Abstract:
Oscillatory crossflow membrane separation apparatus and methods are disclosed for effluent treatment. The apparatus include a membrane module with a housing containing a membrane element, said module having an input for receiving effluent for treatment and a treated effluent output. A crossflow pump is connected for moving oscillating fluid through the membrane module and a feed pressure pump is connected with the membrane module for applying membrane operating pressure. A fluid oscillator is active with either pump for pulsating fluid received thereat.

Description:
RELATED APPLICATION 
       [0001]    This Application is a Continuation of now pending U.S. patent application Ser. No. 12/452,774 filed Jan. 22, 2010 by the inventors herein and entitled Oscillatory Crossflow Membrane Separation, which prior application is a continuation of U.S. patent application Ser. No. 11/888,512 filed Aug. 1, 2007 by inventors including the inventors herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to effluent treatment, and, more particularly, relates to membrane separation apparatus. 
       BACKGROUND OF THE INVENTION 
       [0003]    Most industrial and municipal processes require water treatment facilities to treat effluents returned to the environment. Such facilities typically represent a significant investment by the business/community, and the performance of the facility (or failure thereof) can seriously impact ongoing operations financially and in terms of operational continuity. 
         [0004]    Moreover, not all effluent treatment requires the same technologies. Industrial effluents (such as is found at coal bed methane facilities or oil production sites, for example) all have different particulate, pollutant and/or biomass content inherent to both the industrial processes as well as the particular water and soil conditions found at the site. Municipal requirements would likewise vary depending on desired end-of-pipe quality and use (and again depending on the feed water present at the site). 
         [0005]    Membrane separation apparatus have been previously suggested and/or utilized. Such apparatus require frequent maintenance and cleaning or replacement of membrane elements fouled over time. Vibration of membranes has been suggested heretofore wherein a membrane module is tortionally vibrated. Such apparatus have typically required use of specially designed, single source (and thus expensive) membranes. In such designs, moreover, each membrane module requires its own vibratory energy source. 
         [0006]    Therefore, improvements directed to such apparatus could still be utilized. Moreover, improved treatment technologies adapted to this and other uses can always be utilized given the criticality of provision and maintenance of clean water. 
       SUMMARY OF THE INVENTION 
       [0007]    This invention provides an oscillatory crossflow membrane separation apparatus and methods wherein membrane modules are not physically moved. The apparatus thus provides for less expensive membrane separation processing (reduced maintenance and replacement costs). Adequate shear in treatment of contaminated water to increase permeate continuity for feedwater having moderate colloidal loading is achieved. The apparatus employs vibratory membrane treatment without moving sensitive membrane elements or modules and associated components. This minimizes energy requirements while simultaneously increasing membrane longevity. Standard membrane elements modules/housings may be used. 
         [0008]    The membrane separation apparatus of this invention includes a membrane module having a housing containing a membrane element, the module provide with an input for receiving effluent for treatment and a treated effluent output. A fluid oscillator pulsates fluid received thereat, and a crossflow pump is connected with the fluid oscillator and the membrane module input for moving oscillating fluid through the membrane module. In another embodiment of the apparatus, the crossflow pump is connected with the membrane module input for moving fluid through the membrane module. The fluid oscillator pulsates fluid applied by the feed pressure pump. 
         [0009]    The methods of this invention include the steps of directing effluent fluid to be treated to a membrane separation module through a fluid feed line, applying fluid through a fluid pressure line at the membrane separation module to establish selected membrane pressure, and oscillating fluid in one of the feed line and the fluid pressure line. 
         [0010]    It is therefore an object of this invention to provide provides an oscillatory crossflow membrane separation apparatus and methods wherein membrane modules are not physically moved 
         [0011]    It is another object of this invention to provide an oscillatory crossflow membrane separation apparatus and methods that promotes less expensive membrane separation processing by reducing energy, maintenance and replacement costs. 
         [0012]    It is another object of this invention to provide an oscillatory crossflow membrane separation apparatus and methods wherein adequate shear in treatment of contaminated water to increase permeate continuity for feedwater having moderate colloidal loading is achieved. 
         [0013]    It is still another object of this invention to provide an oscillatory crossflow membrane separation apparatus and methods employing vibratory membrane treatment without moving sensitive membrane elements or modules and associated components. 
         [0014]    It is yet another object of this invention to provide a membrane separation apparatus for effluent treatment that includes a membrane module including a housing containing a membrane element, the module having an input for receiving effluent for treatment and a treated effluent output, a fluid oscillator for pulsating fluid received thereat, and a crossflow pump connected with the fluid oscillator and the membrane module input for moving oscillating fluid through the membrane element. 
         [0015]    It is another object of this invention to provide a membrane separation apparatus for effluent treatment including a membrane module including a housing containing a membrane element, the module having an input for receiving effluent for treatment and a treated effluent output, a crossflow pump connected with the membrane module input for moving fluid through the membrane element, a feed pressure pump connected with the membrane module for applying fluid establishing membrane pressure, and a fluid oscillator for pulsating fluid applied by the feed pressure pump. 
         [0016]    It is yet another object of this invention to provide a method for vibratory membrane separation of an effluent fluid to be treated that includes the steps of directing effluent fluid to be treated to a membrane separation module through a fluid feed line, applying fluid through a fluid pressure line at the membrane separation module to establish selected membrane pressure, and oscillating fluid in one of the feed line and the fluid pressure line. 
         [0017]    With these and other objects in view, which will become apparent to one skilled in the art as the description proceeds, this invention resides in the novel construction, combination, and arrangement of parts and methods substantially as hereinafter described, and more particularly defined by the appended claims, it being understood that changes in the precise embodiment of the herein disclosed invention are meant to be included as come within the scope of the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The accompanying drawings illustrate a complete embodiment of the invention according to the best mode so far devised for the practical application of the principles thereof, and in which: 
           [0019]      FIG. 1  is a diagram illustrating an oscillatory fluid column crossflow membrane separation system of this invention utilizable in primary treatment of effluents; 
           [0020]      FIG. 2  is a diagram illustrating a vibratory retentate membrane separation system of this invention utilizable in primary treatment of effluents; and 
           [0021]      FIG. 3  is a diagram illustrating another alternative oscillating retentate membrane separation system of this invention. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0022]    In accordance with another aspect of this invention, a first embodiment of a membrane separation apparatus and method utilizable with known membrane separation systems is shown in  FIG. 1 . This invention relates to apparatus and methods for fluid filtering utilizing membrane separation (for example nanofiltration and/or reverse osmosis filtration) that combines vibratory shear techniques with adjustable crossflow techniques. This and further embodiments of the membrane separation apparatus and methods (set forth hereinafter) are particularly well adapted to effluent (water) treatment options generically referred to hereinafter as membrane treatment systems (often typically high frequency applications are utilized). 
         [0023]    High frequency membrane separation herein refers to vibrating, oscillatory motion relative to membrane elements. Vibration direction is perpendicular to the floor of an installation for gravity assisted membrane separation systems. The vibration curve is preferably a regular curve, which corresponds mathematically to a zero centered sine or cosine, a sinusoidal or simple harmonic. The amplitude is preferably steady and frequency high. 
         [0024]    The shear wave produced by axial vertical vibration causes solids and foulants to be lifted off membrane surfaces and remixed with retentate flowing through the parallel or tunnel spacer or other specially designed spacers of spirally wound elements or through flow channels of tubular or capillar membrane elements. Movement continuity is maintained through the adjustable crossflow, reducing further additional membrane fouling tendency. 
         [0025]    This hybrid approach using adjustable crossflow and high shear processing exposes membrane surfaces for maximum flux (volume of permeate per unit area and time) that is typically higher than the flux of conventional vibratory membrane technology alone. In the conventional vibratory membrane design, each membrane module requires its own vibratory energy source. Only a single vibratory source needs to be utilized for multi-membrane module designs (up to thirty-two 2.5″, sixteen 4″ or eight 8″ membrane modules). 
         [0026]      FIGS. 1 through 3  illustrate the oscillatory crossflow membrane separation apparatus and methods of this invention. The apparatus and methods of this aspect of the invention achieve adequate shear in treatment of contaminated water to increase permeate continuity for feedwater having moderate colloidal loading. The apparatus employs vibratory membrane treatment without moving sensitive membrane elements  3405  or modules  3311  and associated components. This minimizes energy requirements while simultaneously increasing membrane longevity. Standard membrane elements  3405  and standard modules/housings  3311  may be used. 
         [0027]    Thickness of the membrane boundary layer is affected by the permeate flux rate. However, oscillatory crossflow shear forces, together with a spacer introduced homogenization effect, reduces the size of the boundary layer by pulling suspended particles back. This, in turn, keeps them from settling and returns the particles to the bulk stream. The bulk stream contains the returned particles between the membrane leaves. 
         [0028]    In apparatus/system  4301  oscillatory shear forces are provided by the pulsing crossflow medium itself, oscillatory crossflow pulsations generated by modified piston or diaphragm pump  4303  (for example, pumps from SPECK, WANNER, CAT, DANFOSS (Nessie), or others). Pump modification consists of the removal of the particular pump suction and discharge check valves. 
         [0029]    This valveless pump  4303  provides no true pumping. Only an up and down, pulsating fluid column is generated by the valveless pump. Since valveless pump  4303  in apparatus  4301  does not function as an operational pump, it will be referred to hereinafter as a fluid oscillator. Since oscillator  4303  does not have to produce a high pressure gradient, its operating energy requirement is very low. Oscillation amplitude (height of the fluid column) depends on the relationship between the combined membrane flow channel displacement volume, geometric displacement volume of fluid column oscillator  4303 , and membrane element  3405  length. 
         [0030]    Crossflow movement of the oscillating fluid column over membrane element  3405  is provided by pump  2909 / 2913 , for example. Valve controlled bypass  4305  is located between the discharge from crossflow recirculation pump  2909 / 2913  and after the discharge end of oscillator  4303  for purposes of bypassing oscillator  4303  and/or fine tuning the pulsation effect. System feed pressure is provided by high pressure pump  2907 / 2911 . 
         [0031]    Feed pressure pump  2907 / 2911  provides the applied membrane pressure after adjusting for the permeate pressure and, if applicable, for the osmotic pressure. Crossflow pump  2909 / 2913  provides a stream of prefiltered (as heretofore discussed and indicated generally herein at  4307 ) feed fluid passing over the surface of membrane element  3405  which flows perpendicular to the permeate stream. Oscillator  4303  provides the pulsating shear force effect to the combined flow volume of the other two pumps and operates in series with pump  2907 / 2911 . 
         [0032]    The primary application for apparatus  4301  and related methods is for membrane systems having small, combined membrane flow-channel displacement volume, wherein, despite a relatively small geometric displacement volume of fluid column oscillator  4303 , an adequate oscillation amplitude height producing an effective shear action to minimize the thickness of the membrane boundary layer is produced. The methods and apparatus  4301  for oscillatory crossflow membrane separation can be applied whenever a crossflow, combined with a reduced permeate flux, is otherwise insufficient to reduce the boundary layer thickness. Upgrade and maintenance situations can make particularly effective use of apparatus  4301 . Apparatus  4301  would also be useful in treatment settings where the medium to be treated shows a high scale formation potential caused by high concentration of dissolved salts. 
         [0033]      FIG. 2  shows an operating principle variation of the system shown in  FIG. 1 . In this embodiment, oscillator  4303  works against pump  2907 / 2911 . This embodiment is particularly useful if the medium to be treated shows a high fouling potential caused by suspended solids of colloidal matter and organics.  FIG. 3  shows yet another variation of the system shown in  FIG. 1 . Fluid column oscillation is provided by double-acting cylinder system  4501  with a single piston. The piston is powered by an electrical crankshaft drive. The double-acting cylinder system enhances the fluid column oscillation over the entire membrane. 
         [0034]    In operation, during a piston upstroke in oscillator  4303 / 4501 , the fluid column within the leaves of membrane element  3405  is accelerated upwards, the upward movement starting at the discharge end of membrane element  3405 . The pneumatic accumulator of a standard membrane module  3311  acts as a hydraulic balancer in the system of this aspect of the invention. Air pressure in the accumulator acts as a weight for raising the piston by pushing the stand pipe&#39;s fluid column against the bottom side (rod side) of the piston thus assisting the column&#39;s upward movement over the entire membrane length and minimizing slip and localized hydroshock. Piston friction is reduced allowing for high oscillating frequency operation. 
         [0035]    During a piston downstroke in oscillator  4303 / 4501 , the fluid column within the leaves of membrane element  3405  is accelerated downward, the downward movement starting at the discharge end of the membrane. The momentary void at the lead end of membrane element  3405  is augmented by the stored energized volume from the hydropneumatic accumulator, thus providing an uninterrupted downward movement of the fluid column over the entire membrane length and minimizing slip and localized cavitation. 
         [0036]    The pneumatic accumulator of module  3311  also serves as a water hammer and surge pressure absorber (shock dampener). The internal hydromechanical shock vibrations introduced by the oscillator  4303 / 4501  could cause damages to membrane element  3405 . The accumulator dampens these hydromechanical shocks without reducing significantly the adequacy of hydromechanical shear to the boundary thickness layer of element  3405 . 
         [0037]    In general, apparatus  4301  works with a low crossflow velocity. In order to secure a reversal in shear direction and produce a useful shear velocity, the crossflow velocity must be lower than the fluid column oscillation velocity. The fluid column up-stroke works against the downward directed crossflow. The oscillatory axial crossflow membrane separation apparatus and method of  FIGS. 1 through 3 , when compared to non-oscillating conventional crossflow membrane systems operating at a standard crossflow velocity of 1 m/s, reveals that these new oscillatory apparatus produce higher shear rates by a magnitude due to motional fluid acceleration. The oscillatory crossflow membrane separation method of this invention produces approximately five times greater a shear rate with the up-stroke, and approximately 14 times greater a shear rate with the down-stroke oscillation than the conventional crossflow membrane separation systems. 
         [0038]    As may be appreciated from the foregoing, apparatus and methods are provided for oscillatory crossflow membrane separation wherein vibratory membrane treatment is achieved without moving sensitive membrane elements or modules and associated components, thus minimizing energy requirements while simultaneously increasing membrane longevity. Standard membrane elements and modules/housings may be used in the apparatus.