Patent Grant
8431022
The present invention relates to liquid treatment systems using flocculate agents and dissolved aeration flotation to clarify liquid streams contaminated with particulates, and especially wastewater containing organic wastes, for example from food processing plants.
Clarification relates to reducing solids content in water or other liquid streams which cannot be efficiently removed by mechanical filtration methods. Often a clarification process is used to remove non-dissolved solids before further waste processing, or may be applied to provide water which is clean enough to recycle into the same process even if not clean enough for discharge. Dissolved aeration flotation (DAF) is a widely used method to remove organic contaminants from wastewater streams such as from food processing plants. The basic process consists of injecting water saturated with gas—either air or another gas selected to be less reactive with a particular waste chemistry—into a flotation tank (“aeration”), where the gas comes out of solution forming bubbles which float to the surface of the tank. The aerated water is created by dissolving gas into the water in a high pressure environment until it reaches saturation level at that high pressure. When the gas-saturated water at high pressure is depressurized the gas comes out of solution. Bubble size and density can be controlled by varying, among other things, the maximum saturation pressure and the rate of depressurization. The rising gas bubbles adhere to particulates in the wastewater and lift them to the surface where they are skimmed off. The floating particulate matter is referred to as “retentate”, and after removal is referred to as “sludge”. Aeration may be accomplished using pressurized saturation tanks or pumps designed for the purpose, such as aeration turbine pumps.
Flocculate agents may be mixed with the wastewater prior to aeration to react with or bind to particulates, creating larger and less dense suspended coagulated particles which are more susceptible to binding with gas bubbles and thereby more effectively driven to the surface for removal. Many flocculating chemicals are known and selected based on the anticipated chemistry of the waste stream and the expected downstream uses of the clarified effluent and retentate sludge. Examples of known coagulants and/or flocculants include cationic polymers, phosphoric acid, lime and anionic polymers. The effectiveness of the system—i.e. the amount of waste removed from the wastewater stream—depends on the size and density of the gas bubbles and the amount of time the wastewater is exposed to the gas bubbles, sometimes referred to as “dwell time”. Retaining wastewater in the flotation tank exposed to aerated water for a longer period provides greater removal effectiveness. Longer dwell times are achieved by increasing the size of the tank relative to the anticipated peak flow. However, when the wastewater stream is low, such as when a plant with multiple production lines is running only a few lines, the larger DAF system will operate at low efficiency.
A persistent problem encountered with DAF systems is that they are not efficient when run at low capacity. A system designed to handle a large peak flow requires a large flotation tank volume in order an optimum dwell time, with a consequently large foot print, large pump capacities, and high expense. In order to run efficiently a low production volumes an intermediate collection system is required to accumulate wastewater and run batches through the DAF system at optimum flow rates. Intermediate collection systems consume valuable production area, cost money to build and install, and add maintenance costs.
Greater treatment capacity requires a longer and higher volume separation tank. However, this imposes minimum flow requirements on the system as a whole because the turbine pump/air injection system requires a minimum flow of either recycled clear water or clean freshwater (but adding fresh water increases the overall volume of processed liquid and essentially defeats much of the purpose of the system, which is to reduce fresh water usage and reduce waste stream volumes). Use of side-by-side systems on the same skid permits ½ to be shut down during low volume waste flow periods, such as when part of the production lines have been shutdown, but still retains full capacity during peak times. The system shares components and provides a compact, energy efficient footprint as well. The system may receive wastewater flows from a single source and split them, or may receive flows from separate sources but utilize certain common components, and still be available for a peak flow from a single source.
Additional problems arise with conventional effluent weir designs, which generally comprise a round pipe with perforations distributed along its surface, including the top surface. This design allows particulates to enter the weir pipe and foul the pipe, reducing flow and potentially contaminating the effluent discharge. This design also creates a problem of sediments accumulating on the upper surface of the weir pipe, which periodically dislodge and create spikes of particulates in the effluent. Maintenance requirements are substantially increased due to more frequent flushing required and more difficult cleaning during shutdowns.
Thus, there is a need for DAF treatment system that: (1) is compact; (2) modular to permit scaled or split operations; (3) provides improved methods for removing effluent; (4) reduces buildup of sediments on surfaces; (5) provides improved solids removal efficiency; (6) maximizes removal of effluent from sludge; (7) improves laminar flow within the separation vessel; (8) reduces water velocity within the separation vessel; (9) improves dwell time within the separation vessel; (10) provides for adjustable height risers to control system liquid level; and, (11) improves overall efficiency and cost effectiveness.
A modular dual vessel dissolved aeration flotation treatment system includes a frame; first and second treatment sections mounted to the frame adjacent to each other, a skimmer to remove retentate, and a sludge collection section to collect and transfer sludge waste, wherein, the first treatment section and second treatment section may operate independently of each other. Each treatment section includes a separation tank with the tanks sharing a common inside wall, an inclined sludge plate extending from the interior of the separation tank at a height below the liquid operating level of the system to at least the upper edge of the separation tank second end wall, a flocculator portion to pre-treat the waste water stream and having an aeration mixing chamber and aeration injection port and a chemical injection port, an effluent weir mounted low within the separation tank and having an enclosed top portion and a bottom inlet, a clear well including a clear well discharge, a clear well riser in fluid communication with the effluent weir to an adjustable height discharge to set the operating level of the system, and, an aeration injector having an inlet in fluid communication with the clear well and a discharge in fluid communication with the flocculator aeration injection port.
A modular dual vessel DAF may include wherein the angle of each of the sludge plates of the first and second separation tanks is angled within the range 30° to 50° pitch.
A modular dual vessel DAF may include a separator plate pack in each separation tank.
A modular dual vessel DAF may include a stilling well to receive and distribute pre-treated water from the flocculator portion.
A modular dual vessel DAF may include a multi-stage flocculator portion.
A modular dual vessel DAF may include a multi-stage flocculator portion wherein each stage includes a horizontal pipe portion with each stage oriented 180° from the preceding stage.
A modular dual vessel DAF may include an effluent weir having an enclosed peaked top portion and open bottom inlet. The effluent weir may include a square diamond shape cross section. The effluent weir may include a cross section which extends beyond the corresponding clear well riser cross section.
A modular dual vessel DAF may include a plurality of effluent weirs in fluid communication with a plurality of corresponding clear well risers, each of which risers may be height adjustable.
A modular dual vessel DAF may include wherein the height adjustable clear well risers include an adjustable discharge member which slides over the open end of a riser and seal members, and including a locking member to selectively lock it at a desired discharge height.
A modular dual vessel DAF may include wherein the aeration injector is an aeration turbine pump which may draw suction from the clear well to recycle effluent.
A modular dual vessel DAF may include wherein the skimmer includes a plurality of paddles coupled to a cyclical drive mounted to the separation tanks, the paddles including a flexible wiper portion to engage the sludge plate.
A modular dual vessel DAF may include a sludge hopper coupled to a sludge pump and abutting the end walls of the separation tanks and disposed under an overhanging sludge plate.
The present invention provides many advantages over existing systems: (1) it is compact; (2) modular to permit scaled or split operations; (3) provides improved methods for removing effluent; (4) reduces buildup of sediments on surfaces; (5) provides improved solids removal efficiency; (6) maximizes removal of effluent from sludge; (7) improves laminar flow within the separation vessel; (8) reduces water velocity within the separation vessel; (9) improves dwell time within the separation vessel; (10) provides for adjustable height risers to control system liquid level; and, (11) improves overall efficiency and cost effectiveness.
Additional advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. Further benefits and advantages of the embodiments of the invention will become apparent from consideration of the following detailed description given with reference to the accompanying drawings, which specify and show preferred embodiments of the present invention.
The accompanying drawings, which are incorporated into and constitute a part of this specification, illustrate one or more embodiments of the present invention and, together with the detailed description, serve to explain the principles and implementations of the invention.
Turning now descriptively to the drawings, in which similar reference characters denote similar elements throughout the several views, the figures illustrate the modular dual vessel dissolved aeration flotation waste water treatment system of the present invention. With regard to the reference numerals used, the following numbering is used throughout the various drawing figures:
Before beginning a detailed description of the subject invention, mention of the following is in order. When appropriate, like reference materials and characters are used to designate identical, corresponding, or similar components in differing figure drawings. The figure drawings associated with this disclosure typically are not drawn with dimensional accuracy to scale, i.e., such drawings have been drafted with a focus on clarity of viewing and understanding rather than dimensional accuracy.
In the interest of clarity, not all of the routine features of the implementations described herein are shown and described. It will, of course, be appreciated that in the development of any such actual implementation, numerous implementation-specific decisions must be made in order to achieve the developer's specific goals, such as compliance with application- and business-related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skill in the art having the benefit of this disclosure.
For ease of reference, because the first and second treatment sections have duplicate portions, items relating to a first treatment section will be designated with an “a” suffix, and duplicate items relating to a second treatment section will be designated with a “b” suffix. For example, reference to “separation tank 20ab” indicates that both treatment sections 14a and 14b include an identical separation tank 20a and 20b, respectively.
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Flocculator portion 52ab includes an inlet 54ab to receive a liquid stream, an outlet 56ab to discharge into the separation tank 20ab, an aeration mixing chamber 58ab disposed between the flocculator inlet 54ab and outlet 56ab, an aeration injection port 60ab proximal to an upstream end 62ab of the aeration mixing chamber 58ab, and a chemical injection port 64ab disposed between the flocculator inlet 54ab and the aeration injection port 60ab.
In the embodiment, effluent weir 66ab is mounted within the separation tank 20ab at a depth proximal to the bottom portions 40ab and 44ab of the inside and outside side walls, respectively, but set off from the bottom wall 22ab. Effluent weir 66ab is mounted low within separation tank 20ab so as to be fully submerged as low as possible to be below the surface region where retentate raised to the surface by gas bubbles accumulates, but still offset from the bottom surface—where non-floating sediment will accumulate—to prevent ingestion of sediment into the clear well. Effluent weir 66ab has an enclosed top portion 68ab and a bottom inlet 70ab to prevent sinking sediments from entering the weir, and a discharge 72ab in fluid communication with a clear well riser 74ab to direct clarified effluent out of the system 10. Clear well 76ab is mounted adjacent to the separation tank 20ab to minimize head loss and footprint. Clear well 76ab is defined by a bottom wall 78ab and enclosing side walls, 80ab, 82ab, 84ab and 86ab, respectively, each clear well side wall 80-86 extending from a bottom portion 88ab, 92ab, 96ab, 100ab, respectively, connected to the clear well bottom wall 78ab to a top portion 90ab, 94ab, 98ab, 102ab, respectively, and further includes a clear well discharge 108ab to discharge clarified effluent for further treatment or reuse.
Clear well riser 74ab extends from a bottom portion 104ab in fluid communication with the effluent weir discharge 72ab to a riser discharge 106ab within the clear well 76ab, wherein the height of the riser discharge 106ab is lower than clear well side wall top portions 90ab, 94ab, 98ab, 102ab, respectively, and defines the liquid operating level L of the system 10.
In the embodiment, a plurality of clear well risers 74ab are provided, each coupled to an individual effluent weir 66ab and discharging into a single clear well 76ab, in order to provide higher volume flow at low water velocity, and to collect flow from throughout the lower portion of separation tank 20ab, thereby maintaining even laminar flow.
Aeration injector 110ab is provided, having an inlet 112ab in fluid communication with the clear well 76ab and a discharge 114ab in fluid communication with the flocculator aeration injection port 60ab.
In the first embodiment, surface skimmer 16 is mounted to the first and second treatment sections 14ab over the tops of separation tanks 20a and 20b. Sludge collection section 18 is adjacent the second end walls 30ab of the first and second treatment sections 14ab to receive retentate from the surface skimmer 16. In the embodiment, sludge collection section 18 includes a sludge hopper 116 which includes a common hopper end wall 118 abutting both treatment section second end walls 30a and 30b. Sludge plates 48a and 48b extend over hopper common end wall 118 to ensure retentate transfers into sludge hopper 116. Sludge collection section 18 includes a sludge pump 120 to transfer collected retentate (aka sludge) for further processing or disposal. In the embodiment sludge pump 120 is an air operated diaphragm pump, but any appropriate pumping system could be used. In the embodiment a separation tank pump down connection 122 is provided with may be selectively aligned to sludge pump 120 so that sludge pump 120 may be used to pump sediment accumulated on separation tank bottom walls 22ab.
First treatment section 14a and second treatment section 14b may operate independently of each other, such that they may be run simultaneously in parallel aligned to a common waste stream, or one section may be operating while the other is idle, or they may be aligned to separate waste streams with different flocculator chemistry and/or aeration injection settings used, different dwell times, and discharging clean effluent from their respective clear wells 74ab to different destinations. In addition, first and second treatment sections 14a and 14b may be aligned in series, such that the effluent discharge 108ab of one section's clear well 74ab feeds into the inlet 52ab of the other section.
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In the first embodiment, surface skimmer 16 comprises paddles 156 coupled to a cyclical drive train, the paddles 156 travelling longitudinally along the surface L of the liquid in the separation tank 20ab to push retentate over sludge plate 48ab. First cyclical drive mechanism 150 is mounted above first treatment section separation tank 20a and extends from a first drive mechanism first end 152 which is approximately at the first separation tank first end wall 24a to a first drive mechanism second end 154 which is approximately at the first separation tank second end wall 30a. A first group of paddles 156 is coupled to first skimmer drive mechanism 150 to extend transversely across the width of first treatment unit separation tank 20a. Like the first cyclical drive mechanism, a second cyclical drive mechanism 158 is mounted above the second treatment section separation tank 20b and extends from a second drive mechanism first end 160 which is approximately at the second separation tank first end wall 24b to a second drive mechanism second end 162 which is approximately at the second separation tank second end wall 30b. A second group of paddles 156 is coupled to first skimmer drive mechanism 150 to extend transversely across the width of second treatment unit separation tank 20b. First and second cyclical drive systems 150 and 158, respectively, cyclically move each paddle 156 of the respective first and second groups of paddles from approximately the first and second treatment section first end walls 24a and 24b, respectively, to approximately the first and second treatment section second end walls 30a and 30b, respectively, and over the respective sludge plates 48a and 48b to skim retentate from the surface of water in the separation tanks 20a and 20b. In the embodiment, first and second cyclical drive mechanisms are closed loop chain drives, each having a pair of parallel chains 172 engaged by drive sprockets 174 coupled to a common drive shaft 176 and idler sprockets 178 coupled to a common idler shaft 180. Skimmer drive motor 182 is coupled to common drive shaft 176 to cycle the chain drives.
Each paddle 156 includes a rigid coupling flange 164 adapted to couple to a cyclical drive mechanism 150 or 158, and a flexible wiper 166 coupled to and extending beyond rigid coupling flange 164. In the embodiment, rigid coupling flange 164 has opposing wing flanges 168 and 170 which are bolted directly to chains 172. Flexible wipers 166 engage against sludge plate 48ab to force retentate against and then over sludge plate 48ab into sludge hopper 118 and to compress clean water from the retentate as it is forced up the inclined sludge plate 48ab. Surface skimmer 16 is mounted at a height such that paddles 156 will extend into the liquid several inches below the operating level L throughout the anticipated range.
In an alternative arrangement, first and second treatment sections 14a and 14b may be used for sequential treatment by aligning the clear well effluent discharge 108ab from one treatment section to the inlet 54ab of the adjacent unit. A temporary pump may be installed in the interconnection to improve flow.
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Each of the first and second treatment sections 1014ab includes a separation tank 1020ab, having a volume defined by a bottom wall 1022ab, first and second end walls 1024ab and 1030ab, respectively, and inside and outside side walls 1036ab and 1038ab, respectively, with inside walls 1036a and 1036b forming a common inside wall 1036. In the embodiment, bottom wall 1022ab is formed from inclined plates to enhance sediment removal. Inside and outside side walls and first and second end walls, 1036ab, 1038ab, 1024ab and 1030ab, respectively, connect to bottom wall 1022ab at their bottom portions 1040ab, 1044ab, 1026ab and 1032ab, respectively, and extend vertically to their top portions 1042ab, 1046ab, 1028ab and 1034ab, respectively. Sludge plate 1048ab extends at an incline from the interior volume of separation tank 1020ab below the operating level L of the system 1010 over the abutting sludge hopper 1116 of sludge collection section 1018. Sludge plate 1048ab is preferably inclined at an angle in the range 30° to 50° from horizontal.
Flocculator portion 1052ab includes an inlet 1054ab, an outlet 1056ab to discharge into separation tank 1020ab, aeration mixing chamber 1058ab disposed between the flocculator portion inlet 1054ab and outlet 1056ab, an aeration injection port 1060ab proximal to the upstream end of aeration mixing chamber 1058ab, and chemical injection ports 1064ab and 1140ab between inlet 1054ab and aeration injection port 1060ab. Flocculator portion 1052ab includes two horizontal stages 1132ab and 1134ab, with first and second stage chemical injection ports 1064ab and 1138ab, respectively. Effluent weirs 1066ab within separation tank 1020ab in fluid communication with clear well risers 1074ab at clear well riser bottom portions 1104ab direct flow of clean effluent into clear well 1076ab, each of which is positioned adjacent its respective separation tank 1020ab on the common frame 1012. In the second embodiment two effluent weirs 1066ab and corresponding clear well risers 1074ab are provided for each clear well 1076ab on this smaller capacity unit, located proximal to the bottoms of the separation tank sidewalls and end walls but above the region where separation tank bottom wall 1022ab slopes downward to prevent ingestion of sediments. Clear well discharge 1108ab directs clarified effluent out of the system for further processing or reuse. Aeration turbine pump 1110ab takes suction 1112ab from clear well 1076ab via supply line 1148ab to recycle effluent, and injects the aerated effluent into aeration injection port 1060ab proximal to the upstream end 1062ab of aeration mixing chamber 1058ab.
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In the second embodiment, surface skimmer 1016 is similar to the first embodiment, having dual chain drives 1150 and 1158 with chains 1172 coupled to paddles 1156 with rigid coupling flanges 1164 and flexible wiper portions 1166. Drive motor 1182 couples to drive shaft 1176 and drive sprockets 1174 to cycle chains 1172. The paddles 1156 push retentate to sludge plate 1048ab and the flexible wipers 1166 engage against sludge plate 1048ab to concentrate and partially dewater retentate as it is pushed over into sludge hopper 1116 with sludge hopper end wall 1118 abutting first and second separation tank second end walls 1130ab.
In operation, the described first and second embodiments operate similarly, so the first embodiment will be described in detail. A liquid stream, for example waste water, to be treated is received through inlets 54ab and passes through flocculator portion stages 132ab, 134ab and 136ab. Treatment chemicals such as flocculate agents are injected through one or more of chemical injection ports 64ab, 138ab and/or 140ab, to pre-treat the waste water before mixing with aerated water. The chemicals react with particulates in the waste water to create larger, less dense agglomerations of coagulated particles which are more susceptible to binding with air bubbles. The elongated, multi-stage flocculator portion 52ab provides a dwell time of 5 to 120 seconds under normal flow conditions. Aeration turbine pump 110ab injects clarified effluent saturated with air into the aeration mixing chamber 58ab inline with the flow of pre-treated waste water to thoroughly mix with the pre-treated waste water and partially expand to form air bubbles. Pre-treated aerated waste water enters the separation tank 20ab through flocculator portion discharge 56ab. The waste water flows along the tank 20ab and downward along the parallel plates 124ab within the plate packs 122ab which causes heavier particles to separate and drop to the tank bottom, and lighter particles to which gas bubbles have adhered to rise to the surface. Clean effluent passes into effluent weirs 66ab through bottom inlets 70ab, through clear well riser lower portions 104ab and clear well risers 74ab, into clear well 76ab through riser discharges 106ab. Clarified effluent in clear well 76ab is either discharged through clear well discharge 108ab, or recycled through aeration turbine pump 110ab via supply line 148ab. The height of clear well riser discharge 106ab determines the operating level L in the system. The total dwell time of the system 10 at normal operating conditions will be in the range 10 minutes to 30 minutes for each treatment section 14ab—measured from waste water entry into the flocculator portion inlet 54ab to the clear well discharge 108ab.
Within separation tanks 20ab, flocculates rise to the surface—referred to as retentate. Paddles 156 are cyclically driven along the liquid surface of separation tanks 20ab to push retentate toward the back of the tank to the “beach”—i.e. sludge plates 48ab. As the retentate is pushed up sludge plates 48ab much of the entrained water drains back into the tank 20ab and the retentate is concentrated, then pushed over the edge into sludge hopper 116. As sludge accumulates in hopper 116 sludge pump 120 will periodically activate to transfer sludge to a removal container or some other receiver for further processing.
Controls may be provided in a common control panel to control the entire skid, or local controls may be provided, or a combination of both, as is known in the art.
Those skilled in the art will recognize that numerous modifications and changes may be made to the preferred embodiment without departing from the scope of the claimed invention. It will, of course, be understood that modifications of the invention, in its various aspects, will be apparent to those skilled in the art, some being apparent only after study, others being matters of routine mechanical, chemical and electronic design. No single feature, function or property of the preferred embodiment is essential. Other embodiments are possible, their specific designs depending upon the particular application. As such, the scope of the invention should not be limited by the particular embodiments herein described but should be defined only by the appended claims and equivalents thereof.
This application is a continuation-in-part of and claims priority to co-pending U.S. Nonprovisional application Ser. No. 12/856,053, filed Aug. 13, 2010, and co-pending U.S. Nonprovisional application Ser. No. 12/683,340, filed Jan. 6, 2010, the disclosures of each of which is hereby incorporated by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4067813 | Pielkenrood | Jan 1978 | A |
| 4193869 | Brucker et al. | Mar 1980 | A |
| 5520806 | Menke | May 1996 | A |
| Number | Date | Country | |
|---|---|---|---|
| 20120006732 A1 | Jan 2012 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12856053 | Aug 2010 | US |
| Child | 13160459 | US | |
| Parent | 12683340 | Jan 2010 | US |
| Child | 12856053 | US |
