The effect of temperature, substrate concentration and water content on carbon recovery and end-points in biofiltration
This biofiltration study investigated the fate of carbon as influenced by temperature, water tension and pollutant concentrations. Soil biofilters degrading toluene were operated with no supplemental nutrient addition. Rigorous control of inlet concentrations, temperature and water tensions were maintained in a differential biofilter. Temperature experiments were conducted at 20 ᵒC, 30 ᵒC and 40 ᵒC and water tension was varied between 10 cmH2O, 20 cmH2O and 100 cmH2O. In addition, biofilms of Pseudomonas putida was also investigated at similar conditions. Carbon endpoints were tracked as CO₂ , total carbon in the liquid/solid phase and microscopic studies looked at polysaccharide production. Overall carbon balances averaged 111 % ± 9 % with the total carbon of the solid phase contributing the most to the uncertainty. Temperature and residual toluene had the strongest impact on the percentage of degraded toluene that was completely mineralized to CO₂ with higher temperatures and lower residual toluene giving the highest percentage mineralisation ranging from ~25 % to 92 %. Differential staining confirmed that the majority of the non-mineralised toluene was deposited in the soil as polysaccharides. This polysaccharide production would potentially contribute to biofiltration pressure drop increases over time.