Effects of Fe2+ concentration on biomass accumulation and energy metabolism in photosynthetic bacteria wastewater treatment.

Photosynthetic bacteria (PSB) wastewater treatment has the advantage of biomass recovery in together with pollutant removal. The effects of different Fe(2+) concentrations on the biomass accumulation through regulating energy metabolism were investigated in PSB wastewater treatment. Results showed that the optimal Fe(2+) dosage was 20mg/L. Optimal Fe(2+) content could significantly increase the biomass production (4800.9 mg/L) and COD removal (93.4%). Addition of 10-30 mg/L Fe(2+) could shorten the hydraulic retention time of wastewater. Mechanism analyses revealed that different Fe(2+) concentrations had different impacting mechanisms on biomass accumulation. Fe(2+) constituted the dehydrogenase active center, and therefore proper addition of Fe(2+) could improve energy production by up-regulating dehydrogenase activity, which was beneficial for biomass accumulation. With 20mg/L Fe(2+), the dehydrogenase activity and ATP production of PSB were improved by 48.1% and 42.4%, respectively. However, excessive addition of Fe(2+) was harmful for biomass accumulation since the ions inhibited the dehydrogenase activity.