Automation and scale-up

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!

Trial No. 1 - Hexagenia culture

This post describes the first application trial using a batch of synthediment(TM) I developed for a government toxicity laboratory.  The director of the tox lab provided specifications of the natural sediment currently used to culture hexagenia in their laboratory.  Their field-collected sediment (from a northern-climate pond/lake) is heavy in the silt fraction and averages about 3.6% total organic carbon.  The challenge with this batch, and all batches of synthediment(TM), is finding a suitable surrogate material for the silt fraction particle size.  Sand and clay components are easy to replicate geochemically; natural silts on the other hand are a mixture of large clay clusters and weathered sand particles.  I'm not aware of one single material composed of such a mixture of geochemical components.

For this batch of synthediment(TM), some of the silt phase included a low-density silica-based material which gave the final dry-solids product an almost fluffy texture.  I was concerned that the solids would float upon hydration, but apparently that did not occur.  I received a photo (below) from the toxicity lab showing the hydrated synthediment(TM) solids (grey material on the left) side-by-side with their natural sediment (reddish-brown material on the right), being prepared for an hexagenia culture trial. 

The texture appears to be replicated rather well.  The coloring is definitely off, very likely due to a greater proportion of iron oxides in the natural sediment than in the synthediment(TM) batch.  This can be addressed very easily in future batches.  The grey color of the synthediment(TM) batch is due primarily to all 16 components in this batch being colored either white or black (with the exception of the minor component of dark brown peat powder).

At last report, overlying water and hexagenia larvae were added to the tanks sometime during the last week of February.  We'll have an update on the progress soon..

My Synthetic Sediment Laboratory

Since my graduate school days at Manhattan College, I've really enjoyed the hands-on experience of field and laboratory work.  The process of planning and gathering data about the environment, then evaluating them to extract useful and interesting information has always been quite satisfying.  So much so, that I've spent the last 10 years or so on online stores slowly purchasing equipment, instruments, glassware, chemicals, and manuals as part of my personal lab.  I know.. I know.. major science dweeb!  My wife never understood it until my synthediment(TM) work showed some promise of success.  She always has been very gracious to put up with the expense and the storage of those items.. so long as they were out of her sight!

I'm showing some photos of the set-up I have currently, partially in my garage and partially in my basement. 

My most recent addition, a Perkin-Elmer Lambda 2S uv-visible spectrophotometer, currently resides in the closet of our home's "mother-in-law" suite.  Gotta protect those electronics, you know...

Having these tools has been critical for furthering my synthediment(TM) development work.  I'm finishing up my literature search work (I have upwards of 2500 citations and associated PDF files) in preparation for a review paper documenting the synthetic sediment development work that has been done by others to date.  I hope to continue my synthetic sediment development effort and post my successes (and trials..) here and elsewhere. 



Synthetic Sediment Stuff

Well, I've ventured into the world of blogging for the first time. And I believe it is for a good purpose, not just to see myself in print on the net. These pages are devoted to talking about all things sediment (aquatic sediment... not the subsurface "geologist" version), an interest that began with my excellent grad-school experience at Manhattan College in the early 1990s, under wonderful professors like Drs. Dominic Di Toro, John Mahony, Bob Thomann, and John Connolly, and with great fellow-students like Michael Fichera and Tom Parkerton.

For the last 10 or so years, that curiosity has focused on synthetic (artificial, formulated) sediment and how to "build a better mouse trap" as the saying goes. Improving the development of synthetic sediment has become my pet project that keeps my brain occupied and entertained while I spend my work days earning a living. The current iteration of the fruits of my labors is a material I've coined synthediment(TM) (.. synth[etic] [s]ediment). It's formulated with a much larger list of components than the common recipes currently in use. I'll be posting more information in the near future about synthediment(TM), the background behind its development, and the progress being made on applications using this material.

It's my hope that others will join in the conversation and share our collective thoughts on this part of the environment. Enjoy!