High-speed settling clarification section with higher adjustment capacity

Abstract

In general, the present invention relates to a system for water or wastewater treatment, wherein the system is designed for a maximum flow rate, the system comprising: two or more reaction tanks, each of the two or more reaction tanks having a capacity less than the maximum flow rate and having a combined capacity to reach or exceed the maximum flow rate, each reaction tank being fluidly connected to a clarification tank, the reaction tank receiving an influent and outputting an effluent; and a clarification tank designed to reach or exceed the maximum flow rate, the clarification tank receiving the effluent from the two or more reaction tanks.

Description

Field of the Invention

[0001] The present invention generally relates to a high rate settling clarification section with increased turndown capability. More specifically, the present invention relates to a high rate settling clarification process system that can utilize multiple reaction tanks in fluid communication with a single clarification / concentration tank. Background Art

[0002] High-speed settling clarifiers have been used for many years. This clarifier typically combines solids contact and solids recirculation to enhance high-speed settling of solids. This system may also be referred to as optimized flocculation using internal and external sludge recirculation systems, which typically includes a coagulation tank, a flocculation / maturation reactor, and a clarifier / thickener.

[0003] Each of these systems provides high-rate solids contact clarification. Applications for the system may include, but are not limited to: combined sewer or sanitary sewer overflows, biological or chemical oxygen demand reduction, total suspended solids reduction, phosphorus removal, wastewater reuse, clarification and softening, organics removal, silica removal, metal precipitation, wastewater treatment from flue gas desulfurization, etc. The flexibility of the system is particularly desirable for a variety of applications.

[0004] However, this system may have several drawbacks. First, the system is often designed for maximum flow conditions. In some applications such as combined sewer overflows / sanitary sewer overflows, this maximum flow (while required for performance) may not represent typical operating parameters. In addition, there are situations where systems or facilities are installed to increase overall treatment capacity. In these cases, the system may also be designed for the maximum flow expected to be reached in the future, but it may not be achieved - or may not be achieved for some time.

[0005] Turndown capacity - i.e., the efficient operating range, or the ratio between the maximum and minimum amounts of water or wastewater that can be processed - is typically a function of the maximum flow rate. Because the required velocity in a piston reactor is necessary or desirable to achieve efficient processing, turndown capacity is typically limited to about 50% of the maximum design flow rate. This velocity typically keeps solids in suspension until the fluid reaches the clarification / concentration zone. Therefore, when a system is designed for a high maximum flow environment, the turndown capacity of the system may be significantly limited. Furthermore, because this maximum flow condition may occur infrequently or periodically, the performance and effectiveness of the overall system may be less than expected during typical use.

[0006] In addressing this deficiency, it is known to install multiple systems. For example, if the maximum desired flow is X, two (2) systems may be installed, each with a maximum flow of 0.5(X). However, both systems would need to be used regularly to avoid corruption or plugging due to sludge. In this case, care must be taken to alternate the flow between the systems regularly and consistently. However, the additional capital and operating expenses of two different systems plus the additional maintenance required during operation would generally offset any advantage provided by the multiple systems.

[0007] Therefore, it is desirable to provide a high-speed solids contact clarification system with a greater turndown range. In addition, it is desirable to provide a high-speed solids contact clarification system that can provide additional capacity when needed in the future without affecting the current operation of the system. Summary of the invention

[0008] Some aspects according to some embodiments of the present invention may include a system for treating water or wastewater, the system comprising: two or more reaction tanks, each reaction tank being fluidly connected to a clarification tank, the reaction tanks each performing the same function of receiving an influent and inducing flocculation in the water or wastewater and outputting an effluent; and a clarification tank, the clarification tank receiving the effluent from the two or more reaction tanks, wherein the flocs in the water or wastewater sink to the bottom of the clarification tank, and thickened sludge and clarified water are removed from the system.

[0009] According to non-limiting embodiments of the present invention, the system may include one or more of the following features:

[0010] - a coagulation tank is in fluid communication with two or more reaction tanks, said coagulation tank introducing a coagulant into the water or wastewater and mixing it;

[0011] - two or more reaction tanks include means for introducing turbulence into the water or wastewater in each reaction tank;

[0012] - The clarifier tank includes a floor scraper to concentrate the flocs that settle to the bottom of the clarifier tank into sludge;

[0013] - at least some of the sludge is recycled to two or more reaction tanks;

[0014] - the clarification tank comprises a sloped lamellae; and / or

[0015] - Each of the two or more reaction tanks is fluidly connected to a clarification tank via a transition chute.

[0016] Some aspects according to some embodiments of the present invention may include a system for water or wastewater treatment, wherein the system is designed for a maximum flow rate, the system comprising: two or more reaction tanks, each of the two or more reaction tanks having a carrying capacity less than the maximum flow rate and having a combined capacity to reach or exceed the maximum flow rate, each reaction tank being fluidly connected to a clarification tank, the reaction tank receiving an influent and outputting an effluent; and a clarification tank designed to reach or exceed the maximum flow rate, the clarification tank receiving the effluent from the two or more reaction tanks.

[0017] According to non-limiting embodiments of the present invention, the system may include one or more of the following features:

[0018] - Two or more reaction tanks each perform the same function of inducing flocculation in water or wastewater, wherein in a clarification tank, the flocs in the water or wastewater settle to the bottom of the clarification tank, and clarified water and concentrated sludge are removed from the system.

[0019] Some aspects of some embodiments of the present invention may include a system for treating water or wastewater, wherein the system is designed for a maximum flow rate, the system comprising: a coagulation tank in fluid communication with two or more reaction tanks, the coagulation tank introducing a coagulant into the water or wastewater and mixing it; two or more reaction tanks, providing flocculant introduction to the two or more reaction tanks, the two or more reaction tanks each having a carrying capacity less than the maximum flow rate and having a combined carrying capacity that reaches or exceeds the maximum flow rate, each reaction tank being fluidly connected to a clarification tank via a transition chute, and each reaction tank comprising An apparatus for introducing turbulence into water or wastewater, the reaction tanks each performing the same function of receiving an influent and inducing flocculation in the water or wastewater and outputting an effluent; a clarification tank having a carrying capacity capable of treating the water or wastewater at or above a maximum flow rate, the clarification tank receiving effluent from two or more reaction tanks, wherein flocs in the water or wastewater settle to the bottom of the clarification tank, and removing clarified water from the system, the clarification tank comprising: an inclined lamella, and a floor scraper to concentrate the flocs that settle to the bottom of the clarification tank into sludge; and a sludge recirculation conduit configured to recirculate at least some of the sludge from the clarification tank to the two or more reaction tanks.

[0020] Some aspects of some embodiments of the present invention may include a method for controlling a water or wastewater treatment system designed for a maximum flow rate, the system comprising two reaction tanks each having a carrying capacity less than the maximum flow rate and a combined carrying capacity reaching or exceeding the maximum flow rate; and a clarification tank having a carrying capacity for treating water or wastewater at or above the maximum flow rate, the method comprising: determining an incoming flow rate of an influent provided to the system; providing the influent to one reaction tank when it is determined that the incoming flow rate is less than 50% of the maximum flow rate; diverting the influent and providing the influent to each reaction tank when it is determined that the incoming flow rate is greater than 50% of the maximum flow rate; outputting effluent from one or more reaction tanks used to a clarification tank; and receiving the effluent from the one or more reaction tanks used at the clarification tank and outputting treated water or wastewater from the system.

[0021] These and other aspects will become apparent from the following description of the invention and from the subsequent drawings, although variations and modifications may be effected without departing from the scope of the novel concepts of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention can be more fully understood by reading the following detailed description and the accompanying drawings, in which similar reference numerals are used to represent similar elements. The accompanying drawings depict certain illustrative embodiments and can help understand the following detailed description. Before any embodiment of the present invention is described in detail, it should be understood that the present invention is not limited to the configuration details and the arrangement of each component / part listed in the following description or shown in the attached drawings in its application. The described embodiments should be understood as exemplary rather than limiting the overall scope of the present invention. In addition, it should be understood that the words and terms used herein are for illustrative purposes and should not be considered as limiting. The detailed description refers to the attached drawings, in which:

[0023] Figure 1 A high-rate settling clarification system known in the art is shown.

[0024] Figure 2 A high rate settling clarification system known in the art is depicted.

[0025] Figure 3 A high rate settling clarification system known in the art is depicted.

[0026] Figure 4 An exemplary high speed adjustment processing system according to some embodiments of the present invention is shown.

[0027] Figure 5 An exemplary high speed adjustment processing system according to some embodiments of the present invention is shown.

[0028] Figure 6An exemplary high speed adjustment processing system according to some embodiments of the present invention is shown.

[0029] Figure 7 An exemplary high speed adjustment processing system according to some embodiments of the present invention is shown.

[0030] Figure 8 An exemplary control sequence for a high-speed conditioning processing system including multiple reactors according to some embodiments of the present invention is shown.

[0031] Fig. 9 An exemplary control sequence for a high-speed conditioning processing system including multiple reactors according to some embodiments of the present invention is shown.

[0032] Fig. 10A and Fig. 10B The space saving advantages of an exemplary high-speed conditioning process system including multiple reactors according to some embodiments of the present invention are shown compared to conventional systems.

[0033] Before any embodiment of the present invention is described in detail, it should be understood that the present invention is not limited in its application to the configuration details and the arrangement of the components / parts listed in the following description or shown in the attached drawings. The present invention can have other embodiments and can be implemented or executed in various ways. In addition, it should be understood that the words and terms used herein are for illustrative purposes and should not be considered as limiting. DETAILED DESCRIPTION

[0034] The matters illustrated in this specification are provided to assist in a comprehensive understanding of the various exemplary embodiments disclosed with reference to the accompanying drawings. Therefore, one of ordinary skill in the art will recognize that various changes and modifications may be made to the exemplary embodiments described herein without departing from the spirit and scope of the claimed invention. For the sake of clarity and brevity, descriptions of known functions and structures are omitted. In addition, as used herein, the singular may be interpreted as the plural, or any plural term may be interpreted as the singular.

[0035] As noted above, the present invention relates to a high rate settling clarification section with increased turndown capability. More particularly, the present invention relates to a high rate settling clarification process system that can utilize multiple reaction vessels in fluid communication with a single clarification / concentration vessel.

[0036] Before delving into the advantages of the present invention, it is useful to first discuss the current system. Figure 1, as is generally known in the art, the system 100 may include: a rapid mixing zone 110, which may be mixed by a mixer 111; a flocculation reactor 120, which may be mixed by a mixer 121; and a clarification / settling zone 130. The sludge in the settling zone may be thickened using, for example, a floor scraper 131. Clarification may be assisted by a laminar module 132. Excess sludge 141 may exit the system, and at least some of the sludge may be recycled 142. The system 100 may generally receive an influent 101 and output a treated effluent 102.

[0037] In operation, raw water may enter the rapid mixing zone 110, where a coagulant may be added, thereby causing the colloidal particles within the raw water to aggregate. Turbulence or agitation may be achieved by using a mixer 111. The fluid may then enter the flocculation reactor 120, where the condensed water may come into contact with the flocculant and concentrated recycled sludge from the clarification / settling zone 130. The recycled sludge may accelerate the flocculation process and help produce dense, uniform flocs.

[0038] The fluid may then be transferred to the clarification / sedimentation zone 130. In some systems, the transfer between the flocculation reactor 120 and the clarification / sedimentation zone 130 may be accomplished by a piston reactor with an upflow. In the clarification / sedimentation zone 130, the flocs may settle to the bottom of the tank due to their size and density. The clarified water may be separated from the descending sludge and may rise through the laminar module 132. The laminar module 132 may generally include small sheets configured in a honeycomb pattern or other geometric shape, which may serve as a polishing stage, capturing lighter, lower density solids that have not settled.

[0039] The settled sludge may be gradually thickened at the bottom of the settling tank using a floor scraper 131. Part of the thickened sludge may be recycled to the coagulation and flocculation zone at 142, while any remaining sludge may be removed at 141 as excess sludge.

[0040] Figure 2 Shows Figure 1 An external view of system 200 is shown, generally including a condensation zone or tank 210 , a reaction zone or tank 220 , and a clarification / concentration zone or tank 230 . Figure 3 The system 300 is depicted in diagrammatic form as seen from above and generally includes a coagulation tank 310 , a reaction tank 320 , and a clarification / concentration tank 330 .

[0041] As mentioned above, this system may be flawed because it is typically designed for maximum flow conditions. However, when designing a system for maximum flow, the controlling factor may be the reaction tank. The coagulation zone, which provides rapid mixing between the influent and the coagulant to cause the colloidal particles to aggregate, is not greatly limited to minimum or maximum flow rates. Similarly, the clarification / concentration zone is efficient over a wide range of flow rates.

[0042] Therefore, in order to provide increased turndown in the system and to provide a system that can be modified over time to achieve a desired (but not required) maximum flow rate, the inventors have created a system that utilizes multiple reaction zones and a single clarification / concentration zone. Since the clarification / concentration zone may be used continuously, having a single clarification / concentration zone can prevent the system from becoming corrupted or plugged or fouled by sludge. Furthermore, since the reaction zones or reactors may be in independent fluid communication with the clarification / concentration zone, the use of only one (1) reactor should not negatively impact any function of the overall system.

[0043] However, there are problems with installing and / or subsequently adding multiple reactors. Typically, the reaction vessels and clarification / concentration vessels are fitted together with a transfer chute. Water or wastewater leaves the bottom of the reaction vessel, is brought to the top of the vessel, and then introduced into the clarification / concentration vessel through a chute. The installation of multiple chutes involves the rigidity and structural integrity of the clarification / concentration tank. In the case where additional reaction vessels can be added subsequently, punchouts can be located in the clarification / concentration vessel to provide quick installation without unforeseen effects on the tank structure.

[0044] Figure 4-9 Possible configurations of systems according to some embodiments of the present invention are shown, as shown in top view. Note that these figures do not depict Figure 1-3 Condensation zone shown.

[0045] Figure 4 A system 400 is shown having a clarification / concentration tank 410 in fluid communication with reactors 420 and 430. In this arrangement, the reactors 420, 430 may be placed adjacent to each other, or may be spaced apart.

[0046] See also Figure 5 , the system 500 according to some embodiments of the present invention may include more than two (2) reactors. The system 500 may include a clarification / concentration tank 510 and three (3) reactors 520, 530, 540. Note that while these reactors are illustrated as being of the same size, the present invention contemplates that the reactors may be of different sizes and have different processing capacities.

[0047] Figure 6A system 600 is shown in which a clarification / concentration vessel 610 can be in fluid communication with four (4) reactors 620, 630, 640, and 650. The size and processing capacity of reactors 620, 630 can be larger than reactors 640, 650. Including multiple reactors of different sizes can allow the operator to have greater flexibility during processing. In addition, as the demand for greater processing capacity increases, multiple reactors 620, 630, 640, 650 can be added to the system 600 in succession.

[0048] Figure 7 A system 700 is shown which may include a clarifier / concentrator tank 710 and two (2) existing reactors 720, 730. However, in this case, additional reactors may be required so space can be reserved for future reactors 740, 750. Additionally, knock-outs may be included in the clarifier / concentrator tank to facilitate rapid and efficient system expansion.

[0049] Note that the present invention provides operators with greater flexibility in multiple areas. First, as described above, by allowing the system to operate at lower flow rates, additional reactors can provide increased regulation. Reactors of different sizes can be used in situations where there is a large deviation between operating flow rates. For example, in a sanitary sewer overflow or combined sewer overflow application, the climate conditions may range from almost no rainfall to no rainfall, to heavy rainfall during the rainy season. In this application, the system may need to reach a maximum flow rate "X", but only 0.25 (X) of the maximum flow rate may be required for nine (9) months of the year. In this case, two (2) reactors can be installed, one capable of handling 0.75 (X) and the second capable of handling 0.25 (X) of the maximum flow rate. In this case, during the dry season, the smaller reactor can handle the lower flow rate, while the larger reactor can be used during the rainy season when close to the maximum flow rate may be required.

[0050] This flexibility is not limited to two (2) reactors. The present invention contemplates that situations may arise where two (2), three (3), four (4) or more reactors may be advantageous. Again, the reactors would be in communication with a single clarification / concentration tank. The use of such reactors can be balanced based on the amount of influent flow.

[0051] For example, see Figure 8 , there may be a system comprising a first reaction tank 801 and a second reaction tank 802, each of which is in fluid communication with a clarification / concentration tank 803. Each reaction tank 801, 802 may be the same size and each configured to process approximately fifty percent (50%) of the maximum flow rate for which the system is designed.

[0052] During operation, the inlet flow rate (or desired process flow rate) may be determined at 810. At 820, it may be determined whether the inlet flow rate is greater than fifty percent (50%) of the maximum flow rate for which the system is designed. If the answer at 821 is no, then at 830, the full inlet flow (less than fifty percent (50%) of the system maximum flow rate) may be provided to a single reactor (reactor 801 or reactor 802). The other reactor may remain inoperative.

[0053] If it is determined at 822 that the incoming flow rate is greater than fifty percent (50%) of the maximum flow rate for which the system is designed, there may be at least two (2) options. At 840, it may be determined whether the incoming flow rate is less than seventy-five percent (75%) of the maximum flow rate for which the system is designed. If so, then at 841, it may be determined that the incoming flow should be shared by the two reactors 801, 802. This is because each reactor cannot efficiently handle less than 50% of its own maximum flow rate (due to the turbulence issues discussed above). Therefore, the system may provide fifty percent (50%) of the incoming flow to the first reactor 801 at 860 and fifty percent (50%) of the incoming flow to the second reactor 802 at 870.

[0054] If it is determined at 842 that the input flow rate is greater than seventy-five percent (75%) of the maximum flow rate for which the system is designed, then at 850 it can be determined whether the input flow rate should be evenly shared by reactors 801, 802, or whether one reactor should be operated at maximum capacity with the second reactor handling the remaining flow rate. If it is determined at 851 that the two reactors should evenly share the incoming flow rate, the system can provide fifty percent (50%) of the incoming flow rate to the first reactor 801 at 860 and fifty percent (50%) of the incoming flow rate to the second reactor 802 at 870.

[0055] If it is determined at 852 that one reactor should be operated at maximum capacity, then at 880 one (1) reactor (401 or 402) may receive an inflow rate approximately equal to fifty percent (50%) of the system design flow rate (or the maximum flow rate for which the reactor is designed). The remaining reactors may handle any excess flow.

[0056] Operators are able to control the flow rate to each reactor, allowing for greater flexibility and variability in processing.

[0057] See also Fig. 9, the control process of a system including three (3) reaction tanks 901, 902, 903 connected to a clarification / concentration tank 900 will now be discussed. In this case, there is one reactor 902 configured to process approximately fifty percent (50%) of the maximum flow rate designed for the entire system. There are also two (2) small reactors 901, 903, each of which is designed to process approximately twenty-five percent (25%) of the maximum flow rate designed for the system.

[0058] During operation, the inlet flow rate (or desired process flow rate) may be determined at 905. At 910, it may be determined whether the inlet flow rate is less than twenty-five percent (25%) of the maximum flow rate. If the determination at 915 is yes, then at 920 the inlet flow may be sent to reactor 901. (Note that it may also be sent to reactor 903).

[0059] If it is determined at 925 that the inlet flow rate is greater than twenty-five percent (25%) of the maximum flow rate, then it can be determined at 930 whether the inlet flow rate is greater than twenty-five percent (25%) of the maximum flow rate, but less than fifty percent (50%) of the maximum flow rate. If the determination at 935 is yes, then at 940, the inlet flow can be sent to the reactor 902.

[0060] If it is determined at 945 that the inlet flow rate is not between twenty-five percent and fifty percent (25-50%) of the maximum flow rate, then it can be determined at 950 whether the inlet flow rate is greater than fifty percent (50%) of the maximum flow rate, but less than seventy-five percent (75%) of the maximum flow rate. If the determination at 955 is yes, then at 960, the inlet flow rate can be sent to reactor 902 and to reactor 901 or 903.

[0061] If it is determined at 965 that the flow rate is not between fifty and seventy-five percent (50-75%) of the maximum flow rate, it can be determined whether the inlet flow rate is greater than seventy-five percent (75%) of the maximum flow rate. If it is determined at 975 that it is, the inlet flow can be divided between the three reactors 901, 902, 903, with the larger reactor 902 receiving approximately fifty percent (50%) of the inlet flow, and the remaining flow divided between the reactors 901, 903.

[0062] If it is determined at 985 that the incoming flow is not greater than seventy five percent (75%) of the maximum flow rate, then an error may be determined at 990 and the process may return to step 905 .

[0063] These examples are hypothetical and are intended to illustrate the flexibility of system processing and treatment using multiple reactors connected to a single influent stream and a single clarification / concentration tank.

[0064] In addition to processing flexibility, the present invention can also allow for greater flexibility in the footprint of the processing system. Using only layered modules in the processing system is often attractive to operators because the modules can reduce the overall footprint of the clarification / concentration zone or tank. The ability to contour the system to a limited or irregular footprint is also advantageous.

[0065] Fig. 10A and 10B The possible space savings using some embodiments of the present invention are shown. Fig. 10A A system 1001 using a clarification / concentration vessel 1010 and a single reactor 1020 is shown. Fig. 10B A system 1002 utilizing a clarification / concentration vessel 1011 and two (2) reactors 1030 , 1040 is shown. Fig. 10B The two reactors and Fig. 10A A single reactor of 1002 can provide the same processing capacity and maximum flow rate. However, the footprint of system 1002 is less than the footprint of system 1001. This reduced footprint may be particularly useful in retrofit situations where increased capacity is required but there is no additional space to support the capacity.

[0066] In addition to the above advantages, the present invention can also reduce the operating costs of the water treatment system. Comparing the first case of a clarification / concentration vessel with a single reactor and the second case of a clarification / concentration vessel with two smaller reactors, during low flow times, the energy required to operate the single smaller reactor may be less than the energy required to operate the single large reactor. This may be due to the reduced size of the reactor turbine drive device, which can be used to agitate the fluid to stir and cause turbulence. The maximum energy consumption of the system may then correspond to the maximum flow rate of the system. In other words, when the operating flow rate is lower, the operating energy cost may also be lower.

[0067] It should be understood that the specific embodiments of the present invention shown and described herein are exemplary only. Those skilled in the art may find multiple changes, variations, substitutes and equivalents without departing from the present invention. Therefore, all themes described herein and shown in the accompanying drawings are intended to be considered only as illustrative, rather than restrictive.

Claims

1. A system for water or wastewater treatment, wherein: Designed for maximum flow rates, the system includes: Two or more reaction tanks, each of the two or more reaction tanks having a carrying capacity less than a maximum flow rate and having a combined carrying capacity reaching or exceeding the maximum flow rate, each reaction tank being fluidly connected to the clarification tank, the reaction tanks receiving an influent and outputting an effluent; A clarifier tank designed to meet or exceed the maximum flow rate, the clarifier tank receiving effluent from two or more reaction tanks, The two or more reaction tanks each perform the same function of inducing flocculation in water or wastewater, wherein in the clarification tank, the flocs in the water or wastewater settle to the bottom of the clarification tank, and clarified water and concentrated sludge are removed from the system.

2. The system of claim 1, further comprising a coagulation tank in fluid communication with the two or more reaction tanks, the coagulation tank introducing a coagulant into the water or wastewater and mixing the water or wastewater.

3. The system of claim 1, wherein: Each of the two or more reaction tanks includes means for introducing turbulence into the water or wastewater in the respective reaction tank.

4. The system of claim 1, wherein: The clarifier tank includes a floor scraper to concentrate the flocs that settle to the bottom of the clarifier tank into sludge.

5. The system of claim 4, wherein: At least some of the sludge is recycled to two or more reaction tanks.

6. The system of claim 1, wherein: The clarification tank comprises an inclined thin layer.

7. The system of claim 1, wherein: Each of the two or more reaction tanks is fluidly connected to the clarification tank via a transition chute.

8. A method of controlling a water or wastewater treatment system designed for a maximum flow rate, the system comprising two reaction tanks each having a carrying capacity less than the maximum flow rate and a combined carrying capacity at or above the maximum flow rate; and a clarification tank having a carrying capacity for treating water or wastewater at or above the maximum flow rate, the method comprising: determining an inlet flow rate of an influent provided to the system; providing an influent to a reaction tank when it is determined that the inlet flow rate is less than 50% of the maximum flow rate; When it is determined that the inlet flow rate is greater than 50% of the maximum flow rate, splitting the inflow and providing the inflow to each reaction tank; outputting the effluent from one or both reaction tanks used to a clarification tank; and The clarifier receives the effluent from one or both of the reaction tanks used and outputs treated water or wastewater and concentrated sludge from the system. The two reaction tanks each perform the same function of inducing flocculation in water or wastewater, wherein in the clarification tank, the flocs in the water or wastewater settle to the bottom of the clarification tank, and clarified water and concentrated sludge are taken out of the system.

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