Feasibility study and process optimization of citric acid wastewater treatment and biomass production by photosynthetic bacteria

Abstract

A B S T R A C TUsing photosynthetic bacteria (PSB) in wastewater treatment could not only eliminate environmental pollutants, but also recycle bacteria biomass. This paper studied the feasibility of using PSB in citric acid wastewater treatment. Some important factors which influence the pollutants removal efficiency and biomass were also examined to determine the optimal conditions. The results showed that PSB could effectively remove pollutants, and biomass production was also achieved. The optimal conditions were initial pH at 7.0, ratio of carbon/nitrogen at 10, initial chemical oxygen demand (COD) of 2,400 mg/L, natural lightmicro aerobic condition, and hydraulic retention time of 40 h. Under these conditions, the removal rate of COD and the biomass could reach 89.4% and 2,250 mg/L, respectively, and the biomass yield was 0.76 mg -biomass /mg -COD-removal . By process evaluation, compared with anaerobic wastewater treatments, this process had better effluent quality and simpler process, compared with aerobic wastewater treatment, this process had the advantage of biomass recovery.

Valorization of volatile fatty acids from the dark fermentation waste Streams-A promising pathway for a biorefinery concept

“…A review by Show et al [282] summarized the types of organic wastes that can be used in citric acid fermentation. During the downstream process, the spent medium can be incorporated into a biorefinery framework and be used in the synthesis of other valuable bioproducts such as biomethane [285] and biohydrogen [286,287]. Alternatively, the effluents from other bioprocesses can be used in citric acid production [288].…”

Purple phototrophic bacteria are outcompeted by aerobic heterotrophs in the presence of oxygen

“…Nevertheless, a number of articles have suggested that photoheterotrophic growth occurred under illuminated, microaerobic (0.5-1.0 mg DO•L -1 ; dissolved oxygen), and even aerobic conditions (2.0-8.0 mg DO•L -1 ). This was suggested by either directly claiming that photophosphorylation occurred in the presence of oxygen (Meng et al, 2017;Peng et al, 2018), by reporting optimal PPB growth conditions under simultaneous light and oxygen supply (Lu et al, 2019a;Yang et al, 2018c;Zhou et al, 2016Zhou et al, , 2015 or by reporting effective carotenoid and BChl synthesis under aerobic conditions (Lu et al, 2019a;Meng et al, 2020Meng et al, , 2017Yang et al, 2018b;Zhi et al, 2020). Conversely, previous studies from the same research group reported oxidative phosphorylation as main ATP generation process in the presence of oxygen, which inherently points towards aerobic chemoheterotrophy, rather than photoheterotrophy (Lu et al, 2013(Lu et al, , 2011a(Lu et al, , 2011bWang et al, 2016).…”

Pathways to Water Sector Decarbonization, Carbon Capture and Utilization

“…PPB photobioreactors for treatment of polluted effluents is an emerging technology. Most of the reported experiences are batch cultures performed in enclosed photobioreactors under artificial infrared illumination (Budiman et al, 2014;Choorit et al, 2002;Madukasi & Zhang, 2010;Zhou et al, 2016). Domestic, agro-industrial and industrial wastewaters have been treated in PPB photobioreactors under laboratory-controlled conditions (Puyol et al, 2020).…”