Bench-scale assessment of three copper-based algaecide products for cyanobacteria management in source water

Abstract

AbstractThree copper-based algaecide products were investigated for use in a drinking water source to address cyanobacteria growth. Bench-scale experiments were used to determine the optimal dose of each product given Lake Rockwell’s indigenous population and reservoir-specific characteristics. The optimal dose of Cutrine Ultra was determined to be a quarter dose (corresponding to 0.125 mg/L Cu) as it decreased 55% of the cyanobacteria population with limited release of microcystin and minimal rebound in the cyanobacteria population. The optimal dose for EarthTec was determined to be a half dose (i.e., 0.5 mg/L). The full dose was optimal for SeClear (1 mg/L Cu). The optimal doses had extracellular microcystin levels of 0.99 ± 0.09 µg/L (quarter dose Cutrine Ultra), 3.69 ± 0.43 µg/L (half dose EarthTec) and 0.92 ± 0.26 µg/L (full dose SeClear) by day 2. EarthTec and Cutrine Ultra facilitated a similar overall response, and the cyanobacteria population was predominately suppressed in the initial 2 days following treatment and then increased between 7 and 14 days after treatment (i.e., rebound). Both the suppression within the first 2 days and the rebound between 7 and 14 days after treatment were a function of dose (e.g., lower dose, larger increase in rebound). Although SeClear suppressed the cyanobacteria population during the initial 2 days after treatment (42,000 ± 3240 cells/mL at the baseline to 4822 ± 841), the cyanobacteria population rebounded significantly (p < 0.05) between 2 and 7 days after treatment.