Advanced treatment of toluene emissions with a cutting-edge algal bacterial photo-bioreactor: Performance assessment in a circular economy perspective

A novel approach for the treatment of VOCs (by using toluene used as a model compound) and the simultaneous conversion of carbon dioxide into valuable biomass has been investigated by using a combination of an activated sludge moving bed bioreactor (MBBR) and an algal photo-bioreactor (PBR). The first unit (MBBR, R1) promoted toluene removal up to 99.9 % for inlet load (IL) of 119.91 g m−3 d−1. The CO2 resulting from the degradation of toluene was then fixed in PBR (R2), with a fixation rate up to 95.8 %. The CO2 uptake was promoted by algae, with average production of algal biomass in Stage VI of 1.3 g L−1 d−1. In the contest of the circular economy, alternative sources of nutrients have been assessed, using synthetic urban wastewater (UWW) and dairy wastewater (DWW) for liquid renewal. The produced biomass with DWW showed a high lipid content, with a maximum productivity of 450.25 mg of lipids L−1 d−1. The solution proposed may be thus regarded as a sustainable and profitable strategy for VOCs treatment in a circular economy perspective. [Display omitted] •A novel biotechnology was designed for gas cleaning and green energy production.•The combined system demonstrated Toluene removals>97 % for load of 24 g m−3 d−1.•The system allowed the mitigation of CO2 emissions (average removal yield of 65 %).•The integrated solution promoted the production of valuable biomass up to 1.3 g L−1 d−1.•The use of dairy wastewater as nutrient source increased algal biomass value.