Patent Application
20050199483
1. Field of the Invention
The invention is related to the field of water treatment, and in particular, to on-line treatment of water.
2. Statement of the Problem
Most modern water systems in the United States and around the world rely upon centralized treatment and then final distribution of the finished water through an elaborate network of piping. This network of pipes leading from the treatment plant to the end user is known as the distribution system. Once the water has entered the distribution network, most systems rely upon the integrity of the pipes and small chlorine residual to maintain water quality until delivery.
The integrity of the distributions system is not absolute and can be breeched either intentionally or accidentally by pipe degradation, breaks in the line, or back flow events. Back flow events occur when a substance is accidentally or intentionally injected into the system across the pressure gradient in the pipes from a source of pressure adequate to overcome that in the pipes. This can occur though inadvertent cross connections and siphoning or through a deliberate attempt to contaminate the distribution system.
The drinking water distribution system is one of the nation's key infrastructure assets that have been deemed vulnerable to deliberate terrorist attacks. While the threat to reservoir systems and water sources is deemed to be minimal, the vulnerability of the drinking water distribution systems to accidental or deliberate contamination due to a backflow event is now a well-recognized possibility. The myriad possible points of incursion into a distribution system, and the ease of mounting a backflow event, combined with the fact that little or no quality monitoring or treatment occurs after water has left the treatment plant, makes the danger of such an attack acute.
A system could be compromised through an assault anywhere in the distribution system by introducing a backflow event using low cost pumps that are readily available from many home improvement stores or over the Internet. The injection point could be the basement of a private home or rental property anywhere in the system. Key infrastructure and icon locations such as hospitals, large hotels, sporting venues, police stations, firehouses, military bases and government buildings could be targeted.
Much Federal and private research money has been spent on detecting such an event if it were to occur. Little or no thought however has been placed on what actions should take place if such an event is detected. There has not here to fore been devised a reliable method for responding to and treating such an event if it were detected. What is needed is a rapid response system deployable in the distribution system that is capable of treating the wide variety of contaminants that may be encountered on a real time basis.
Therefore there is a need for a system and method for providing on-demand on-line treatment of water.
A system and method for the on-demand on-line treatment of water is disclosed. The system uses ultra high energy UV light coupled with the introduction of a strong oxidant to induce photo-catalytic degradation of chemical compounds and biocidal activity. When an agent or substance is detected in the water the treatment system would be activated.
In one example embodiment of the invention, the ultra high levels of UV energy would be generated using pulsed UV light. Typically pulsed UV uses xenon flash lamps to deliver ultra high energy pulses of UV light that contain orders of magnitude more energy than standard UV technologies. (Peak UV power output Pulsed=6,000,000 Watts, Mid-pressure UV Lamp 494 Watts, Low Pressure UV Lamp 27 Watts) (Average UV power output Pulsed=2400 Watts, Mid-pressure UV Lamp 494 Watts, Low Pressure UV Lamp 27 Watts). Studies have shown that pulsed UV is capable of delivering UV dosages that are capable of destroying a wide variety of biological contaminants including very hard to destroy organisms such as Anthrax spores. In addition to the power provided by pulsed UV technology, the size of pulsed UV units are orders of magnitude smaller than conventional UV systems designed to treat an equal quantity of water. Also the ability of pulsed UV to be effective in an instant-on mode with no warm up time, as opposed to conventional UV which can take up to an hour to fully power up, may be preferable in an on-demand system. Another advantage of pulsed UV is that pulsed UV typically contains a broader spectrum of energy than continues UV sources. The broader spectrum of energy causes different chemical bonds to break during exposure. One example of a pulsed UV source is the LightStream Technologies, inc. LSi product. Some UV sources may be able to very the wavelength of the peak UV energy to match the bond energy for the substance detected in the water.
Pulsed UV in and of itself may not be completely effective against all compounds. Research has shown that the combination of pulsed UV with a sensitizer can increase its biocidal efficiency. Most of these sensitizers tend to be strong oxidants such as hydrogen peroxide. Oxidants are also known to degrade chemicals. The combination of a strong oxidant with pulsed UV reduces the time needed to destroy contaminants. See table below.
Testing revealed the following destruction times:
There are many candidates for the strong oxidant required to enhance the degradation efficiency of pulsed UV.
To be a useful sensitizer/oxidant in an on-line deployed distributed treatment system a chemical needs to have a high oxidation potential, be safe for addition to water used for human consumption, be safe to store for long periods without presenting a danger or losing its effectiveness, be able to be instantly deployed and be relatively inexpensive.
Fluorine is not safe for human consumption unless converted to fluoride which has no oxidation power, Hydrogen Peroxide, Chlorine Dioxide and Chlorine may be difficult to store safely, Potassium Permanganate rapidly degrades, may be difficult to store safely and imparts an unpleasant purple color to water, and Ozone does not as yet exist in an instant on form. In a preferred embodiment the sensitizer/oxidant Potassium peroxymonopersulfate (Oxone®) will be used.
The active ingredient of the Dupont product Oxone® is potassium peroxymonopersulfate, KHSO5, commonly known as potassium monopersulfate, which is present as a triple salt with the formula 2KHSO5.KHSO4.K2SO4 (potassium hydrogen peroxymonosulfate sulfate). The oxidation potential of Oxone® is derived from its peracid chemistry; it is the first neutralization salt of peroxymonosulfuric acid H2SO5 (also known as Caro's acid).
The standard electrode potential (E0) of Oxone® is shown in the following reaction:
HSO4−+H2O→HSO5−+2H++2e−−1.44 v
This potential is high enough for many room temperature oxidations to occur. Oxone® is a relatively stable peroxygen, and loses less than 1 percent of its activity per month under storage. Oxone® is also readily soluble and can be rapidly dissolved at >250 g/L when needed to form a concentrated solution that can be metered into a system with standard water treatment equipment to the desired level. Even after dissolution the compound is fairly stable and can be stored for several weeks.
Oxone® is not currently approve for addition to drinking water supplies but has a long history in the pool and spa industry as a secondary oxidant for shocking pools where its non-toxicity and safety as opposed to chlorine are well documented. Oxone® has a low order of toxicity when taken internally, based on animal studies. The LD-50 for rats is 2250 mg/Kg while the corresponding LD-50 for Sodium Hypochlorite is 8.9 mg/kg. Another advantage for using Oxone® as the oxidant is that the amount of oxidant needed to treat a large volume of water fits in a relatively small space. For example, 24 cubic feet (the size of a small desk 2×2×6) of Oxone® would treat approximately 4.4 million gallons of water at 50 mg/per L. The amount of chlorine needed to treat the same amount of water would fill several rooms.
One type of sensor system that may be used is disclosed in co-pending patent application 60/438,358 filed on Jan. 7, 2003 entitled “Classification of Deviations in a Process” with Karl L. King as the first named inventor, which is hereby incorporated by reference. Using a sensor as disclosed in the King et. al. patent application, substances may not only be detected, but also identified.
Some sensors can detect the concentration of the substance in the water, for example inductively coupled plasma-mass spectrometry (ICPMS), GCMS, MENs, Lab on a chip, and ion mobility spectroscopy. The treatment levels may be changed based on the concentration of the detected substances. For example, when the concentration of the substance is high the treatment level would be increased. The treatment may be increased by increasing the amount of oxidant added per unit volume of water, or by increasing the amount of UV energy, or by some combination of the two. When using pulsed UV light, the energy level may be changed by changing the pulse duration, the intensity of the pulse, the number of pulses per second, or a combination of pulse length, pulse rate and intensity level.
When the substance is unknown a default level of oxidant is added to the flow of water (702) and then the water is exposed to a default level of ultra high UV energy (704). Once the water and oxidant have been exposed to the ultra high UV energy, the water is monitored for substances (716). The process continues in step 718 as describe above. In the preferred embodiment, the ultra high energy UV light is generated using a pulsed UV system and the oxidant used is Oxone®. With this combination the system is small in size and can be turned on quickly, even after long periods of inactivity.
In another example embodiment of the invention (not shown), the treatment system only has one sensor system placed in a downstream position. By placing the sensor in the downstream location, the sensor may be used as a trigger to start the system when a substance is detected, and also used as a feedback control to ensure that all the substances have been destroyed. This may save cost compared to the two sensor design. Unfortunately some substances must have already passed through the system before detection can occur. To prevent the contaminated water from reaching the protected facility, the water flow may be diverted until the treatment system has been activated and all of the substances are being destroyed in the water flow.
The flow of water through the systems used in the examples above have been shown as simple straight line configurations for clarity. In operation, the flow of water through the systems may be more complex. For example, to expose the water to the proper level of UV energy, there may be multiple UV sources, or the water may make multiple passes through the UV source. There may be flow control devices configured to control the flow of water through the UV source to allow the water to be exposed to the UV energy for a controlled duration. The water may not flow through all of the system until a substance has been detected. For example the water may not be flowing through the UV source until a triggering event occurred.
This application claims the benefit of U.S. provisional application No. 60/553,640 filed on Mar. 15, 2004 entitled “A System and Method for the On-Demand On-Line Treatment of Water,” which hereby is incorporated by reference into this application.
| Number | Date | Country | |
|---|---|---|---|
| 60553640 | Mar 2004 | US |
