Liquid purification or separation – Processes – Making an insoluble substance or accreting suspended...
Reexamination Certificate
2000-11-06
2002-06-25
Hruskoci, Peter A. (Department: 1724)
Liquid purification or separation
Processes
Making an insoluble substance or accreting suspended...
C210S712000, C210S721000, C210S725000, C210S730000, C210S735000, C210S743000, C210S746000, C210S754000, C210S755000, C210S756000, C210S759000, C210S764000, C210S908000, C210S916000, C210S752000
Reexamination Certificate
active
06409926
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the maintenance of aquatic facilities, particularly to the optimization of the feed rates of a sanitizer/oxidizer and peroxygen compound to eliminate the accumulation of undesirable halogenated compounds, thereby increasing water and air quality within such facilities and most particularly to the incorporation of a coagulant effective to reduce oxidizer demand.
BACKGROUND OF THE INVENTION
The use of closed recirculating water reservoirs for use by the general public, for example, swimming pools, spas, hot tubs, decorative fountains, cooling towers and the like, has led to a variety of water quality problems. For instance, improper chemical balances in the water can lead to various types of contamination including bacterial and viral contamination.
The use of chemical sanitizers is a fairly standard water sanitation method. Addition of so-called halogen donor compounds, such as chlorine or bromine are effective sanitizers so long as they are maintained at well defined and constantly controlled concentration levels in the water. It is important that the concentration of these chemical sanitizers is not allowed to become too high which may cause irritation to the users and damage to the water system. Insufficient sanitizers result in a contaminated condition.
The difficulties in maintaining a proper balance of sanitizers may arise from numerous load factors that are difficult, if not impossible, to predict. For instance, in a pool the load factor is typically caused by varying numbers of users. In hot tubs the use of air jets and high water temperatures tend to destroy or remove the sanitizer from the water. Cooling towers are subject to environmental conditions, such as fluctuations in temperature. Indoor decorative fountains may be affected by the air quality in the building, while the fountain water can also affect the air in the building.
Various testing devices exist for determining the chemical balance of the water of pools, spas and the like, for example, colormetric chemical test kits are available that utilize liquid droplets, test strips or tablets which dissolve in the water to indicate a particular level or concentration of sanitizing agents. By removing a test sample of water, for example via a scoop or cup, a seemingly representative sample is deemed to have been taken. A staining agent is then added by means such as an eye dropper or the like. The degree of staining relates to the amount of sanitizer in the water. The amount of sanitizer present is determined by visually comparing the degree of coloring of the test sample against a test scale previously formulated. Further complicating the task of maintaining sanitary conditions in such bodies of water is the fact that studies now indicate there is little correlation between the free halogen, e.g. chlorine, residual readings which are normally used to monitor such bodies of water and the actual bacteriological quality of the reservoirs themselves. Pool and spa maintenance officials have long gone under the assumption that maintaining a free chlorine residual of two milligrams per liter or two parts per million will insure a safe water condition. Thus, the parts per million reading which is determined via the stain comparison, is actually a reflection of the sum of the free chlorine and combined chlorine compounds such as chloramine which are present in the water. These combined chlorine derivatives do not protect from bacteria and/or viral contamination. Additionally, since organic and chemical loading drastically reduce the ability of free chlorine to overcome bacteria, the available free chlorine test kits are of questionable value unless the exact levels of organic contaminants and the particular pH of the water being tested is known.
U.S. Pat. No. 4,752,740 suggests the use of monitoring the oxidation-reduction potential (ORP) as a method of measuring the sanitization levels of water. ORP defines the potential of a sanitizer such as chlorine, bromine or ozone to react with various contaminants. These compounds are known as oxidizers and have the property of “burning off” impurities in the water, for example, body wastes, algae and bacteria. The use of an ORP sensor allows the pool maintenance engineer to measure the potential generated by the active form of the sanitizer and not the inactive forms such as the combined chlorine derivatives. Additionally, ORP monitoring has an advantage in that it is an ongoing electronic process requiring no test chemicals or agents and monitoring of sanitation levels is constantly performed as opposed to being performed on some predetermined schedule basis. Since the potential for disease transmission due to organic loading is far more significant in public spas and pools, use of ORP measurement could be of great benefit in reducing the risk of contamination and disease transmission.
In accordance with standards set forth by the World Health Organization in 1972, maintenance of an ORP level of 650 millivolts is deemed to result in a water supply that is disinfected and in which viral inactivation is virtually instantaneous.
Chlorine is the most widely used oxidizer in the aquatic industry, the primary use being for sanitation of the water in pools and spas. Chlorine, being an oxidizer, is also involved in oxidation reactions with various organics, as well as inorganic and organic nitrogen based substances such as urea, uric acid, amino acids, etc. One of the drawbacks of chlorine is the production of chlorinated byproducts resulting from incomplete oxidation. These byproducts are often volatile and produce undesirable side effects such as irritation of the eyes, sinuses, skin, foul smelling air, and corrosion of air handling equipment.
The health department generally regulate the concentration of Free (HOCL & OCL) chlorine in the water. In some locations, sufficient HOCL is not available to maintain a sufficient rate of oxidation of the demand being contributed to the water. This allows for the accumulation of these undesirable substances. Substances which oxidize following substoichiometric oxidation react with the chlorine producing substoichiometric and/or stoichiometric compounds. Further oxidation with HOCL eventually leads to increased concentration of substances that follow stoichiometric oxidation, such as monochloramines. If enough HOCL is not maintained to meet the stoichiometric ratios needed to drive oxidation of the chloramines, no demand on the HOCL is experienced. However, when the chlorine donor(s) are controlled using ORP control with an optimized ORP setting of between 780-800 mV, the buffering effect chloramines place on the ORP becomes a significant factor. The buffering effect provided by the chloramines reduces the impact on ORP provided by the addition of more chlorine donor(s). The controller feeds more chlorine donor(s) to achieve the optimized ORP. This often leads to levels of Free Chlorine which exceed local maximum limits. In order to meet the maximum limits of free chlorine, the ORP is reduced so as to not exceed the established limit. This allows for the volatile chlorinated compounds to accumulate, thereby. increasing the partial pressure which promotes fouling of the air.
Numerous attempts have been made at addressing this problem. “Shocking” of the pool water requires dosing the water with stoichiometric concentrations of chlorine to oxidize the substances. One problem with this method is that there cannot be any bathers present due to the excessive concentrations of chlorine required to meet the stoichiometric levels needed when said undesirable substances have been allowed to accumulate. Another issue is this method is generally applied after the symptoms have appeared, i.e. high combined chlorine, foul odors, etc. In many cases this method fails to rid the water and air of these substances since the concentration of chlorine required is at best a rough estimate (incorporates measuring the combine chlorine in the water). Measuring the concentration of combined chlorine in the water does not ta
Hruskoci Peter A.
United States Filter Corporation
Wolf Greenfield & Sacks P.C.
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