Doctor of Philosophy (PhD)


Oceanography and Coastal Sciences

Document Type



active compounds (PhACs) have been detected in the aquatic environment as a result of loading from various sources. In Louisiana, USA, many municipalities treat wastewater using natural systems, such as lagoons and wetlands, rather than using conventional wastewater treatment technologies and may discharge PhACs into the environment. These treatment systems are not designed to remove PhACs from wastewater, nor is it currently a regulatory requirement. Research on the fate of PhACs in the environment is needed to understand impacts on Louisiana’s important coastal system. Wastewater sampling for PhACs at the Mandeville, LA wastewater treatment plant (WWTP) determined that this system significantly reduces the concentrations of PhACs prior to discharge into the environment. Most of the concentration reduction occurred in the first phase of treatment, where research suggests sorption may have been the major removal pathway. A wetland soil similar to the forested wetland at the Mandeville WWTP was tested for sorption and desorption of ciprofloxacin, ofloxacin and norfloxacin. Two HPLC methods were developed for compound analyses in this experiment. It was determined that sorption to wetland soil is a major and potentially long-term removal pathway for these pharmaceutical compounds from wastewater. The presence of antibiotics in the environment may have the ability to alter the microbial community in soils. We observed the greatest effect of antibiotics on soil microbial respiration followed this trend: sulfamethoxazole>ciprofloxacin>tetracycline. Most antibiotic effects were seen in the mineral, not the peat soil. Suppression of microbial respiration was observed, at low or high concentrations, depending on the antibiotic and soil examined. This result indicates that antibiotics can have negative impacts on microbial functions in treatment wetlands at “environmentally relevant” concentrations. Based on the findings of these studies, WWTPs systems similar to the Mandeville plant are effective at reducing the concentrations of many PhACs discharged into surface waters. Furthermore, sorption appears to be a major pathway for this concentration reduction. However, antibiotics showed the potential to exhibit a negative influence on microbial activity in wetland soil. These natural treatment systems appear to be ideal for effectively treating PhACs in surface waters.



Document Availability at the Time of Submission

Student has submitted appropriate documentation to restrict access to LSU for 365 days after which the document will be released for worldwide access.

Committee Chair

White, John R