Diatomite, Diatomaceous Earth

For offshore, marine, municipal and industrial applications one current technique is to use a bed of media, usually sand though there are other substances in layers within the vessel as well, as a depth filter.

A recently-installed sand filter installed in Dagenham and operating on borehole water with 1ppm of finely-divided "ochre" in it worked completely successfully: when backwashing to remove the dirt, the waste stream resembled Brown Windsor Soup in appearance.

Tell me more. Was DE layered in the sand media. I am working on some filter devices to be used in Africa in the poor and remote areas. There are deposites of DE there. Natural DE is very fine and very restrictive to water flow.

There was no diatomaceous earth in this particular filter.

Most suppliers of media filters for water will use a greensand. It has the property of a more-or-less uniform particle size with very little in the way of fines to be lost upon the first backwash. It is an established technology, with much written about it in textbooks across the globe. They just "work".

I have used slow sand technology. I am also familiar with greensand and the chemical properties it has. In East Africa there are large deposits of DE and since I am into appropriate technology I am trying to use what is readily available. DE is an excellent media for removing turbidity from water and with the turbidity much of the contaminants.

WaterAid is also working in Africa along similar lines: http://www.wateraid.org.uk/.

Any improvement to the functioning of diatomaceous earth will be of interest to them. Please share the findings when completed.

If you working in africa, you must now the Okavanga Delta. The water from the north is flowing undergrond into the Botswana's Okavanga Delta. The water is filtered through the desert sand and it is one of the purest waters available. Same is in drinking water filter, a sand filter is commonly used over the diatomeciuos earth filters. During My trip in Botswana I met camps producing drinkingwater by flowing over (activated) carbon wals. These worked very well.

"...one of the purest waters available..." needs to be qualified with the words, "for drinking" and quantified with an analysis. It is inappropriate to supply water with too low a level of total dissolved solids [TDS] for drinking, as it is unpalatable and can be seriously harmful, as it will remove minerals from the body as it passes through. Drinking water produced by evaporation or reverse osmosis processes is usually passed through a palatability filter containing CaCO₃ to increase and buffer its pH and to improve its taste.

For information, water used for washing silicon chip wafers during their manufacture will contain TDS levels in the small parts-per-billion (1 x 10^-9) region, on the simple basis that the higher the TDS is, the lower is the yield of the chip wafers. This is called "ultrapure water", and nothing else in the known universe approaches this level of purity. An ultrapure plant will typically have seventeen stages of processing starting with a good town mains water before it can be classed as ultrapure. Even "water for injection" used in pharmaceutical manufacture is full of impurities in comparison. Television advertising claims by French water bottlers of "high purity" are absurd in comparison, and self-evidently simply marketing ploys arranged to sell more product.

Many local water problems in developing economies can be solved by the application of simple home-brew technologies, and any improvement in the quality of diatomaceous earth manufacture is well worth pursuing, among others.

Ultra pure water is fairly easy to produce. Distilled water run through a resin will bring it to less than 1 ppm. I have used this for my ionic silver production which in turn is used for impregnation of water filter media.

I met a fellow who worked where ultra pure water was available and used regularly. They were drinking it but quit when it began giving them the stomach ache. They also noticed that the spillage on the floor was eating away at the soles of their shoes.

Appropiate technology is my goal for safe drinking water. Water is available where the people are or else they wouldnt last long. The quality is the major concern in many instances.

Healthy disagreement is valuable sometimes. Some would disagree that 1ppm is "ultrapure". 1ppb would be a better qualification of the term, requiring rather more than resin to produce water like this, particularly in the 40-80m3/d region, though this is outside the remit of the original post looking at diatomaceous earth.

On a recent visit to the Okavango Delta, the surface water was as clean and free as it could be, and was certainly palatable. A package water treatment plant was sandwiched into an ISO 20' container and fed from electricity produced by a package generator. There were hazardous biological impurities present in the groundwater, though. Like hippopotami. And crocodiles.

Here is a similar project

http://www.potpaz.org/pfpfilters.htm

About as low tech as possible, it may be possible to work the Diatomite into the clay body & increase the effectiveness of the filter!

That is a good thought. Since the DE is normally fired to increase porosity it may even be advantageous. I considered doing this with natural zeolite but the zeolite would collapse at to low of a temperature.