Patent Application
20090127199
The present invention relates to a method and device for removing fluoride from drinking water.
Potable (i.e., drinking) water is a necessity to which millions of people throughout the world have limited access. There is no standard for how much water a person needs each day, but experts usually put the minimum at 100 liters for adults. Most people drink two or three liters. The rest is typically used for cooking, bathing, and sanitation. Adult Americans consume between four hundred and six hundred liters of water each day.
By 2050, there will be at least nine billion people on the planet, the great majority of them in developing countries. If potable water were spread evenly across the globe, there might be enough for everyone. But rain often falls in the least desirable places at the most disadvantageous times. For example, some cities in India get fewer than forty days of rain each year—all in less than four months. Somehow, though, the country has to sustain nearly twenty percent of the Earth's population with four percent of its water. China has less potable water than Canada—and forty times as many people. With wells draining aquifers far faster than they can be replenished by rain, the water table beneath Beijing has fallen nearly two hundred feet in the past twenty years.
More than a billion people lack access to drinking water. Simply providing access to clean water could save two million lives each year. Nearly two billion people rely on wells for their water. There were two million wells in India thirty years ago; today, there are twenty-three million. As the population grows, the freshwater available to each resident dwindles, and people have no choice but to dig deeper. Drill too deep, though, and saltwater and arsenic can begin to seep in.
Water purification processes are well known and used throughout the world. Water purification is the removal of contaminants from untreated water to produce drinking water that is pure enough for human consumption. Substances that are removed during the process include parasites (such as Giardia or Cryptosporidium), bacteria, algae, viruses, fungi, minerals (including toxic metals such as lead, copper and arsenic), and man-made chemical pollutants. Many contaminants can be dangerous. Other contaminants are removed to improve the water's smell, taste, and appearance.
It is not possible to tell whether water is safe to drink just by looking at it. Simple procedures such as boiling or the use of a household charcoal filter are commonly used as a best practice for reducing risk in drinking water, but may not be sufficient for treating water from an unknown source. Even natural spring water—considered safe for all practical purposes in the 1800s—must now be tested before determining what kind of treatment is needed. Brackish water is water that has up to 2000-5000 ppm (parts per million) total dissolved solids (TDS). “Mildly” brackish water has a TDS of about 500 to 1000 ppm.
Fluoride is one of the chemical constituents found in water sources. Fluoride is found in all water sources at some concentration level. The amount of fluoride in groundwater or surface water may be low or high, depending on a number of factors. High fluoride concentrations are expected in groundwaters in calcium poor aquifers and in areas where fluoride releasing minerals are prevalent.
Fluorosis, the adverse health effects from excessive fluoride, is a significant problem in a number of developing countries including parts of India. According to a 1999 UNICEF report, 17 of the 32 states of India were found to have naturally occurring unhealthy levels of fluoride in their water sources. This included serious problems with elevated fluoride levels found in Gujarat, Tamil Nadu, and Punjab among others. This report found that Haryana water sources tested at 48 mg/l of fluoride.
Generally, fluoride from drinking water sources is the largest contributor to fluoride intake, especially in developing countries. The dose of fluoride is dependent on the amount of fluoride in the water and the amount of water consumed by each individual. In hot and humid countries, the amount of water consumed increases, increasing the fluoride dose. Equitorial countries are thus at greater risk for problems with fluoride consumption based in higher water consumption in these countries.
Excessive levels of fluoride lead to a number of adverse health effects. These include dental fluorodosis, which is characterized in degradation of dental enamel, and skeletal fluorosis, which can be characterized by skeletal deformity, calcification of ligaments, and osteosclerosis.
Acceptable drinking water specifications (IS:10500-1191) include the following recommended and “acceptable” levels: a TDS of 500 ppm (up to 2000 ppm, if no other source is available); 0.3 ppm iron (up to 1.0 ppm); 1.0 ppm fluoride (up to 1.5 ppm); 0.05 ppm arsenic; 0.03 ppm aluminum (up to 0.2 ppm); with a pH of 6.5-8.5.
There are many potential sources of water, though none is safe for drinking without prior treatment and purification. The water emerging from some deep groundwater may have fallen as rain many decades or even hundreds of years ago. Soil and rock layers naturally filter the groundwater to a high degree of clarity before it is pumped to the treatment plant. Such water may emerge as springs (e.g., artesian springs) or may be extracted from boreholes or wells. Deep groundwater is generally of very high bacteriological quality (i.e., a low concentration of pathogenic bacteria such as Campylobacter or the pathogenic protozoa Cryptosporidium and Giardia) but may be rich in dissolved solids, especially carbonates and sulfates of calcium and magnesium. Depending on the strata through which the water has flowed, other ions may also be present including chloride, and bi-carbonate. There may be a requirement to reduce the iron or manganese content of this water to make it pleasant for drinking and cooking. Disinfection is also required. Where groundwater recharge is practiced, it is equivalent to lowland surface waters for treatment purposes.
A method and device for simply removing fluoride from drinking water would be advantageous.
Embodiments of the present invention include a water filtration device in which water flows from a water intake into an enclosed chamber holding iron oxide material. The iron oxide material, such as oxidized iron ball bearings, iron particulate matter, mesh, or other iron material, is disposed within this chamber such that water flowing through the intake will flow through the iron oxide material, allowing ionic fluoride to react and form an insoluble percipitate. The water flowing through this chamber next flows through an ultrafiltration membrane (e.g., into an ultrafiltration membrane cartridge.) The cartridge contains a plurality of ultrafiltration membrane tubes disposed within a cartridge. Water flows through walls of the ultrafiltration membrane tubes, into an interior of said ultrafiltration tubes and out an open end of said ultrafiltration membrane tubes. The open ends are secured through a barrier layer that prevents unfiltered water from mixing with filtered water. Purified water then flows from an outlet from the cartridge on a side of the barrier layer having the open ultrafiltration membrane tubes ends.
In an associated method embodiment, water is first passed through a chamber having an iron oxide material to remove ionic contaminants. The water is then purified by ultrafiltration purification as above. The size of iron oxide materials (e.g., ball bearings, particles, ion mesh, etc.) could be selected based on the flow rate of water filtered, the concentration of fluoride in the water, or other factors.
With reference to
With respect to
The ends of the membranes are secured into potting compound 16. The attachment disc 12 is secured onto the side of cartridge housing 18. The filter holding structure may be a plastic clip fused to the cartridge bell housing.
With respect to
1. The ultrafiltration membrane tubes are cut to the proper length.
2. The ends of the ultrafiltration membrane tubes are secured to the attachment disc.
3. The attachment disc is secured to the housing of the cartridge.
4. The potting material is added to the top side of the attachment disc.
5. A centrifugal force is applied to the potting material. This ensures that the potting material is distributed evenly, and that all of the ultrafiltration membrane tubes are secured at the ends.
6. The potting material is cut along lines A of
7. A top is secured onto the cartridge to provide an upper chamber into which filtered water flows. This top may be secured by threads, allowing the cartridge to be partially disassembled.
With reference to
With respect to
Referring to
Chemically, the reaction that takes place is believed to be:
Water containing fluoride ions+iron oxide=water with suspended iron fluoride (an insoluble salt)+hydroxyl ions (which would be soluble in water) Fe2O3+6F+3H2O=6N(OH)-+2FeF3
Water flowing out of housing 513 would flow into an inlet 515 into cartridge 521. As noted above, these cartridges contain a plurality of ultrafiltration membrane tubes 517 within cartridge 521. As noted above, this filtration membrane has the ability to remove submicron microns from the water. Also particles that are larger than a few microns would be removed from the water. This would include most scale particles from the oxidized iron surface. The purified water would leave the cartridge through exit passageway 519.
This process first binds ionic fluoride to oxidized iron before the water is further purified using an ultrafiltration membrane present as a network of ultrafiltration tubes. This ultrafiltration membrane filters out particles as small as a few microns, which would include most scale particles or particles of ferric fluoride. In other fluoride removal methods, the purification (e.g. clay, bone charcoal, etc.) would have to be removed and disposed of. The purification material could potentially release fluoride into a water source. In the present device and method, the iron fluoride collected from the filter would be in a much less soluble form and could be burned for disposal.
Fluoride ions in the water have an ion exchange reaction with the oxidized iron. This fixes the fluoride onto the surface of the iron as iron fluoride.
Water with about 4 ppm sodium fluoride was passed through 100 g of particulate oxidized iron particles (size 0.1 mm to 5 mm) contained within a chamber that allowed water flow through. The water was then filtered using an ultrafiltration membrane similar to those described above. The non-soluble iron fluoride percipitate that was produced was inhibited from passing through the ultrafiltration membrane. The suspended matter, which is retained on the surface of the ultra filtration membrane, shall be washed off periodically and fixed in a practically non-soluble matrix to avoid re intrusion of removed fluoride into the environment. The water which was filtered was reduced to a level of about 1 ppm fluoride.
The process for passing the water through the iron oxide requires taking into consideration the pressure of the water, the form of the iron oxide, the specific surface area/weight and weight of the iron oxide, consumption (reaction) of the iron oxide materials, and cost. The above example used iron oxide oval/round particles in granular form. This material was packed into a housing.
Other embodiments are envisioned. For example, with regard to
A hand pump, such as a MARK II style hand pump, is able to provide sufficient amounts of water to allow a single pump to provide a small community sufficient drinking water. As shown in 7, this pump would include ground supports 776 and in intake tube 744. The pump mechanism 738 is driven by arm 742. A pivot linkage 762 may drive a second pump 740 by means of arms 760 and pivot linkages 768, 764 and 770. One these pivot linkages is attached to fixed mount 766.
Water pumped by this pump flows into reservoir 746, and flows into pipe 748. The water then flows into tube 772, which it is driven by pump 740 through iron oxide particles 750 contained in tube 755, through pipe 778, and through ultrafiltration cartridges 752, 754. The water flowing from tube 756 has been purified and is drinkable. If excess water is pumped, or if backpressure occurs, the excess water can flow from tube 774, and be used for purposes other than drinking, such as irrigation.
It is believed that to treat water having 4 ppm fluoride, 100 grams of iron oxide should be sufficient to treat 15,000 liters of water. Iron oxide in the range of 0.1 gram to 10 grams per 1000 liters of water is projected to have a positive effect on removing fluoride from the water, and allowing subsequent removal of the precipitated fluoride on the ultrafiltration membrane. The size of the chamber containing the iron oxide may be manufactured to specific designs. The size of iron oxide particles is sufficiently great to allow water flow under low pressure (for example, at about 50 liters/hour flow rate) as would be produced by a hand pump. In any of the embodiments of
This application claims priority from provisional application Ser. No. 60/979,157, filed Oct. 11, 2007.
| Number | Date | Country | |
|---|---|---|---|
| 60979157 | Oct 2007 | US |
