Uses for synthetic sediment: Part 1

Seasons greetings after a long absence from the blogging world.  Since my last post, circumstances have limited the time available for making progress.  The little bit of time spent on synthediment has brought some challenges, and on-going trials with my two partner-laboratories have been very insightful to me.  Although the trials "failed" to achieve the original goals, they uncovered factors that I had not recognized to be so important to synthetic sediment uses.  Edison made lemonade from his lemons in similar fashion.

To get back into a more regular posting schedule, I am starting a mini-series of blog posts dealing with theoretical uses and benefits of using synthetic sediment.  Not only will this provide me with blog material during lulls in lab-development, but ideas presented in these blog entries might seed your (the reader's) mind with other ideas for possible uses of synthetic sediment in the real world.  Theoretical applications shared in this and future "uses and benefits" posts may be so specific that they would require extremely detailed and nuanced synthetic sediment formulations (recipes).   It is my belief that these theoretical applications might only be realized through my "synthediment" procedural system of synthetic sediment preparation [... sorry for the crass commercial statement].

The first application envisioned for synthetic sediment is as a microcosm habitat for organisms that are kept and cultured in laboratories.  Here's why:

[1] Commercial laboratories exist that provide testing services for assessing sediment quality. A common activity those labs do is to test a field-sediment sample for toxicity to live organisms (a bioassay).  Scientists try to set up their tests so that all conditions are controlled and none of their test conditions will cause negative effects on the live organisms in the test.  The only negative effects (if any) need to be attributed to the sediment sample with a high level of confidence.  Since live organisms are complex entities, they can be a challenge to "control."  If they are not, negative effects in the tests can be caused by poor health of the organisms.  For this reason, organisms captured in the wild are seldom used in sediment toxicity tests. 

[2] To minimize the chance of poor organism health being the cause for negative test results, labs cultivate and maintain their own population of organisms.  Some of the more common test organisms cultured in biological laboratories are called aquatic macro- (visible to the unaided eye) or micro- (undetectable to the unaided eye) invertebrates ("lacking a vertebral column").  They are the river/lake/stream equivalent of spiders, worms and beetles we find on land.  Proper care for these lab cultures requires expertise in the biology and physiology of these organisms.  Such cultures are meticulously cared-for by maintaining consistent feeding, water, lighting and temperature conditions, among others. 

[3] Aquatic systems (lakes, rivers, streams, ponds, etc.) are complex systems containing a range of habitats suitable for an even wider array of organisms.  Some aquatic invertebrates are free-floating, swimming organisms that live and feed in the water column (e.g., plankton, water fleas, bacteria).  Others exist almost entirely on the surface bottom sediment, at the junction of the water column above and the sediment material below.  Those organisms (called epibenthic invertebrates) may burrow into the sediment a bit, but only into the very surface layer and never more than a few body lengths deep before coming back up to the surface.  They may swim in the water column a times, but always very close to the sediment surface (e.g., snails, shrimp-like amphipods, copopods, etc.).  A third group of organisms are true benthic organisms, spending the majority of their development cycle "underground" within the sediment material (e.g., worms, midge larvae, clams, etc.).  Each type of organism, and at times even individual species, require their own specific "living conditions" or habitat for maximum growth, metabolism and reproduction.

[4] Organisms that naturally associate with sediment material as part of their normal development cycle in nature (the epibenthic and benthic invertebrates) will require some form of sediment substrate for maximum growth, metabolism and reproduction.  If these types of organisms are cultured in the laboratory, their growing tanks or containers must contain some form of sediment substrate.  The question is: What substrate can be used?  If field sediment is used, there is a chance the sediment is contaminated and detrimental to the organisms in the lab.  Material not collected in the field may be used to act as a surrogate substrate or artificial sediment.  In this case, although the material can be guaranteed to be "clean" (not chemically harmful to the organisms), there is a chance that the artificial material is not suitable for the organisms' growth and health.  It could be too fine, not fine enough, too fluid, or not containing organic material in sufficient quantities or of appropriate composition, for examples.  The more realistic that substrate is, the better the benthic or epibenthic organisms may respond during culturing.

[5] Synthetic sediment, composed of a set of components that represent natural components in field sediment, can be created and conditioned in such a way that organisms will thrive in the laboratory.  Substrates used currently are good enough; they include sand, nylon mesh, shredded paper towel, etc.  However, could those same cultures be improved with more realistic synthetic sediment used as their culture substrate?  Would organisms cultured in the realistic synthetic sediment provide better response when used in sediment bioassays?  If so, those organisms can provide good quality data that helps environmental managers make good decisions about the true conditions of sediment in the field.  That's the theory, at least...

What is Synthediment(TM)???

I've had so many people ask me what exactly am I doing in the garage, and why exactly are you doing it, I started thinking how I might get the concept across to non-technicals.  There are so many fields of study involved in sediment toxicology and sediment geochemistry, that it can be an overwhelming chore for a non-technical person to grasp.  So after some thought and re-thought, here's my summary explanation for synthediment(TM):

Short Explanation:

I am developing a process/method to create a synthetic sediment (artificial lake/river/stream mud) that will act almost exactly like real lake/river/stream mud.  This material can be used by scientists who want to test real-world mud but don’t have a good reference to which to compare their results.  My artificial sediment can provide them the ability to get better test data and to make better decisions based on those data.

Long Explanation:

Cleaning the environment depends on having good data for three items: what part of the environment is contaminated (e.g., air?, soil?, water?, mud?), what is the identity of the contaminants present, and how much of each contaminant is out there.  Sometimes, environmental scientists suspect that the bottom mud of some lakes and rivers/streams may be contaminated.  In those cases, before clean-up can start, testing is done to find out what contaminants are in the mud, and in what amounts. 

Many small organisms (worms, clams, etc.) live in lake/river/stream mud; it is their preferred habitat.  When contaminant amounts in the mud get too high, the small critters either move or suffer biological harm.  Environmental scientists use this fact in their testing of lake/river/stream mud.  They collect samples of the mud and send them to a lab.  The lab scientists culture “clean and healthy” lab-organisms in their laboratory, and they use these lab-critters to test the mud samples.  A known number of lab-critters are added to smaller portions of the mud sample, and those lab-critters are fed for a known number of days.  At the end of the test period, lab scientists look through the mud to see if they find any of the lab-critters they added, and (if some are found) how they are doing biologically.  Contaminated mud can sometimes cause harm to the lab-critters, anything from DNA damage to slow growth or reproduction, all the way up to mortality. 

However, all good scientists know that there are many factors, or “experimental variables,” that can affect the outcome of a lab test, not just contaminants.  In the mud testing example, not only can contaminants cause harm to the lab-critters, but other things like improper habitat can also seem to harm lab-critters.  For instance, if a particular organism likes sandy textured river mud, it will not be healthy if forced to live in clay textured river mud.  In order to tell what factor is causing the outcome, all factors expect one must be matched.  Unfortunately, nature is so diverse that no two lakes, no two streams, or even no two mud locations in the same creek, are exactly the same.  So for mud testing, there is a lot of question as to what REALLY caused the outcome of a lab test.  Currently, lab scientists make educated guesses, apply reasonable assumptions, or they use mud from a lake/river/stream that they THINK is clean as the test “reference.”

The only way for a mud sample to be the same as a real/natural mud sample (except for the contaminants) is to create that mud sample.  A very few number of scientists have thought about this since 1980, and have proposed a very simple “mud” material made up of only 4 or 5 ingredients.  This simple artificial mud material is no where near equivalent to a real mud sample found in nature, which is a highly complex mixture of several dozen components or ingredients.  So it is my opinion that using this one recipe as a “reference” for testing all the different kinds of mud found in nature is not much better than using a mud sample from a lake/river/stream that they THINK is clean.

This is the problem that my project aims to address.  My method/procedure will create synthetic mud using as many as 30 ingredients, each ingredient designed to be the equivalent of a component found in real mud in nature.  The exact procedures I am developing for selecting ingredients, pre-cleaning or pre-treating raw materials, creating other complex ingredients found in real mud, and combining all these ingredients are based on over 10 years of researching scientific reports and papers in scientific fields of study such as toxicology, geology, marine biology, environmental engineering, and others.  My methods can produce not just one artificial mud material, but can be adapted to match almost any real mud sample found in nature.  This will allow me to offer the equivalent of hundreds of artificial mud materials, tailor-made to meet the lab scientists’ needs.

I am at the stage of development where I have developed all my procedures on paper, and now I am testing the implementation and scale-up of these procedures.  I am marketing my ideas to laboratories in hopes that they will agree to test some samples of my material in their laboratories, side-by-side with real mud samples.  The information I hope to gather from these collaboration tests with labs is whether my material is suitable as habitat for lab-critters they may have growing in their laboratories, and whether I can reproduce the results consistently.  Eventually, I hope to be a supplier of synthetic mud to all commercial laboratories, university departments of environmental studies, and government agencies (both State, Federal and international) involved with dealing with contaminated lake/river/stream mud.

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!