The impact of environmental parameters on the conversion of toluene to CO2 and extracellular polymeric substances in a differential soil biofilter.

Abstract

The fraction of pollutant converted to CO2 versus biomass in biofiltration influences the process efficacy and the lifetime of the bed due to pressure drop increases. This work determined the relative quantitative importance and potential interactions between three critical environmental parameters: toluene concentration (Tol), matric potential (ψ) and temperature (T) on % CO2, elimination capacity (EC) and the production rate of non-CO2 products. These parameters are the most variable in typical biofilter operation. The data was fit to a non-linear model of the form y=a(Tol)bTcψd. A rigorous carbon balance (100.5\u202f±\u202f7.0%) tracked the fate of degraded toluene as CO2 and non-CO2 carbon endpoints. The % CO2 mineralization varied from (34-91%) with environmental parameters: temperature (20-40\u202f°C), matric potential, (-10 to\xa0-100 cmH2O) and residual toluene, (20-180\u202fppm). The highest conversion to CO2 was at the wettest conditions (-10 cmH2O) and lowest residual toluene concentration (18\u202fppm). Matric potential had twice the impact of toluene concentration on % CO2, while temperature had less impact. The elimination capacity varied from 11 to 50 gC⋅m-3h-1 and was highest at 40\u202f°C, the wettest conditions with limited impact by toluene concentrations. Temperature increased the EC and non-CO2 production rates strongly while matric potential and toluene concentration had less influence (4x - 10x less). This study illustrated the quantitative significance and simultaneous interaction between critical environmental parameters on carbon endpoints and biofilter performance. This kind of multivariable parameter study provides valuable insights which can address performance and clogging issues in biofilters.