Student Intern Research Activities - Riverbank Filtration

Hello folks!   Since this is my first post, I'll introduce myself quickly - I'm Tom Voltz from western Suffolk County, Long Island, I have as of this past May a Bachelors degree in Civil Engineering from Lafayette College (Easton, PA), and will be heading to Penn State University this coming August as a Teaching Assistant in the Masters degree program within the Water Resources Engineering Department there.  Thus far I've thoroughly enjoyed all my time here, interacting with the others and learning tons from the great people at the University, and I am glad to finally have a chance to use some of the German I've been learning!

Before I say anything else, I feel as though I ought to briefly address the question of Barge Traffic, albeit not having dug very deep.  Firstly, is it really true, Ms. Wellington, that barge traffic wasn't too common in the DDR back in those days?  Until reading your comment, I hadn't really thought what the agreement was between the BRD and the DDR when it came to traffic on a river running through both.  I suppose potentially not having access to the North Sea would have meant no access to international shipping for the DDR, but maybe they still ran ships between cities further upstream?  Interesting question... As far as RBF-related impacts go, I could see how the presence of ships or barges running diesel engines might lead to contaminants from fuel entering the river and potentially the RBF wells.  A quick glance in Dr. Ray's book led me to a chapter about the fate of organic micropollutants, one of which is called Methyl Tertiary-Butyl Ether (MTBE).  I won't pretend to know much about it, but as written it is "used worldwide as fuel oxygenate in high quanities"  (Ray, 2002).  I read also that it has a tendency to travel quickly through groundwater and to not undergo much microbial degradation, meaning it isn't very likely to be broken down biologically as it moves through soil.  Therefore, if in fact MTBE (among other potential fuel-derived pollutants) does enter the river water from fuel burned by barges and other ships, then it seems likely to find its way into bank filtration wells, where it could potentially pose a health concern or at least warrant consideration in the context of the water treatment that follows withdrawal from RBF wells.  Depending on the sort of cargo that is shipped up- and downstream, which might require some inquiry into shipping records or shipping companies themselves, I suppose there would also be the potential for contaminants entering the river in the event of a mishap.  All in all, it might be interesting to look into, although it doesn't seem to be a serious threat to the process.

Now to Görlitz:

Last Monday the 23rd, we spent our final day in the field gathering data, conducting experiments and collecting samples under the lead of Wolfgang Macheleidt (who is responsible for all laboratory and field work within the Water Resources Department) at the riverbank filtration site in the charge of the Görlitz waterworks.  Görlitz is a city located on the eastern edge of Saxony on the west bank of the river Neisse, which is today one of the rivers that marks the Polish-German border - in times past Görlitz was located on both sides of the river in what was then all German territory (something interesting I learned just yesterday from my former German professor).  One type of measurement carried out was the recording of vertical temperature profiles of the groundwater inside of an observation well (very important information used in groundwater flow modeling with heat transport), which had by then become rather familiar to us, and Lelemia and our Costa Rican colleague Luis took charge of measuing these profiles in the many observation wells at the site.  We were also met there by two other German colleagues from the University, who similarly measured ground water temperature profiles in wells located at sundry points throughout the site.

Here, Lelemia takes a brief moment of rest above one of the RBF wells amidst the endless temperature profile measurements.

Another feature of the bank filtration site at Görlitz is the presence of variously sized 'infiltration ponds,' which are intended to provide additional water to the pumping wells.  The basic process involves pumping surface water through a separate pipe to the highest in a series of shallow ponds (all located on the opposite side of the RBF wells as the river), where it then fills the subsequent ponds and in the process ideally leads to greater infiltration of the water through the ground and into the ground water stored in the aquifer.  This is known as artificial recharge, thus named because water is being caused by human effort to seep through the ground, thereby 'recharging' the water stored in the aquifer.  In addition to providing greater flow into the wells from the land side, this can conceivably serve as a means of creating a water divide in the aquifer, thus preventing the groundwater located further from the river beneath the urbanized area (potentially a source of greater pollutants derived from urban surface water runoff, among other things) from flowing into the wells and mixing with the future drinking water.  In theory this process can be effective on both counts, and from what I understand I believe there are actual examples of its successful implementation at other waterworks, but past visits to this site by University students and colleagues have led to doubts about whether the process works at Görlitz in particular.

To that end, the second intention of the trip was to assess this artificial recharge process by conducting infiltration experiments in the largest infiltration pond there, to see how effectively the sediment at the bottom of the pond allows water to flow into the ground.  The first step was to have the Waterworks employees deactivate the pump that pumped river water to the ponds, thus removing the inflow and permitting the water to infiltrate solely under the influence of gravity.  The next important step was to post Ren at the edge of the pond to monitor the water level as it varied (or didn't vary) throughout the day.

Here Ren sat in suspense for the whole day, as the water level plummeted nearly 1 centimeter in 7 hours.  She used a fine-measurement instrument to obtain exact measurements by making slight adjustments that lowered the tip of the measuring stick fractions of a millimeter at a time.

The other three members of the field crew undertook the two different types of column infiltration experiments in the pond itself.  Once set up, the columns were allowed to sit for several hours as the water slowly infiltrated through the pond bottom.  If repeated physical contact wasn't enough, it was evident from the appearance of the pond bottom that it was composed of a thick layer of mud, meaning small-grained particles that do not typically allow much in the way of infiltration.  By the appearance, I refer the formation of mud cracks, which happens when, following deposition of the fine-grained mud particles (which can only occur in very still water), the mud layer becomes periodically exposed to air and heat, which dries it out and causes cracks to form in the ensuing shrinking.

Here we installed the larger of the two infiltration test columns, which we subsequently filled with water to create the necessary hydraulic head difference to cause the water to infiltrate rapidly and allow us to return home before nightfall.  Rubber waders were required to navigate the perilous 20-cm depths of the pond.

While the two infiltration experiments were underway, we extracted relatively 'undisturbed' samples of the material from the pond bottom, for the purpose of conducting further infiltration experiments in the laboratory back at the University.  Samples were taken by driving a steel column into the pond bottom and then sealing one end of the column with cap containing a porous filter stone, to be used in the future experiments.

Here Ben and Wolfgang are returning one of four undisturbed soil samples to the container on dry land.  In the background is the second type of infiltration column.

"Did the water really only infiltrate that much?"

The much-anticipated conclusion regarding the infiltration experiments was that because water was certainly not infiltrating very much into this pond, the intended artificial recharge undertaken by the waterworks is probably ineffective.  The situation was explained to us further upon a later meeting with Professor Grischek, where we learned that the motivation for building these infiltration ponds in the first place wasn't grounded very much in science, rather in the need for more water and the assumption that such a process adds to their available discharge.  While it may have worked at first, however, enough fine-grained sediment has settled in the pond by now such that very little water seems to be able to penetrate into the aquifer below, and it is possible that the money spent pumping the water to these ponds is wasted.  This was an important lesson to us in never assuming that things which have been done in the field were done based on sound scientific study, and while such study may not usually be necessary to know that something will work, it seems it can certainly be useful in knowing whether something has stopped working.

Many thanks to Lelemia for all of his diligent photography, at Görlitz and everywhere else.

What effect has the reunification (1989) had on barge traffic, much of which was previously diverted around the DDR? Has there been significan impact to water quality and the associated ecosystems?

 On Tuesday, June 9, 2009, we conducted fieldwork at Torgau as well as toured the Torgau-East Waterworks. The main purpose of the field study was to measure water levels and associated temperature profiles in observation wells arranged in along on bank filtrate flow paths between the Elbe river and abstraction wells. Temperature can be used as a tracer when modeling groundwater flows due to Riverbank Filtration. Based upon the observed data a model will be developed using U.S. Geological Survey VS2DHI software.

Picture 1. IRES interns Ben Emm and Ren Ishii at Torgau conducting water level and temperature profile measurements

Picture 2. Johannes Arns (IRES Instructor) and Tom Voltz in the field 

Picture 3. IRES interns touring the Torgau-East Waterworks

Picture 4. IRES interns returning back to Dresden from Torgau field site (Joshua Lelemia Irvine pictured)

At the Tolkewitz site, we measured about 30-40 wells for water table depths, temperature profile, electro-conductivity, and oxygen concentration. Comparisons from previously gathered information accompanied with a data analysis are being realized so inferences can be drawn on operating RBF systems.

Picture 1. Initial well calibration

Picture 2. Interns taking well measurements along the Elbe River