Adrian Beirise, who is working on a master's degree in biological engineering, won the Graduate Poster Competition at the annual Institute of Biological Engineering meeting in Greenville, South Carolina. The title of his poster was, "Evaluating a Measure-Calculate Method for Determining Sediment Oxygen Demand." Beirise's adviser is Scott Osborn, associate professor of biological and agricultural engineering.

"Adrian has done a thorough job and I'm proud of him and happy to see him recognized on a national level," said Osborn. "The research he is doing is difficult and makes an important contribution to improving the health of our water and of the aquatic environment."

Beirise's poster presented his research on water quality. One important aspect of water quality in streams and lakes is the amount of oxygen that is available not only for the fish that live in the water, but for biological and chemical processes that determine the quality of the water. When water is polluted with excess nutrients like nitrogen and phosphorus, this encourages the growth of phytoplankton such as algae, which will eventually die, settle into sediment and decompose. During the process of decomposition, bacteria consume oxygen from the water, leaving less available for other aquatic life and causing chemical changes that lead to dissolved iron, manganese and phosphorus in the water that can harm quality.

In order to correct this problem, engineers must first measure all the factors that affect the amount of oxygen in the water. In addition to plant life and bacteria in the water, the sediment at the lake bottom is a major consumer of oxygen. Currently, measuring the amount of oxygen absorbed by the lake sediment is a complicated, time consuming and expensive procedure, and it is prone to error. Beirise has been testing a simpler method that has been used in streams to determine if it can be effective in lakes.

One existing method for calculating the oxygen demand of sediment is called the intact core incubation method. With this method, researchers collect sediment and water from a lake in a clear plastic cylinder. This sample is called a core. In the lab, they pump a slow, continuous feed of water into one side of the bottom of the sealed cylinder, and they release water from the top side. By measuring the difference in the amount of oxygen dissolved in the entering water and the amount of oxygen dissolved in the exit water, researchers can determine how much oxygen is absorbed by the sediment.

This method takes a large investment of time and equipment, and because it takes place in the lab, it cannot account for all of the conditions in the lake. For example, the water in the core is not flowing over the sediment as it might in a natural body of water.

Beirise is testing a method called the measure-calculate method, which solves these issues, but has not been proven in lakes. The measure-calculate method relies on math and on established rules of physics to calculate the oxygen demand from simpler measurements than required of the core method.

Osborn, whose company, BlueInGreen, specializes in using dissolved oxygen to improve water quality, helped develop the method as a way of determining how much oxygen must be added to a body of water to restore it. It involves an equation that takes inputs, such as the temperature of the water, the speed that the water is moving, the amount of oxygen in the water, and the density and porosity of the sediment. Researchers using the method must also determine how many grams of oxygen per cubic meter of sediment could be absorbed per day, or the volumetric uptake rate of the sediment. By putting these numbers into the equation, researchers should be able to predict how much oxygen is being absorbed by the sediment in the given circumstances and as inputs change throughout the year.

Beirise took samples and measurements from three lakes—Lake Fayetteville and Lake Wedington in Northwest Arkansas, and Lake Wister in Oklahoma. He used both methods to determine sediment oxygen demand, and compared the results. He concluded that the measure-calculate method was comparable to the intact core incubation method, but more research is needed to ensure that the results are as accurate as possible.

"The challenge is that we don't know a way to determine sediment oxygen demand with 100 percent accuracy, so it is difficult to determine if the new method is accurate," he explained. "There are accepted methods, but none of them are perfect. They are the best measurement."

When he finishes his master's degree, Beirise plans to work in water resources engineering.