DOI: https://doi.org/10.15368/theses.2019.112
Available at: https://digitalcommons.calpoly.edu/theses/2092
Date of Award
10-2019
Degree Name
MS in Civil and Environmental Engineering
Department/Program
Civil and Environmental Engineering
College
College of Engineering
Advisor
Nirupam Pal
Advisor Department
Civil and Environmental Engineering
Advisor College
College of Engineering
Abstract
Nitrogen pollution is a growing problem that is detrimental to the environment and the economy. Traditional treatment of nitrogen is a multi-stage process, expensive, operationally intensive, and requires large land areas. This research studied the effects of BiOWiSH® Aqua (Aqua), a biological enhancement product, on the simultaneous nitrification and denitrification process in a membrane aerated bioreactor (MABR) to determine if it is a feasible application for wastewater treatment. The MABR used during experimentation was a small-scale batch reactor with a continuous flow of air through a silicone membrane.
The effect of carbon source and concentration on nitrogen removal rates and biomass growth/behavior were determined through a series of laboratory experiments with Aqua and wastewater. With glucose and solely Aqua cultures, average reduction rates in nitrogen concentrations were 1.2 mg-N/L/hour for all C:N ratios investigated. When wastewater was used as the main carbon source, creating a mix of wastewater and Aqua bacteria in the MABR, average reduction rates were 10.9 mg-N/L/hour. A maximum reduction rate of 21.3 mg-N/L/hour occurred at a 2:1 C:N ratio.
This research concluded that pure Aqua cultures are not efficient at removing nitrogen or greatly augment the nitrogen reduction process. MABRs can use the biochemical oxygen demand in wastewater as a useful/viable carbon source. High carbon to nitrogen ratios (C:N ratio of 30:1) did not result in faster nitrogen reduction rates but did experience rapid biofilm growth and death. This shows that high C:N ratios are not an efficient operationally for MABRs due to the excess sludge created. C:N ratios of v approximately 3:1 provided the most consistent nitrogen reduction for both glucose and wastewater. This research concluded that C:N ratios, pH, and oxygen diffusion heavily affect the MABR’s performance. In addition, MABRs can utilize low C:N ratios during treatment, particularly during the treatment of high-strength wastewater.