Liquid purification or separation – Processes – Utilizing electrical or wave energy directly applied to...
Reexamination Certificate
2000-12-22
2002-02-26
Hoey, Betsey Morrison (Department: 1724)
Liquid purification or separation
Processes
Utilizing electrical or wave energy directly applied to...
C210S764000, C210S095000, C204S273000, C204S280000, C204S286100, C204S287000, C205S742000
Reexamination Certificate
active
06350385
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to methods and devices used with water systems. More particularly, it relates to a method and apparatus for exposing water which flows through a water system to an ion generator whereby ions which are generated are fed into the water flow to prevent fouling of the water system by algae, nuisance invertebrates, microorganisms, and inorganic salts.
BACKGROUND OF THE INVENTION
It has long been known that algae, nuisance invertebrates, microorganisms, and inorganic salts may foul water systems and lead to very significant water system inefficiencies. These inefficiencies result in increased energy consumption and increased maintenance demands which, in turn, increase overall operational and maintenance costs by several orders of magnitude. Ion generators have been employed in previous attempts to control algae, nuisance invertebrates, and microorganisms. Such ion generators are based on well-known principles of electrochemical reactions, one of which is referred to as electrolysis. Electrolysis is an electrochemical process by which electrical energy is used to promote chemical reactions that occur on the surface of functionally cooperating electrodes. One electrode, called the anode, involves the oxidation process where chemical species lose electrons. A second electrode, called the cathode, involves the reduction process where electrons are gained. In water, for example, oxygen is generated at the anode and hydrogen is generated at the cathode. The generation of hydrogen and oxygen in fresh water by the process of electrolysis will be weak due to the low electrical conductivity of the water. The oxygen generated aids in the prevention of the deposit of inorganic salts on the electrodes. The function of an ion generator is also to produce metal ions, typically copper ions or silver ions. Metal ion production is accomplished by use of an electrically charged metal anode which comprises atoms of the metal ions which are to be generated. It is the purpose of the ion generator to feed the metal ions out of the generator before they can be deposited on a cathode. Such depositing completely defeats the purpose of the ion generator as it is intended to be used in the application described here. The metal ions and oxygen, both of which are produced by the ion generator in the present application, are feed into the water stream of the water system to prevent fouling of the system by algae, nuisance invertebrates, microorganisms, and inorganic salts.
Copper, in its dissolved form, is one anthropogenic heavy metal that, although essential to biological functions in trace amounts, can be toxic at higher concentrations. The toxicity of copper to aquatic organisms is well established although the exact mechanism is not well defined. Copper toxicity is related to the form and, in general, copper must be in an ionic form in order for it to be toxic to invertebrates, microorganisms and algae. The eradication of microorganisms with copper ions is attributed to positively charged ions which are both surface active and microbiocidal. These ions attach themselves to the negatively charged bacterial cell wall of the microorganism and destroy cell wall permeability. This action, coupled with protein denaturation, induces cell lysis and eventual death. The in-water residence time for the biologically toxic portion of ionized copper may well be on the order of hours. One advantage to the use of copper ionization is that eradication efficacy is wholly unaffected by water temperature. Chlorine, a commonly used antifouling chemical, is somewhat temperature dependent. Furthermore, the copper ions actually kill the microorganisms, and other microorganism promoting bacteria and protozoa, rather than merely suppress them, as in the case of chlorine. This minimizes the possibility of later recolonization. Other advantages of copper ionization compared to other eradication techniques include relatively low cost, straight forward installation, easy maintenance, and the presence of residual disinfectant throughout the system.
A copper ion generator is, by way of specific example, an effective method for controlling legionella which is likely to be present in most water systems. Legionella is predominantly present in water cooling systems in microbial biofilms which become attached to surfaces submerged in the aquatic environment. These biofilms are typically found on the surfaces of pipes and stagnant areas of the water cooling system. Many components of most any man-made water system can be considered to be an amplifier for the organism (i.e., the organism can find a niche where it can grow to higher levels, or be amplified) or a disseminator of the organism. Examples of man-made amplifiers include cooling towers and evaporative condensers, humidifiers, potable water heaters and holding tanks, and conduits containing stagnant water. Showerheads, faucet aerators, and whirlpool baths may serve as amplifiers as well as disseminators. Human infection from exposure to legionella, or legionosis, can result in a pneumonia illness that is commonly referred to as Legionnaire's disease, namesake of the famous 1976 outbreak in Philadelphia. Since the Philadelphia outbreak, about 1,400 cases are officially reported to the Center for Disease Control annually.
Other bacteria and protozoa can also colonize water cooling system surfaces and some have been shown to promote legionella replication. Amoebae and other ciliated protozoa are natural hosts for legionella. Legionella multiply intracellularly within amoebae trophozoites.
Logionella pneumophila
is known to infect five different genera of amoebae, most notably
Hartmanella vermiformis
and Acanthamoeba. Legionella can also multiply within the ciliated protozoa, Tetrahymena. Bacterial species that appear to provide legionella with growth promoting factors include Pseudomonas, Acinetobactor, Flavobacterium, and Alcaligenes. Copper ions are an effective method of control for each of these bacteria and protozoa.
The controlled release of copper ions has also been known to serve as an effective attachment and growth control for such marine organisms as algae, mussels, oysters and barnacles. Copper ions can eliminate and control algae, for example, by inhibiting photosynthesis which leads to its demise. And copper ions have been shown to be more lethal to the zebra mussel than other metal ions. For effective zebra mussel control in freshwater, for example, copper ion concentrations of eight parts per billion are estimated to be required, which is a level well below that recommended by the Environmental Protection Agency for freshwater aquatic protection.
The design of ion generators for salt water can generally be considered trivial. Due the high electrical conductivity of salt water, factors such as electrode spacing are not important. In fact, electrodes used in salt water application can be spaced many tens of centimeters apart without any consequential effect on system operation. Problems such as “bridging” of inorganic salts between the anode and the cathode, which leads to electrical shorting and conductivity stratification, are not a factor. The design and operation of copper ion generators in fresh water systems is consequentially different than the design employed in salt water systems. Simply put, the design and operational differences of salt water and fresh water copper ion generation systems are fundamentally related to the large differences, of several orders of magnitude, in electrical conductivity. Because of those differences, the present art employed in the design and operation of commercial copper ion generators for fresh water cooling systems has significant operational problems. In the experience of these inventors, users of present copper ion generators in industrial cooling water systems have reported problems such as bridging which leads to electrical shorting, electrical conductivity stratification which results in uneven electrode erosion, and plating of copper on the cathode.
Bridging, as pr
Holt William
Kraft John V.
Heino Joseph S.
Hoey Betsey Morrison
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