Liquid purification or separation – Recirculation – From bottom of separator
Reexamination Certificate
1999-04-07
2001-03-06
Upton, Christopher (Department: 1724)
Liquid purification or separation
Recirculation
From bottom of separator
C210S208000, C210S266000, C210S305000, C210S520000, C210S521000, C210S523000
Reexamination Certificate
active
06197190
ABSTRACT:
BACKGROUND OF THE INVENTION
This disclosure relates to a system and method for removing contaminants, both colloidal and suspended particles, from raw water at a high rate of treatment. The disclosed method and system use previously known water treatment procedures that have been shown to be effective, efficient and reliable; but the disclosed method and system combine the known elements of water treatment in a single-tank procedure with tapered radial-blade mixing that achieves even greater water purity with higher flow application rates.
DESCRIPTION OF THE PRIOR ART
As stated, the system and process in this disclosure borrow heavily from proven water treatment techniques developed over the past 100 years. For instance, the idea for initially treating raw water with a chemical coagulant such as alum, ferric chloride and the like to destabilize suspended particles in raw water by neutralizing the electrochemical charges typically found on colloidal particles and contaminants is well known, and the destabilization of suspended particles in raw water by using chemical coagulants continues to be employed in the disclosed system.
Similarly, the use of polyelectrolyte flocculates to facilitate the attachment and growth of neutralized particles is also known in the art and unabashedly incorporated as part of the disclosed system.
Also the use of a granular medium to increase the size and weight of agglomerated and flocculated particles is previously known from French Patent 1,411,729.
U.S. Pat. No. 4,927.543 describes a commercial process called “Actiflo” which uses lamella separator plates or tubes in a process that uses sand to assist in flocculation and settling. The sand is injected into the “upfront” rapid mixing tank—usually two rapid-mix tanks are used—followed by a separate flocculating tank. Then, the flocculated flow is passed on to a separate settling tank having lamella plates or tubes. The Actiflo™ process, by using two rapid-mix tanks, a flocculating tank and a separate settling tank, is a refinement of prior art sand-assisted flocculation and settling.
Furthermore, the prior art typically calls for precise chemical additions in the first tank and high-energy mixing in the range of 1,000 to 1,500 Gs to prepare the coagulant to flow to a second rapid-mix tank. In the second rapid-mix tank, sand and a flocculating chemical are added and, again, high energy mixing in the range of 1,000 to 1,500 Gs is applied. The mixture then flows to a separate flocculation or maturation tank with lower energy mixing in the range of 400 to 900 Gs. After the maturation tank, the sand/floc. mixture goes to the settling tank while lamella plates or tubes assist in clarification. More recently, U.S. Pat. No. 5,730,864 has contributed to the prior art by disclosing precise chemical additions in two separate mixing tanks and high-energy mixing in the range of 900 to 1,400 Gs for each tank. Fine sand is added to the second rapid-mix tank along with polymers and high-energy mixing. Then, the mixed flow moves to a separate maturation or flocculating tank and finally to a separate settling tank. In the '864 patent, no lamella plates or tube is used. The inventive aspect of the '864 document also involves the creation of a vortex or cyclone to assist in solids removal efficiency in the settling tank. No other device or mechanism is utilized in the separation of solids from the water in or beyond the settling zone, and specific settling rates greater than 15 m/h are alleged.
U.S. Pat. No. 3,343,680 describes an upflow filtration process using a buoyant medium. This technique was designed to be a final step in a water filtration process, but inefficiencies in cleaning the filter medium have become apparent resulting in commercial dissatisfaction.
U.S. Pat. No. 4,115,266 also discloses the use of a buoyant medium in a treatment process. Typically, a series of tanks is used and air is bubbled under the medium for cleaning the medium to remove entrapped contaminants.
U.S. Pat. No. 4,547,286 describes a commercial process known as “Trident™” using a buoyant medium filter in its process. This disclosure specifically describes the use of a buoyant medium as an upflow filter followed by a non-buoyant medium downflow filter. In addition to using two media, the Trident system utilizes 2 or 3 separate tanks and alleges that flocculation and adsorption occur within the buoyant media filter, thereby eliminating a settling zone.
SUMMARY OF THE INVENTION
Notwithstanding the attributes of the components and steps of the prior art, the disclosed system, using known elements in combination with a mixer having a plurality of tapered radial blades generating high-energy mixing followed by tapered flocculation, produces higher treatment rates with no deterioration of effluent quality. Furthermore, the disclosed system and process provide for solids removal with a decrease in chemical costs, a reduction in energy use and a reduction in the civil “footprint”.
Specifically, what is disclosed herein is an improved water treatment system for separating contaminants from raw water. The system utilizes a continuous-flow, single-tank process that begins by introducing into said tank, raw water that has been injected with a coagulating agent for neutralizing charged particles and a flocculating agent for agglomerating the neutralized particles; and includes;
mixing, in the mixing area of said tank, the neutralized and agglomerated particles with a granular medium to increase the size and weight of the particles;
directing the particles and water from the mixing area of said tank to a baffled quiescent zone for settling;
further directing said water, free of settlement, from said quiescent zone through a buoyant medium to entrap unsettled particles; and
wherein the improvement is characterized by conducting tapered flocculation in the mixing area of said tank with a turbine mixer having a plurality of radial blades of varying area, said blades tapered in decreasing area as the distance from the influent increases.
REFERENCES:
patent: 2352772 (1944-07-01), Varby
patent: 3300047 (1967-01-01), Hirsch
patent: 3615025 (1971-10-01), Rice et al.
patent: 4293416 (1981-10-01), Keotehlian
patent: 4303517 (1981-12-01), Love et al.
patent: 550842 (1932-04-01), None
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