Initial experiments on the application of ground penetrating radar to troubleshoot biofilters for air pollution control

Biofiltration is a biologically based technique for air pollution control. While biofilters are a major step forward for environmental protection, some problems such as heterogeneities in the packed bed exist. Ground penetrating radar (GPR) holds promise for the detection of heterogeneities in biofilters since EM responses are known to be a function of changes in the physical properties of the subsurface material. A GPR experiment was set-up to investigate an existing field biofilter located in Christchurch, New Zealand. The resulting GPR profiles (225 and 450 MHz) did image layering of the biofilter bed and revealed irregularities in the biofilter packing. At selected locations, local measurements of airflow rate were taken; high local airflow appeared to correlate with heterogeneous bed structure. The results from this initial experiment have revealed that GPR is a promising technique for the detection of heterogeneities within biofilters.