Biomass and pigments production in photosynthetic bacteria wastewater treatment: Effects of photoperiod

• Different photoperiods were used for the cultivation of PSB.
• PSB showed the highest biomass production and COD removal with light/dark of 2 h/1 h.
• PSB showed higher biomass production and biomass yield with higher light frequency.
• Pigments contents were much higher with low light frequency of 2–4 times/d.

This study aimed at enhancing the bacterial biomass and pigments production in together with pollution removal in photosynthetic bacteria (PSB) wastewater treatment via using different photoperiods. 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.

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