State Water Resources Research Institute Program


Project ID: 2012OK241B
Title: Impact of Wastewater Treatment Plant Effluent on Nitrogen Cycling by Stream Bacteria
Project Type: Research
Start Date: 3/ 1/2012
End Date: 2/28/2013
Congressional District: 2
Focus Categories: Nutrients, Wastewater, Hydrogeochemistry
Keywords: nitrogen cycle, bacteria, wastewater treatment plant effluent, antibiotics
Principal Investigators: Cisar, Cindy; Fisher, Johathan (Northeastern State University); Van Nostrand, Joy
Federal Funds: $ 25,000
Non-Federal Matching Funds: $ 50,557
Abstract: The objective of this project is to initiate an analysis of the effects of wastewater treatment plant (WWTP) effluent on nitrogen use by bacteria in Oklahoma streams. In addition to baseline information on nitrogen cycling, new information will be obtained on the effect(s) of antibiotics on stream bacteria. The PIs will include the preliminary data obtained from this study in a grant proposal to be submitted to the National Science Foundation.

Antibiotics are a common contaminant of WWTP effluent and have been detected in water downstream of the Tahlequah WWTP. Antibiotic resistant bacteria are more common in Tahlequah Creek sediments downstream of the plant than in upstream sediments indicating that the effluent has an impact on bacteria in this stream. Another common contaminant of WWTP effluent is ammonium (NH4+). Nitrogen (N) is both an essential nutrient and a potential pollutant in aquatic ecosystems. High concentrations of ammonium in a stream can lead to a decline in water quality and stream health. Last summer blue-green algal blooms occurred in several lakes in Oklahoma due in part to excessive nutrient levels. Many Oklahoma towns and cities including Tahlequah discharge large volumes of treated wastewater into small streams that feed into Oklahoma lakes and reservoirs. The ammonium and antibiotics in WWTP effluent are deposited in downstream sediments. The hypothesis that will be tested is that Tahlequah WWTP effluent affects nitrogen cycling by bacteria in downstream sediments. The experiments described below will provide information on the bacteria present in Tahlequah Creek sediments, the capacity of these bacteria to metabolize ammonium, and the effects of antibiotics on nitrogen cycling by stream bacteria. The results from this project will not only help to identify possible negative effects of the WWTP effluent on the environment, but will also increase our knowledge base on the effects of antibiotics on environmental bacteria and better understand the response of stream bacteria to WWTP effluent.

Experiments include 1. comparison of the bacterial species present in upstream and downstream sediments, 2. examination of the uptake and use of ammonium by downstream bacteria (in-stream and genetic studies), and 3. examination of the effect(s) of antibiotics on nitrogen use in stream bacteria. Bacterial populations in sediments upstream and downstream of the Tahlequah WWTP will be characterized and compared using DNA-based methods. Use and conversion of nitrogen in Tahlequah Creek will be characterized by adding ammonium chloride to the stream and then analyzing downstream water samples for ammonia, nitrite, nitrate, and total nitrogen. In addition, nitrogen metabolism by sediment bacteria upstream and downstream of the WWTP will be characterized using GeoChip microarrays. Microarrays are commonly used by scientists to learn about the capacity of cells to perform particular functions such as metabolize ammonium. Lastly, the effect of antibiotics on nitrogen use and conversion by sediment bacteria will be examined in the laboratory. Bacteria taken from upstream and downstream of the WWTP will be exposed to ammonium chloride and antibiotics that have been detected in Tahlequah Creek or nearby streams. Nitrogen conversion will be determined by analyzing water for ammonia, nitrite, nitrate, and total nitrogen similar to the stream study described above.

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