Fungal Based Treatment for Nitrogen and Phosphorus Decrease in Wastewater

Biological nutrient removal (BNR) technology can suffer poor performance or complete failure due to the fastidious nature of the bacteria used in the system. The bacteria involved necessitate strict operating conditions, multiple zones with one or more recycling lines, carbon source augmentation, and efficient aeration. For wastewater treatment plants receiving significant combined sewer overflows and industrial wastewater, maintaining a stable BNR system can be
costly and challenging.

Shoun et al (1991) demonstrated filamentous fungi also had a biochemical pathway to perform denitrification. Based on this discovery, Guest and Smith (2002) proposed that fungi have significant advantages over bacteria denitrifiers, including fungi have both biochemical pathways for nitrification and denitrification, higher rates of nitrification-denitrification, greater resistance to toxic-inhibitory compounds, lower oxygen and carbon source concentration requirements. Overall, it appeared that fungi could overcome several of problems associated with bacterial based BNR that could result in a simplification of process engineering and operation while improving upon carbon and nitrogen treatment. The primary objective of this research was to investigate and assess the potential for development of a fungal based nitrogen and phosphorus treatment system. This involved proving the hypothesis that fungi could perform denitrification in wastewater, and the development of understanding as to the basic factors affecting the process in an applied wastewater environment.

Fungi were isolated form the Gold Bar Wastewater Treatment Plant in Edmonton, Alberta, Canada. Five isolates were studied in 2L batch reactors using primary treated wastewater. A paired comparison block experimental design was employed to minimize the variation in wastewater, innoculum and culture conditions. Experiments were conducted with pure fungal culture strains in sterile wastewater medium to ensure only the fungal action was evaluated. Three oxygen tensions were created for testing, aerobic, microaerophilic and anoxic removal of nitrogen and phosphorus. Further experiments were conducted with fungi using attached growth medium (25 and 50 m2/m3) in a batch and fed-batch configuration. Batch reactors were sampled to give a change in parameters over time in order to establish the kinetic relationship and rate of fungal removal of nitrogen in wastewater. Parameters measured included: ammonia, nitrate, nitrite, total kjeldahl nitrogen (TKN), ortho-phosphate, chemical oxygen demand (COD) and solids analysis.

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