understood that in  FIG. 3 , filtering elements  310  of filtering module  308  may be membranes having a filtering capacity less than the high filtering capacity of the membranes described in connection with  FIG. 1 . More specifically membranes of membrane filtering module  308  in this embodiment can be membranes designed for use with source water having less than 100 mg/l TSS, as opposed to high capacity or capability membranes which operate with 5-12,000 mg/l TSS and therefore have a range of operation from greater than 100 mg/l up to about 12,000 mg/l compared to less expensive membranes. Thus, by use of one embodiment of MBR-lite, it is understood that by removing additional materials from the source water by the hydrodynamic separation, it is not necessary to use the more capital expensive membranes, but rather the lower cost membranes (i.e., the less than 100 mg/l TSS) may be implemented. Therefore, the MBR-lite system may be understood to be a low cost membrane bioreactor (MBR) design for source water treatment. The hydrodynamic separator concentrates and removes much of the TSS. The reduced TSS allows the use of the less-expensive membranes for reducing capital expenditures. Further, even if the more expensive membranes (5-12,000 mg/l) are used, there is less necessity of cleaning, replacing, etc., which means there would be lower operational costs in the form of lower energy requirements, parts costs and lower maintenance. 
         [0055]    Alternative to the system design shown in  FIG. 3 , in another embodiment shown in  FIG. 4  hydrodynamic separator  400  is located prior to pretreatment system  108 , i.e., between pretreatment system  108  and solid removal process module  106 , wherein the sludge material is provided to line  112  via output line  402  and acted-upon source water is moved to pretreatment system  108 , via line  404 . In a further embodiment shown in  FIG. 5  hydrodynamic separator  500  is located after the aeration zone  114  prior to the source water  102  being supplied to filtering module  308 . Thus, in this embodiment hydrodynamic separator  500  will again remove TSS and pass the sludge component via line  502  to line  112 , prior to the source water reaching filtering or membrane module  308  via line  504 . 
         [0056]    The foregoing are examples of positions where the hydrodynamic separator may be located in the MBR-lite source water processing system. It is to be appreciated that the hydrodynamic separator may also be positioned at other locations within the water treatment system. A concept common to each of the embodiments is, however, directed to removing TSS and other fouling matter prior to having an interaction with filtering module  308 . 
         [0057]    The MBR-lite process systems of  FIGS. 3-5  optionally employs prescreening to remove hair, fibers, etc., and in some embodiments use the same type of screens (down to 0.1 mm) used for pretreatment of existing MBR systems (i.e., those that use the high-cost hollow fiber membrane systems). It is noted prescreening used ahead of the aeration basin further reduces the organics and solid loads to the aeration basin and the hydrodynamic separator, improving overall performance. 
         [0058]    Turning to  FIG. 6 , set forth is a diagram of a portion  600  of a MBR-lite source water treatment system similar to that of  FIGS. 3-5 , which addresses energy requirements of such systems. In particular this figure focuses on head-losses occurring in the systems. Head-loss has to do with the total amount of energy in the water. The amount of head is expressed in length and defines how high the water can rise. A common equation that is used with head is Bernoulli&#39;s equation. Head loss, more particularly, is a measure of the reduction in the total head (sum of elevation head, velocity head and pressure head) of the fluid as it moves through a fluid system. Head loss is unavoidable in real fluids. It is present because of: the friction between the fluid and the walls of the pipe; the friction between adjacent fluid particles as they move relative to one another; and the turbulence caused whenever the flow is redirected or affected in any way by such components as piping entrances and exits, pumps, valves, flow reducers and fittings. The head loss for fluid flow is directly proportional to the length of pipe, the square of the fluid velocity, and a term accounting for fluid friction called the friction factor. The head loss is inversely proportional to the diameter of the pipe. 
         [0000]    
       
         
           
             
               Head 
                
               
                   
               
                
               Loss 
             
             = 
             
               f 
                
               
                 
                   Lv 
                   2 
                 
                 D 
               
             
           
         
       
     
         [0059]    One known manner of calculating head loss is by use of the Hazen-William Equation. Another formula is Manning&#39;s formula which is common for gravity driven flows in open channels. In this equation, the friction factor f is determined by the relative roughness of the pipe and the Reynolds number, which is R=(DV/nu), where D is the diameter of the pipe and nu is the kinematic viscosity and V is the velocity of the fluid. It is known that if there is too much head-loss then water will not flow, in such situations pumps are then needed to produce water flow. 
         [0060]    System portion  600  of  FIG. 6 , starts at the aeration zone  602  (such as aeration zone  114 ) is noted to have a height defined as X+Y. The water from the basin is passed through a micro-screen  604  (not shown in  FIGS. 3-5 , but understood to be included in alternative implementations). Passing the source water through micro-screen  604  results in a source water head-loss equal to a height X. The source water from micro-screen  604  is then provided to hydrodynamic separator  606  (such as hydrodynamic separator  308 ), having a height Y. Passing through hydrodynamic separator  606  therefore results in a source water head-loss equal to height Y. The filtered output (e.g., TSS or sludge) from the hydrodynamic separator  606  is passed back to aeration zone  602  as a recycled concentrate via line  608 , with the assistance (in some embodiments) of pump  610 . The source water from which the TSS has been removed is then provided to submerged filter module  612  (such as MBR type membranes  310 ). The filtered source water is then passed to transfer pump  614  and output via line  616 .  FIG. 6  is intended to show an understanding that there will be certain headloss/energy loss occurring through the screen  604  and hydrodynamic separator  606 . In particular, the energy from the height of the aeration basin being X+Y, there is a headloss equal to X in the screen  604 , and a headloss equal to Y in the hydrodynamic separator  606 . Therefore there is a need for the described pumps. 
         [0061]    By review of existing systems by the inventors it is understood by the inventors that approximately 40% of the energy used to treat municipal wastewater with MBR based systems is required to prevent solids from plugging the MBR membranes. The hydrodynamic separator described herein substantially eliminates this energy requirement. However, as shown in  FIG. 6 , the present embodiments of MBR-lite do require energy (e.g., use of pumps) to address head-loss due to the use of the hydrodynamic separator. Nevertheless, as shown in the chart below, dependent upon the height of the aeration basin  602 , net energy savings would exist by implementation of MBR-lite as compared to the operational energy requirements of existing MBR systems. Thus, for example, for an aeration basin 20 feet in height (i.e., X+Y=20 ft.), the overall operational energy requirements for an MBR-lite system which implements membranes having filtering capabilities of less than 100 mg/l TSS, compared to existing MBR systems which include membranes for filtering of up to 12,000 mg/l TSS, is believed to be approximately 28%-32% less. Since at 20 ft. the savings versus MBR is between about 70%-83% and the percent of the overall system energy is 40%, so about 70%-83% of 40% is between about 28%-32%. 
         [0000]    
       
         
               
               
               
             
           
               
                   
               
               
                 X + Y 
                 kwh/m3* 
                 % Savings vs MBR** 
               
               
                   
               
             
             
               
                 10 ft 
                 0.015 
                 79%-92% 
               
               
                 20 ft 
                 0.030 
                 70%-83% 
               
               
                 30 ft 
                 0.045 
                 62%-75% 
               
               
                   
               
               
                 *Pump energy (kwh/m3) = 0.00146 × head-loss and assumes 60% pump efficiency and 95% motor efficiency. 
               
               
                 **MBR energy assumed to be 0.18 kwh/m3, for aeration requirements of MBR alternatives as reported in Black and Veatch, “Cost Effective &amp; Energy Efficient MBR Systems” by C. L. Wallis-Lage, S. D. Levesque, which reported a range of 0.18 to 0.73 kwh/m3. 
               
             
          
         
       
     
         [0062]    Turning to  FIG. 7 , illustrated is another diagram of a portion  700  of a MBR-lite source water treatment system similar to those of  FIGS. 3-5 . This system portion is substantially similar to that of  FIG. 6 , except instead of the submerged UF of  FIG. 6 , pressurized membranes  702  are used. In this design, as the membranes  702  are not submerged, a pump  704  is located to take the output from the hydrodynamic separator  706  ( 606  of  FIG. 6 ) and pump the output to the pressurized membranes  702 . A further difference is that a portion of the source water output  708  from the pressurized membranes  702  is shown as being provided to the aeration zone as recycled backwash for cleaning purposes. Thus the foregoing illustrates the energy requirements of such a MBR-lite system. 
         [0063]    In  FIG. 8  a more detailed example of a pressurized membrane  800  as used in  FIG. 7  is shown. Source water  802  from the hydrodynamic separator is input into the pressurized membranes  804 , which have UF fibers or tubes  806  running through a center portion. As the source water passes through the UF fibers or tubes  806  this filtered source water exits the membrane via the left and right sides as filtered water  808 . The UF fibers or tubes  806  are periodically cleaned, by performing a flush of cross-flow bleed of the membranes, whereby the waste water is removed via output  810 . 
         [0064]    Turning to  FIG. 9  depicted is another embodiment of the present application, where a moving bed bioreactor (MBBR) water treatment system  900  incorporates hydrodynamic separator  902 . Implementation of the hydrodynamic separator  902  provides higher concentration source water for the MBBR, allowing for higher efficiency. Additionally, faster dissolved Chemical Oxygen Demand (COD) removal and higher rates of methane generation may be accomplished at lower energy requirements by use of the hydrodynamic separator. 
         [0065]    Moving bed bioreactors (MBBRs) use fixed biomass on fluidized plastic media to allow for space savings. In existing systems only 30 minutes of MBBR aeration time is required to remove soluble COD. The TSS load is, however, at the high end for conventional UF type membranes, especially if iron salts are used to remove phosphates. The hydrodynamic separator  902  inserted as shown in  FIG. 9 , between high rate moving bed bioreactor (MBBR) (also called a moving bed biofilm membrane reactor—MBB-M-R)  904  and the UF type membranes  906  mitigate this issue. More particularly, in  FIG. 9 , MBBR source water processing system  900  provides the integration of hydrodynamic separator  902  and UF membrane  906  with high rate moving bed bioreactor (MBBR)  904 , which results in significant energy, space and cost advantages. In the system, source water  908  is provided to a pretreatment system  910 , such as known in the art. This pretreatment system performs initial separation operations (such as separation by use of gravity) and a certain amount of separated sludge water is removed via line  912  while source water  908  to be further acted upon is passed via line  914  to the MBBR  904 . A passive screen  916  is provided to maintain the individual elements of fluidized plastic media having fixed biomass  918  within the body of the reactor. Aeration is supplied via air input line  920 . As previously mentioned the acted upon source water  908  is then provided to hydrodynamic separator module  902  for TSS removal. Thus, the TSS is removed prior to the water being processed by the membranes  906 . Then water to be maintained is output via line  922 , and wastewater is moved via line  924 . 
         [0066]    Thus, in this embodiment, adding the hydrodynamic separator within the MBBR water treatment system reduces the TSS load to the membranes resulting in improved filtering performance, which in turn reduces potential fouling, cleaning frequency (e.g., backwash frequency for membrane filters, cleaning chemical costs), and membrane replacement frequency. It is to be understood, that while the hydrodynamic separator is in this embodiment positioned between the MBBR module  904  and the membranes  906 , the hydrodynamic separator  902  can be located in other locations within the system such as between the pretreatment system  910  and the MBBR module  904 , among others. 
         [0067]      FIG. 10 , depicts a portion  1000  of another MBBR water treatment system. In particular,  FIG. 10  focuses on the MBBR module  1002 . This embodiment incorporates hydrodynamic separator  1004  submerged into the MBBR module  1002 . As shown, the hydrodynamic separator  604  is in the form of two separate towers  1006  and  1008 , where each tower in turn is made up of individual hydrodynamic separator devices  1006   a - 1006   n  and  1008   a - 1008   n . Source water  1010  is input into the MBBR module  1002 . Air diffusers  1012  receive air  1014  from air input line  1016  which is supplied by air generator  1018 , similar to that as shown in  FIG. 9 . Also similar to  FIG. 9 , the system includes the fluidized plastic media having fixed biomass (media)  1020 , which are maintained within the reactor  1002  by passive screen  1022 . The hydrodynamic separator towers  1006  and  1008  also act as draft tubes for aeration and media recirculation, by allowing movement of the air from diffusers to be circulated in the MBBR module. The air is also used to keep the media retention passive screens  1022  from being blocked with the media. In this embodiment, the source water from the hydrodynamic separator  1004  is output via line  1018  and the water containing removed particulates (TSS) is output via line  1024 . Thereafter, the separated water is moved via line  1026  to membrane module  1028  for further processing, such as by a submerged or pressurized ultra-filtration membrane system as shown in previous figures. Valves  1030  and  1032  permit for the addition of coagulant feed when further floc development is desired and also for the provision of cleaning chemicals when the system is being cleaned. In the embodiment of  FIG. 10 , the MBBR module  1002  a 12 ft. square basin on its top, with a 20 ft. depth. 
         [0068]    Turning to  FIG. 11 , additional illustrations of a single hydrodynamic separator device  1102 , a hydrodynamic separator tower arrangement  1104 , and a hydrodynamic separator unit  1106  are shown. The hydrodynamic separator tower  1104  is comprised of multiple single separator devices  1102  having capabilities of, for example, separating 40,000 gallons per day. A tower of six separators would therefore be able to filtrate or separate 240,000 gallons per day. Then four individual towers, when combined as a unit is able to separate 1 million gallons per day. In such a unit each tower might have a 2 ft. diameter, and each tower may have 6 separate devices. Each device flow equals 100 liters per minute, such that, again, the unit (formed of four towers) has the capability of acting on 1 million gallons of water per day. The overall unit  1106  footprint could be as small as 5 ft. by 5 ft., for example, at its base. 
         [0069]      FIG. 12  shows that use of the hydrodynamic separator units of the present description allows for the formation of a water processing system having a smaller footprint than is possible using existing system components such as conventional secondary clarifiers. This difference in size is shown more particularly in  FIG. 12  where the footprint for a 1-million-gallon-a-day hydrodynamic separator unit  1202  using the present embodiments may, as mentioned above, have an overall unit footprint of 5 ft×5 ft, whereas a 1-million-gallon-a-day secondary clarifier  1204  would have a diameter of approximately 60 ft, thus, allowing the present system to operate in much smaller areas. 
         [0070]    With continuing attention to the hydrodynamic separators, these components may come in a variety of formats and designs as described, for example in various ones of the previously hereby incorporated by reference documents. Therefore as examples of such configurations but not being limited thereto, it is noted  FIGS. 13-17  depict some of such noted variations. 
         [0071]    With reference now to  FIG. 13 , a single planar spiral separation device  1300  is illustrated. The device  1300  has an inlet  1302 , at least one curved or spiral portion  1304  and outlets  1306 . This planar multi-turn spiral channel device  1300 , in one form, may be cut from plastic. The type of plastic may vary as a function of the specific application and the environment in which it is implemented. In one variation of the device  1300 , the center region of the device  1300  near the inlet  1302  may be removed to allow access for an inlet coupler to be described hereafter. The spirals portion  1304  of the device may take a variety of forms. For example, the spiral portion  1304  may be converging or diverging. As a further example, the outlet  1306  and inlet  1302  locations may be interchanged to suit the application, e.g. for increasing or decreasing centrifugal forces. A centrifugal force generates a flow field in the fluid, e.g., water, that will sweep suspended particles to one side of the channel, including neutrally buoyant particles (e.g., particles having substantially the same density as water, or the fluid in which the particles reside). Separation efficiency depends on many parameters, including, for example, geometry of the channel and flow velocity. Forces on the particles include centrifugal forces and pressure driven forces, among others. 
         [0072]    It should be appreciated that the fundamental operation of individual curved or spiral hydrodynamic separation devices to separate particles in fluid, such as device  1300  or other devices contemplated herein, is described in detail in selected portions of the above referenced patent applications (which are incorporated herein by reference). Therefore, such operation will not be described herein except to the extent that such description will enhance the description of the presently described embodiments. 
         [0073]    With reference to  FIG. 14 , a system  1400  is representatively shown and comprises a plurality of devices  1300  (shown in  FIG. 13 ) stacked in a parallel manner to allow for N-layers of parallel processing of fluid. Also representatively shown in  FIG. 14  is an inlet coupler  1402 —which allows for input fluid to be provided to each device  1300  within the entire stack from a common supply source. The inlet coupler  1402  may take a variety of forms; however, in one example, the inlet coupler  1402  is cylindrical and has perforations formed therein. The perforations correspond to inlets of the devices  1300  stacked in the system  1400 . Outlet couplers of a similar configuration may also be implemented. Two outlet couplers  1404  and  1406  are representatively shown here, although the number of outlet couplers could vary based on the number of outlet paths or channels for each stacked device. The inlet coupler may be joined only with the top channel through an external Al plate, for example. Fluidic connection to all layers may be achieved by punching through all the top layers except for the bottom. At least two fluidic outlets, or outlet couplers such as those shown at  1404  and  1406 , may be connected in the same manner on the top plate. All inlet and outlets connections may also be implemented on the bottom plate. 
         [0074]    With reference to  FIG. 15 , a system  1500  comprises multiple planar curved arc segments  1502  (e.g. fractional arc segments) that are vertically stacked as parallel channels to increase throughput. These planar curved arc segments do not complete a loop for any one segment  1502 , although the characteristics and functions of a spiral device will nonetheless apply to these segments  1502  in this case. The arc segments or curved portions  1502  comprise an inlet  1504 , curved or arc section  1506  and an outlet  1508 . Also shown in  FIG. 15  is an inlet coupler  1510  that, again, allows for an inlet of fluid from a common source to all of the separate arc segments shown. It should be appreciated that the inlet coupler may take a variety of forms. In one form, the inlet coupler is a cylinder and has perforations or a continuous slot corresponding to the inlet of each layer. Like the system  1400  of  FIG. 14 , the system  1500  provides for increased throughput for fluid particle separation. At least one outlet coupler (not shown) may also be implemented. The outlet coupler(s) could resemble the inlet coupler of  FIG. 14 , for example. 
         [0075]    With reference to  FIG. 16 , another planar curved structure  1600  comprising stacked channels (not shown individually) is shown. The curved structure  1600  has an inlet  1602  (which may include an inlet coupler), curved portions  1604  and  1606 , and at least one outlet  1608  or  1610 . As shown, there is an outlet  1608  for selected particles such as particles of a particular size or density (e.g. buoyant particles). The outlet  1608  is positioned midway around the curve between the curved portion  1604  and curved portion  1606 . A second outlet  1610  for selected particles of a second size or density (e.g. neutrally buoyant particles) is positioned at an end of the curve opposite the inlet  1602 . In general, these outlets  1608  and  1610  can be used to remove particles of varying sizes or densities from the fluid flow. As above, at least one outlet coupler may also be utilized. 
         [0076]    With reference to  FIG. 17 , a system  1700  is shown. The system  1700  comprises a plurality of devices  1600 , as shown in  FIG. 16 , that are stacked in a configuration to allow for increased throughput by way of parallel processing. It should be appreciated that the system  1700  may also comprise a single device of increased width. Of course, as above, an inlet coupler and/or at least one outlet coupler may be implemented in the system. 
         [0077]    The described separators can remove &gt;90% of total suspended solids (TSS) continuously and without a filtration barrier. The described hydrodynamic separators also allow variable flow splitting of effluent/waste streams to cater to design needs—50:50 is a good operational spec but such separators can be configured to vary up to a 90:10 split between cleaned water which is the portion of the source water from which sufficient TSS has been removed so that it may be used for its final intended purpose or is in a state that further processing may be undertaken so it becomes appropriate for an end purpose and water that is defined as waste water that is either disposed of or resent through the system for further separation. 
         [0078]    The described systems have low energy requirements, small footprints, and are low cost, simple, robust low-maintenance operation and construction that allow for substitution of expensive MBR membranes with less expensive ones. 
         [0079]    It has also been shown that the hydrodynamic separator can be incorporated with a moving-bed bioreactor (MBBR). This design provides more concentrated feed water allowing for higher efficiency—faster dissolved COD removal, and higher rates of methane gas generation. Removal of TSS by the hydrodynamic separator in turn lowers stress on the membranes, which reduces fouling potential, cleaning frequency (e.g., backwash frequency for membrane filters, cleaning chemical costs) and membrane replacement frequency for MBR membranes. The present systems also increase average energy efficiency of MBR system by reducing slope of flux decline curve from TSS foul. As well as reducing waste sludge volume, treatment costs, and offsite disposal costs. 
         [0080]    It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.