Performance, 5-aminolevulinic acid (ALA) yield and microbial population dynamics in a photobioreactor system treating soybean wastewater: Effect of hydraulic retention time (HRT) and organic loading rate (OLR)

• Effects of HRT and OLR on a photobioreactor performances were investigated.
• The highest biomass production of 2655 mg/L and ALA yield of 7.40 mg/g-biomass were achieved.
• HRT and OLR have important impacts on microbial dynamics.

Effects of hydraulic retention time (HRT) and influent organic loading rate (OLR) were investigated in a photobioreactor containing PNSB (Rhodobacter sphaeroides)-chemoheterotrophic bacteria to treat soybean wastewater. Pollutants removal, biomass production and ALA yield in different phases were investigated in together with functional microbial population dynamics. The results showed that proper HRT and OLR increased the photobioreactor performance including pollutants removal, biomass and ALA productions. 89.5% COD, 90.6% TN and 91.2% TP removals were achieved as well as the highest biomass production of 2655 mg/L and ALA yield of 7.40 mg/g-biomass under the optimal HRT of 60 h and OLR of 2.48 g/L/d. In addition, HRT and OLR have important impacts on PNSB and total bacteria dynamics.