A Test of the Effects of Lime on Algal Biomass and Total Phosphorus Concentrations in Edmonton Stormwater Retention Lakes

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Abstract
Lime, calcium carbonate and/or calcium hydroxide were added eight times to three stormwater retention lakes in Edmonton from June to August 1988. The goal was to evaluate short-term effects of lime on algal biomass and phosphorus concentrations in rapidly-flushed systems – those designed with a water retention period of 0.25 to 0.5 yr. Most of the water flow occurs from May to September and varies greatly depending on annual precipitation. These lakes also provided an opportunity to evaluate lime treatment effects on hardwater lakes with unusually high sulfate and calcium concentrations (average summer concentrations were 334 and 65 mg/L, respectively). Within one week of applying at least 50 mg/L calcium hydroxide with or without calcium carbonate, chlorophyll a (used to estimate algal biomass) and total phosphorus concentrations decreased significantly (P < 0.05). In the lake treated solely with calcium carbonate (in doses of 50 and 100 mg/L), neither total phosphorous nor chlorophyll a decreased significantly (P > 0.05). Test results for lime controlling phosphorus levels and algal biomass in rapidly-flushed lake systems are promising.