Membrane bioreactor system using reciprocating membrane

Abstract

The present invention relates to membrane bioreactor (MBR) system that includes a mechanical membrane reciprocation system to reduce or eliminate membrane fouling. The disclosed MBR system can be operated with higher flux and lower fouling than MBR systems using air scouring. Furthermore the system can remove nitrogen and phosphorous with one RAS and one or no internal recirculation line. The membrane can be reciprocated by a low RPM motor connected to a pulley via belt to rotate rotor to convert rotational motion into reciprocating motion of membrane. Various mechanical means can also be employed to create the reciprocating motion.

Claims

1. A method of reducing membrane fouling of a membrane in a sequencing batch reactor of a reciprocating membrane bioreactor system, comprising: providing a reciprocating membrane bioreactor system comprising: a biological treatment train (50) for receiving influent (10) to be treated, the biological treatment train (50) producing treated wastewater; a membrane tank (60) housing a membrane (70), the treated wastewater from the biological treatment train (50) being filtered through the membrane (70) to produce effluent (40); a reciprocation apparatus (80) for reciprocating the membrane (70), the reciprocation reducing fouling on the membrane (70), wherein the reciprocation apparatus (80) comprises a motor (103) connected to a pulley (101) via a belt (102) to rotate a rotor (100) so as to convert rotational motion into reciprocating motion of a sliding frame (90) through a shaft (110), wherein the sliding frame is interconnected to the membrane so as to move the membrane submerged in the membrane tank in a horizontal reciprocating motion determined by a speed at which the rotor rotates, wherein the sequencing batch reactor includes the membrane tank, an anoxic tank, and an anaerobic tank within the biological treatment train, the method further comprising: submerging the membrane in the membrane tank of the sequencing batch reactor; mechanically moving the submerged membrane, by the reciprocation apparatus, in a horizontal reciprocating motion with respect to the membrane tank while the membrane is submerged in the membrane tank, thereby shaking foulants from the membrane surface and reducing membrane fouling of the membrane; returning activated sludge, using recirculation lines, from the membrane tank to an anoxic tank and an anaerobic tank of the sequencing batch reactor.

2. A method of reducing membrane fouling of a membrane in a sequencing batch reactor of a reciprocating membrane bioreactor system, comprising: providing a reciprocating membrane bioreactor system comprising: a biological treatment train (50) for receiving influent (10) to be treated, the biological treatment train (50) producing treated wastewater; a membrane (70), the treated wastewater from the biological treatment train (50) being filtered through the membrane (70) to produce effluent (40); a reciprocation apparatus (80) for reciprocating the membrane (70), the reciprocation reducing fouling on the membrane (70) and providing oxygen depleted conditions in the biological treatment train (50), wherein the reciprocation apparatus (80) comprises a motor (103) connected to a pulley (101) via a belt (102) to rotate a rotor (100) so as to convert rotational motion into reciprocating motion of a sliding frame (90) through a shaft (110), wherein the sliding frame is interconnected to the membrane so as to move the membrane submerged in a membrane tank in a horizontal reciprocating motion determined by a speed at which the rotor rotates, wherein the sequencing batch reactor includes the membrane tank, an anoxic tank, and an anaerobic tank within the biological treatment train, the method further comprising: submerging the membrane in a membrane tank of the sequencing batch reactor; mechanically moving the submerged membrane, by a reciprocation apparatus, in a horizontal reciprocating motion with respect to the membrane tank while the membrane is submerged in the membrane tank, thereby shaking foulants from the membrane surface and reducing membrane fouling of the membrane; returning activated sludge, using recirculation lines, from the membrane tank to the anoxic tank and the anaerobic tank of the sequencing batch reactor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which:

(2) FIG. 1 is a general process diagram illustrating the MBR system of the present invention.

(3) FIG. 2 is a general embodiment of the reciprocation apparatus of the present invention.

(4) FIG. 3 is a detailed view of an alternative embodiment of the reciprocation apparatus.

(5) FIGS. 4-12 are process diagrams illustrating various alternative MBR processes of the present invention.

(6) Similar reference characters refer to similar parts throughout the several views of the drawings.

(7) TABLE-US-00001 PARTS LIST 10 Influent 20 Mixed Liquor Flow 21 Anaerobic to Anoxic Flow 22 Anoxic to Aerobic Flow 23 Aerobic to Membrane Tank Flow 24 Anoxic to Anaerobic Flow 25 Anaerobic to Aerobic Flow 30 Activated Sludge Return 31 Activated Sludge Return (Membrane Tank to Anoxic) 32 Internal Recirculation (Anoxic to Anaerobic) 33 Activated Sludge Return (Membrane Tank to Anaerobic) 34 Internal Recirculation (Aerobic to Anoxic) 40 Effluent 50 Biological Treatment Train 51 Anaerobic Tank 52 Anoxic Tank 53 Aerobic Tank 60 Membrane Tank 70 Submerged Membrane, membrane cassette 80 Reciprocation Apparatus 90 Sliding Frame 91 Linear Bearing with Pillow Block 92 Sliding Rail 93 Membrane Cassette Connection Point 94 Dampener 100 Rotor 101 Pulley 102 Belt 103 Low RPM motor 110 Shaft

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(8) The present invention relates to membrane bioreactor (MBR) system that includes a mechanical apparatus for reciprocating a membrane cage (or membrane cassettes) back and forth. The apparatus eliminates the use of air scouring. Repetitive reciprocation of the membrane cage/cassette creates an inertia force acting on the membrane fibers, which shakes foulants off from the membrane surface. The system includes a membrane cage/cassette containing membrane modules that are submerged in either an aerobic tank or a separate membrane tank. The membrane cage/cassette can be mechanically reciprocated via reciprocation apparatus, which enable the disclosed MBR system to be operated with higher flux and lower fouling than MBR systems using air scoring. Various mechanical means can be employed to create the reciprocating motion. The various details of the present invention, and the manner in which they interrelate, are described in greater detail hereinafter.

(9) FIG. 1 illustrates the basic components of the disclosed vibration MBR system. The system includes a biological treatment train 50 for receiving influent 10 to be processed. Various anaerobic, anoxic, and aerobic biological treatment processes can be carried out within treatment train 50. Mixed liquor 20 from treatment train 50 is then passed into membrane tank 60. Membrane tank 60 includes a submerged membrane 70 (or a series of membranes 70). Membrane(s) 70 may be, for example, a low pressure microfiltration (MF) or ultrafiltration (UF) membrane used as a physical barrier for a complete solid-liquid separation. Membrane cage/cassette 70 is mechanically interconnected to a reciprocation apparatus 80. In accordance with the invention, reciprocation apparatus 80 is used in reciprocating membrane 70. Reciprocation apparatus 80, in one non-limiting embodiment, uses a mechanical device for converting rotational motion into reciprocating motion. Filtration through membrane 70 in membrane tank 60 produces effluent 40. Membrane 70 may be continually reciprocated during filtration. Alternatively, membrane 70 can be selectively reciprocated as need to eliminate fouling. A portion of the activated sludge 30 (i.e. return activated sludge or RAS) goes back to biological treatment train 50 to maintain a sludge concentration within train 50.

(10) FIG. 2 illustrates a general embodiment of the reciprocation apparatus 80. Membrane cassette 70 can be connected to a sliding frame 90. A motorized rotor 100 is connected to a sliding frame 90 via shaft 110. The depicted apparatus 80 thereby converts the rotational motion of rotor 100 into the reciprocating motion of the sliding frame 90. The frequency of reciprocation will be dictated by the speed at which rotor 100 is rotated.

(11) An alternative embodiment of such an apparatus is depicted in FIG. 3 and includes a low RPM motor 103 connected to a pulley 101 via belt 102 to rotate rotor 100 to convert rotational motion into reciprocating motion of sliding frame 90 through a shaft 110. Shock load due to reciprocating motion can be reduced by dampener 94 in between sliding frame 90 and shaft 110. Sliding frame 90 can move along sliding rail 92 with linear bearing and pillow block 91 supports (FIG. 3). There are many different types of mechanical equipment that can provide the required reciprocal motion. Those of ordinary skill in the art will appreciate other suitable mechanical devices after considering the invention.

(12) Various alternative embodiments of the present process invention are described in connection with FIGS. 4-12. With regard to FIG. 4, the system consists of a series of biological treatment tanks. These include anaerobic treatment tank 51, anoxic treatment tank 52, aerobic treatment tank 53, and membrane tank 60. The membrane 70 is submerged within membrane tank 60 and can is reciprocated by reciprocation apparatus 80.

(13) The anaerobic treatment tank 51 receives influent 10 to be treated. Thereafter anaerobic treatment tank 51 biologically treats the influent in the absence of dissolved oxygen to release phosphorous for luxury uptake in the following aerobic conditions. In anoxic tank 52 the wastewater is denitrified in oxygen-depleted conditions. Dissolved oxygen is excluded from anoxic tank 52, although chemically bound oxygen may be present. Nitrification and luxury phosphorous uptake occur in the Aerobic treatment tank 53 in the presence of dissolved oxygen. Filtration in the membrane tank 60 produces effluent 40.

(14) There are two recirculation lines for the activated sludge. A line 31 delivers return activated sludge (or RAS) from membrane tank 60 to anoxic tank 52. Additionally, an internal recycle line 32 delivers a portion of the activated sludge from anoxic tank 52 to anaerobic tank 51 to maintain mixed liquor suspended solids (or MLSS). In this invention, RAS takes two roles in conventional activated sludge or MBR processes. In prior art systems, the return flow of activated sludge from membrane tank contains dissolved oxygen (DO). Thus, in prior art systems, the activated sludge from the membrane tank could not be returned to the anoxic 52 or anaerobic 51 tanks due to the high amounts of dissolved oxygen effects on denitrification or phosphorous release. However, with regard the present invention, since physical membrane reciprocation is utilized instead of vigorous air bubbling, the DO in the RAS is minimal compared to conventional MBR. Therefore, only one sludge return line is required for both sludge and nitrate return in the present invention.

(15) The system depicted in FIG. 5 includes anoxic 52 and aerobic 53 treatment tanks which is similar to the well-known Modified Ludzack and Ettinger (MLE) process. As described above, RAS 31 goes to anoxic tank 52 directly from membrane tank 60 for nitrate and sludge return in this invention. FIG. 6 represents another embodiment which consists of same reactors depicted in FIG. 4. However, return activated sludge 33 goes to anaerobic 51 treatment tank and an internal recycle 34 is made in between aerobic 53 and anoxic 52 tanks. FIG. 7 illustrates an embodiment similar to the process described in FIG. 6. However, there is no internal recirculation and the RAS goes to the anoxic tank where denitrification occurred. FIGS. 8, 9, 10 and 11 are modified systems depicted in FIGS. 4, 5, 6 and 7 respectively. The difference is in the existence of the membrane tank. The systems in FIGS. 4-7 have a separate membrane tank 60, but the systems in FIGS. 8-11 do not have a separate membrane tank 60. Namely, tanks 53 in FIGS. 8-11 function as both a membrane tank and as bioreactor. FIG. 12 shows further example of the processes developed in this invention which consists of simplest reactor configurations. Reciprocating membrane is submerged in a single bioreactor where both biological removal and membrane separation occur. The reactor can be aerated tank, pond or sequencing batch reactor (SBR) where aerobic and anoxic conditions are made in cyclic sequence.

(16) The present disclosure includes that contained in the appended claims, as well as that of the foregoing description. Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention.