July 2004 Update

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A Look at Pottery Filter Systems in Nepal

1. To Begin With. The goal is to make available at low cost, appropriate, silver ceramic systems like the one shown above. Until now the great benefits of silver ceramic filters have not been realized by the poor. An express objective of this site is to provide information, which is as complete as possible, on any and all advances in the understanding of silver ceramic water systems, for bacteria removal. The fact has been that the silver ceramic, household water systems can be difficult to find. And these systems have either been too expensive or they have not been user-friendly.

To put this state of affairs into perspective, the fact is that it has been only about three years since the experts in water and health became convinced that there are great benefits in using silver in ceramic filtration media. It has become understood that silver, situated within the medium kills (some say 'disables') the passing bacteria on contact. There is a new opportunity to introduce silver ceramic purifiers to communities that are vulnerable to waterborn illnesses, along with the necessary hygiene education.

Described, in brief, are findings that should help make
possible a new generation of low cost, silver ceramic
water purifiers for low income households.

About, 'pottery purifier media,' for the candle purifiers, what has brought about good flow rates in a pottery, earthenware clay, is the initial development of an open structure, wherein clay and grog are combined. See the link: April 2001 presentation as to why the pottery purifier medium gives excellent flow rates, Briefly speaking, while a newly formed candle is drying, as well as being fired, the clay shrinks away from the grog. The grog does not shrink because it's already done this, in its previous firing. So there is a network of voids between the clay and grog particles, and this facilitates good flow. This network of voids brings about an interconnectedness of the pores and voids, the spaces within the medium. The simple addition of such combustibles as sawdust to clay does not ordinarily bring about an interconnectedness of the open spaces, pores and voids, so flow rates are not substantially improved.

In the candle system of the pottery purifier media described above there are several distinct advantages: 1. a high degree of effectiveness, 2. a tried-and-true candle system, and, 3. a remarkably low cost. Further- more, 4. production is sustainable, depending only on resources that are available almost anywhere. Following are some additional, newly developed household water options for those of low income.

   

Shown at left are canisters for prospective, particulate grog systems. These are contained in pvc pipe, which tends to be available and low cost. The canisters at left and center of the picture are 11.0 and 7.5 cms. diameter, respectively. The picture at right shows cross sectional drawings for these systems. The darker, terracotta color indicates the purification bed, the terracotta at the two ends is for backflush.

2. Particulate Grog Purifiers. Following the success of developing the pottery purifier candles, the systems as shown at the page header, we now have several additional system alternatives. In addition to the solid medium of the candle there is now a particulate system, comprising a porous grog or brick grog, which is packed into pvc pipe. And for each of the different media it is possible to utilize the new methodologies of saturating the filters, with silver nitrate and also with silver chloride. Recent lab tests have indicated that silver saturated, particulate grog which is packed into pvc in this way, will give a system that is effective in removal of e coli, for example. In this case there is a great advantage over other particulate systems, such as sand, in that there is far less height of media bed required for the disinfection. So now there is the option of a small sized particulate system.

The particulate grog, water systems shown above are household sizes, the large canister projected to give 4.0 to 6.0 liters per hour, the smaller canister to give 2.0 to 3.0 liters per hour. The pvc pipe sizes are those that are commonly available, used everywhere in plumbing, so the fabrication of the systems would ordinarily be quite sustainable. Within the system, at either end of the central, silver grog bed, shown, there are shallower beds, in a lighter terra cotta color. These areas represent a coarse grog, between 20 to 40 mesh, and are intended as backflush beds. When particles collect in these ends, resulting from turbidity, a clogging comes about, the flow rate of the water diminishing. When this happens the column is turned upside-down. In this manner the particles that lodge in the system due to turbidity are eliminated from the backflush bed.

It is thought that the need to periodically up end the column is a disadvantage of sorts, ill disposed to the capabilities of very young children. On the other hand this particulate grog purifier system should have a clear advantage in that it can be very easy to produce, not requiring the services of a ceramist. Neither is a ceramist required in order to treat such brick grog with silver chloride, provided a project accepts this option. The simple process of treating a grog with silver chloride is explained below.

Mr. Chitra Gurung of the IDE, Nepal project, presides over production of the concentrated colloidal silver, used to saturate the large candles, as shown at page top. At 520 parts per million, the CS of one flask is sufficient for saturation of sixteen candles.

3. Silver Alternatives. Quite aside from the development of particulate grog systems, on another front is research into the options of appropriate alternatives for silver saturation. How sustainable is production if projects must always import the concentrated colloidal silver from, for example, Mexico, or Germany, or Korea? More and more projects will spring up once the simplicity of the silver alternatives is understood. All that may need importation is the very pure silver. Click the CS link for the latest information on alternatives.

Among those first projects around the world that are treating ceramic filter elements with silver, on a humanitarian basis, the colloidal silver has been the material of choice. Now we are also coming to understand a methodology that was documented in 1972, in an Indian ceramics institution. In this case with a silver nitrate candle, a reducing agent is run through, prior to firing. So nitrates go away and there is a silver metal bond to the ceramic. This methodology is explained further at the CS link.

Yet another alternative treatment results in silver chloride, within the media. Here is a simple methodology: 1. Saturate a candle, or grog, with silver nitrate, then dry. 2. Place the dried candle or dried grog, in it's containment, buckets for the candle, pvc pipe for the grog. 3. Run salt water through the media, candle or grog. There is an ion exchange that results in silver chloride within the media. The grog can be as simple as crushed brick, of good porosity and strength.

Our project staffers feel proud that our concentrated CS is a first for a silver ceramic filter, in that we pro- duce our own CS. It is our hope that other projects will adopt the CS generator methodology, and more information about trainings and demonstrations will soon be available on this site. Otherwise silver nitrate could be used, as described, the point being that there are now alternative choices for silver treatment.

Candle purifiers are immersed into the concentrated colloidal silver of our own production, in the process as shown above. By contrast to the simpler treatments with AgNO3 or AgCl, CS is generated by electrolysis.

It is granted that some projects may want to await further comment from the experts as to the merits of the simpler, silver chloride methodology. So in the present situation of our project the concentrated CS methodology is timely. A first application of the Indian, AgNO3 methodology will soon be undertaken. This method differs from our prior work with silver nitrate in that the reduction of the silver salts is undertaken prior to firing.

Because silver nitrate is easy to produce this option should be available. But it is expected that no one option will fit all situations, so the choices need to be made clear. Otherwise, so simple is the methodology of silver chloride treatment that this could be undertaken on a kitchen table, or in a garage. What may take such production out of this humble scenario is a rigorous need for quality control. To begin with, orderliness on the production line would be de rigeur.

For the time being our project has decided to saturate our first candles with the concentrated CS, not presuming to treat with silver nitrate or silver chloride. For the saturation of our first 100 candles , we are using the generator of the two pictures above, producing about 50 ppm of CS per hour.

On a per flask basis, six hours production gives enough CS to saturate eight candles, while twelve hours gives enough for sixteen candles. In this last case the result- ant CS is diluted 50/50 with tap water before saturation.

The electrical unit for the generator can be quite inexpensive, a 24 volt, DC converter. And there is a timer, shown at bottom center, necessary for the one minute intervals of polarity switching. Below is an inset picture of the timer.

Concerning the issue of cost of the CS per candle, materials required in the electrolysis include: de-ionized distilled water, pure silver and the bottled gas, used for the double boiler. Of these materials the most expensive part is the distilled water. At sixteen candles per flask, the de-ionized distilled water of the electrolysis, 2.4 liters, is calculated to cost US$0.09, i.e. 9 cents per candle. Silver per candle is 3 cents.

Minimizing all costs of a system for the poor is important, and for the pure water that's used in production of the CS there are several possible methods of making this a lot cheaper. The water is de-ionized and distilled to a high degree of purity. One way of making the CS cheaper is to run the generator for a longer time, so less CS can be used, and more tap water in dilution. Another method of minimizing water cost, to only a couple of U.S. cents per candle, would be to run tap water through a bed of ion exchange resins. Such resins also tend to be available, and can last for many years.

A lot of time and effort has gone into the proper methodology of the CS generator, in order to get the routine correct, three years of trial and error, and now we are quite happy to share all information. For the present the electrical unit is a final piece in the CS puzzle, which approaches completion.

The project would like to sincerely thank the gentle- men who designed, fabricated and donated the elec- trical unit, which is pictured above, for production of the concentrated CS. Mike Mares designed this DC converter/ timer, John Heasley, Jr., undertaking the assembly. Click Here for further details.

This timer is shown magnified, an inset from the above picture, the manufacturer and part type shown. The timer is for polarity reversal of the silver electrodes, every minute. Thus the system and reaction rate are stable. Note, the timer shown is tiny, about two cubic inches.

It's important to note that the electrical component shown can also be used for much bigger volumes of CS than would be suggested by one or two flasks. The amperage capability of the unit should be such that at least six to eight of the flasks could be put within the system. Then production should be sufficient for more than 100 candles daily.

Note also that the electrical unit shown can be quite a simple device, costing a maximum of $150.00 in parts, and often a lot less. In general it may be that the only part of the device that cannot be procured or fabricated in any given area would be the timing device, shown here at right. So for projects that opt for CS the only imports needed may be the pure silver and the timing device.

4. In Summation. The new purification devices and the silver alternatives shown here are advanced from the standpoint of new understanding, yet they are appropriate and low cost. The pottery clay is common, making possible a universal model for production of small sized pottery purifiers. And certainly, other silver ceramic systems can be chosen in an informed way.

For the candle pottery purifier system, its model for
production and use is the first and only of it's kind. This can
be replicated anywhere and for small populations.

For humanitarian purposes no other small sized ceramic model has shown such signs of comparable appropriate- ness. The choices here are pottery purifiers, candles and grog; silver application, self made CS, AgNO3 or AgCl. Here is a set of models that can be applied to many different locations and circumstances, public health or emergency. Bear in mind that the criteria for comparisons are: effectiveness, low cost, user friendliness and sustainability.

Many researchers are doing creative work in the humanitarian aspects of water purification, and such systems as solar disinfection, sand filtration, chlorine and others are also well suited to household purification. Now that the methodologies of silver ceramics are being resolved and understood isn't it time for such purifiers to take their place along side these other, worthy systems?

News of the Low cost water filter project of IDE

Now the silver treatment of candles is beginning, using the concentrated colloidal silver of our own production. The assembled candle systems are destined for the vulnerable communities, starting with 100 systems (as shown in the picture above). The project has already concluded that the candles have passed all tests with flying colors, and as-soon-as- possible the systems of the new CS will be placed. There is partnering with several Kathmandu based NGOs, who will carry out hygiene education, monitoring and evaluation, completion at the end of six months. The vulnerable communities that are designated for the system introduction are being chosen on the premise that other water purification methods, such as boiling, etc., have not worked for them.