We have prided ourselves here, that purifier candles are quite solid.  Yet we are now intent on a new medium, that starts with an amorphous pile of grog particles, something that's not solid at all. In this case robustness is achieved when silver treated grog of this type is tamped into a device like the one shown. This purifier system can be expected to remove virtually 100% of the fecal coliform indicators.  Furthermore it can be made locally almost anywhere, using available resources, without the services of a ceramist.  And it's remarkably inexpensive. 

The lab model shown will be emulated in a prototype for a household version.  While the small lab canisters shown are 50 mms. diameter by 14 cms. high, these  contain 200 ccs. of grog.  The eight canisters tested in the lab indicated an average of 500 ml. flow per hour.  So for a scaled up household system the grog may be contained in a canister of 75 mms. diameter and 21 cms. high.  Then this household version will give 2.0 liters, and more, per hour of bacteria free water. 

The number 5 denotes a pvc canister which is identical to the one at bottom right.  This contains silver saturated, particulate grog, for a purifier that is proving to be virtually 100% effective at removal of e coli.  Above the canister is a water column of pvc pipe.  Beneath it is a tripod, also made of pvc pipe.

This device for purified drinking water may be made from such simple materials as:  pvc plumbing parts, particulate brick and chemists' silver nitrate.  And for fabrication of this low cost household water purification system the resources needed are common, available almost anywhere.

The successful lab tests were recently undertaken using membrane filtration on eight of the particulate grog canisters.  Four canisters contained silver saturated grog, and the other four canisters contained grog that had not been treated with silver.  Using raw water of 90,000 bacteria colony units, the four silver saturated candles all indicated zero BCU, for a 100% removal rate.  By contrast the four canisters that did not contain silver grog each showed some small percentage of BCU that remained, ranging between 400 and 600 BCU.  So the e coli removal rates were between 99.4% and 99.6%.

The testing regime was intended to compare the performance of silver purifiers versus non silver purifiers. Considering that all eight purifiers functioned under much the same circumstances, the tests showed that the four silver treated purifiers did indicate that silver had killed (some say inactivated) the bacteria. Along with this the four purifiers not treated with silver were less effective.

For particulate grog purifiers tested, as per the table, the raw water indicated 90,000 bacteria colony units. All silver canisters were 100% effective, while all canisters that were not treated with silver were less effective. 

As to grog preparation, proper sizing of particles is important. For example, in using grog as it is directly from the mill, unless some of the sub 100 mesh particles are removed the flow rate is much too slow.  For the lab tests, the proper rate of flow was achieved by removing half of the original amount of fine particles.

One disadvantage of the system, by comparison to that of the candle, is the need to do periodic maintenance, backflushing when using turbid water.  For the particulate grog purifiers it will be necessary to disengage the canister, turn it over and put it back in place. On the other hand, with the candles, as particles accumulate on the outside these are simply brushed off. . 

But particulate grog systems do offer a clear advantage with respect to the system production, a very simple process, however, this does require careful monitoring.  The production involves a simple, step-wise approach:  1. acquiring brick, crushing and sizing,  2. preparing pvc parts,  3. saturating grog particles with silver, then drying, 4. filling the canisters with grog, then assembling the systems. Granted the important need for quality control, the procedures are simple enough to be undertaken on a kitchen table. 

The cover caps at the two ends are shown in dotted lines. These are standard end caps.  Note that prototype end caps are filled with coarse grog, between 20 to 40 mesh.  If turbid water is filtered then particles collect within the space of the cover cap.  These can be back flushed accordingly when the rate of flow diminishes. 

The simplicity of this approach should further prove attractive in emergency situations.  This is also true since there is little or no capital cost in starting up production, in any given location. And a rapid response is possible. 

Those who would like to research silver saturated, particulate brick grog water purifiers, can simply do so by pursuing the following steps.  Here is a resource list:

1.  Procure and process particulate fired clay of three sizes:  fine, medium and coarse.  Or contract crushing to a business that has a hammer mill, as used in agricultural applications.  Crushing is done to porous, red brick, of the type commonly available for housing construction.  Brick of this type can vary in porosity from about 20 to 40%. The higher percentages porosity are preferred, in order to impart attributes of good water retention and flow.  Note that porosity is calculated as water of absorption, the difference in the wet and dry weights of the brick, divided by the dry weight. 

2.  Processing of particles is important in determination of the particle size distribution.  For the tests described here, the composition was, 55% coarse particles, above 100 mesh, and 45% of fine particles, less than 100 mesh.  In changing percentages, a decrease of fine particles weight will increase the rate of flow.  Similarly an increase in weight of fine particles will decrease the rate of flow. 

3.  For four canisters of the type used in these tests, 800 ccs. of grog was prepared.  The mix included 440 grs. of coarse grog, above 100 mesh, and 360 grs. of sub 100 mesh grog.  While weighing out the material, it is important to mix upwards the grog particles from the bottom of the container, by hand.  This prevents the finer grog from settling to the bottom. 

4.  Have on hand several canisters of the type shown, pvc pipe parts and fittings.  Prepare round plastic screens, with pin pricks, to allow water in and out of the unit, while keeping particles inside.  The plastic can be cut from a plastic file folder. 

5.  Have on hand the silver grog, previously processed.  This is done by pouring the grog particles into the silver solution, then taking off the excess solution.  Following this, the grog is spread out to dry.  As to the silver solution, two options are: colloidal silver and silver nitrate.  In treating the grog for the tests, silver nitrate was used.  Then the first water through the purifiers contained salt.  So an ion exchange brought about grog that is saturated with silver chloride. (If using silver chloride a further step is necessary, using tap water to flush the salt and extraneous nitrates.)  Following silver treatment of grog, and drying, this loose material is packed into the canisters. 

6.  The end caps of the canister should be filled to their depth of 2.5 cms. with a coarse grog, in this case sieved to between 20 and 40 mesh. In use of the up-coming, prototype system the space within the end cap will accumulate the particles resulting from the use of turbid water. Thus the canister is periodically turned up-side-down, in order to flush particles by backflushing. 

Meanwhile work continues on preparation of many 
additional tests for particulate grog purifiers. These tests 
are to verify the correct flow parameters for proper disinfection. Then the household systems will be optimized for simplicity of use and low cost.

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