Comparative Evaluation of a Biotrickling Filter and a Tubular Photobioreactor for the Continuous Abatement of Toluene

摘要

Volatile Organic Compounds (VOCs) are among the gas pollutants with a higher detrimental impact on humanhealth and the environment. The increasing awareness of the population on the importance of air quality andthe enforcement of stricter environmental regulations regarding the anthropogenic emissions of thesehazardous pollutants have triggered the development of cost-efficient, environmentally friendly off-gastreatment technologies. Biological technologies such as biotrickling filters have been consistently proven aswell stablished technologies for the treatment of VOC emissions, although the low solubility of oxygen mightlimit the aerobic degradation when treating high concentrations of VOCs. In this context, the synergic effectsbetween microalgae and bacteria represent a sustainable platform to promote the simultaneous abatement ofVOCs and CO2 by increasing the dissolved oxygen concentration as a result of the photosynthetic process. Inthis study, a conventional biotrickling filter (BTF) and an innovative tubular photobioreactor (TPBR) inoculatedwith a microalgal-bacterial consortium, and interconnected to an external absorption, column werecomparatively evaluated for toluene removal. Operating parameters such as the gas residence time (GRT)and the mineral salt medium renewal rate were optimized in order to boost toluene removal. In this sense,both bioreactors were capable of achieving removals > 85 % at a GRT of 45 s and a medium renewal rate of800 mL d~(-1). Maximum toluene elimination capacities of ～21 g m~(-3) h~(-1) were recorded in both the BTF and theTPBR. Despite the satisfactory performance of both systems, the photobioreactor presented a competitiveadvantage due to the capacity of algal biomass to fix the produced CO_2, considerably reducing the emissionsof this greenhouse gas, while increasing the concentration of dissolved oxygen in the cultivation broth up to7.7 mg O_2 L~(-1).