Biofiltration of wastewater liftstation emissions: A comparison and evaluation of VOC removals with two field scale unit designs.

摘要

Biological treatment is an emerging technology for the treatment of emissions from wastewater lift stations. Lift stations pump domestic and industrial wastewater to wastewater treatment plant and in the process, due to anaerobic decomposition, gases like hydrogen sulfide (H2S) and existing volatile organic compounds (VOCs) are emitted to the atmosphere. In one of the lift stations in Brownsville, South Texas, these gases are captured and treated in the existing open biofilter and engineered biofilter (Biotrickling filter coupled with biofilter). The engineered biofilter is an enclosed system with plastic hollow spherical balls filled with mixture of compost in the biofilter section and structured packing in the biotrickling filter section. The open biofilter was a traditional in-ground biofilter filled with wood chips and compost. The hypothesis in this research is that the engineered biofilter (biotrickling filter coupled with biofilter) would perform more effectively than traditional in-ground biofilters in treating low concentration VOC emissions, in the presence of high concentrations of H2S gas. In addition, the effect of H2S concentration and the pH of the media on the VOC removal efficiency of the two biofilters were also studied. Samples were collected in canisters over a period of four months and were analyzed in the laboratory using GC/MS. The characterization of the gases indicated the presence of a varied mixture of VOCs, the most significant being toluene. The VOC removal efficiency of the two biofilters was similar, but the elimination capacity of the engineered biofilter is significantly higher than the traditional open biofilter. Furthermore, the presence of high concentration H2S did not inhibit the VOC removal in the biofilter section of the engineered system exhibiting high removal efficiency at very acidic pH.