Ultraviolet treatment for aqueous liquids

Details Ultraviolet treatment for aqueous liquids Ultraviolet treatment for aqueous liquids

2000-11-13

2004-08-10

Barry, Chester T (Department: 1724)

Liquid purification or separation

Processes

Utilizing electrical or wave energy directly applied to...

C210S150000, C210S205000

Reexamination Certificate

active

06773608

ABSTRACT:

FIELD OF INVENTION
The present invention is directed to an ultraviolet (UV) treatment for aqueous liquids such as water or biological fluids.
BACKGROUND OF INVENTION
There are many approaches to treating aqueous liquids. The approach taken depends upon a number of factors including the nature of the liquid, the object of the treatment, and the site of treatment, among other factors.
In the case of water to be used for human consumption, the object of treatment might be: to remove certain toxins, such as halogenated hydrocarbons or lead; to reduce the pathogenic content, e.g., render bacteria or viruses less virulent; or to remove components that detract from the taste or smell, but which are otherwise relatively harmless. The site of treatment might be a communal source such as a municipal water treatment plant, or it could be at the point of use, such as in the home.
The present invention involves the use of UV radiation in treatment of aqueous liquids. When the liquid is drinking water, for example, an object is to reduce its pathogenic content. It has been known for quite some time that UV light has bactericidal properties (U.S. Pat. No. 1,193,143, issued Aug. 1, 1916; U.S. Pat. No. 1,200,940, issued Oct. 10, 1916; United States). It is now understood that UV radiation can act to degrade genetic material of a microorganism, i.e., RNA and DNA, to render the microorganism unable to reproduce. This renders the population of microorganisms less virulent and possibly completely harmless to humans.
The use of UV radiation in treating biological fluids is known in a variety of contexts. Exemplary objectives include inactivation of viruses (U.S. Pat. No. 5,789,150, issued Aug. 4, 1998) and inhibition of aggregation of blood platelets (U.S. Pat. No. 5,591,457, issued Jan. 7, 1997). The treatment might involve a person's own blood (international patent application published as WO/98/22164 on May 28, 1998), or the treatment might be in preparation of donated blood or a blood product for administration to another person.
The patent literature describes a large number of apparatuses and methods of UV treatment of aqueous liquids.
One early approach is described in the specification of U.S. Pat. No. 1,193,143, issued Aug. 1, 1916 to Henri et al. This document describes an apparatus in which a UV lamp is placed outside the liquid and the liquid is caused to flow through a trough. The lamp is provided with a reflector and the sides of the troughs and baffles are made of a reflecting material, in order to utilize the rays emitted from the lamp to their fullest possible extent. In all illustrated arrangements, the lamp is located over the liquid. The liquid is caused to pass and re-pass through the rays in several different ways. In two illustrated embodiments, the liquid is caused to move up and down between baffles. In a third illustrated embodiment, the trough takes the form of a zigzag tube arranged in a horizontal plane. In a fourth illustrated embodiment, the trough is of a spiral form and is arranged so that the liquid in its passage therealong is exposed at all parts to the influence of the UV light.
The specification of U.S. Pat. No. 1,200,940, issued Oct. 10, 1916, also to Henri et al., describes an apparatus in which the UV lamp is immersed in the treatment liquid in order to increase efficiency of exposure of the liquid to UV rays. The lamp is protected from contact with the lamp by a quartz window.
The specification of U.S. Pat. No. 1,367,000, issued Feb. 1, 1921 to Pole, describes another apparatus in which the UV lamp is immersed in the treatment liquid. Again, the lamp is shielded from contact with the liquid by a quartz window. In this case, the treatment liquid flows through a narrow channel defined by quartz plates, the channel being located near a UV lamp.
The specification of U.S. Pat. No. 1,473,095, issued Nov. 6, 1923, again to Henri et al., describes an apparatus in which the treatment liquid is passed through one or more compartments located adjacent a UV lamp. Each compartment has a quartz window to permit exposure of the liquid within each compartment to UV light.
The specification of U.S. Pat. No. 2,504,349, issued Apr. 18, 1950 to Prieto, describes a water purification apparatus having a tray which defines a tortuous path which is sloped for the water to travel therealong under the force of gravity. Troughs are defined by the tray to permit the water to travel in a comparatively shallow sheet from the inlet point to the point of discharge. UV lamps are mounted to overlie the troughs. The troughs are formed of a material having high reflecting and low absorption factors. The specification states that the tortuous path which the water takes and the slope of the troughs are such that sufficient time elapse between the delivery of the water to the troughs and its discharge therefrom to enable the UV light from the lamp to be completely effective in disposing of all of the bacteria therein. The angularity or slope of the troughs is such that the water will flow in a stream of substantial uniform depth with a minimum of turbulence throughout its tortuous travel over the tray. There may be a series of parallel (in plan) longitudinal troughs connected in series to each other, or there can be a single trough in the form of a gradually declining spiral. Each lamp is provided with a reflector (semi-circular or parabolic in cross-section) to increase exposure of treatment liquid to UV rays.
The specification of U.S. Pat. No. 4,102,645 describes a sterilization apparatus having a UV lamp located above the liquid being treated, there being a quartz window located between the treatment area and the lamp. An inlet conduit leading into the treatment area is provided with a venturi for introducing air into the liquid. The air is introduced so that an air pocket is maintained above the liquid in the treatment area to prevent direct contact of the liquid with the quartz window and thereby prevent the accumulation of mineral deposits thereon, which deposits would interfere with transmission of UV rays.
There are UV water purifiers which can be connected in-line to water systems. Examples of such purifiers are described in specifications of U.S. Pat. No. 4,968,437 (issued to Noll et al. on Nov. 6, 1990), Canadian Patent Application No. 2,119,543 (published on Sep. 23, 1994 in the names of Kuennen et al.), and Canadian Patent Application No. 2,132,929 (published on Mar. 27, 1996 in the name Szabo).
An example of a system for monitoring the intensity of UV radiation within the treatment chamber of a water purifier is described in the specification of U.S. Pat. No. 4,849,100, which issued to Papendrea on Jul. 18, 1989. The system is suitable for a portable, gravity system in which the UV lamp is housed in a quartz sleeve.
The specification of U.S. Pat. No. 5,039,402, which issued to Himelstein on Aug. 13, 1991, describes a water purifier incorporated into a household coffee maker.
The specification of U.S. Pat. No. 5,628,895, which issued to Zucholl on May 13, 1997, describes a UV water treatment system in which a UV lamp is located above a container of water.
The use of a laser beam has been suggested by Goudy, Jr., in the specification of U.S. Pat. No. 4,661,264, for disinfection of liquids, typically as part of a larger wastewater treatment facility. Water is passed through a laser beam light produced at a suitable UV wavelength, in one embodiment, the laser source is positioned out of contact with the fluid but with its beam filling the cross-section of the stream of fluid to treat the liquid. A sensor (photocell) is trained at the reflected laser beam and is responsive to the amount of light which is reflected back up toward the surface. The less the light, the greater the turbidity. The photoelectric cell is used to control the oscillator or potentiometer of the laser source and thereby to control the pulse rate of the laser in response to changes in turbidity. Other means for determining turbidity are described. Flow meters are provided which adjust the rate of pulsing of th

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