Liquid purification or separation – Flow – fluid pressure or material level – responsive – Diverse sensing means
Reexamination Certificate
2000-03-13
2001-12-25
Hruskoci, Peter A. (Department: 1724)
Liquid purification or separation
Flow, fluid pressure or material level, responsive
Diverse sensing means
C210S109000, C210S188000, C210S192000, C210S195100, C210S199000, C210S205000, C210S221200, C210S202000, C261S122100, C366S338000
Reexamination Certificate
active
06332980
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to systems for removing contaminants from liquids and, more specifically to a system for removing volatile gases, pesticides and particles such as algae, other suspended organic solids, dissolved oils and other particles including large and heavy particles and light, fine or buoyant particles from water.
BACKGROUND OF THE INVENTION
Water supplies for domestic drinking water, process water for chemical plants or other liquids are often contaminated with a variety of contaminants, such as toxic chemicals, algae, dissolved oil and various organic and inorganic particles of various sizes. These contaminants must be removed in a reliable, cost effective manner.
Many older water treatment plants use gravitational separation methods, typically in sedimentation systems or dual-media sand filtration systems that may not be acceptable under the newer water quality standards. In some cases, these systems can meet the standards through the use of properly mixed polymer chemical filter aids. The required expensive and complex polymer chemical mixing equipment requires constant attention, since the amount of the chemicals being added to raw water must be frequently readjusted to match the continually changing chemistry of the water being filtered. Slow sand filters require a considerable investment, but generally can be operate for longer periods without cleaning. Unfortunately, even with pre-treatment, both dual-media and slow sand filters fail to meet water quality standards for hours or several days after each backwash cleaning.
Ordinary chemical flocculation and sedimentation processes do not prevent toxic chemicals, pesticides and algae from passing through the ordinary filter bed. If algae spores are present when chlorine is added, toxic disinfection byproducts are formed, which is highly undesirable and a violation of the USEPA Safe Drinking Water Act. The inability of older municipal filtrations systems to remove algae is apparent in the lack of clarity found when a swimming pool is filled with “clean” tap water. Most pool contractors have to shock tap water with large doses of chlorine chemical pool oxidizer to achieve the desired clear pool water appearance.
Particulate material has also been removed from liquids by floatation, another gravitational method, in which bubbles of a gas, such as air or oxygen, are introduced into the lower levels of the liquid and float to the top, carrying fine particles with them. Various chemical additives, such as flocculation aids, typically alum polymers, are required with these systems. Flotation is a gravitational method because the rise of bubbles is due to the gravitational acceleration acting on the mass of the liquid in accordance with the basic force equals mass time acceleration relationship. A force balance relative to a pocket of gas phase within liquid (a bubble), where the mass of the bubble is its volume times its density, shows that the bubble must rise to find equilibrium, because the density of a gas is generally less than that of a liquid. Large flotation tanks are required to allow adequate time for air bubbles to reach the surface.
Failure to remove algae prior to filtration also leads to clogged filters, increases filter operation costs and wastes water required for frequent filter cleaning cycles. The use of flocculation promoting chemicals increases the volume of sludge to be dewatered and removed.
Thus, there is a continuing need for a separation system that will rapidly and efficiently remove particles and volatile gases from liquids while treating a liquid, will efficiently remove algae and volatile gases such as MTBE during pretreatment prior to filtration and will reduce overall treatment costs and conserves water through less frequent filter cleaning and a smaller sludge volume.
SUMMARY OF THE INVENTION
The above noted problems, and others, are overcome in accordance with this invention by a particle separation system that includes a pretreatment section for economically removing algae and other contaminates prior to filtration. The pretreatment includes injecting millions of extremely small air bubbles per liter into the incoming raw water. This dissolved air flotation technology increases a plants daily capacity and reduces the potential formation of toxic chlorine-chemical and post-treatment byproducts.
Initially, recirculated plant output water under high pressure and air under high pressure are mixed in a an air contactor element, generally consisting of one tank or two or more tanks in series. Preferably, the tank contains a suitable media that provide a high surface areas that increases adsorption of air into the water. All pressures referred to hereinafter are gauge pressures.
The air saturated recirculated water enters a particle mixing system where it is mixed with raw influent water. The mixed water passes along a tubular spiral to cause intimate mixing. Preferably, a pattern of dimples is provided on at least part of the inner wall of the spiral tube, to increase flow turbulence and assure optimum mixing.
The mixed water then passes to an air bubble separator unit where a toroidal flow is induced as the water moves upwardly in the unit, producing a vortex that cause air to move to the center and form an elongated axial air column with the water rotating between the vessel wall and the air column. Heavy solid particles drop to the bottom of the unit. Water largely cleaned of algae and other light particles exits near the top of the unit, with light float particles being removed adjacent to the top of the unit. Air and volatile gases exit at the very top of the unit.
The cleaned water from this air bubble separation unit may be used for many purposes. However, in some cases further removal of the small amount of remaining contaminates is desirable. In that case cleaned water from the air bubble separator then passes to a second air contactor element at a lower, but above atmospheric, pressure. Oxygen, preferably containing a suitable quantity of ozone, is then absorbed or forced into the air contactor tank under pressure higher than the water pressure. The water now containing a suitable quantity of dissolved oxygen/ozone passes to a second particle mixing system similar to the first particle mixing system as described above. As the process water enters the second particle mixing system, hydroxyl radicals(dissolved ozone) are mixed with the remaining suspended particles and non-volatile dissolved organic matter.
Water from the second particle mixing system then passes to a second air bubble separator, similar to the first one as described above. Bubbles with microscopic suspended particles coalesce along the unit centerline due to the vortex effect and are extracted at the top of the unit. The process water, now further cleaned of algae and other organic particles, may proceed to any desired conventional filtration system, where any remaining heavy solid particles are removed. Since the pretreatment system removes over 85% of the suspended solids in the original untreated water, filter cycles will be much longer than before, with much lower operating and filter maintenance costs.
REFERENCES:
patent: 2793185 (1957-05-01), Albrektsson et al.
patent: 3772190 (1973-11-01), Eisenmann
patent: 3966598 (1976-06-01), Ettelt
patent: 4029578 (1977-06-01), Turk
patent: 4094783 (1978-06-01), Jackson
patent: 4156648 (1979-05-01), Kuepper
patent: 4165360 (1979-08-01), Casper et al.
patent: 4211651 (1980-07-01), Thomas
patent: 4627922 (1986-12-01), Viator et al.
patent: 4897359 (1990-01-01), Oakley et al.
patent: 5437784 (1995-08-01), Meinecke et al.
patent: 5736059 (1998-04-01), Mackelvie
patent: 6106711 (2000-08-01), Morse et al.
Hruskoci Peter A.
Morkunas Frank G.
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