Feasibility Testing of a Pilot-Scale Two-Stage Biofiltration Unit for Mitigating VOC Emissions from a Wastewater Sump

摘要

Volatile organic compounds(VOCs)present in crude oil can be released to the atmosphere from storage tanks,wastewaters and equipment leaks in petroleum industries.A pilot-scale sequential biotricklingbiofiltration(BTF-BF)unit as an environmentally safe and economical treatment procedure was designed and tested for removal of VOCs from a wastewater sump at the CITGO Corpus Christi Refinery.To identify and quantify VOC emissions from the refinery wastewater sump,the air was sampled using 6 L canisters and characterized using gas chromatography-mass spectrometry.The pilot-scale unit included a BTF for removal of more water soluble compounds followed by a BF for removal of poorly soluble compounds.Performance of the BTF and BF units containing plastic cross flow and compost-based media were investigated at pollutant loading rates of 6 g/m3hr to 1750 g/m3hr.The characterization results of the pilot test showed benzene as the main constituent of the vapor stream(85% of vapor)emitted from the wastewater sump.The ratio of benzene to toluene and xylene was determined to be 12:2:1 in these samples.The high concentration of benzene as an amenable food and energy source for the microorganisms lead to high biomass growth and more than 85% removal efficiency(RE)for total emitted VOCs.Application of an innovative sequential biotrickling-biofiltration unit was also demonstrated to effectively handle the cyclic emissions of VOCs at most oil and gas industries.Although several researches have been done to evaluate the performance of BFs and/or BTFs in the laboratory,this pilot study can be used to design and optimize the performance of a bio-oxidation unit under actual refinery operating conditions.