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

ABSTRACT

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 ${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$ 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 ${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$ removal and protein content fitted the Boltzmann equation, and the ${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$ 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) ${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$ removal was positively related with the content of protein and pigments.

GRAPHICAL ABSTRACT

KEYWORDS:

• Photosynthetic bacteria
• lactic acid wastewater
• ${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$ removal
• protein
• pigment

Acknowledgements

Authors are thankful for financial support from the Key Research and Development Plan of Shandong Province (No. 2017CXGC1005).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Authors are thankful for financial support from the Key Research and Development Plan of Shandong Province [grant number 2017CXGC1005].