Foam flotation can remove and eradicate ciliates contaminating algae culture systems

Abstract We demonstrate, for the first time, the efficacy of a surfactant-aided foam flotation system to remove and eradicate ciliates contaminating microalgae cultures. Using sodium dodecyl sulphate (SDS) as the surfactant, ciliates removal efficiencies of up to 86.6% were achieved from pure ciliates cultures at an SDS concentration of 40 mg L − 1 . At this concentration the majority of ciliates were lysed due to increase in SDS concentration in the collected foamate. The removal efficiency decreased to 55.0% in mixed algae-ciliates cultures however, this was compensated by employing a multistage flotation and SDS (50 mg L − 1 ) reuse strategy that achieved removal efficiencies of 96.3%, lysing all collected ciliates, but not affecting microalgae growth. The chemicals cost for the process was US$ 0.0025 per m 3 substantially less than comparator treatments. Building upon its applications in biomass dewatering, pre-processing and sterilising, we add metazoan contamination control to the utilitarian properties of foam flotation for the microalgae biotechnology sector.