Investigating the effect of algal blooms on water quality in passive wastewater treatment systems
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Wastewater stabilization ponds (WSPs) are low-cost, effective and sustainable passive wastewater treatment technologies. However, algal blooms may occur in WSPs under certain conditions, affecting the complex interactions between water quality parameters. This thesis is an investigation on the effect of algal blooms on water quality and treatment performance of a WSP located in a temperate climate. Studies were conducted at a WSP located in southeastern Ontario, experiencing reoccurring excessive algal growth and pH fluctuations, exceeding government regulatory limits. A full range of water quality parameters were monitored for the system and the biochemical dynamics in the WSPs were assessed through multivariate statistical analysis. One study was conducted to provide an enhanced understanding of the relationships between algal blooms, water quality and meteorological factors. Water temperature, pH, DO and NO3- were determined to be the most significant parameters describing the spatial variations in surface algal blooms. A second study examined the seasonal disinfection performance using Escherichia coli, and three novel bacterial indicators, Enterococci, Clostridium perfringens and total coliforms, in the presence and absence of the previously studied algal blooms. Temperature, pH and DO were shown to be significant (p<0.05) factors in disinfection. A long-term assessment of seasonal fluctuations in treatment performance and water quality was also performed. Removal efficiency of nutrients and bacteria were observed to have strong seasonal fluctuations and water temperature, pH, DO and TP accounted for majority of the temporal variations observed in water quality. This research provides practical knowledge and uncovering key trends and factors involved in algal bloom dynamics and treatment performance, contributing to the continued improvement of WSPs design and performance in temperate climates.