Abstract:
A syphon filtration system is a low head, small foot print, long operating cycle, gravity filtration system for treatment of water and wastewater, with one-stage or two-stage filtration in one vessel with different filtration media of sand, anthracite, granular activated carbon or other proprietary filtration media. The one-stage filtration system removes suspended solids or dissolved impurities and the two-stage filtration system removes suspended solids and dissolved impurities. In the two-stage filtration system, each filtration stage can be backwashed independently or both stages can be backwashed simultaneously. Novel syphon piping and controls design extend the filtration operating cycle and reduce the filter apparatus headroom, and the filter backwash water volume requirements.

Description:
FIELD OF THE INVENTION 
     The invention is an apparatus and process for treatment of water and wastewater for removal of suspended solids and dissolved impurities. 
     BACKGROUND OF THE INVENTION 
     Filtration systems are used for treatment of water and wastewater for removal of suspended and/or dissolved impurities. 
     The filtration systems are usually one-stage, gravity or pressure flow systems. Filters can operate in a horizontal or vertical flow pattern: however, the vertical flow pattern is predominant. In the vertical flow pattern the liquid flow through the filter can be downward or upward during the production cycle and the filter backwashing is usually with upward liquid flow, however a combination of upward and downward liquid flow is also possible. Single or multiple filters can be used and multiple filters can be operated in series or in parallel arrangements. Filters can use filtration media with specific gravity higher or lower than the specific gravity of the liquid filtered. 
     The gravity flow filtration systems depend on a static water pressure (head) above the filter media for the water to flow through the media. The available static water pressure above the filter media is directly proportional to the filter vessel height above the filter media. Therefore, the higher the filter vessel above the filter media the longer the operating cycle is expected for the same water quality and flow rate treated. 
     The filtration systems are usually provided for removal of suspended solids or dissolved impurities and each usually requires an independent filtration apparatus. 
     If two stage suspended and/or dissolved solids filtration system is required, two independent filtration apparatus, operating in series are used. 
     Similarly, if suspended solids filtration and dissolved impurities filtration processes are required two independent filtration apparatus, operating in series are used. 
     Filter media need to be backwashed and preferably rinsed after they are plugged with the impurities which they remove. Each filtration apparatus is backwashed and preferably rinsed independently. The backwash and rinse water is predominantly wasted. The rinse water is predominantly the same as the backwash water and the rinse cycle follows the backwash cycle, although, the backwash water flow rate can be different or the same as the rinse water flow rate. 
     The invention offers several advantages over the conventional filtration systems as follows:
         The novel syphon piping and control system, used in this invention, allows for reduction of the filter headroom requirements and it extends the filter operating cycle between the filter backwashings.   The novel syphon piping and control system design prevents the filter media from being exposed and disturbed on the surface during the filtration process.   The novel piping and control system design uses simple open/close automatic control valves to control the water level above the filter media and to perform the production, backwashing and rinsing processes, and minimizes the number of the control valves needed to perform all the processes.   The two-stage filtration system in one vertical apparatus reduces the foot print requirements and permits use of the same or different filtration media in each stage of the filtration apparatus.   The two-stage filtration system permits independent and simultaneous backwashing and rinsing of the filter media in both stages of the filtration system which reduces the backwash water and time requirements.   The two-stage filtration system in one apparatus requires less extensive controls and reduces the costs of the treatment system.       

     BRIEF SUMMARY OF THE INVENTION 
     The filtration system of the present invention is a process and apparatus for treatment of water and wastewater for removal of suspended solids and dissolved impurities. 
     The filtration system as shown on  FIG. 1  uses a novel siphon piping and control system design which results in a lower head room requirements, an extended filtration cycle, a less frequent backwashing, a lower backwash wastewater volume and a lower filtration down time. 
     The two-stage filtration system in one apparatus, as shown on  FIG. 2 , results in a smaller footprint requirement and it lends itself to performing two different filtration processes such as a roughing and polishing filtration for removal of suspended solids, and a filtration process for removal of suspended solids and an adsorption filtration for removal of dissolved impurities in one apparatus. 
     The two-stage filtration system uses the one-stage syphon piping and control system design. 
     The two-stage filtration system backwashing of the filtration media can be done separately for each stage or jointly for both stages which results in a reduction of the backwash water volume requirements. 
     The filtration system comprises:
         A vessel of steel, plastic, concrete or wood construction, vertical and preferably round, square or rectangular in cross section, approximately two to four meters in height. Open or close on the top, non-pressure vessel, one continuous vertical vessel for the one-stage filtration process and divided approximately in the middle of its height, with a solid horizontal plate (floor), for the two-stage filtration process.   Filtration media of sand, anthracite, activated carbon or other proprietary adsorption or non-adsorption type media.   Piping and control valves with a syphon arrangement.   A water level sensor and controller for activation of the syphon piping and the first-stage filtration media backwashing.   A deferential pressure control gauge for activation of the second stage filtration media backwashing.   A main controller for control of the operation of the piping syphon action and operation of the control valves, and the first and the second stage filter backwashing and rinsing processes.       

     Both, the one-stage and two-stage filtration systems operation can be fully automated with a PLC control system. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       Having thus generally described the invention, it will be referred to more specifically by reference to accompanying drawings illustrating preferred embodiments, and in which: 
         FIG. 1  is a diagrammatic illustration in vertical cross-section of the one-stage syphon filtration system. 
         FIG. 2  is a diagrammatic illustration in vertical cross-section of the two-stage syphon filtration system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     According of the embodiment of the invention, as shown on  FIG. 1 , the syphon filtration system comprises; a filter unit  1 , filter external piping and control valves  28 , and a filter controller  41 . 
     The filter unit  1  comprises; a filter vessel  2 , filter media  3 , a filter underdrain system  4 , an outlet water internal pipe  5 , a water level sensor and controller  6 , an inlet water internal distribution pipe  14 , and a backwash water collector trough  15 . 
     The filter external piping and control valves  28  comprise; an inlet water pipe  12 , an inlet water valve  13 , an outlet water pipe  16 , an outlet water control valve  17 , an outlet water syphon pipe  18 , an outlet water discharge pipe  19 , a syphon control valve  20 , a syphon vent pipe  21 , a rinse water discharge pipe  22 , a rinse water discharge control valve  23 , a backwash water supply pipe  25 , a backwash water supply control valve  26 , a backwash water rate of flow control valve  27 , a backwash water discharge pipe  29 , and an air vacuum pump  30 . 
     The filler controller  41  comprises indicating lights, switches, relays, and a PLC, and it is connected to the water level sensor and controller  6  and the control valves  17 ,  20 ,  23 , and  26 , and to an external command station to activate the filtration system production and idle operation cycles, with control wires  42 . 
     The water level sensor and controller  6  provides inputs to the filter controller  41  on water levels  8  and  9  in the filter vessel  2 . 
     The filter controller  41  controls open and closed status of the control valves  17 ,  20 ,  23  &amp;  26  according to the water levels  8  &amp;  9  in the filter vessel and a time logic program contained in the PLC for the filter media backwashing and rinse cycles and an external command for production or idle cycles. 
     The filter media  3  can be a single or multi-media composed of sand, anthracite, activated carbon or other proprietary media designed to remove specific suspended solids or dissolved impurities. 
     The filter underdrain system  4  can be made of sand and gravel, single or multilayer or constructed with a false bottom with slotted or perforated nozzles provided with metering tubes for air scour before the water backwashing. 
     The inlet water external pipe  12  is provided with an inlet water valve  13  which is a non-return valve, mounted horizontally, low hydraulic head open/close operation, full port design, equal to the cross section of the inlet water external pipe  12  preferably a swing type in a gravity inlet water supply system. The inlet water external pipe  12  is connected horizontally to the filter vessel  2  above the water level  7  and below the water level  8 , and preferably not lower than one-third of the filter media depth above the filter media. 
     The backwash water collector trough  15  is a slotted or perforated pipe grid to uniformly collect the backwash water from the entire cross-section of the filter vessel  2 . 
     The outlet water syphon pipe  18  is located above the filter media  3 , preferably minimum 150 to 200 mm, to ensure a minimum water level  7  of 150 to 200 mm in the filter above the filter media  3  to ensure that the filter media are always fully submerged in water during the filter production and rinse cycles and not disturbed by the water falling of the internal distribution pipe  14 . 
     The inlet water enters the filter through the inlet water external pipe  12 , the non-return valve  13  and the internal distribution pipe  14 , and it flows downward as indicated by an arrow  10 . The inlet water passes through the filter media  3 , the underdrain system  4 , the outlet internal pipe grid  5 , the external outlet pipe  16 , the control valve  17 , the syphon pipe  18  and the discharge pipe  19 . The outlet internal pipe grid  5  is made of perforated or slotted pipes arranged such to evenly collect the filtered water during the filtration and rinsing cycles from the entire cross section of the filter and to evenly distribute the backwash water throughout the entire cross section of the filter during the backwash cycle with a preferred water velocity in the mind pipe and the pipes perforations/slots of approximately 1.0 m/s to 1.5 m/s. 
     The backwash water is provided through the backwash water supply pipe  25 , the control valve  26  and the rate of flow control valve  27  into the pipe grid  5 , and the underdrain system  4 , the filter media  3 , and it flows upward, as indicated by an arrow  11 , into the backwash water collector trough  15 , and the discharge pipe  29 . 
     During the rinse cycle, the inlet water flows through the filter media  3  into the underdrain system  4  and the outlet pipes  5  and  16  and the rinse water discharge pipe  22  to the backwash water discharge pipe  29 . The rinse water discharge pipe  22  is connected to the backwash water discharge pipe  29  at the same level as the outlet water syphon pipe  18  to prevent exposure of the filter media  3  during the rinse cycle as the hydraulic head loss through the filter media  3  during the rinse cycle is very low. The filter media rinse flow rate is the same as the filter production flow rate in a constant inlet water flow rate operation. 
     The filter operating cycles comprise a filtration cycle without syphon action, a filtration cycle with syphon action, a backwashing cycle, a rinsing cycle and an idle cycle. 
     During the filter operating cycles the control valve status is as follows:
         Filtration cycle without syphon action or idle cycle:
           The control valve  17  is open.   The control valve  20  is open.   The control valve  23  is closed.   The control valve  26  is closed.   
           Filtration cycle with syphon action:
           The control valve  17  is open.   The control valve  20  is closed.   The control valve  23  is closed.   The control valve  26  is closed.   
           Backwashing cycle:
           The control valve  17  is closed.   The control valve  20  is closed.   The control valve  23  is closed.   The control valve  26  is open.   
           Rinsing cycle:
           The control valve  17  is closed.   The control valve  20  is open.   The control valve  23  is open.   The control valve  26  is closed.   
               

     The filtration with the syphon action is provided by the filter discharge pipes  16 ,  18  &amp;  19  arrangement in an inverted ‘U’ shape and closure of the control valve  20 . By opening of the control valve  20  the syphon action is lost and the filter operates without the syphon action. 
     The syphon action is activated by closing the control valve  20  when the water in the filter vessel  2  reaches the level  8 . This operation is controlled by the water level sensor and controller  6  and the filter controller  41 . 
     The syphon action causes the water level in the filter vessel  2  to drop initially, but the water level will rise again, after a certain time, as the filter media  3  are further plugged with the water impurities retained by the filter media. 
     When the water level in the filter vessel  2  reaches the level  9  the backwashing cycle is activated and it continues for a predetermined period of time, controlled by the filter controller  41 . 
     The filter rinsing cycle follows immediately the backwashing cycle for a predetermined period of time, controlled by the filter controller  41 . 
     After the rinsing cycle, the filter operation returns to the filtration cycle without the syphon action or to the idle cycle which has the same control valve position as the filtration cycle without syphon action. 
     During the filtration cycle with the syphon action air or other gas may be released from the water and it may accumulate in the filter syphon pipe  18 . If this condition is detected the air vacuum pump  30  is activated to remove the air or other gas from the syphon pipe  18 . This ensures an efficient action of the syphon piping system. 
     The rinse water discharge pipe  22  is connected to the backwash water discharge pipe  29  at the same level as the syphon pipe  18  elevation, to ensure that the water level in the filter vessel  2  does not drop below the low water level  7  during the filter rinsing cycle. This prevents the filter media  3  from being exposed and disturbed on the surface by the inlet water. 
     A second embodiment of the invention is shown on  FIG. 2 . 
     For the various embodiments disclosed here, the same reference numeral numbers are used for the same or substantially similar features. 
     The filter vessel  2  is divided into upper and lower compartment by a solid horizontal plate/floor to accommodate first and second stage filtration and comprises two independent filter media  3  and  31 , two independent underdrain systems  4  and  32 , two independent water outlet pipes  5  and  33 , two independent backwash water collecting troughs  15  and  34 , and two independent backwash water supply pipes  25  &amp;  38  and control valves  26  &amp;  39  and rate of flow control valves  27  &amp;  40 . 
     The other additional features comprised in this embodiment are control valves  35 ,  36  &amp;  37 , and a differential pressure switch  43 . 
     The filter operating cycles are the same in this embodiment as those outlined in the first embodiment and they comprise:
         Filtration without the syphon action or idle cycle.   Filtration with the syphon action.   Backwashing cycle.   Rinsing cycle.       

     The filter backwashing can be performed jointly or independently for both filter media  3  and  31  followed by a joint or independent rinsing cycles of each filter media respectively. 
     If a joint filter backwashing and rinsing cycles are performed for both filter media  3  and  31 , the filter media  3  backwashing and rinsing cycles can be extended beyond those performed for the filter media  31  as required. 
     The various combinations of the backwashing and rinsing cycles are outlined as follows:
         Joint backwashing of both filter media  3  and  31 :
           The control valves  35  &amp;  39  are open, the backwash water supply is provided from pipe  38 .   The control valves  17 ,  20 ,  23 ,  36 ,  37  &amp;  26  are closed.   The backwash water flows upward through the filter media  31  and  3  to the backwash water collecting trough  15  and discharge pipe  29 .   
           Joint rinsing of both filter media  3  &amp;  31 :
           The control valves  20 ,  23  &amp;  35  are open.   The control valves  17 ,  26 ,  36 ,  37  &amp;  39  are closed.   The rinse water flows downward through the filter media  3  and  31  to the discharge pipe  33  and the rinse water discharge pipe  22  and the backwash water discharge pipe  29 .   
           Independent backwash and rinsing cycles of the filter media  3 :
           Backwashing Cycle   The control valve  26  is open.   The control valves  17 ,  20 ,  23 ,  35 ,  36 ,  37  &amp;  39  are closed.   The backwash water supply is provided from the pipe  25  and the water flows upward through the filter media  3  to the backwash water collecting trough  15  and the backwash water discharge pipe  29 .   Rinsing Cycle   The control valves  37 ,  23  &amp;  20  are open.   The control valves  17 ,  35 ,  36 ,  37  &amp;  39  are closed.   
           Independent backwashing and rinsing cycles of the filter media  31 :
           Backwashing Cycle   The control valves  39  &amp;  36  are open.   The control valves  17 ,  20 ,  23 ,  26 ,  35  &amp;  37  are closed.   Rinsing Cycle   The control valves  23 ,  35  &amp;  20  are open.   The control valves  17 ,  36 ,  37 ,  39  &amp;  26  are closed.