So this month, I have had a fair bit of activity on the synthediment development front. First of all, I had the privaledge of giving a platform presentation on Synthediment(TM) at the 21st Tennessee Water Resources Symposium. Also, in addition to a continuing collaboration trial with a toxicology lab using Hexagenia species, I've made contact with two other potential trial-partners. With this increase in synthetic sediment development activity, I'm starting to think about how I might process larger volumes of material. This would include not only receiving and handling raw materials ("ingredients") such as sand, silt particles and clays, but also (and more importantly) washing/purifying prior to use in a composition, and homogenizing large volumes of ingredients during the synthediment composition process.
At this point, I'm graduating from jars, tubes and other bench-scale equipment to plastic pails (e.g., 5-gallon buckets). The relative volumes of materials I'm dealing with at this point are in the 1-20 kilogram range, with corresponding volumes in the 1-20 liter range. For now, these amounts are easily processed in small pails.
One of the most important activities I have to do on raw materials is washing/rinsing/purification, and I greatly wish to automate this process. For now, I have configured a closed-loop rinse process consisting of a small submersible aquarium pump, two plastic pails and a 100-micron filter sock. Here are some photographs of the current setup that shows the major components.
The submersible pump (~2 gallons per minute) is placed into the bucket containing some type of rinse fluid (distilled water, dilute acid, hydrogen peroxide, dilute caustic solution, etc., according to the type of rinse process required). I'm not at all thrilled with having to use a submersible pump due to the unavoidable contact of the pump with my rinse fluid. I'm forced to do this for now based on available funds, but at some time in the future I plan to replace this with an external chemincal feed-type pump that will not be in contact with the rinse fluid except for the inner surface of the pump tubing.
The outlet of the fluid pump is fitted with a length of chemically-resistent tubing, and the end of the tubing is directed into the second pail which contians the raw material to be rinsed/treated. This is the only part of this particular setup that requires some hands-on manipulation to ensure that the fluid flow coming out of the tubing reaches the entire volume of solids to be rinsed.
The second container holding the raw material has been fitted with an outlet spigot, created by drilling a hole into the side roughly 4 inches from the top and inserting a threaded PVC tube (obtained from a local aquarium store). A PVC nut is screwed down the threads up against the outside of the pail to secure a liquid-tight seal. This configuration allows fluid (and ligher than water fines) to exit that pail and fall back into the fluid-source bucket by gravity.
In order to trap unwanted particles and fines leaving the raw material pail, I placed a 100-micron filter sock (also obtained from a local aquarium store) directly below the outlet spigot. Thus, before the fluid completes the circuit, it is strained of any suspended material (such as residual organic matter) larger than 100 micrometers.
Of course dissolved materials captured by the rinse water will be recycled back through the raw material over time. In the case of acids, bases, or oxidizing agents, this is actually preferred since total reagent usage is minimized. Released metals, dissolved organic matter, or oxidation byproducts are NOT wanted to be returned to the raw material, but this can easily be addressed with a post-treatment, water-only rinse to remove those treatment byproducts.
The raw sand rinse that I have performed has removed a substantial amount of extraneous dirt and organic solids, as shown in these photographs.
So, the development process for synthediment is moving into the scale-up phase. More information on the hexagenia-exposure trials and other field trials will be posted when available. Visit again soon for more updates!
