Available at: https://digitalcommons.calpoly.edu/theses/2982
Date of Award
6-2023
Degree Name
MS in Civil and Environmental Engineering
Department/Program
Civil and Environmental Engineering
College
College of Engineering
Advisor
Tryg Lundquist
Advisor Department
Civil and Environmental Engineering
Advisor College
College of Engineering
Abstract
Removal of nutrients, especially nitrogen, from wastewater helps to protect public health and the environment from nutrient pollution but traditional methods can be a major draw on municipal energy consumption. Raceway ponds utilizing the chemically symbiotic relationship between algae and bacteria are capable of reducing the energy consumption of nutrient removal compared to traditional treatment methods. However, both conventional and algal-bacterial pond systems see reduced nitrogen removal in the winter months. Past laboratory work has attempted to determine the factors that might be implemented to improve nitrogen removal in raceways when these conditions occur, however, there is a need for outdoor pilot-scale research on the subject to more accurately represent field conditions. Predicting the nitrogen removal rates in raceway ponds treating wastewater is complex since nutrient removal with biological systems is dependent on a plethora of environmental conditions being optimal for the organisms. Therefore, this study aimed to investigate several key variables that could improve nitrogen removal rates and create a mathematical model for predicting removal at pilot-scale. Pilot scale ponds (1000-L) were operated with a single varied operational condition including hydraulic retention time, solids retention time, dissolved oxygen concentrations and water temperature. Pond conditions such as pH and other water quality constituents were monitored and analyzed as well. The complete set of data was used to train a multi-variate linear regression model capable of predicting Total Ammonia Nitrogen (TAN) removal rate that was dependent on hydraulic retention time (HRT), minimum dissolved oxygen concentrations, and influent TAN concentration (R2=0.771). The experiments also indicated that the optimal range of volatile suspended solids concentration was between 400 – 800 mg/L. Finally, reducing the hydraulic retention time to 8-days allowed for year-round ammonia removal to less than 5 mg/L. Identification of these potential operating conditions for improving nitrogen removal from wastewater can provide a basis for further research to improve full-scale pond treatment systems.
Included in
Environmental Chemistry Commons, Environmental Engineering Commons, Other Civil and Environmental Engineering Commons