Effective removing of rotifer contamination in microalgal lab-scale raceway ponds by light-induced phototaxis coupled with high-voltage pulse electroshock

Rotifer reproduction control in open microalgae cultivation systems poses a significant challenge for large-scale industries. Conventional methods, such as electric, meshing, and chemical techniques, are often expensive, ineffective, and may have adverse environmental -health impacts. This study investigated a promising control technique through light -induced phototaxis to concentrate rotifers in a specific spot, where they were electroshocked by local -limited exposure dose. The results showed that the rotifers had the most pronounced positive and negative phototropism with phototaxis rates of 66.7 % and -78.8 %, respectively, at blue -light irradiation of 30 mu mol center dot m- 2 center dot s- 1 and red-light irradiation of 22.5 mu mol center dot m- 2 center dot s- 1 for 20 min. The most effective electroshock configuration employed 1200 V/cm for 15 min with a 1 -second cycle time and a 10 % duty cycle, resulting in a 75.0 % rotifer removal rate without impacting microalgae growth. The combination of the two light beams could effectively lead rotifers to designated areas where they were electrocuted successfully.