Projects from 2014
Power Generation Through Water Enhanced Reverse Electrodialysis
REU Student: Ms. Kassidy Boyle
Project Mentor: Dr. Jamie Hestekin
Project Supervisor: Mr. Alex Lopez
As the world’s population increase it has become increasingly necessary to find more
renewable energy sources. Research reveals that the potential energy that can be generated
when different saltwater concentrations mix and can be used as a renewable energy
source. In theory, there is an increase in entropy when equal quantities of river
and saltwater mix. Studies have found the potential energy generated, by the differing
concentrations, is estimated at 2.8 TW. Reverse Electrodialysis (RED) has been identified
as a promising method to capture this energy. RED consist of a stack of cell membranes
that alternate anion and cation (AEMs and CEMs) exchanges. Theoretically, the greater
number of cell membranes the higher voltage that can be generated. This student’s
research focused on expanding knowledge of the RED method in order
to increase the voltage measured. They sought to do this by adding additional membranes to increase voltage to 5V per square foot, creating thinner ion wafers, and improving stack design and efficiency. Results showed that voltages achieved were significantly lower than expected. Further research needs to be done in order to redesign the stack and capture greater amounts of energy.
The Effect of Stream Drying on Relative Weight and Diet of Smallmouth Bass
REU Student: Mr. Tevin Douglas
Project Mentor: Dr. Daniel D. Magoulick
Project Supervisor: Mr. Christopher Middaugh
Smallmouth bass are an important top predator in many freshwater systems in north America. Further, smallmouth bass can be an indicator of water quality due to its preference for clear and clean waters. In many of these systems, seasonal drying can potentially affect smallmouth bass population dynamics. Global temperature increase and changes in precipitation patterns could lead to a longer drought period. This student examined the effects of seasonal drying on smallmouth bass to determine if there is a potential threat to smallmouth bass populations due to change in climate and precipitation. They hypothesized that as the seasonal drying period progressed there would be a decrease in relative weight as well as a change in diet and increase in number of empty stomachs of smallmouth bass over time. Ten sites (5 drying, 5 non-drying) were sampled every two weeks, where bass weight and diet were recorded. No significant differences were found between stream categories, likely due to the fact that this portion of the study ended prior to drought conditions. Further investigation of the effects of drought conditions on smallmouth bass can help determine if action will need to be taken in the future to stabilize the smallmouth bass and help maintain its existence.
Using Nutrient Rich Hypolimnetic Water as an Alternative to Chemical Fertilization in Lakes: How Efficient is Artificial Upwelling?
REU Student: Ms. Delaney Hall
Project Mentor: Dr. J. Thad Scott
Project Supervisor: Mr. Bryant Baker
Forested lakes often do not receive enough nitrogen and phosphorus input to sustain a robust food web. The typical means of introducing nutrients into the lakes is chemical fertilization, but this can become expensive, time consuming, and labor intensive. Artificial upwelling could be an alternative to chemical fertilization. The upwelled water, however, may not be circulating throughout the lake in a manner conducive to whole lake fertilization. To determine the efficiency of the upweller, the student conducted a water tracing experiment using Rhodamine (RH) dye. In the laboratory, the student conducted a proof-of-concept experiment to determine how long it will take to detect the RH in the lake. Study findings indicated that it will take approximately 48 hours for the RH concentration to reach 1 µg/L, equating to an efficiency of fifty percent.
Effects of Light and Phosphorus Concentrations on Algal Growth on Oak Litter Detritus
REU Student: Mr. Scott Hamby
Project Mentor: Dr. Michelle Evans-White
Project Supervisor: Mr. Brad Austin
Human activities have caused increases in nutrient concentrations that are typically available to stream and other ecosystems. This can cause changes in biofilm communities on detritus, potentially affecting the detritus’s decomposition rate, quality as a food source, and stoichiometric ratios. In this study the student focused on the effects of light and phosphorus (P) concentrations on the algal communities on the detritus. The student found that algal growth depends more on light early in the decomposition process. Phosphorus uptake rates only varied significantly in the highest treatment, suggesting increased P assimilation into the biofilm. This is an ongoing study and further sampling will provide a more clear perspective of the processes and effects of light and P on algal communities associated with leaf litter.
Anion Exchange Membrane Selectivity When Removing Organic Acids From a Fermented Broth
REU Student: Mr. Royal McCloyen
Project Mentor: Dr. Jamie Hestekin
Project Supervisor: Mr. Alex Lopez
Electrodialysis is a very versatile technology for the removal of difficult mixtures. Ion exchange membranes are an integral part of the electrodialysis process, and play an important role in today’s chemical process industry. Anaerobic decomposition of biomass is associated with bacteria such as Clostridium Acetobutylicum. These microbes produce organic acids such as butyric and acetic acid which, when removed, are beneficial industrially and to the bacterial communities. The primary goal of this student’s research was to determine if different membranes could successfully recover acetic acid from a fermented broth. To determine the effectiveness of 4 different membrane types, 2 tanks containing 250mL of sodium butyrate each were connected to the electrodialysis stack via inflow/outflow tubes. Three runs of duration 180 minutes each were run on each membrane. Conductivity was measured in the dilute and concentrated tanks. All membranes showed similar patterns in conductivity values and changes over time, with conductivity increasing in the dilute tanks and decreasing in the concentrated tanks. To better understand the effectiveness of each membrane, existing samples should be run using HPLC to determine actual ion concentrations.
Estimating Carbon Sequestration of the Sefor Land Holdings of the University of Arkansas
REU Student: Mr. Nick McElhaney and Ms. Erin Cooper
Project Mentor: Dr. Marty Matlock
Project Supervisor: Mr. Eric Cummings
Global climate change is one of the leading problems facing scientists today. A leading cause of this upward trend is growing carbon dioxide emissions. Several mitigation strategies have arisen to combat this climate change, among them being carbon sequestration which is the process of capturing carbon dioxide from the atmosphere and holding it for an extended period of time. These REU student’s sought to determine the carbon sequestration potential of the woody biomass of a portion of the Ozark Forest. To accomplish this, trees were inventoried at the University of Arkansas’ Sefor land holdings area to the southwest of Greenland, Arkansas. The land holdings parcel data was acquired from the Center for Advanced Spatial Technologies (CAST) office of the University of Arkansas. ArcGIS software was used to divide the parcels up into 12 non-uniform sections. The sections were defined by natural discrepancies of the land such as streams, density changes (seen by darker colorations of tree sections), and grassy areas. After inventory, population data was characterized and sequestration rates were modeled. Current results only include data for 1 of 12 sections. Section 11 had four transects totaling 200 trees. The largest tree group was the Juniperus virginiana (Eastern Red Cedar) with 56 trees. Eastern Red Cedars sequester between 37.87 pounds/tree/year and 247.28 pounds/tree/year. The average density of section 11 was .1444 trees/ m2 . Further processing is necessary.
Productivity of Periphytic Algae in Response to Pulsed and Constant Flow of Swine Wastewater
REU Student: Ms. Shelby Owens and Ms. Arlena Tran
Project Mentor: Dr. Thomas A. Costello
Project Supervisor: Mr. Jerry Jackson and Mr. Lee Schrader
The eutrophication of freshwaters is a widespread concern. Wastewater from swine and dairy farms is enriched with nutrients such as phosphorous (P) and nitrogen (N) which build up in soil and are released in runoff after large storm events. An Algal Turf Scrubber (ATS) is a technology that can reduce nutrient inputs from farm wastewater by allowing algae to grow from the uptake of P and N and energy from the sun. In this study, the students sought to determine the best flow rate and/or type of flow for optimal algal growth productivity and minor energy usage. A small scale ATS consisting of 8 lanes each 9.5 in. wide and 10 ft in length was used to test two types of flow; pulsed and constant. Within these two types, variations of flow were also tested. These trials were performed, each with an average growth period of about 6 days. Energy consumption by pumps, DO, conductivity, pH, and temperature of wastewater were recorded. Influent wastewater as well as effluent wastewater was sampled and tested for ammonia-nitrogen concentration (NH3-N), total phosphate concentration (PO43-), and turbidity. Algae was harvested to determine its growth productivity. Findings suggested that lanes with constant flow gave higher mean algal productivity rates than those with pulsed flow. However, there was no statistical difference of productivity between the two types of flow, p<0.05. In both pulsed and constant flow, the lowest variation correlated with the highest algal productivity. It appeared that lanes with pulsed flow consumed less power than those with constant flow. However, there was some speculation into the reduction of energy consumption if designing with smaller pumps. Ammonia-nitrogen concentration was nearly completely removed between influent and effluent for both pulsed and constant flows. This was perhaps due to volatilization instead of algal uptake. Lanes with pulsed flow showed a decrease in phosphate concentration, while lanes with constant flow showed an increase in phosphate concentration.
Crayfish occupancy in Response to Hydrologic Regime and Geomorphology in Ozark Streams
REU Student: Ms. Allyson Yarra
Project Mentor: Dr. Daniel D. Magoulick
Project Supervisor: Ms. Lindsey A. Bruckerhoff
Crayfish are a keystone species and play a number of roles in a stream ecosystem. Crayfish are known to show a high level of endemism and are highly susceptible to habitat degradation. Each summer in the Ozark region in northwest Arkansas and southwest Missouri, a number of streams experience drying. This student sought to determine if crayfish occupancy is impacted by hydrologic regime (i.e., consistent groundwater-fed streams vs. intermittent streams that dry in summer). Program PRESENCE 6.4 was used to relate crayfish occupancy to hydrologic regime and other covariates. Preliminary analysis indicated that the most important covariates for crayfish occupancy are water depth (> 12 cm) and current velocity (< .20 m/s) (i.e., crayfish occupancy is higher when velocity is higher and water is deeper). Substrate composition, hydrologic regime, and Rapid Habitat Assessment scores also impacted crayfish occupancy. Since flow permanence appears to be crucial for crayfish, appropriate water resource management should ensue to promote the well-being of aquatic biota in the Ozark region.