WASTEWATER TREATMENT SYSTEM

Abstract

A system for treating wastewater comprising a coagulation-flocculation assembly having a raw wastewater inlet and a coagulated-flocculated wastewater outlet; and a slurry separator comprising an intake area configured for receiving wastewater slurry from the coagulated-flocculated wastewater outlet, a liquid outlet, a sludge outlet, and a filtration module configured to facilitate percolating of liquid therethrough and forming of a filter cake thereon. The slurry separator being configured to receive slurry at the intake area, separate the slurry to liquid and sludge by the filtration module, remove the liquid via the liquid outlet, and convey the sludge from the intake area to the sludge outlet. The system further comprises a level maintaining arrangement configured to maintain at least a minimal level of the filter cake.

Claims

1. A system for treating wastewater, comprising: a coagulation-flocculation assembly having a raw wastewater inlet, a coagulated-flocculated wastewater outlet, a coagulating agent inlet configured to facilitate introduction of coagulating agent to the coagulation-flocculation assembly, said coagulation-flocculation assembly being configured to receive raw wastewater through said raw wastewater inlet, facilitate mixing of the raw wastewater with the coagulating agent therein so as to form coagulated wastewater, facilitate flocculation of coagulated wastewater so as to form coagulated-flocculated wastewater slurry, and dispense the coagulated-flocculated wastewater slurry through said coagulated-flocculated wastewater outlet; and a slurry separator comprising an intake area configured for receiving wastewater slurry from said coagulated-flocculated wastewater outlet, a liquid outlet, a sludge outlet, and a filtration module configured to facilitate percolating of liquid therethrough and forming of a filter cake thereon; said slurry separator being configured to receive slurry at said intake area, separate said slurry to liquid and sludge by said filtration module, remove said liquid via said liquid outlet, and convey said sludge from the intake area to said sludge outlet; wherein the system further comprises a level maintaining arrangement configured to maintain at least a minimal level of the filter cake.

2. The system according to claim 1, wherein at least one of—the removal of the sludge through the sludge outlet, or the dispensing of wastewater slurry through the coagulated-flocculated wastewater outlet, is performed at an adjustable rate, controlled by a respective actuator thereof.

3. The system according to claim 2, wherein the level maintaining arrangement comprises: a sensor configured to sense a level parameter indicative of the height of the filter cake on the filtration module, and produce a corresponding level signal indicative of the value of said level parameter; and a controller configured to receive said level signal and produce a corresponding rate signal configured to be received by the respective actuator so as to adjust the respective rate thereof, to maintain at least a minimal level of the filter cake on the filtration module.

4. The system according to claim 3, wherein the actuator is configured to adjust the removal rate of the sludge through the sludge outlet.

5. The system for treating wastewater according to claim 1, wherein said coagulation-flocculation assembly comprises: a coagulation tank comprising said raw wastewater inlet, a coagulated wastewater outlet, and said coagulating agent inlet, said coagulation tank being configured to receive raw wastewater through said raw wastewater inlet, facilitate mixing of the raw wastewater with the coagulating agent therein, and facilitate evacuating of coagulated wastewater therefrom through said coagulated wastewater outlet; and a flocculation tank comprising a coagulated wastewater inlet being in flow communication with said coagulated wastewater outlet, and said coagulated-flocculated wastewater outlet; said flocculation tank being configured to receive coagulated wastewater through said coagulated wastewater inlet, facilitate flocculation of the coagulated wastewater therein, and facilitate dispensing of said coagulated-flocculated wastewater therefrom through said coagulated-flocculated wastewater outlet.

6. The system according to claim 1, wherein the coagulation-flocculation assembly further comprises a flocculating agent inlet configured to facilitate introduction of flocculating agent to the coagulation-flocculation assembly.

7. The system according to claim 6, wherein said flocculation of the coagulated wastewater includes mixing of the coagulated wastewater with said flocculating agent.

8. The system for treating wastewater according to claim 1, wherein the system further comprises a turbidity sensor configured to sense a turbidity parameter indicative of a turbidity of said liquid.

9. The system according to claim 8, wherein the introduction of at least one of said flocculating agent and said coagulating agent is performed at an adjustable supply rate determined according to readings of said turbidity sensor so as to maintain at least a maximal level of turbidity of said liquid.

10. The system according to claim 1, further comprising a floc-size sensor configured to sense a size parameter indicative of size of flocs in said slurry at an area of said coagulated-flocculated wastewater outlet.

11. The system according to claim 10, wherein the introduction of at least one of said flocculating agent and said coagulating agent is performed at an adjustable supply rate determined according to readings of said floc-size sensor so as to maintain the size of the flocs in said slurry at an area of said coagulated-flocculated wastewater outlet within a predetermined range.

12. The system according to claim 1, wherein said filtration module is a conveyer configured to convey sludge from said intake area to said sludge outlet, while facilitating percolating of liquid therethrough.

13. The system according to claim 12, wherein said conveyer is at least partially sloped upwards towards said sludge outlet so as to contribute to the forming of the filter cake.

14. A method for treating wastewater, the method comprising: (a) providing a coagulation-flocculation assembly; (b) providing a filtration module configured to facilitate percolating of liquid therethrough and forming of a filter cake thereon; (c) introducing raw wastewater to the coagulation-filtration assembly; (d) mixing the raw wastewater with a coagulating agent in the coagulation-flocculation assembly so as to achieve coagulated wastewater; (e) flocculating the coagulated wastewater in the coagulation-flocculation assembly, so as to achieve coagulated-flocculated wastewater slurry; (f) applying the coagulated-flocculated wastewater slurry onto the filter cake at the filtration module so as to separate the coagulated-flocculated wastewater slurry to liquid and sludge; (g) removing sludge from the filtration module; and (h) responsive to the level parameter, generating a rate control signal configured to alter at least one of a rate of application of coagulated-flocculated wastewater slurry onto the filter cake, and a rate of removal of sludge from the filtration module.

15. The method according to claim 14, wherein the flocculation of the coagulated wastewater includes mixing of the coagulated wastewater with the flocculating agent, further comprises: (a) sensing a turbidity parameter indicative of turbidity of the liquid; and (b) determining the amount of at least one of coagulating agent and flocculating agent being mixed, according to the value of the turbidity parameter so as to maintain at least a maximal level of turbidity of liquid.

16. The method according to claim 14, further comprising: (a) sensing a size parameter indicative of size of flocs in slurry at an area of the coagulated-flocculated wastewater outlet; and (b) determining the amount of at least one of coagulating agent and flocculating agent being mixed, according to the value of the size parameter so as to maintain the size of the flocs in the slurry at the area of coagulated-flocculated wastewater outlet within a predetermined range.

17. A level maintaining arrangement configured to maintain at least a minimal level of a filter cake configured to receive a slurry intake at an adjustable rate, filter liquids out of said slurry, and produce a sludge outtake at an adjustable rate, both adjustable rates being determined by a respective actuator; the level maintaining arrangement comprising: a sensor configured to sense a level parameter indicative of the height of the filter cake, and produce a corresponding level signal indicative of the value of said level parameter; and a controller configured to receive said level signal and produce a corresponding rate signal configured to be received by the respective actuator so as to adjust the respective rate thereof, to maintain at least a minimal level of the filter cake on the filtration module.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

[0068] FIG. 1 illustrates a block diagram of a wastewater system according to an example of the presently disclosed subject matter, in use in a dairy farm facility;

[0069] FIG. 2A illustrates a side view of an example of the system of FIG. 1, where some walls have been removed to reveal objects behind them;

[0070] FIG. 2B illustrates a side perspective view of the system of FIG. 1;

[0071] FIG. 3A illustrates a front perspective view of a conveyor of the system;

[0072] FIG. 3B illustrates a top perspective view of a conveyor of the system;

[0073] FIG. 3C illustrates a schematic cross section of the conveyor of FIGS. 3A and 3B;

[0074] FIG. 4A illustrates a block diagram of a feedback process between a sensor and a controller according to an example of the presently disclosed subject matter,

[0075] FIG. 4B illustrates a block diagram of a feedback process between another sensor and the controller according to an example of the presently disclosed subject matter,

[0076] FIG. 5A illustrates a side perspective view of a system according to another example of the presently disclosed subject matter,

[0077] FIG. 5B illustrates a top view of the system of FIG. 5A, where an upper wall of a coagulation-flocculation tank thereof has been removed; and

[0078] FIG. 6 illustrates a block diagram of a feedback process between a processor and the controller according to an example of the presently disclosed subject matter.

DETAILED DESCRIPTION OF EMBODIMENTS

[0079] Attention is first directed to FIG. 1 of the annexed drawings, illustrating a block diagram of a wastewater treatment system 1, according to an example of the presently disclosed subject matter, used for example in a dairy farm facility [not illustrated]. The system 1 is configured to receive wastewater intake, rich with suspended solids, from a wastewater reservoir 3, e.g., of the dairy farm, remove suspended solids therefrom, and produce a clearer liquid outtake, containing less suspended solids than the wastewater intake.

[0080] The system 1 comprises a coagulation-flocculation assembly 2 and a slurry separator 4.

[0081] The coagulation-flocculation assembly 2 is configured to receive the raw wastewater, facilitate coagulation and flocculation processes thereto so as to flock the suspended solids in the raw wastewater, and thereby turn the raw wastewater into a coagulated-flocculated wastewater slurry. The coagulation-flocculation assembly 2 is further configured to dispense the coagulated-flocculated wastewater slurry to the slurry separator 4 for separation thereof to liquid and sludge. The slurry separator 4 is configured to separate the wastewater slurry to liquid and sludge, dispense the liquid, optionally, to an effluent discharge, optionally directed to a municipal sewage system 8, and dispense the sludge, optionally, to a drying pile 9, where it can dry up and turn into manure, which can be later used for example for fertilizing fields.

[0082] With further reference being made also to FIGS. 2A and 2B, the coagulation-flocculation assembly 2 comprises a main tank 20 having a raw wastewater inlet 21 configured to receive raw wastewater from the wastewater reservoir 3 of the cowshed, through a supply line [not illustrated] coupled thereto. The raw wastewater inlet 21 is positioned in a bottom wall 21′ of the main tank, thereby inducing flow of the raw wastewater entering the main tank 20. The main tank 20 further comprises two coagulated-flocculated wastewater outlets 23, each of which wider than the raw wastewater inlet, thus, it should be appreciated that the flow of coagulated-flocculated wastewater slurry out of the main tank 20 through the coagulated-flocculated wastewater outlet 23 is slower than the flow of raw wastewater into the main tank 20 through the raw wastewater inlet 21. The coagulated-flocculated wastewater outlets 23 are positioned in mid-height of a vertical exit wall 23′ of the main tank, thereby constituting an overflow arrangement configured to facilitate passage therethrough for an upper portion of a given volume of wastewater. This upper portion is normally more sludgy and foamy than a respective lower portion of the same volume of wastewater, and is thus more suitable for separation thereof at the slurry separator 4.

[0083] The slurry separator 4 comprises two filtration modules 40, each having a coagulated-flocculated wastewater inlet 41 in flow communication with a respective coagulated-flocculated wastewater outlet 23 of the main tank 20, and is configured to receive coagulated-flocculated wastewater slurry therefrom. The flow communication herein is established via an auxiliary duct 44, configured to prevent splashes of coagulated-flocculated wastewater slurry when the latter passes from the outlet 23 to the inlet 41. In other embodiments of the presently disclosed subject matter, the outlet 23 and the inlet 41 can both be constituted by a single aperture.

[0084] On top of the main tank 20 there are two coagulating agent inlets 25, each of which is connected to a dispenser 25′, configured to dispense coagulating agent therethrough to the main tank 20. According to an example of the present disclosure, the dispenser 25′ is configured to release predetermined doses of coagulating agent to the main tank 20 at predetermined time lapses, optimized by an installer of the system 1 according to needs of a user of the system 1. The time lapses, as well as the size of the doses, can be pre-programmed to the dispenser 25′ to determine a dosing rate of the flocculating agent, or be adjusted in real time by an actuator thereof [not illustrated], optionally coupled to a control system. The coagulating agent can be in the form of a solution, particulate material, or any other form which allow it to be mixed with the raw wastewater, and comprise for example salts of aluminum, iron, titanium, zirconium, or any other material being effective as a coagulating agent.

[0085] In operation, raw wastewater, rich with suspended solids, enter the main tank 20 through the raw wastewater inlet 21, where they are being mixed with coagulating agent being dispensed to the main tank 20 through the coagulating agent inlets 25 by the respective dispensers 25′, causing the raw wastewater to go through a coagulation process and become coagulated wastewater.

[0086] The coagulated wastewater continues to mix by inertia inside the main tank 20, and thereby inducing a flocculation process thereto where the suspended solids come out of suspension and flock to turn the coagulated wastewater into a coagulated-flocculated wastewater slurry. The coagulated flocculated wastewater slurry exits the main tank 20 through the coagulated-flocculated wastewater outlets 23, and is being received at the coagulated-flocculated wastewater inlets 41 of the filtration modules 40, to be separated thereat into liquid and sludge, as will be explained hereinafter. According to an example of the presently disclosed subject matter, the main tank 20 further includes a mixing arrangement configured to boost the mixing to the raw wastewater with the coagulating agent. The description hereinabove refers to a journey of a given volume of raw wastewater. It should be appreciated that this coagulation-flocculation process is continuous, i.e. raw wastewater continuously enter the main tank 20 through the raw wastewater inlet 21, and go through coagulation-flocculation, while coagulated-flocculated wastewater slurry continuously exits the main tank 20 through the coagulated-flocculated wastewater outlet 23.

[0087] The raw wastewater inlet 21 and the coagulated-flocculated wastewater outlets 23 are arranged on the main tank 20 such that a flow regime within the main tank 20 is created, which causes a given volume of raw wastewater entering through the raw wastewater inlet 21 to spend sufficient mixing time in the main tank 20 to allow sufficient coagulation and sufficient flocculation to occur. In other embodiments of the presently disclosed subject matter, the system 1 can further include a valve arrangement configured to open and close at least the coagulated-flocculated wastewater outlets, to facilitate sufficient mixing time.

[0088] The two filtration modules 40, each comprising a conveyor 49, seen in FIGS. 3A and 3B, configured to facilitate percolating of liquid therethrough and forming of a filter cake 80 thereon, and thereby separating the coagulated-flocculated wastewater slurry to sludge and liquid. Each conveyor 49 comprises an intake area 42 and a sludge outlet 45 disposed distal from the intake area, and is configured to receive coagulated-flocculated wastewater slurry at the intake area 42, and convey the slurry from the intake area 42 to the sludge outlet 45, while allowing liquid to percolate therethrough during the conveyance, so that by the time the slurry reaches the sludge outlet 45, it is in the form of sludge.

[0089] According to other embodiments of the presently disclosed subject matter, the slurry separator can be a multi-stage slurry separator with two or more conveyors arranged sequentially one after the other, such that the sludge dispensed through the sludge outlet of the first conveyor, lands in the intake area of the sequential conveyor instead of the drying pile. Such arrangement can facilitate dryer sludge dispensed to the drying pile.

[0090] According to an example of the presently disclosed subject matter the conveyor 49 comprises rows 46 of rotating blades 48, arranged parallel to one another from the intake area 41 to the sludge outlet, configured for pushing the slurry/sludge towards the sludge outlet 45 with every rotation thereof, while allowing liquid to percolate therebetween.

[0091] The liquid percolating through the conveyor 49 drops onto a gutter-like element 47 in the form of a slide configured to funnel the liquid to the liquid outlet 43, from where it can be directed to the municipal sewer, optionally, by means of gravity. The sludge outlet 45 can be disposed above a designated piling area 81 of sludge, and can be configured to drop sludge onto the piling area 81, where it can dry up and turn into manure which can be later used for example for fertilizing fields.

[0092] The conveyor 49 can be a self-cleaning conveyor configured to prevent clogging thereof. According to an example of the presently disclosed subject matter, the rows 46 of rotating blades 48 are arranged such that each row 46 is aligned with its adjacent other to cause each blade 48 in the row to slide over a mating blade 48 in the adjacent row with every rotation, and thereby clean it.

[0093] An example of such conveyor is a wave separator/multi-disc roller separator by: Kendensha/Trident/Benenv et cetera

[0094] As seen in FIG. 3C, the conveyor 49 is sloped upwards towards the sludge outlet 45, such that the intake area 42 is disposed at a lowermost portion thereof. Further, the coagulated-flocculated wastewater inlet 41 of each filtration module 40 is disposed above that intake area 42, creating appropriate conditions for forming of the filter cake 80 thereat. The filter cake 80 can lean on a wall 26 containing the coagulated-flocculated wastewater outlet 41, disposed oppositely to the sloped conveyor 49, and thereby enhance its stability. In other embodiments of the presently disclosed subject matter [not shown], instead or in addition to the sloped conveyor 49, the filtration module can further include a barrier at the intake area 42, configured to partially block the passage of wastewater slurry/sludge on the conveyor, so as to maintain a minimal level of slurry/sludge, i.e., filter cake 80 at the intake area 42.

[0095] Since the wastewater slurry is initially received at the intake area 42 of the conveyor 49, most of the separation between sludge and liquid occurs thereat and is being facilitated by the filter cake 80. For that reason, the level of the filter cake 80 at the intake area 42 is important for determining the quality of liquid at the liquid outlet 43.

[0096] It should be appreciated that the conveyor 49 is configured such that the rate of conveyance of slurry/sludge from the intake area 42 to the sludge outlet 43, i.e. the rate of rotation of the rotating blades 48 is adjustable, e.g. by an actuator [not illustrated] of the conveyor 49. This adjustable rate affect the rate of removal of slurry/sludge from the intake area where the filter cake 80 is positioned, and thus affect the level of the filter cake 80. The higher the rate of rotation/conveyance is, the less slurry/sludge is accumulated at the intake area 42, thus the lower the filter cake 80 is. An effective level of the filter cake 80 should facilitate liquid outtake in a quality which meets the standards of local environmental regulations for disposal thereof through the effluent discharge, optionally to the municipal sewage system, as well as rapid conveyance of sludge to the sludge outlet.

[0097] To maintain this effective level of the filter cake 80, the wastewater treatment system 1 further comprises a level maintaining arrangement. The level maintaining arrangement comprises a sensor configured to sense a level parameter indicative of the level of the filter cake 80 at the intake area 41, and a controller 54 configured to adjust the level of the filter cake 80 responsive to the readings of the sensor, by controlling the actuator of the conveyor 49.

[0098] According to an example of the presently disclosed subject matter, the sensor herein is a level sensor 52, in other embodiments of the presently disclosed subject matter, the sensor can be an optic sensor or any other sensor configured to sense the level of the filter cake 80. The level sensor 52 is positioned within the main tank 20, so as to sense the level of wastewater within the main tank 20. Since there is free flow from the coagulated-flocculated wastewater outlet 23 to the intake area 42, i.e. onto the filter cake 80, through the coagulated-flocculated wastewater inlet 41, it can be appreciated that the level of wastewater within the main tank 20 is indicative of the level of the filter cake 80 at the intake area 42.

[0099] The sensor 52 is configured to produce a level signal to the controller 54, indicative of a current level of wastewater within the main tank 20. i.e. indicative of the level of the filter cake 80. The controller 54 is configured to continuously receive the level signal from the sensor 52, and produce corresponding conveyance rate signals to the actuator [not illustrated] of the conveyor 49, so as to adjust the conveyance/blade rotation rate of the conveyor 49, and thereby adjust the level of the filter cake 80. Specifically, the controller 54 is configured to increase the conveyance/blade rotation rate when the level of wastewater within the main tank 20 rises, and decrease the conveyance rate of sludge when the level of wastewater within the main tank 20 lowers, and thereby maintain a predetermined level of filter cake 80 at the intake area 41.

[0100] The level sensor 52 can be analog or digital, it can have a continuous scale sensitive to a plurality of different levels of wastewater, or a binary scale sensitive to one or two threshold values of the level parameter. In the latter case, the sensor 52 can be configured to produce a level signal only when the level parameter rises above/goes below that threshold value.

[0101] The sensor can be positioned on an inner face of a mounting wall 29 of the main tank 20, containing the coagulated-flocculated wastewater outlet 23, so as to sense the level of wastewater in the main tank most proximal to the coagulated-flocculated wastewater outlet 23. The controller can be positioned anywhere in the system 1 from which it can receive the level signals from the sensor 52 and produce control signals to the actuator of the conveyor 49. An example of a feedback process between the sensor 52 and the controller 54 is illustrated in FIG. 4A, where the conveyance rate of sludge/slurry on the conveyor 49 is determined according to readings of the level sensor 52 disposed within the main tank 20, by the controller 54.

[0102] According to an example of the presently disclosed subject matter, the dosing of coagulating agent to the main tank 20 is also performed at an adjustable dosing rate, controlled by an actuator [not illustrated] of the dispenser 25′, being also controlled by the controller 54. In this example, this adjustable dosing rate determines the extent of flocculation of the coagulated-flocculated wastewater, i.e. the amount of sludge which can be separated from a volume of coagulated-flocculated wastewater slurry. The higher the dosing rate of coagulating agent to the main tank 20 is, the more sludge can be separated from a given volume of coagulated-flocculated wastewater slurry, and the clearer the liquid is at the liquid outlet. The amount of sludge in a given volume of wastewater slurry should facilitate liquid outtake in a quality which meets the standards of local environmental regulations for disposal thereof through the effluent discharge, optionally to the municipal sewage system. On the other hand, it is a purpose to avoid clogging of any component of the system 1, which can be caused due to creating to much sludge in a given volume of wastewater slurry, i.e. due to excessive dosing of coagulating agent.

[0103] The system 1 can further include a turbidity sensor 60 configured to sense a turbidity parameter indicative of the turbidity of liquid at the liquid outlet 43. The sensor 60 can be positioned at an outlet pipe 61 of the system funneling the liquid to the effluent discharge and can be configured to work in conjunction with the controller 54 to prevent turbidity to exceed a pre-determined level.

[0104] The turbidity sensor 60 can be optic, configured to illuminate the liquid passing in the outlet pipe 61, and measure the incident light scattered therefrom, optionally by a photodiode, which can produce corresponding turbidity signals to the controller 54 indicative of the concentration of suspended solids in the liquid, i.e. turbidity of the liquid.

[0105] The turbidity sensor 60 can be analog or digital, it can have a continuous scale sensitive to a plurality of different turbidity levels, or a binary scale sensitive to one or two threshold values of the turbidity parameter. In the latter case, the turbidity sensor 60 can be configured to produce a turbidity signal only when the turbidity parameter rises above/goes below that threshold value.

[0106] The controller 54 can be configured to receive these turbidity signals from the turbidity sensor 60, and produce corresponding dosing rate signals to the actuator [not illustrated] of the dispenser 25′ so as to adjust the dosing rate of coagulating agent to the main tank 20.

[0107] Specifically, the controller 54 can be configured to increase the dosing rate of coagulating agent to the main tank 20 when the level of turbidity of liquid at the liquid outlet 43 rises, and decrease the dosing rate when the level of turbidity of liquid at the liquid outlet 43 lowers, so as to maintain a predetermined level of turbidity of liquid at the liquid outlet 43.

[0108] An example of a feedback process between the sensor 60 and the controller 54 is illustrated in FIG. 4B, where the dosing rate of coagulating agent to the main tank 20 is determined according to readings of turbidity sensor 60 disposed on the outlet pipe 61, by the controller 54.

[0109] FIGS. 5A and 5B illustrate another example of a wastewater treatment system 100 in which the main tank is divided to a coagulation tank 120a configured to facilitate coagulation of raw wastewater therein to achieve coagulated wastewater, and a flocculation tank 120b configured to facilitate flocculation of the coagulated wastewater therein to achieve coagulated-flocculated wastewater slurry.

[0110] The coagulation tank 120a comprises the raw wastewater inlet 21, whilst the flocculation tank 120b comprises the coagulated-flocculated wastewater outlets 23. The two tanks are disposed adjacent to each other such that they have a common wall 122 between them, with an aperture [not seen] allowing free flow therebetween, and thereby constituting an outlet of the coagulation tank 120a as well as an inlet of the flocculation tank 120b.

[0111] In this example, the two coagulation agent inlets 25 are disposed on top of the coagulation tank 120a and are configured to facilitate the dosing of coagulating agent to the coagulation tank 120a.

[0112] In operation, raw wastewater, rich with suspended solids, enter the main tank 20 through the raw wastewater inlet 21, where they are being mixed with coagulating agent being dispensed to the main tank 20 through the coagulating agent inlets 25 by the respective dispensers 25′, causing the raw wastewater to go through a coagulation process and become coagulated wastewater.

[0113] The system 1 further comprises two flocculation agent inlets 27 disposed on top of the flocculation tank 120b, each of which being connected to a dispenser 27, configured to dispense flocculating agent therethrough to the flocculation tank 120b.

[0114] According to an example of the present disclosure, the dispenser 27 is configured to release predetermined doses of flocculating agent to the flocculation tank 120b at predetermined time lapses, optimized by an installer of the system 1 according to needs of a user of the system 1. The time lapses, as well as the size of the doses can be pre-programmed to the dispenser 25′, or be adjusted in real time by an actuator thereof [not illustrated], optionally coupled to a control system, to determine a dosing rate of the coagulating agent. The flocculating agent can be in the form of a solution, particulate material, or any other form which allow it to be mixed with the coagulated wastewater, and comprise for example salts of aluminum, iron, calcium, magnesium, or any other material being effective as a flocculating agent.

[0115] In operation, raw wastewater, rich with suspended solids, enter through the raw wastewater inlet 21 into the coagulation tank 120a, and continue from there to the flocculation tank 120b through the aperture in the wall 122. Simultaneously, coagulating agent and flocculating agent are dispensed to the coagulation tank 120a and the flocculation tank 120b respectively, through their respective inlets 25,27 by their respective dispensers 25′,27′, at a predetermined rate. The raw wastewater are mixed by inertia within the coagulation tank 120a together with the coagulation agent and turn into coagulated wastewater, which exits the coagulation tank 120a through the aperture in the wall 122 to reach the flocculation tank 120b and mix thereat, also by inertia with the flocculation agent. The raw wastewater inlet 21 and the aperture in the wall 122 are arranged such that a flow regime within the coagulation tank 120a is created, which causes the raw wastewater entering through the raw wastewater inlet 21 to spend enough time mixing in the coagulation tank 120a to allow sufficient coagulation to occur, before exiting the coagulation tank 120a through the aperture in the wall 122 as coagulated wastewater.

[0116] The coagulated wastewater enter the flocculation tank 120b through the aperture in the wall 122, and mix there by inertia with the flocculation agent, before exiting the flocculation tank 120b through the coagulated-flocculated wastewater outlet 23 as coagulated-flocculated wastewater slurry.

[0117] It should be appreciated that the aperture in the wall 122 and the coagulated-flocculated wastewater outlet 23 are arranged on the flocculation tank such that a flow regime within the flocculation tank 120b is created, which causes the coagulated wastewater entering through the aperture to spend enough time mixing in the flocculation tank 120b to allow sufficient flocculation to occur, before exiting the flocculation tank 120b as coagulated-flocculated wastewater.

[0118] As a whole, in the coagulation-flocculation process as described, raw wastewater enters through the raw wastewater inlet 21, and turns into coagulated-flocculated wastewater slurry exiting through the raw wastewater outlet 23.

[0119] According to an example of the presently disclosed subject matter, the dosing of flocculating agent to the flocculation tank 120b is also performed at an adjustable dosing rate, controlled by an actuator [not illustrated] of the dispenser 27, being also controlled by the controller 54. In this example, this adjustable dosing rate determines the extent of aggregation of solids in the coagulated-flocculated wastewater slurry, i.e. the amount of flocks of solids, which either precipitate to the bottom or float to the surface of the liquid, in a given volume of coagulated-flocculated wastewater slurry. The higher the dosing rate of flocculating agent to the flocculation tank 120b is, the more flocks of formerly suspended solids will be present in a given volume of coagulated-flocculated wastewater slurry. The amount of flocked solids in a given volume of wastewater slurry should facilitate liquid effluent in a quality which complies with limits of local environmental regulations. On the other hand, it is a purpose to avoid having small flocks, since these flocks can percolate together with the liquid through the filtration module 40.

[0120] The system 1 can further include a floc-size sensor configured to sense parameter indicative of the common size of flocs in the coagulated-flocculated wastewater slurry at an area of the coagulated-flocculated wastewater outlet. The floc-size sensor can be positioned in the auxiliary duct 44 funneling the coagulated-flocculated wastewater slurry from the outlet 23 of the flocculation tank 120b to the inlet 41 of the filtration module.

[0121] According to an example of the presently disclosed subject matter, the floc-size sensor is in the form of a camera 70 configured to monitor the slurry passing in the duct 44. The camera 70 can be configured to work in conjunction a processor 71 equipped with an image processing module, configured to process images from the camera 70 to evaluate the common size of flocs in the slurry. The camera 70 together with the processor 71 can be configured to work in conjunction with the controller 54, to form a floc-size maintaining arrangement, configured to maintain the floc-size in the slurry at an area of the duct. i.e. at an area of the coagulated-flocculated wastewater outlet 23, within a predetermined range.

[0122] The processor 71 can have a continuous scale sensitive to a plurality of different floc-sizes, or a binary scale sensitive to two threshold values of floc-size. In the latter case, the processor 71 can be configured to produce a size signal when the common size of flocks rises above and goes below each of the two threshold values.

[0123] The controller 54 can be configured to receive these size signals from the processor 71, and produce corresponding dosing rate signals to the actuator [not illustrated] of the dispenser 27′ so as to adjust the dosing rate of flocculating agent to the flocculating tank 120b.

[0124] Specifically, the controller 54 can be configured to increase the dosing rate of flocculating agent to the flocculation tank 120b when the floc size in the slurry at the duct 44 rises above a first threshold, and decrease that dosing rate when the floc size in the slurry at the duct 44 goes below a second threshold, lower than the first, so as to maintain the floc-size in the slurry at the duct 44 within the predetermined range.

[0125] An example of a feedback process between the processor 71 and the controller 54 is illustrated in FIG. 6, where the dosing rate of coagulating agent to the flocculation tank 120b is determined according to readings of the camera 70, by the controller 54.

[0126] Overall, the process of receiving wastewater, rich with suspended solids, and performing coagulation-flocculation thereon to turn them into coagulated-flocculated wastewater slurry, and then performing separation of the slurry to liquid and sludge, as performed by the systems 1 and 100 includes: [0127] (a) providing a coagulation-flocculation assembly e.g., the main tank 20, or the coagulation tank 120a together with the flocculation tank 120b; [0128] (b) providing a filtration module, e.g., the filtration module 40, configured to facilitate percolating of liquid therethrough and forming of a filter cake thereon; [0129] (c) introducing raw wastewater to the coagulation-filtration assembly, e.g. through the raw wastewater inlet 21; [0130] (d) mixing the raw wastewater with a coagulating agent in the coagulation-flocculation assembly so as to achieve coagulated wastewater, [0131] (e) flocculating the coagulated wastewater in the coagulation-flocculation assembly, so as to achieve coagulated-flocculated wastewater slurry; [0132] (f) applying the coagulated-flocculated wastewater slurry onto the filter cake at the filtration module so as to separate the coagulated-flocculated wastewater slurry to liquid and sludge; [0133] (g) removing sludge from the filtration module, i.e. from the filter cake, at an adjustable rate; [0134] (h) sensing a level parameter indicative of a level of the filter cake; [0135] (i) responsive to the level parameter, generating a rate control signal configured to alter at least one of a rate of application of coagulated-flocculated wastewater slurry onto the filter cake, and a rate of removal of sludge from the filtration module.

[0136] According to an example, the flocculation of the coagulated wastewater includes mixing of the coagulated wastewater with the flocculating agent.

[0137] The method can further comprises the steps of: [0138] (a) sensing a turbidity parameter indicative of turbidity of the liquid, e.g., at the liquid outlet 43, e.g. sensing the turbidity of liquid at the liquid outtake supply line by the turbidity sensor 60; and [0139] (b) determining the amount of at least one of coagulating agent and flocculating agent being mixed, according to the value of the turbidity parameter so as to maintain at least a maximal level of turbidity of liquid, e.g., at the liquid outlet 43, by the controller 54.

[0140] The process can further comprise the steps of: [0141] (a) sensing a size parameter indicative of size of flocs in the slurry at an area of coagulated-flocculated wastewater outlet 23, i.e. monitoring the floc-size thereat by the camera 70 together with the processor 71. [0142] (b) determining the amount of at least one of coagulating agent and flocculating agent being mixed, according to the value of the size parameter so as to maintain the size of the flocs in the slurry, e.g., at the area of the coagulated-flocculated wastewater outlet 23 within a predetermined range, e.g., by the controller 54.

[0143] It should be appreciated that although the raw wastewater intake to the coagulation-flocculation assembly 2 originates in the wastewater reservoir of the dairy farm, according to some embodiments of the present disclosure, these raw wastewater has gone through preliminary mixing in a mixing tank 9 after being pumped from the reservoir and before entering the coagulation-flocculation assembly 2.