Date of Graduation


Document Type


Degree Name

Bachelor of Science in Civil Engineering

Degree Level



Civil Engineering


Zhang, Wen

Committee Member/Reader

Williams, Rodney D.

Committee Member/Second Reader

Edwards, Findaly G


The discharge of nutrients (such as nitrogen and phosphorus) from wastewater treatment plants (WWTP) has become an increasingly important issue in the United States. Ammonia (NH3) is a common contaminant found in domestic wastewater and agricultural runoff. It can cause toxicity in fish if left untreated. The United States Environmental Protection Agency (EPA) recommends low national criteria for ammonia limits in freshwater. With these greater restrictions, ammonia-nitrogen limit compliance (5 mg/L) has become an issue at the Massard WWTP in Fort Smith, Arkansas. The purpose of this research is to assess the ammonia removal in the Massard WWTP in order to improve the ammonia-nitrogen removal in the future. This purpose led to the testing of Nitrosomonas europaea in monitored wastewater samples. The addition of N. europaea in the wastewater did not result in improved ammonia removal, indicating inhibitions were present. When analyzing the activated sludge and trickling filter biomass using fluorescence in situ hybridization (FISH) and polymerase chain reaction (PCR), indigenous nitrifiers were found present, though not in great quantity. Future studies are needed to determine the identity of the nitrifying-inhibiting factors.