Date of Award
Wastewater treatment and disposal is an integral part of mining operations. Water must be carefully managed to prevent waterborne contaminants from entering the surrounding environment. Mining companies rely on regulatory compliance and social acceptance to continue operations. The Stillwater Mining Company operates two underground mines in southern Montana, the Stillwater Mine and the East Boulder Mine, to extract platinum group metals from the J-M Reef geological formation. The East Boulder Mine operates an on-site wastewater treatment plant to remove waterborne contaminants from the water pumped to the surface from the underground mining operations. The main contaminant of concern at the East Boulder Mine is nitrate. The nitrate is a residue of blasting operations and is highly soluble in water. This thesis research focuses on analyzing the current nitrogen removal efficiencies by the wastewater treatment operations to identify abnormalities and recommend operational adjustments to remedy atypical results.
The nitrogen removal efficiencies were investigated using weekly wastewater treatment plant samples conducted for compliance purposes. The examination of this data identified anomalies in the nitrification and denitrification treatment processes. The initial denitrification treatment was found to have increasing ammonium concentrations in the effluent. This ammonium increase is unexpected and the cause is cannot be identified with the currently available data. A second anomaly from the data analysis is the difference in treatment performance between the two Moving Bed Biofilm Reactors (MBBRs). The Moving Bed Biofilm Reactors utilize nitrification and denitrification treatment cells to remove forms of nitrogen from the wastewater. The two systems are identical, yet one MBBR averages 2.8 times greater Total Kjehdahl Nitrogen effluent concentrations than its counterpart. This finding warrants further investigation into possible differences in aeration and mixing rates in the reactors. Treatment modeling of the existing treatment system was attempted to understand these abnormalities but could not be executed with the available data.
This research identified gaps in sampling methods, monitoring capabilities, and sample analysis. These gaps could be easily remedied with relatively low costs. The additional data gained by implementing the recommendations could provide enough additional data to better troubleshoot the treatment abnormalities identified by this research.
Greyn, Courtney, "Nitrogen Removal in Biological Wastewater Treatment Plant" (2015). Graduate Theses & Non-Theses. 23.