Method for purification and disinfection of water

Details Method for purification and disinfection of water Method for purification and disinfection of water

2002-11-05

2004-10-12

Lawrence, Frank M. (Department: 1724)

Liquid purification or separation

Processes

Making an insoluble substance or accreting suspended...

C210S748080, C210S806000, C210S760000, C204S176000, C205S756000

Reexamination Certificate

active

06802981

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a technique for the purification and disinfection of water, and more particular to a system and method for the purification and disinfection of water by a treatment including electrical discharge applied across a water stream.
BACKGROUND OF THE INVENTION
A significant amount of research and development has been undertaken in recent years towards environmental clean-up operations, and in particular to the purification and decontamination of ground water, waste water, and drinking water. A variety of techniques have been used in the prior art to destroy or remove contaminating and toxic materials such as trace organic and inorganic compounds; substances which produce color, taste and odor; pathogenic bacteria; and harmful suspended materials.
These techniques include the use of shock waves created by ultrasonic vibrations and exposing the water to ultraviolet radiation (see, for example, U.S. Pat. No. 6,071,473 to Darwin; U.S. Pat. No. 5,230,792 to Sauska and EP 959046 to Yoshinaga et al.).
Electricity has also been employed as a decontamination agent, such as by introducing positively charged ions into a water stream to cause coagulation and separation of particles, and by the passing of electric current within a fluid chamber (see, for example, U.S. Pat. No. 4,917,782 to Davies; U.S. Pat. No. 5,531,865 to Cole; U.S. Pat. No. 6,346,197 to Stephenson; and U.S. Pat. No. 6,331,321 to Robbins). In this case, the current flowing between the anode and cathode has a toxic effect on microorganisms nearby.
One of the common methods for water disinfection is the use of chlorine as a disinfectant, which is readily available and can be rather easily employed (see, for example, U.S. Pat. No. 4,051,034 to Amon; U.S. Pat. No. 5,039,423 to Kelley; U.S. Pat. No. 5,141,652 to Moore and U.S. Pat. No. 6,296,744 to Djeiranishvili). Chlorine diffuses through the cell wall of the bacterium and operates by disrupting the outer membrane of the cellular organisms, causing organic cellular internal material to spill into the water. However, this method cannot be utilized for purifying water from organic pollutants. The use of chlorine also has its drawbacks because of the formation of compounds that impart a disagreeable taste and odor of the water. In addition, Apart from the unpleasant odor and taste, chlorine also may increase corrosion of water supply pipelines. Additionally, some of chlorine compounds (e.g., trichlorethylene and trihalomethanes), which are also frequently present in the water, are potentially toxic and may pose health hazards.
The utilization of ozone for the purification and disinfection of water is a known and effective technique (see, for example, U.S. Pat. No. 4,352,740 to Grader et al.; U.S. Pat. No. 4,382,044 to Baumgartner; U.S. Pat. No. 4,767,528 to Sasaki et al.; U.S. Pat. No. 5,266,216 to Agueda; U.S. Pat. No. 5,683,576 to Olsen; U.S. Pat. No. 5,711,887 to Gastman et al.; U.S. Pat. No. 6,068,778 to Steiner at al; U.S. Pat. No. 6,146,524 to Story U.S. Pat. No. 6,419,831 to Wang; and U.S. Pat. No. 6,402,945 to Swales et al.). However, it has not yet come into widespread use, such as the general acceptance and widespread use of chlorine.
In recent years, there has been an increased interest in the use of ozone in view of its powerful oxidizing properties and almost instantaneous action, as well as the absence of the formation of a permanent residual material. In particular, ozone has the advantage over chlorine in that it kills bacteria on contact much faster than chlorine and destroys some viruses that are not effected by chlorine. In addition, ozone destroys algae, fungus, mold and yeast spores, oxidizes oils and sulfur, and precipitates metals, e.g., iron, aluminum and manganese. Furthermore, in swimming pool purification systems, the need of periodically adding chlorine to the water and the generally unpleasant effects of chlorine on the eyes and nose make an ozone purification system particularly attractive.
The utilization of hydrogen peroxide injection is also known in the art. This technique in combination with ultraviolet radiation provides for the creation of the —OH radicals necessary to combine with the organic compounds. Notwithstanding that this technique provides effective purification, it did not receive a broad application, mostly due to the strict requirement for high purity hydrogen peroxide and the effects of the inorganic contamination of the surface of ultraviolet lams.
Various techniques for water purification containing organic concomitants based on contacting the water with ozone in the presence of various mixed catalysts are described in U.S. Pat. No. 4,029,578 to Turk; U.S. Pat. No. 5,620,610 to Ishii; U.S. Pat. No. 6,149,820 to Pedersen; and U.S. Pat. No. 6,251,264 to Tanaka.
In particular, the heterogeneous catalyst utilized in U.S. Pat. No. 4,029,578 comprises water insoluble salts, for example, insoluble carbonate, sulfate, oxide, halide or sulfide of such metals as copper, cadmium, and group VIII metals, etc.
According to U.S. Pat. No. 6,149,820, the water enriched with ozone is passed through a catalyst, consisting of activated carbon as the carrier for metal oxides including iron oxide, cobalt oxide, nickel oxides, manganese oxide. Furthermore, the catalyst can contain one or more of the noble metals, e.g., platinum or palladium.
A method for water purification described in U.S. Pat. No. 6,251,264 includes the steps of dispersing photo-catalyst particles and an inorganic coagulant and oxidizing the organic matter contained in the water by activating the photo-catalyst particles by irradiating them with light.
A variety of techniques are known in the art which utilize a filtration process. For example, a filter can be made of a combination of a porous media, activated carbon and ion exchange filters. One of the disadvantages of this water purification technique is that the structure of the filter provides a breeding ground for microorganisms, thereby multiplying the danger. Such techniques, especially effective when used in combination with ultraviolet irradiation, ozonation and chlorination can effectively purify and disinfect the water (See, for example, U.S. Pat. No. 4,077,877 to Orensten et al.; U.S. Pat. No. 5,236,595 to Wang; U.S. Pat. No. 5,536,403 to Sugimoto; U.S. Pat. No. 5,728,305 to Hawkinson; U.S. Pat. No. 5,766,488 to Uban, et al.; and U.S. Pat. No. 6,358,407 to Liao, et al.). However, since activated carbon filters as well as other biological and chemical filters are extremely costly and must be changed regularly, these techniques did not receive wide popularity.
A technique is known in the art, sometimes under the name electro-hydraulics, which utilize high-energy electrical discharge into a volume of liquid for the purpose of disinfecting water, changing chemical constituents and recovering metals and other substances from liquids or slurries (see, for example, U.S. Pat. No. 3,366,564 to Allen; U.S. Pat. No. 3,402,120 to Allen et al.; and U.S. Pat. No. 4,957,606 to Juvan). According to this technique, an electro-hydraulic shock wave within the liquid, intensive light radiation and thermo-chemical reactions are initiated by arc discharge into a spark gap formed by the electrodes immersed in the liquid. One of the drawbacks of this technique is associated with the fact that in the repeated discharging of a high-energy electrical arc across the gap between electrodes, the electrodes are rather rapidly eroded and burned up. Similarly, switching components are consumed by burnup.
U.S. Pat. No. 5,464,513 to Goriachev and U.S. Pat. No. 5,630,915 to Green et al. describes a water purification technique which concurrently uses a synergistic combination of pulsed mechanical shock waves, ultraviolet radiation, and ionization of the water stream, as disinfecting and purification actions within the water to be treated. The water treatment system of this technique includes a pair of electrodes extending transversely across and through a discharge chamber. Contaminated water is introduced int

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