BIOREACTOR DESIGN EFFECTS ON BIODEGRADATION CAPABILITIES OF VOCS IN WASTE-WATER

Volatile organic chemicals are a wastewater pollution problem that can be handled by ultrafiltration, stripping, or biodegradation. Ultrafiltration and stripping transfer the dissolved organics to another phase which should then be further treated to finally destroy or utilize the organic chemicals. Biodegradation, on the other hand, converts the water soluble molecules to bio-molecules which can then be separated or directly discharged. Biodegradation of aromatic chemicals requires air and tests have conclusively shown that traditional biodegradation designs result in VOC stripping losses to the air stream rather than biodegradation. Computer models and experimental data are presented comparing batch (plug flow), CSTR and packed bed bioreactor designs for their abilities to degrade VOC chemicals. Batch or plug flow reactors are shown to be a very poor method for biodegradation. CSTRs work well but require a large process residence time. A new packed bed column bioreactor will be shown to provide much faster biodegradation and still minimize air stripping losses. Mass transfer and fluid mechanic parameters have been measured with and without biomass and compared to traditional chemical engineering correlations. The packed column minimizes the demand for air flow while increasing the throughput rate of wastewater as compared to a CSTR design. The efficiency of VOC biodegradation will be seen to be greatly improved.