Different light/dark cycles and light/dark cycle frequencies were examined. Results showed that PSB
had the highest biomass production, COD removal and biomass yield, and light energy efficiency with
light/dark cycle of 2 h/1 h. The corresponding biomass, COD removal and biomass yield reached
2068 mg/L, 90.3%, and 0.38 mg-biomass/mg-COD-removal, respectively. PSB showed higher biomass production
and biomass yield with higher light/dark cycle frequency. Mechanism analysis showed within a
light/dark cycle from 1 h/2 h to 2 h/1 h, the carotenoid and bacteriochlorophyll production increased with
an increase in light/dark cycle. Moreover, the pigment contents were much higher with lower frequency
of 2–4 times/d.