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This study involved the evaluation of time-series relationships between chlorophyll-a (chl-a), dissolved oxygen (DO), and pH in three facultative wastewater stabilization ponds (WSPs) operated in series at a wastewater treatment plant in eastern Ontario, Canada.

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This study involved the evaluation of algae and macrophyte species distributions in three wastewater stabilization ponds (WSPs) at a wastewater treatment plant in Ontario, Canada, which has experienced high pH levels at the final effluent and excessive algae growth during the summer since 2003. From samples collected from the system, the relative abundances of specific algae and aquatic plant (macrophyte) taxa were assessed and correlated to water chemistry data. A strong shift from the dominance of green algae, chlorophyceae, in WSP#2, to the dominance of aquatic macrophytes, embryophyta, in WSP#4, was observed and corresponded to field observations. Correlation of the abundances to nutrient parameters suggested that the macronutrient rich conditions in WSP#2 allowed floating green algae to proliferate against macrophytes. In WSP#1 and WSP#4, macrophytes competed against algae and thrived, due to their adaptability to lower nutrient conditions. The pH increases occurred primarily in WSP#2 and were not buffered or reduced in WSP#1 and WSP#4. Two alternatives strategies for pH control were recommended for the system: decreasing algae growth in WSP#2 through duckweed OPEN ACCESSWater 2015, 7 3226 seeding or macronutrient loading reduction; or designing and implementing a constructed wetland (CW) in WSP#4 with soil and vegetation to buffer pH prior to release.