Carbon dioxide infusion reduces invasive mussel biofouling (quagga mussel; Dreissena rostriformis bugensis) in raw water systems
The efficacy of carbon dioxide (CO 2 ) to reduce biofouling by quagga mussels ( Dreissena rostriformis bugensis ) in raw water systems was investigated. Experiments were conducted in a mobile laboratory located at Bureau of Reclamation Davis Dam Hydropower Facility and supplied with raw water from Lake Mohave, a reservoir of the Colorado River, USA. Incoming water was split between five chambers, each infused with CO 2 at a different rate. Raw reservoir water containing quagga larvae (veligers) was mixed with CO 2 chamber outflows and delivered to tanks containing settlement plates. Two experiments were conducted. Experiment 1 tested continuous infusion at target concentrations of 30, 45, 60, 75, and 100 mg L -1 dCO 2 (dissolved CO 2 ). Experiment 2 evaluated intermittent infusion schedules: 24 h on/off with 50, 75, and 100 mg L -1 dCO 2 and 24 h once/week with 100 mg L -1 dCO 2 . In Experiment 1, the percent settlement decreased with mean CO 2 concentration, ranging from 5.0% to < 0.1% in 28.7 and 92.2 mg L -1 dCO 2 , respectively. In Experiment 2, the efficacy of 24 h on/off at dCO 2 > 72.2 mg L -1 was similar to continuous treatment. The least effective treatment was 24 h once weekly at 95 mg L -1 dCO 2 . These results demonstrate that CO 2 treatment may reduce mussel biofouling in raw water systems.