Abstract:
Taught herein is a reclaimed water reuse device, comprising a biological reaction tank, a membrane module, a water pool, an inlet-drainage device, an outlet device, a water-generating device, a first aeration device, a backwash device and a membrane filtering pool, wherein the inlet-drainage device feeds water into or drains water from the biological reaction tank; the water generating pipe supplies clean water from the membrane module to the water pool; the first aeration device cleans the membrane module; the membrane module is disposed in the membrane filtering pool; the backwash device is connected to the membrane module via the outlet device; and the backwash device washes back the membrane filtering pool. A method for cleaning a reclaimed water reuse device is also taught herein.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority to Chinese Patent Application No. 200610062687.7 filed on Sep. 21, 2006, the contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates to the field biochemical engineering, and particularly to a reclaimed water reuse device and a method for cleaning the same.  
         [0004]     2. Description of the Related Art  
         [0005]     The importance of the use of membranes in treatment of waste water is growing rapidly. With the advent of submerged membrane processes in which membrane modules are immersed in a large feed tank and filtrate is collected through suction applied to the filtrate side of the membrane, membrane bioreactors (MBRs) combining biological and physical processes into one stage promise to be more compact, efficient and economic. However, a non-neglectable problem with the MBR is that membrane modules are prone to contamination due to a lack of physical and chemical cleaning.  
         [0006]     The most frequently used methods of physical cleaning include backwash and aeration. These methods need to be performed frequently and thus may influence the filtering process. During backwash, permeation through the membrane is stopped momentarily. Air or water flows through the membranes in a reverse direction to physically dislodge solids off of the membranes. During aeration, bubbles are produced in the tank water below the membranes. As the bubbles rise, they agitate or scrub the membranes and thereby dislodge some solids while creating an air lift effect and circulation of the tank water to carry the solids away from the membranes. The physical cleaning requires a large amount of aeration and energy, long cleaning time, and features comparatively poor cleaning quality.  
         [0007]     Chemical cleaning is typically performed by removing membrane modules from the MBRs, and then immersing the membrane modules into a chemical solution. The chemical cleaning process may be complex and time-consuming.  
       SUMMARY OF THE INVENTION  
       [0008]     In view of the above-described problems, it is one objective of the invention to provide a reclaimed water reuse device that is simple, effective, and features good cleaning quality.  
         [0009]     It is another objective of the invention to provide a method for cleaning a reclaimed water reuse device that is simple, effective, and features good cleaning quality.  
         [0010]     To achieve the above objectives, in accordance with one aspect of the present invention, there is provided a reclaimed water reuse device, comprising a biological reaction tank, a membrane module, a water pool, an inlet-drainage device, an outlet device, a water-generating device, a first aeration device, a backwash device and a membrane filtering pool.  
         [0011]     In certain classes of this embodiment, the inlet-drainage device feeds water into or drains water from the biological reaction tank.  
         [0012]     In certain classes of this embodiment, the water generating pipe supplies clean water from the membrane module to the water pool.  
         [0013]     In certain classes of this embodiment, the first aeration device cleans the membrane module.  
         [0014]     In certain classes of this embodiment, the membrane module is disposed in the membrane filtering pool.  
         [0015]     In certain classes of this embodiment, the backwash device is connected to the membrane module via the outlet device.  
         [0016]     In certain classes of this embodiment, the backwash device washes back the membrane filtering pool.  
         [0017]     In certain classes of this embodiment, a separating plate is disposed in the biological reaction tank.  
         [0018]     In certain classes of this embodiment, the membrane filtering pool is formed by spaces separated via the separating plate.  
         [0019]     In certain classes of this embodiment, water in the biological reaction tank overflows a top the separating plate and pours into the membrane filtering pool.  
         [0020]     In certain classes of this embodiment, a contaminated-soil backflow device is disposed in the membrane filtering pool.  
         [0021]     In certain classes of this embodiment, the contaminated-soil backflow device is connected to the inlet-drainage device and the biological reaction tank.  
         [0022]     In certain classes of this embodiment, the reclaimed water reuse device further comprises a control module for controlling operating state of all devices according to preset data or according to an operating signal of the water-generating device.  
         [0023]     In certain classes of this embodiment, the water-generating device comprises a water-generating device, a self-priming pump, an electromagnetic valve and a pressure gauge.  
         [0024]     In certain classes of this embodiment, the membrane module is connected to the water pool via the water-generating device.  
         [0025]     In certain classes of this embodiment, the self-priming pump, the electromagnetic valve and the pressure gauge are disposed in the water-generating device.  
         [0026]     In certain classes of this embodiment, the pressure gauge detects self-priming pressure of the self-priming pump, and transfers a pressure signal to the control module.  
         [0027]     In certain classes of this embodiment, the control module detects operating state of the membrane module according to the pressure signal, and performs physical or chemical backwash of the membrane module.  
         [0028]     In accordance with another aspect of the present invention, there is provided a method for cleaning a reclaimed water reuse device of the invention comprising: (a) detecting an operating signal of the water-generating device, (b) enabling the first aeration device or the backwash device according to the operating signal, so as to perform backwash on the membrane module, and (c) completing the wash back and restoring to a normal operating state.  
         [0029]     In certain classes of this embodiment, the method for cleaning a reclaimed water reuse device further comprises setting a timing period and enabling the contaminated-soil backflow device when the timing period is up.  
         [0030]     In certain classes of this embodiment, the step of setting a timing period and enabling the contaminated-soil backflow device as the timing period is up comprises (a) starting and entering an operating state by the reclaimed water reuse device, (b) setting the timing period, and (c) alternately enabling the contaminated-soil backflow device and the first aeration device and the second aeration device.  
         [0031]     In certain classes of this embodiment, the step of enabling the first aeration device or the backwash device according to the operating signal, so as to perform backwash on the membrane module comprises (a) setting a pressure threshold and a frequency threshold; (b) receiving a pressure signal from the pressure gauge by the control module, the pressure signal indicating a self-priming pressure of the self-priming pump; (c) comparing the pressure threshold with the self-priming pressure; and (d) if the self-priming pressure exceeds the pressure threshold, detecting whether the frequency at which the self-priming pressure of the self-priming pump exceeds the pressure threshold is greater than the frequency threshold.  
         [0032]     For example, if the frequency threshold is set to 1, then, if in a given time interval, the self-priming pressure of the self-priming pump exceeds the pressure threshold three times, the frequency at which the self-priming pressure of the self-priming pump exceeds the pressure threshold is 3, and is larger than the frequency threshold of 1.  
         [0033]     In certain classes of this embodiment, the step of enabling the first aeration device or the backwash device according to the operating signal, so as to perform backwash on the membrane module further comprises (a) if the frequency at which the self-priming pressure of the self-priming pump exceeds the pressure threshold is greater than the frequency threshold, performing chemical backwash of the membrane module, and (b) if the frequency at which the self-priming pressure of the self-priming pump exceeds the pressure threshold is less than the frequency threshold, enabling the first aeration device and the backwash device to perform physical backwash of the membrane module.  
         [0034]     Advantages of the invention include:  
         [0035]     (a) cleaning and regeneration of the membrane module in the membrane filtering pool can be accomplished without removing the membrane module from the membrane filtering pool, which greatly simplifies an operating process;  
         [0036]     (b) while the membrane module is cleaned and regenerated, the activity in the biological reaction tank will not be affected (namely, a seamless operation between cleaning and normal operation is implemented), and the MBR can be restored to normal operation in a relatively short amount time;  
         [0037]     (c) since the invention integrates the first aeration device with the backwash device, it is easy to apply physical (aeration) backwash, chemical backwash, or a combination thereof, to facilitate complete cleaning, and to regenerate the membrane module to a great extent; therefore, the invention features simple operation and good cleaning efficiency;  
         [0038]     (d) space separated by the separating plate forms a membrane filtering pool, which makes it applicable to all types of water processing systems such as normal active contaminated-soil processing device, oxidation ditch processing device, contact oxidation processing device, and so on, in a cost-effective and simple manner;  
         [0039]     (e) the contaminated-soil backflow device is connected to the inlet-drainage device, so that the high concentration contaminated soil in the membrane filtering pool is able to flow back, which reduces the concentration of the contaminated soil, mitigates pollution of the membrane module caused by the high concentration of contaminated soil, and further improves applicability and reliability of the invention; and lastly  
         [0040]     (f) the control module controls operating states of all devices, and thus facilitates automation of operation and standardization or MBR devices, improves operation efficiency, and makes the invention applicable to large-scale production. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0041]     The invention is described hereinafter with reference to accompanying drawings, in which:  
         [0042]      FIG. 1  is a schematic diagram of a reclaimed water reuse device according to one embodiment the invention;  
         [0043]      FIG. 2  is a block diagram of a reclaimed water reuse device according to one embodiment of the invention;  
         [0044]      FIG. 3  is a partial enlarged view of grooves at the top of the separating plate  5 ;  
         [0045]      FIG. 4  is a high-level flowchart diagram illustrating a method for cleaning of a reclaimed water reuse device according to one embodiment of the invention; and  
         [0046]      FIG. 5  is a detailed flowchart diagram illustrating a method for cleaning of a reclaimed water reuse device according to one embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0047]     Detailed description will be given below with reference to accompanying drawings.  
         [0048]     I. Structure  
         [0049]     As shown in  FIGS. 1 and 2 , a reclaimed water reuse device of the invention comprises a biological reaction tank  1 , a membrane module  2 , a water pool  3 , a membrane filtering pool  4 , a control module  6 , an inlet-drainage device  11 , a water-generating device  21 , an outlet device  31 , a first aeration device  22 , a second aeration device  12 , a backwash device  23 , and a contaminated-soil backflow device  41 .  
         [0050]     The membrane module  2  is disposed in the membrane filtering pool  4 .  
         [0051]     A separating plate  5  is disposed in the biological reaction tank  1 , and separates the membrane filtering pool  4  from the biological reaction tank  1 . Water in the biological reaction tank  1  overflows a top of the separating plate  5  and pours into the membrane filtering pool  4 . The ratio between the volume of the biological reaction tank  1  and that of the membrane filtering pool  4  is between 1:1 and 10:1, and more particularly, the ratio is 3:1.  
         [0052]     A groove  51  is disposed at the top of the separating plate  5 . In this embodiment, the groove  51  is tooth-shaped.  
         [0053]     The inlet-drainage device  11  comprises an inlet pipe  111 , a drainage pipe  112 , and a plurality of electromagnetic valves M 0  and M 1 . The electromagnetic valve M 0  is disposed in the inlet pipe  111 , and the electromagnetic valve M 1  is disposed in the drainage pipe  112 .  
         [0054]     The outlet device  31  drains water from the water pool  3 . The outlet device  31  comprises an outlet pipe  311 , a clean water pump  312 , and an electromagnetic valve M 9 . The clean water pump  312  and the electromagnetic valve M 9  are attached to the outlet pipe  311 .  
         [0055]     The water-generating device  21  comprises a water-generating pipe  211 , a self-priming pump  212 , an electromagnetic valve M 8 , a manual valve H 8 , and a pressure gauge P. The water-generating pipe  211  connects the water pool  3  to the membrane module  2 . The self-priming pump  212 , the electromagnetic valve M 8 , the manual valve H 8 , and the pressure gauge P are connected to the water-generating pipe  211  and disposed between the membrane module  2  and the water pool  3 . The pressure gauge P detects self-priming pressure of the self-priming pump  212 , and transfers the pressure signal to the control module  6 .  
         [0056]     The first aeration device  22  aerates the membrane module  2 , and comprises a first aeration pipe  221 , an electromagnetic valve M 5  and a manual valve H 5 . The electromagnetic valve M 5  and the manual valve H 5  are connected to the first aeration pipe  221 . The first aeration pipe  221  extends to the bottom of the membrane module  2 .  
         [0057]     The second aeration device  12  aerates the biological reaction tank  1 , and comprises a second aeration pipe  121 , an electromagnetic valve M 3  and a manual valve H 3 . The electromagnetic valve M 3  and the manual valve H 3  are connected to the second aeration pipe  121 . The second aeration pipe  121  extends to the bottom of the biological reaction tank  1 .  
         [0058]     The aeration pipe  221  and the second aeration pipe  121  have a common entrance.  
         [0059]     The backwash device  23  washes back the membrane filtering pool  4  and connects the outlet device  31  to the membrane module  2 .  
         [0060]     The backwash device  23  comprises a backwash pipe  231 , a first backwash supporting pipe  232 , a second backwash supporting pipe  233 , electromagnetic valves M 6  and M 7 , and a manual valve H 6 .  
         [0061]     One end of the backwash pipe  231  is connected to the outlet pipe  311 , and the other end of the backwash pipe  231  is a common end of the first backwash supporting pipe  232  and the second backwash supporting pipe  233 . The first backwash supporting pipe  232  is, at its other end, disposed in the membrane filtering pool  4 . The second backwash supporting pipe  233  and the water-generating pipe  211  are connected to the membrane module  2   
         [0062]     The electromagnetic valve M 6  is connected to the first backwash supporting pipe  232 , and the electromagnetic valve M 7  is connected to the second backwash supporting pipe  233 .  
         [0063]     The contaminated-soil backflow device  41  is disposed in the membrane filtering pool  4 , and is connected to the inlet-drainage device  11  and the biological reaction tank  1 .  
         [0064]     The contaminated-soil backflow device  41  comprises a backflow pipe  411 , a first backflow supporting pipe  412 , a second backflow supporting pipe  413 , a backflow pump  414 , and electromagnetic valves M 2  and M 4 .  
         [0065]     The backflow pump  414  is disposed at the bottom of the membrane filtering pool  4 , and connected to one end of the backflow pipe  411 . The other end of the backflow pipe  411  is a common end of the first backflow supporting pipe  412  and the second backflow supporting pipe  413 . The first backflow supporting pipe  412  terminates at the top of the biological reaction tank  1 , and the second backflow supporting pipe  413  is connected to the outlet pipe  112 .  
         [0066]     The electromagnetic valve M 4  is connected to the first backflow supporting pipe  412 , and the electromagnetic valve M 2  is connected to the second backflow supporting pipe  413 .  
         [0067]     II. Operation  
         [0068]     As shown in  FIG. 2 , the control module  6  controls operation of the inlet-drainage device  11 , the water-generating device  21 , the outlet device  31 , the first aeration device  22 , the backwash device  23 , the contaminated-soil backflow device  41 , and the water-generating device  21  according to preset data and/or signal received from the water-generating device  21 . The preset data comprises a timing period T 0 , a delay time T 1 , a pressure threshold F 1 , a frequency threshold f 1 , and so on. The operating signal of the water-generating device  21  comprises a pressure signal of the pressure gauge P, etc. Based on the pressure signal, the control module  6  detects the operating state of the membrane module  2 , and correspondingly performs physical or chemical backwash of the membrane module  2 .  
         [0069]     Referring to  FIG. 2 , the control module  6  directly controls operating states of the electromagnetic valves M 0  . . . . M 9 , the self-priming pump  212 , the clean water pump  312 , and the backflow pump  414 .  
         [0070]     As the reclaimed water reuse device of the invention is in a normal operating state, the backflow pump  414 , the self-priming pump  212 , the clean water pump  312 , and the electromagnetic valves M 4 , M 3 , M 5 , M 8  and M 9  are enabled; the other valves are disabled. Manual valves H 3 , H 5  and H 6  may be manually adjusted to change gas flux and water flux. During normal operation, contaminated water flows in via the inlet pipe  111 , after biological processing and being filtered by the membrane module  2  in the membrane filtering pool  4 , clean water is generated.  
         [0071]     As shown in  FIG. 4 , a method for cleaning a reclaimed water reuse device comprises the following steps:  
         [0072]     i. the reclaimed water reuse device is enabled, and enters a normal operating state;  
         [0073]     ii. a timing period T 0  is set, and saved in the control module  6 ;  
         [0074]     iii. as the timing period T 0  is up, the reclaimed water reuse device is disabled; after a delay time T 1 , the control module  6  enables the contaminated-soil backflow device  41 , so that contaminated soil deposited at the bottom of the membrane filtering pool  4  flows back to a front portion of the biological reaction tank  1 ;  
         [0075]     iv. the control module  6  detects an operating signal of the water-generating device  21 , and enables the first aeration device  22  or/and the backwash device  23  according to the operating signal, so as to perform physical or chemical backwash of the membrane module  2 ; and  
         [0076]     v. after the backwash is completed, the reclaimed water reuse device restores to a normal operating state under the control of the control module  6 , and the process returns to step iii.  
         [0077]     As shown in  FIG. 5 , a detailed method for cleaning a reclaimed water reuse device comprises the following steps:  
         [0078]     1. the reclaimed water reuse device is enabled, and enters a normal operating state;  
         [0079]     2. a timing period T 0  is set, and saved in the control module  6 ;  
         [0080]     3. the control module  6  detects whether the timing period is up, if the timing period is not up, the process proceeds to step 4, otherwise the process proceeds to step 9;  
         [0081]     4. if the timing period is up, the control module  6  detects whether contaminated-soil backflow is enabled. In this embodiment, the control module  6  detects whether contaminated-soil backflow is enabled by checking the signal from the backwash pump  414 , or an operating history saved in the control module  6 . If the contaminated-soil backflow is enabled, the process proceeds to step 5, otherwise the process proceeds to step 6;  
         [0082]     5. after a deposit time T 1 , the control module  6  stops the contaminated-soil backflow and starts aeration. In this embodiment, the control module  6  switches on the electromagnetic valve M 5  in the first aeration device  22  and the electromagnetic valve M 3  in the second aeration device  12 , so that gas is led to the bottom of the membrane module  2  and the biological reaction tank  1  via the first aeration pipe  221  and the second aeration pipe  121 , respectively;  
         [0083]     6. the control module  6  detects whether aeration is enabled. In this embodiment, the control module  6  detects whether aeration is enabled by checking states of the electromagnetic valve M 5  and the electromagnetic valve M 3 . If the aeration is enabled, the process proceeds to step 7, otherwise the process proceeds to step 8;  
         [0084]     7. the control module  6  stops the aeration, and enables the contaminated-soil backflow after the deposit time T 1 ;  
         [0085]     8. the control module  6  enables the contaminated-soil backflow after the deposit time T 1 ;  
         [0086]     9. the control module  6  sets a pressure threshold F 1  and a frequency threshold f 1 . In this embodiment, the pressure threshold F 1  is between +0.04 and −0.04 MPa with respect to the standard pressure of 760 mmHg (101,325 Pa).  
         [0087]     10. the control module  6  receives a pressure signal from the pressure gauge P, the pressure gauge indicating self-priming pressure of the self-priming pump  212 ;  
         [0088]     11. the control module  6  detects whether the self-priming pressure is greater than the pressure threshold F 1 . If the self-priming pressure is greater than the pressure threshold F 1 , the process proceeds to step 12, otherwise the process returns to step 3;  
         [0089]     12. the control module  6  detects whether a frequency at which the self-priming pressure of the self-priming pump  212  exceeds the pressure threshold F 1  is greater than the frequency threshold f 1 . If the frequency at which the self-priming pressure of the self-priming pump  212  exceeds the pressure threshold F 1  is greater than the frequency threshold f 1 , the process proceeds to step 13, otherwise the process proceeds to step 14. In this embodiment, the frequency at which the self-priming pressure of the self-priming pump  212  exceeds the pressure threshold F 1  is equal to 1/(the amount of time the self-priming pressure of the self-priming pump  212  exceeds the pressure threshold F 1  during this time interval—the amount of time the self-priming pressure of the self-priming pump  212  exceeds the pressure threshold F 1  during the immediately preceeding time interval);  
         [0090]     13. the control module  6  exits the normal operating state, and performs chemical backwash on the membrane module  2 ;  
         [0091]     14. the control module  6  exits the normal operating state, and enables the first aeration device  22  and the backwash device  23 , so as to perform physical backwash on the membrane module  2 ; and  
         [0092]     15. under the control of the control module  6 , the reclaimed water reuse device is restored to its normal operating state, and then the process returns to step 3.  
         [0093]     The above steps 4-7 alternately enable contaminated-soil backflow and aeration. The above steps 10-14 implement combination of the physical backwash and the chemical backwash. The membrane module  2  is not required to be taken out of the membrane filtering pool  4  for cleaning. All of this contributes to a good cleaning efficiency.  
         [0094]     A detailed process of the physical backwash is as follows: the control module  6  enables the electromagnetic valves M 5  and M 7  and the clean water pump  312 , the clean water pump  312  pours filtered water into a membrane tube and a membrane hole in the membrane module  2 , so as to perform backwash thereon. Meanwhile, blowing aeration is performed at the bottom of the membrane module  2 , and contaminant deposited on an upper surface of the membrane module  2  is cleaned. The entire process lasts for 2-10 minutes.  
         [0095]     A detailed process of the chemical backwash is as follows: cleaning chemical agent such as acid, alkali, oxidant (sodium hypochlorite) and so on is added to the water pool  3 , and let the biological reaction tank  1  and the membrane filtering pool  4  stand for 5-15 minutes. In this embodiment, the soaking time is 10 minutes. The control module  6  enables the electromagnetic valve M 1  to drain clean water from the upper portion of the biological reaction tank  1 . And then disables the electromagnetic valve M 1 .  
         [0096]     The control module  6  enables the contaminated-soil backflow pump  414  and the electromagnetic valve M 4 , so that active contaminated soil in the membrane filtering pool  4  flows back to the biological reaction tank  1 .  
         [0097]     The control module  6  disables the electromagnetic valve M 4  and enables the electromagnetic valve M 2  after the backflow is completed, so as to discharge clean water in the upper portion of the membrane filtering pool  4  to outside via the contaminated-soil backflow pump  414 .  
         [0098]     The control module  6  disables the contaminated-soil backflow pump  414  after the membrane filtering pool  4  is evacuated.  
         [0099]     The control module  6  enables the clean water pump  312  and the electromagnetic valve M 6 , and allows the cleaning chemical agent to flow into the membrane filtering pool  4 , so as to immerse the membrane module  2 .  
         [0100]     The control module  6  disables the electromagnetic valve M 6  after the cleaning chemical agent immerses the membrane module  2 , enables the electromagnetic valves M 5  and M 7 , and performs chemical backwash on the membrane module  2 . Meanwhile, a membrane surface is scrubbed via aeration.  
         [0101]     The control module  6  disables the electromagnetic valves M 5  and M 7  and the clean water pump  312 , enables the contaminated-soil backflow pump  414  and the electromagnetic valve M 2 , so as to evacuate the cleaning chemical agent in the membrane filtering pool  4 , and then disables the contaminated-soil backflow pump  414  and the electromagnetic valve M 2 .  
         [0102]     While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.