Liquid purification or separation – Processes – Utilizing electrical or wave energy directly applied to...
Reexamination Certificate
2001-11-30
2004-07-13
Hoey, Betsey Morrison (Department: 1724)
Liquid purification or separation
Processes
Utilizing electrical or wave energy directly applied to...
C210S791000, C210S321690, C210S333010, C422S024000, C422S186300
Reexamination Certificate
active
06761826
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to use of high-intensity, typically pulsed, broadband or deep ultraviolet wavelength electromagnetic radiation for providing non-chemical flux enhancement and virus kill in microfiltration hollow-fiber membrane water treatment.
BACKGROUND OF THE INVENTION
Current water purification technologies, including distillation, reverse osmosis, and carbon filtration usually produce suitable water quality, but their high capital, operating and maintenance costs have limited their use to only those situations where water shortages are most extreme or where cost is less important. Water contaminated with pesticide or gasoline contaminants are especially difficult and costly to remove with conventional technologies.
Both advantages and disadvantages of the prior art technologies are summarized below:
Vapor compression (VC), including distillation technology systems are used on drinking water for both pathogen and chemical contamination remediation, remove total dissolved solids (TDS) and are excellent for desalinization. Drawbacks include a relatively high price, a generally large size, non portability and fairly complex construction and operation.
Reverse Osmosis (RO) removes TDS with a relatively simple mechanism. Removal of non-volatile organics, pathogen is easy. However, the systems are subject to contaminating product water if feed water pressure and turbidity are out of operating parameters, involve a high price rate, does not remove dissolved organic compounds and are complex and sophisticated.
Air stripping (AS) is generally the least expensive form of water remediation and is fairly good at removing volatile organics. However, these systems are also large, very noisy and unsightly, do not remove non-volatile organics, do not remove pesticides or pathogens, depend on ancillary technology, like the use of granulated activated carbon (below), resulting in more O&M cost as well as air pollution (the volatile organics are transferred into the atmosphere).
Granulated activated carbon (GAC) are effective at removing volatile and non-volatile organics like pesticides, is likewise effective at removal of pathogens, and can be reactivated in most cases. However, GAC also requires resupply of heavy, bulky material, typically has a large adsorption ratio, such as about 1000 pounds GAC to 1 pound contaminant, and itself becomes a source of contamination of product water if allowed to saturate. Furthermore, saturated GAC is a hazardous waste product and must be handled as such, especially when considering issued including transportation, disposal or reactivation cost.
Low and medium pressure mercury vapor ultraviolet (UV) radiation is also effective at destroying or inactivating pathogens, but only very slightly effective on organic or synthetic organic compounds at practical flow rates. Sometimes UV is used as part of a polishing loop on larger treatment systems. However, as a practical matter, use of UV radiation in the past has been impossible. These systems are not practical for treating chemically contaminated water, the available low pressure lamps are typically not self cleaning, would require hundreds of lamps to equal the dosage of a lamp of the present invention, and provide a larger footprint for any type of alternative remediation application.
Mercury lamps emit wavelengths from excited mercury, though not in a smooth arc continuum like the radiator of the present invention, but rather in discrete “atomic lines” that have very narrow bandwidths. Most of the energy is contained in the 254-nm line with lesser amounts in the 185-nm and 365-nm lines. Mercury lamps also produce especially in the case of medium pressure mercury lamps a low emissivity continuum. That is, a very small level of “background” UV that spans from 185 nm to 400 nm.
Ozone saturation is effective at reducing counts and effects of pathogens and leaves no dangerous chemicals in the water. However, providing a system which injects ozone into a water supply or stream leaves physically a rather large footprint, i.e., requires a larger operation to achieve equivalent effect, is complex to build and operate, involves high operation and maintenance costs, involves the production of ozone a dangerous and reactive gas, and is not practical or feasible for treatment of chemical contaminants alone.
Finally, the use of chlorine (Cl) is known to act aggressively against pathogens but has few remedial effects on chemical contaminated water except for elimination of cyanides. Current competing technologies for chemical contamination of groundwater include reverse osmosis (RO), air stripping, and Activated Carbon filtration. Although the popularity of RO has gained substantially in market share in recent years, different technology solutions continue to dominate the various niches. RO membrane production is dominated by a few companies (DuPont, Sow-Filmtec, Fluid Systems, Toyoba, etc.), but there are thousands of companies that act as integrators of RO systems. Air stripping is older technology and lower cost, but is noisy, unsightly, pollutes the air, and has limited effectiveness in removing MTBE to current and foreseeable EPA standard levels. Activated Carbon filtration involves large quantities of carbon supplied by companies like Calgon, Inc.
Pathogen removal from drinking water is sometimes accomplished with the addition of chlorine, distillation techniques, or the use of banks of low or medium pressure ultraviolet lamps. Distillation suppliers include large European, Japanese, and Korean manufacturers and contractors, and this technology excels at the removal of TDS (total dissolved solids). Current ultraviolet lamp suppliers include Aquafine, Fisher & Porter, and Puress, Inc. There exists a need for technology which is more energy efficient and can simultaneously remove, inactivate or destroy pathogenic and chemical contamination. Such equipment could also be used for post-treatment at desalination facilities to remove chemical contaminants.
Traditional UV technology relies on low and medium pressure UV lamps, similar to the fluorescent lamps used in office buildings. Medium pressure lamps are operated at higher power levels than the low pressure lamps and, consequently, are slightly more efficient than the standard low-pressure variety. The typical low-pressure lamps operate in a range from about 30 to about 100 watts while the medium pressures radiators average about 3000 watts. Typically, both lamp types are known as atomic line radiators. They produce light energy in very narrow wavelength bands at 10-20% electrical efficiency. Both types operate with AC-type current and are controlled by electrical ballast.
Though the lamp life is generally very long, maintenance cost are generally very high, especially in the case of low-pressure lamps. Cleaning is a significant problem. Lamps become fouled in the water environment from precipitated dissolved solids and “scum”. This fouling action gradually reduces the UV output rendering the individual lamp wholly or partly useless. Therefore, these lamps must be removed on periodic bases and manually cleaned. Furthermore, low- and medium-pressure lamps do not produce the radiative power levels to effectively dissociate the chemical bonds of many common types of contaminants. They find their principle usage in the wastewater reclamation industry for biological degradation. At a single installation, these lamps are used hundreds and sometimes thousands at a time, thus amplifying the operating and maintenance (O&M) costs.
Improvements to this type of technology include: enhanced chemical doping of the glass used in the envelope of the lamp to increase its UV conversion efficiency, improved cold cathodes to prolong lamp life and improved reaction chambers or effluent channels to maximize dosage and throughput and to minimize head loss.
U.S. Pat. No. 5,891,399 issued to Owesen teaches a device, used in an air purifying system. The device includes an Ultraviolet (UV) radiation source, a pre-filter, and a post-filter.
U.S. Pat. No.
Hoey Betsey Morrison
New Star Lasers, Inc.
Shahani, Esq. Ray K.
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