Patent Application
20160221845
The present invention relates to the process of treating of water specifically to the use of magnetic material to enhance the clarification of water and to specific designs and methods to improve the efficiency of magnetic ballast clarification.
Clarification, that is the removal of suspended solids from water, is an important part of water treatment. There are many methods practiced for separating suspended solids from water such as gravity clarification, membrane filtration, and ballast clarification.
A series of improvements to these clarification technologies have been made to reduce their cost, reduce their size, and improve their operation. However one of the most cost effective and trouble free methods to clarify water quickly is ballast clarification, that is the use of dense materials in combination with flocculating polymers to speed the settling rates of suspended solids present in water.
Veolia perfected the use of sand as a ballast material to speed the clarification process with their Actiflo system. Actiflo uses a flocculating polymer to attach suspended solids in water to sand to form a dense floc that settles more rapidly. Settling is by gravity and is dependent on the density and particle size of the sand.
The major deficiency of the Actiflo design is it only relies on gravity for the removal of suspended solids so when there are rapid increases in hydraulic flow, there is no positive barrier to prevent the discharge of suspended solids. Also, the method used to remove and clean the sand ballast produces a dilute waste. Ballasted floc that settles to the bottom of the Actiflo clarifier has to be raked to the center of the clarifier so it can be pumped as dilute slurry to a hydrocyclone where the sand ballast is separated by centrifugal force to be reused. This process consumes a large amount of energy, has high capital cost, causes wear on critical pump parts, and because the sand slurry is dilute, the waste generated from Actiflo is also dilute.
It was then discovered that magnetite was a better ballast material than sand. Magnetite is denser than sand (twice as dense) and therefore settles more rapidly to make the clarification system smaller. Also magnetite is ferromagnetic (iron based material that is attracted to a magnet) so as described by the methods of this patent application, the magnetite can be removed from the system for cleaning by a magnetic device. This leaves much of the water out of the magnetite cleaning system and therefore produces a more concentrated waste.
The use of magnetite as a ballast material was first practiced over thirty years ago in Australia with the development of the Sirofloc technology. This technology did not use a flocculating polymer to attach suspended solids to the magnetic ballast, which in Sirofloc was magnetite, but rather used the electric charge of the magnetite to attract fine suspended solids of opposite charge to the magnetite. Sirofloc technology does not use a final magnetic collector but only gravity to remove the magnetite. The magnetite, after it adsorbs negatively charged colloidal sized suspended solids contained in the water, settles out of the water in a gravity clarifier. The magnetite is then pumped from the gravity clarifier to a cleaning system that uses caustic to change the charge of the magnetite so it can be reused in the clarification process to attract new negatively charged colloidal sized suspended solids. This process produced a large volume of caustic waste, could not handle water that contained high concentrations of suspended solids, and still relied on gravity settling. The Sirofloc technology has not been adapted to clarify wastewater.
The Comag system, developed by Cambridge Water Technologies, improved the Sirofloc technology by using a flocculating polymer and adding a final magnetic collector that uses a magnetic field produced by electromagnets to remove magnetic floc from the water. This modification made the system smaller and made it possible to treat water that contained a higher level of suspended solids, eliminated the use of magnetite cleaning chemicals, and initially eliminated the need for a gravity clarifier. However, the use of electromagnets in a final magnetic collector posed some significant disadvantages. First, electromagnets are expensive and use more electricity than permanent magnets. Second, the magnetic stainless steel wool that is used in the Comag magnetic collector is easily fouled and cannot process a high level of suspended solids in the water, much in the same way a sand filter cannot process a high level of suspended solids. When the concentration of suspended solids is high, the Comag final magnetic collector quickly fills with suspended solids and has to be frequently cleaned with a water and air backwash. This frequent backwashing produces a large quantity of waste, which is very dilute. Third, the final magnetic collector has to be de-energized for cleaning, which interrupts the treatment process. Therefore to correct some of these deficiencies, Cambridge Water Technologies added a gravity clarifier placed before the final magnetic collector to handle high solids loading and to reduce the backwashing frequency of the final collector. This addition of a gravity clarifier negated much of the initial size advantages of Comag.
The Cort U.S. Pat. No. 7,255,793 overcame many of the disadvantages of the Comag and Actiflo systems with the Magnetic Ballast Clarifier (MBC) system. The new MBC process that overcame the disadvantages of Actiflo and Comag is described in detail in the Cort US Pat. No. 7,255,793.
Cambridge Water Technologies then developed and promoted the use of magnetite to improve the settling characteristics of biosolids in a gravity clarifier. Woodard U.S. Pat. No. 7,695,623 describes how magnetite can be imbedded into a biological floc found in an activated sludge (AS) treatment system to increase the biofloc's weight and therefore improves its settling rate in a gravity clarifier. This improvement in floc settleability causes a two to threefold increase in gravity clarifier capacity, however, this approach to increase the settleability of a biofloc is not new and the Woodard U.S. Pat. No. 7,695,623 therefore only claims a collection of multiple physical devices working together to improve the performance of a gravity clarifier. The system claimed by Woodard U.S. Pat. No. 7,695,623 also has several disadvantages that are overcome by this patent application.
First, Woodard U.S. Pat. No. 7,695,623 describes a method that returns biofloc weighted with magnetite (Returned Activated Sludge (RAS)) to the aeration basin of an AS system. This approach increases the amount of energy needed to keep the weighted biofloc in suspension. Also, any magnetite that separates from the biofloc can settle to the bottom of the aeration basin potentially causing a major operating and cleanout problem.
Second, since in the Woodard U.S. Pat. No. 7,695,623 magnetite is added to the aeration basin, the magnetite has to be very fine so it can be kept in suspension. Also in laboratory tests conducted by Cort, course magnetite will not effectively imbed into a biofloc without the use of a flocculating polymer. However, a fine magnetite will not settle well in a gravity clarifier. This dilemma is eliminated since in this patent application magnetite is not added to the aeration basin; a more course magnetite can be used to enhance settling in the secondary gravity clarifier.
Third, Woodard U.S. Pat. No. 7,695,623 shows no inline mixing device to enhance the flocculation of biofloc, virgin magnetite and recycled magnetite with the addition of a flocculating polymer.
Fourth, Woodard U.S. Pat. No. 7,695,623 does not have a way to concentrate the Waste Activated Sludge (WAS) and therefore reduce disposal costs. Biofloc weighted with magnetite settles to the bottom of the secondary gravity clarifier where it is removed and split into WAS and Returned Activated Sludge (RAS). The RAS, which contains magnetite is pumped back to the activated sludge basin and the WAS, which also is a dilute concentration of magnetite and biosolids is pumped as a dilute slurry to a magnetite cleaning and recovery system. The amount of water in dilute RAS is not much of a problem because it is sent back to the aeration basin and only increases pumping costs. However, RAS containing magnetite is a problem going back to the aeration basin because it results in greater energy use to keep this heavy floc in suspensions and operating and cleanout problems when magnetite settles to the bottom of the aeration basin. Another problem is the WAS and RAS contain magnetite which is abrasive to pumps and piping system. The approach taken in this patent application has a number of advantages over the approach described in Woodard U.S. Pat. No. 7,695,623. Following the art described in this patent application has many advantages over the art described in Woodard U.S. Pat. No. 7,695,623.
First, since the approach described in this patent application does not allow magnetite to enter the aeration basin, there is no increase in energy required to keep weighted biofloc in suspension and no resulting operating or cleanout problems associated with magnetite settling to the bottom of the aeration basin.
Second, since the approach described in this patent application can use a courser magnetite (between 40 and 200 microns) because it does not get into the aeration basin where it has to be kept suspended, biofloc weighted with a courser magnetite will settle more rapidly in the secondary gravity clarifier and thereby increase its capacity.
Third, since the approach described in this patent application contains a well-designed in-line mixer, a channel hydraulic flocculator, or in-tank mixer, flocculation is more efficient and better water clarity will be achieved.
Fourth, the Biomag magnetite cleaning process first shears the WAS to separate the magnetite from the other biosolids. This sheared dilute slurry then passes over a magnetic drum, which collects the separated magnetite and returns it back to the aeration basin. The dilute WAS not collected on the magnetic drum is disposed of, but because it is so dilute, it is more economic to first put it into a settling tank to concentrate the solids before it is dewatered. This patent application removes magnetic floc from the water by a magnetic collector that raises the magnetic floc out of the water leaving much of the excess water behind. This approach produces a much more concentrated WAS.
In summary, adding magnetite to the biological treatment process will significantly improve the settleability of bioflocs formed. However, in the Woodard U.S. Pat. No. 7,695,623, the methods described have shortcomings that are mostly overcome by this patent application. Specifically not adding magnetite to the aeration basin and controlling the amounts of weighted solids that can flow to the secondary gravity clarifier are two major advantages of this patent application. No other patent or information in the public domain describes the ideas contained in this patent application to improve clarification capacity in a way that reduces energy use, minimizes operating problems, and reduces the amount of waste generated. Applying the principles contained in this patent application will increase the treatment capacity of a municipal wastewater treatment plant two to threefold without increasing its footprint.
Being able to clarify water inline or with a small mix tank with the MBC allows it to be mounted inside or on top of an aeration basin or any biological or chemical treatment system, which has significant installation and operating benefits. Large flow rate systems such as municipal wastewater treatment systems have large transfer pipes between biological treatment and clarification. These pipes are normally installed underground and are often made of concrete. Retrofitting any treatment process that involves cutting into a large underground concrete pipe is costly and will cause a major interruption to system operation. The process presented in this patent application can be installed with no interruption to system operation and does not involve any major piping changes or penetrations.
The Actiflo, Biomag, and Comag processes all produce dilute wastes because of the way they have to clean their ballast material. Each process includes a gravity clarification step that allows weighted floc to settle to the bottom of a gravity clarifier. In order to recover and reuse the ballast material (microsand in the case of Actiflo and magnetite in the case of Biomag and Comag) dilute slurry of weighted floc is pumped from the bottom of the gravity clarifier to the ballast cleaning system. Since no process is used in these three technologies to remove water from these dilute slurries before the ballast material is cleaned and separated from the slurry, the resulting waste material is extremely dilute, in the order of less than 0.5 weight % dry solids. This is a major disadvantage of these technologies especially when waste solids have to be dewatered further before disposal. Increasing the concentration of dry solids in the waste product will reduce costs and benefit the environment. This patent application presents a novel way to reduce the amount of waste produced when magnetite is used as the ballast material.
As shown in
The MBC system described in Cort U.S. Pat. No. 7,255,793 uses magnetite as a ballast material in a way that is a significant improvement over the prior art. In the Cort U.S. Pat. No. 7,255,793, a plurality of magnetic disks is used to prevent magnetic floc from exiting the system. These magnetic disks are only partially submerged to prevent water from leaking past the rotating the shaft, and therefore only less than half of the magnets are capable of treating the water. Since magnetite is used as the ballast material and permanent magnets used instead of electromagnets, the system is smaller, uses less electricity, and produces less waste; yet future improvements were possible to increase the efficiency of the final magnetic collector that are now described in this patent application. This patent application among other things contains effective and novel ideas that enhance the performance of the MBC final magnetic collector. Specifically the positioning of the final magnetic collector and the flow path of water through the magnetic collector has significantly increased the capacity of the magnetic collector over five fold.
Filtration is an effective way to remove suspended solids from water but its disadvantages are it causes a significant pressure drop, is not capable of handling high solids levels, and is labor intensive and costly to replace disposable cartridges. This patent application describes a novel way for magnetite to be held in place by a magnetic field so it can act as a filter media. Therefore, if properly designed and operated, the magnetite filter will have a high capacity flow rate, will not foul, and is continuously cleaned, which minimizes labor and cartridge replacement costs. This is a significant advantage over a rotating disk filter that uses a cloth filter media to collect suspended solids that forms a filter cake, which creates a high pressure drop, is prone to fouling, and produces more waste from backwashing.
There are two primary methods for flocculating suspended solids with the use of a flocculating polymer. Each method has it specific advantages. One method is flocculation in a stirred tank. The mixing action provides enough motion and energy for particles to floc together. This method uses more energy, takes up more space, and does not provide completely uniform mixing conditions. However it can adjust to varying flow rates more effectively. The other primary method is inline mixing, which takes up less space, uses less energy and provides more uniform mixing conditions. However it does not adjust to varying flow rates effectively.
Heretofore, inline flocculation has not been incorporated into a magnetic ballast clarification system. The use of inline flocculation is effective in high flow rate applications where space is limited. This approach is advancement to the state of the art for magnetic clarification and is fully described in this patent application.
This patent application also describes novel production methods and materials to improve the cost effectiveness of MBC technology. Heretofore, these production methods and materials have not been used in the production of clarification technology that uses magnetite.
With the exception of membrane technology all other clarification systems operate at atmospheric pressure. Therefore if water is pumped into an atmospheric clarification process, the energy of the pressurized water in the pipeline is lost in some cases this is not an issue if the water only has to flow by gravity thereafter. However, if the water has to be pumped again, having a clarification system that operates under pressure is an advantage and a cost saver.
Aside from the preferred embodiment or embodiments disclosed below, this invention is capable of other embodiments and of being practiced or being carried out in various ways. Thus, it is to be understood that this invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. If only one embodiment is described herein, the claims hereof are not to be limited to that embodiment. Moreover, the claims hereof are not to be read restrictively unless there is clear and convincing evidence manifesting a certain exclusion, restriction, or disclaimer. It is therefore an objective of this invention to provide a system and method for enhancing the high rate clarification of water with new methods to use magnetic ballast materials effectively.
Furthermore, it is an objective of this invention to provide such a system and method, which is novel and cost effective.
Furthermore, it is an objective of this invention to provide such a system and method, which is reliable and simple to operate.
Furthermore, it an objective of this invention to provide such a system and method which is robust and replete with few operating problems.
Furthermore, it is an objective of this invention to provide such a system and method, which is effective in removing high concentrations of suspended solids from wastewater.
Furthermore, it is an objective of this invention to decrease the amount of waste generated by increasing the concentration of solids in the final waste stream, preferably a solid cake.
Furthermore, it is an objective of this invention to provide such a system and method, which reduces capital and operating costs.
Furthermore, it is an objective of this invention to combine water treatment processes into one unit to minimize space requirements.
Furthermore, it is an objective of this invention to retrofit existing water treatment systems to enhance performance and to reduce costs without increasing the footprint of the treatment system.
Furthermore, it is an objective of this invention to provide such a system and method, which will provide a high quality water effluent.
Furthermore, it is an objective of this invention to provide such a system and method, which improves the treatment efficiency of treating large flow applications because of a more efficient final magnetic collector.
Furthermore, it is an objective of this invention to provide such a system and method, which meets local, state and federal regulations for water and wastewater treatment.
The subject invention, however, in other embodiments, need not achieve all these objectives and the claims hereof should not be limited to structures or methods capable of achieving these objectives.
In previous MBC designs, the final magnetic collector is separate from the magnetite cleaning system. In the preferred embodiment of the Cort U.S. Pat. No. 7,255,793, the final collector is composed of a plurality of magnetic disks affixed to a rotating shaft but could also be a drum, which is less efficient. The magnetic disks are positioned in a floc tank and positioned between each disk is a scraper blade that removes the magnetite floc from the disks and causes the magnetite to fall back into the floc tank. The separate magnetite cleaning system is composed of one magnetic drum that removes dirty floc from the floc tank and deposits the floc into a horizontal shear tube or into a vertical shear tank that separates the magnetite from other suspended solids. The sheared solids discharge onto another magnetic drum that separates the magnetite from the non-magnetic solids. The non-magnetic solids leave the system as waste and the cleaned magnetite is returned to the floc tank for reuse. The novel design contained in this patent application (shown in
Heretofore, the state of the art was that magnetic disk collectors have been built so that the centerline of the disks is above the waterline to prevent submerging rotating bearings into water that contained magnetite, which is abrasive to bearings. Therefore, only less than half the disks were submerged and the capacity of the magnetic disk collector was reduced.
This limit to the capacity of the magnetic disk collector has been eliminated by the design described in this patent application.
Mounting the magnetic disk collector in a horizontal position mostly submerged with only a portion of the magnetic disk exposed above the water line increases the effective collection area of the magnetic disk and allows magnetite to be raised out of the water so it can be cleaned and reused with a minimum production of waste. The speed of the magnetic disks can be varied to control the amount of water that enters the magnetite cleaning system. At a high speed, more water is entrained with the magnetite and therefore the amount of waste is increased. At low speeds, much of the water is allowed to drain back into the MBC unit and therefore the amount of waste is decreased.
In prior art, the flow of water was always across the diameter of each magnetic disk. In this patent application, the flow of water is from the perimeter of the magnetic disk to its center and out through a center cutout in the magnetic disk and along the drive shaft that rotates the magnetic disks. This change increases the capacity of the magnetic disk as long as the center cut hole in the magnetic disk has enough capacity to handle the increased flow.
The reason that this new design for the magnetic disk has an increased capacity to collect magnetic particles is that the ability of a magnetic disk to capture and hold magnetic particle is a function of the velocity of the magnetic particle. The higher the velocity of the magnetic particle, the more difficult it is to capture and hold onto a magnet. Specifically, the velocity of water through the magnetic collector is the flow rate in cubic feet per second divided by the cross-sectional area in square feet. As the cross-sectional area is reduced, the velocity of water flow increases proportionally and therefore it becomes more difficult to collect magnetic particles with a magnet. Now in the case of previous designs, the flow velocity and therefore the capacity through the space between two magnetic disks was equal to less than its radius of the magnetic disk (because it was only half in the water) times the distance between magnetic disks. For example, if a magnetic disk is twenty (20) inches in diameter and there is one (1) inch gap between the magnetic disks, the effective cross-sectional area for flow between two disks is the radius of the disk times the distance between the disks. Therefore the effective cross-sectional area for flow between two disks is equal to about 9 square inches.
However, when water flows radially from the perimeter of the magnetic disk to the center of the magnetic disk, then the cross-sectional area is the circumference of the magnetic disk times the gap between the magnetic disks. Therefore, flow radially from the perimeter of a magnetic disk to its center and out through a center cutout in the magnetic disk, will have a lower velocity than if the flow is across the diameter of the magnetic disk. In comparison to the case where a 20-inch magnetic disk is only half submerged and flow is across the diameter of the magnetic disk, the velocity and therefore the flow capacity is proportional to the effective 9 square inches of cross-sectional area. When the magnetic disk is almost fully submerged and the flow is radially from the perimeter of the magnetic disk to the center of the magnetic disk, the cross-sectional area is equal to 3.14 times 16 inches (average circumference of the area containing magnets) times 1 inch, which is equal to 50.11 square inches. Therefore, when a magnetic disk is almost completely submerged and the flow is radially over the whole surface of the magnetic disk from its perimeter to its center cutout, the flow capacity is over five and a half times the flow capacity of a similar magnetic disk that is only half submerged having the flow of water across the diameter of the magnetic disk.
In summary, one aspect of this patent application describes a novel and cost effective magnetic collector (shown in
The risen magnetic floc flows into a magnetite shear device that is composed of a series of abrasion resistant shear disks (see
The rotating shear disks have depressions cut or formed into its face to cause increased turbulence (see
A magnetic drum following the magnetite shear device (see
Magnetic disks can also act as a magnetite filter (see
The Ferrite magnets are just strong enough to hold magnetite in place to form a bridge between the outer rings of magnets. This bridge of magnetite acts like a solid filter barrier but since this filter barrier is not strongly held by the ferrite magnets so more powerful rare earth magnets can easily remove the barrier.
The magnetite bridge between opposing magnets in each magnetic disk that has now filtered out suspended solids from the flowing stream of water is remove magnetically by more powerful rare earth magnets mounted in a revolving drum that is in contact with the perimeter of the magnetic disk.
When the magnetite and suspended solids move away from the force of the weaker ferrite magnets and on to the more powerful rare earth magnets contained in the rotating drum, the magnetite is cleaned with scrapers and cleaning sprays to separate the suspended solids from the magnetite so the cleaned magnetite can redeposit back onto the magnetic disks containing the less powerful ferrite magnets and the magnetite filtration bridge is then re-established.
The production of magnetic drums to separate magnetite from non-magnetic solids requires the nesting of permanent magnets inside a hollow plastic duct, preferably a commercially available PVC duct. Nesting the magnets close together increases the magnetic field strength and therefore the collection capacity of the magnetic drum. However, placing unrestrained magnets in close proximity to each other will cause them to clump together and make it impossible to place the magnets inside the hollow PVC duct in contact with the inner surface of the PVC duct. In order to prevent this from happening, as iron metal sheet (see
An important part of the MBC is the floc tank that is used to cause suspended solids to be attached to magnetite with the use of a flocculating polymer. This patent application shows the novel flow of water into the MBC system to quickly come into contact with cleaned magnetite coming from the magnetic drum (see
A baffle is placed in the floc tank that prevents the short-circuiting of floc through the floc tank (see
Mounting the final magnetic collector horizontally inside the floc tank requires a rotating seal between the outboard magnetic disk closest to the wall of the floc tank and the wall of the floc tank. This is a potential source of leakage of magnetic floc from the MBC system. To prevent this from happening, either the permanent magnets are placed on the perimeter of the magnetic disk closest to the discharge from the floc tank to form a magnetic seal, which prevents magnetic particles passing through the rotating seal or permanent magnets are placed inside the rotating seal. The rotating seal is made of abrasion plastic with one half of the seal attached to the wall of the floc tank (fixed seal) and the other half of the seal attached to adjacent rotating magnetic disk (rotating seal). Another alternative is to place permanent magnets in the fixed seal part that is affixed to the tank wall. Therefore as magnetite enters the space between the fixed seal and the rotating seal, the magnetite is held in place by the permanent magnets causing a seal between the two seal faces. A preferred approach is to place the outboard disk closest to the tank wall against the tank wall so the magnets in the disk will collect any magnetite that is attempting to exist the floc tank (see
The original design of the magnetic disks was three circular disks of PVC cemented together with permanent magnets contained in the inner PVC disk. In this inner disk of PVC, one-inch diameter holes were punched in strategic locations to contain the permanent magnets. This laminated construction can delaminate and allow water to come into contact with the permanent magnets causing rusting. Also, there are limits to the size of disks that can be constructed with this manufacturing method due to the warping of the disks when they are too large. A preferred construction method is to cast the disks with a thermosetting plastic such as polyurethane. This eliminates the possibility of disk delamination and allows stiffeners to be placed within the magnetic disks, which allows a larger size disk to be fabricated. Disks can also be injection molded using thermoplastics.
One factor that limits the capacity of the MBC is the residence time in the floc tank. Laboratory tests demonstrate that a one-minute residence time is preferable but if preflocculation inline is practiced by adding flocculating polymer upstream of the floc tank, the floc tank as a limitation on the capacity of the MBC system can be reduced. This preflocculation of solids before contacting the magnetite can be accomplished outside the floc tank or inside the floc tank with a series of static or hydraulic mixers. Inline preflocculation of solids before the MBC is a new and novel idea and has not been practiced or contemplated before (see
Drum scrapers are usually mechanical devices that have to be adjusted for wear.
This can be done automatically by a combination of springs or as demonstrated in the patent application it can be done magnetically. A ferromagnetic stainless steel such as a 400 series stainless steel (to prevent corrosion) can be inserted as a strip in a plastic scraper material. This strip is attracted to the magnetic drum so as it wears it always stays into contact with the magnetic drum (see
The Woodard et al U.S. Pat. No. 7,695,623 describes a treatment process called Biomag (see
To accomplish this benefit, as described in the Woodard U.S. Pat. No. 7,695,623, fine magnetite is added to the aeration basin. The reason for using a fine magnetite is; particles of different sizes do not comingle well without the use of a flocculating polymer. In fact, Cort learned from laboratory experiments that a course magnetite would not effectively imbed into a biofloc without the aid of a flocculating polymer. Also for good clarification, it is necessary to use a flocculating polymer. However when a fine magnetite was used, it imbedded into the biofloc but did not settle as quickly as when a course magnetite was used and the supernatant after settling was not clear. Therefore, course magnetite is good to use in a gravity clarifier to speed settling with the aid of a flocculating polymer but is not good for use in an aeration basin because it will not effectively imbed into the biofloc, will cause settling and cleanout problems and will increase the amount of energy needed to keep the biofloc in suspension. The Woodard U.S. Pat. No. 7,695,623 does not contemplate using flocculating polymer in the aeration basin only in the pipeline leading to the secondary gravity clarifier.
The Woodard U.S. Pat. No. 7,695,623 then shows magnetic floc, which has settled to the bottom of the secondary clarifier, is pumped either back to the aeration basin as Returned Activated Sludge (RAS) or to a magnetite cleaning and recovery system as Waste Activated Sludge (WAS). This approach has two problems. The problem of putting magnetite into the aeration basin is it increases mixing energy requirements, causes additional wear and tear on equipment due to the abrasive nature of magnetite, and can settle out in the aeration basin causing operational and clean out problems. Another problem is pumping magnetic floc out of the secondary gravity clarifier produces a dilute waste product and increases the size of the magnetite cleaning system.
This patent application describes a system where no magnetite enters the aeration basin (see
When a Biomag system is installed, it increases the footprint of the facility, increases the electrical usage, increases chemical usage, causes additional wear and tear on plant equipment, and can cause potential problems with magnetite collecting in the aeration basin. However, it is effective in increasing the clarification capacity of a plant. Then the bottleneck in the plant can revert to the biological treatment system.
When a MBC is installed, it does not increase the electrical usage to any significant amount and will not cause problems with magnetite in the aeration basin. The inline MBC can be placed inside the aeration tank and therefore does not increases the footprint of the plant.
This patent application proposes using a courser magnetite (greater than 40 micron) to enhance settling in the gravity clarifier and because this magnetite does not enter the aeration basin it does not cause problems with increased mixing energy to keep it in suspension, will not deposit in the aeration basis, and will not have problems imbedding into a biofloc since flocculation is aided by a flocculating polymer.
There is little value in adding magnetite to an aeration basin, and in fact, this practice results in higher costs to add more magnetite to fully treat the whole aeration basin. A better solution is to add magnetite to the biofloc after it exist the aeration basin and before it enters the MBC system that is mounted inside the aeration basin.
In summary, when you add magnetite after biological treatment to form a magnetic floc inline, you can use a courser magnetite, which is cheaper and more readily available in the marketplace. You do not have to worry about magnetite settling out in the aeration basin or how well the magnetite imbeds into a biofloc without the aid of a flocculating polymer or using extra energy to keep magnetic biofloc in suspension in the aeration basin. Using a courser magnetite will greatly increase the settleability of the weighted biofloc in the secondary clarifier and therefore increase its capacity.
One way to increase the biological treatment capacity of the plant is to add biocarriers to increase the amount of biofilm in the aeration basin. This patent application describes the combination of magnetic clarification technology either Biomag or MBC with the conversion of the activated sludge system to a MBBR, which contains biocarriers. This is by far the best combination of biological treatment technology and magnetic clarification technology because the MBBR produces a lesser amount of biosolids, improves water quality, reduces sludge generation, and is tolerant of toxic shock. In an activated sludge system the Mixed Liquor Suspended Solids (MLSS) ranges from 2000 to 5000 mg/I. In a MBBR, the MLSS ranges from 300-800 mg/I. This lower level of suspended solids reduces the load on the MBC or Biomag magnetite cleaning systems.
Gravity clarification and DAF are operated under atmospheric pressure conditions and in most applications this is advantageous because water can flow by gravity through these systems, however there are some applications where operating a clarification technology under pressure is advantageous. For example, if a clarifier is followed by final filtration, the final filter may be a pressure filter to save space or if the effluent has to be raised for final discharge, operating the MBC under pressure will eliminate a final transfer pump. This patent application describes a novel way to operate a MBC under pressure (see
A technology that is used to treat large flow rates of storm water is the vortex separator. It uses centrifugal forces to cause suspended solids in storm water to separate from the storm water and settle to the bottom of the vortex separator to be discharged as waste. Its main advantages are it is a passive system that can startup up quickly and can treat large amounts of storm water in a small amount of space. It can effectively remove large solids called grit that settles rapidly and it can effectively remove floatables. However, it cannot effectively remove fine suspended solids that do not settle well. Therefore the water looks a lot better because floatables have been removed and build up of settleable solids is reduced downstream, however the vortex separator does not remove a majority of the pollutants such as oil and grease, heavy metals, and nutrients are not removed by a vortex separator. This is because the majority of pollutants are associated with the fine solids because of their large surface area and since vortex separators do not remove fine suspended solids well, a high percentage of pollutants remain in from the water and the water usually does not look any clearer. Therefore, there is a significant need to improve the operation of vortex separators to treat storm water and this patent application shows how MBC can be integrated with a vortex separator to remove those fine suspended solids than cannot be removed by a vortex separator by itself (see
This patent application describes the placement of a floating suction in a pond or lagoon to withdraw water at a constant rate. The water flowing out of a pipeline connected to the pond or lagoon is preferably a floating pipeline made of lightweight plastic. As the water flows through the pipeline, magnetite and flocculating polymer is added to cause the magnetite to floc together with the fine suspended solids in the wastewater. This magnetic floc then flows to a magnetic collector that is designed to remove the magnetic floc from the water so a magnetite cleaning system can break the floc separating the magnetite from the suspended solids. The suspended solids are then disposed and the magnetite reused in the treatment process.
Storm events produce large quantities of polluted water that damage the environment. A common strategy to reduce this impact on the environment is the use of impoundment structures to allow suspended solids that contain much of the pollution to settle out by gravity. However, these suspended solids are often very small in size and do not settle well and in some cases not at all. Therefore, to treat these large flows of storm water that can in some cases also contain sanitary wastes, it is necessary to increase the settling clarification capability of these impoundment structures that can be manmade concrete basins, lagoons, or ponds.
The preferred approach to increasing the clarification capacity of impoundment structures it to use magnetite and flocculating polymers to form a magnetic floc that captures the suspended solids contained in the storm water. The suspended solids can be organic or inorganic in nature. When there are dissolved pollutants contained in the storm water, it is often necessary to add precipitating agents. In the case of heavy metals this can be the addition of sulfides to precipitate the heavy metals to form suspended solids. In the case of phosphorous, this can be the addition of metal salts such as iron or aluminum to precipitate phosphorus as either iron phosphate or aluminum phosphate.
Storm water flows through a conveyance system such as a culvert, pipeline, or open channel into an impoundment structure. It is in this conveyance system that magnetite, flocculating polymer, and possibly a precipitating agent is added to form a magnetic floc that can be easily removed by a magnetic device or will rapidly settle by gravity in the impoundment structure. Due to the high flow rates while it is possible to remove the magnetic floc from the flowing stream of water, it is preferable to allow the magnetic floc to settle by gravity in the impoundment structure and then at a later date remove the magnetic floc to remover the magnetite and to disposes of the suspended solids attached to the magnetite.
Flow of the storm water containing the magnetic floc into the impoundment structure can be directed in a way that enhances settling and the recovery of the settled magnetic floc. For example, flow can be directed to the perimeter of the impoundment structure so that magnetic floc will settle into areas that facilitate the removal and treatment of the magnetic floc. Also, the flow can be directed in a circular path that lengthens the pathway of the water flow through the impoundment structure to prevent short-circuiting. This will lengthen the time allowed for settling.
Magnetic floc that has settled in the impoundment structure can be removed either magnetically by a magnetic device that raises the magnetic floc from the bottom of the impoundment structure to the water's surface where the magnetic floc can be treated to recover the magnetite or a the magnetic floc can be pumped off the bottom of the impoundment structure with a dredging device.
In summary, this invention converts an impoundment structure into a clarifier that functions much like a vortex separator (see
Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which:
While this invention is susceptible to embodiment in many different forms, there is shown in the drawings and will herein be described in detail specific embodiments, with the understanding that the present disclosure of such embodiments is to be considered as an example of the principles and not intended to limit the invention to the specific embodiments shown and described. In the description below, like reference numerals are used to describe the same, similar or corresponding parts in the several views of the drawings. This detailed description defines the meaning of the terms used herein and specifically describes embodiments in order for those skilled in the art to practice the invention.
Provisional application Ser. No. 61/935,613 filed on Feb. 4, 2014.
