Lactic acid wastewater treatment by photosynthetic bacteria and simultaneous production of protein and pigments.

Photosynthetic bacteria (PSB) can be used in wastewater treatment to simultaneously remove pollutants and produce valuable biomass. In this study, PSB were used to treat lactic acid wastewater and produce high-value substances (protein, carotenoid and bacteriochlorophyll). The results showed that the PSB biomass increase, COD and NH4+-N removal reached 55%, 89% and 94% in 5 days, respectively. The protein content, carotenoid and bacteriochlorophyll concentrations reached 69.1%, 2.3 and 0.8 mg/L, respectively. Furthermore, kinetic analysis showed that both NH4+-N removal and protein content fitted the Boltzmann equation, and the NH4+-N removal was positively related with the content of protein and concentration of pigments. This novel wastewater treatment method can adapt to the changes of light-oxygen condition, F/M and pH conditions.Highlights(1) PSB effectively treated real lactic acid wastewater with zero excess sludge.(2) 69% of protein and 2.3 mg/L of carotenoid were produced in the process.(3) NH4+-N removal was positively related with the content of protein and pigments.