Biofiltration of dichlorobenzenes.

Area of Science:

• Environmental Engineering
• Biotechnology
• Industrial Wastewater Treatment

Background:

• Refinery wastewater often contains dichlorobenzenes (DCBs), posing environmental risks.
• Conventional treatment systems may lead to volatilization of DCBs into ambient air.
• A combined stripping and air biofiltration system offers a viable solution for DCB removal.

Purpose of the Study:

• To evaluate the efficacy of air biofiltration for dichlorobenzene (DCB) degradation at a refinery.
• To assess the performance of a two-step treatment process involving stripping and biofiltration.
• To investigate the impact of naphthalene co-contamination on DCB biodegradation.

Main Methods:

• A full-scale air stripping unit was employed to volatilize DCBs from contaminated groundwater.
• Two large-scale biofilters, filled with peat moss, manure, wood chips, and contaminated soil, were used for gas-phase DCB treatment.
• Laboratory tests were conducted to assess microbial activity and degradation rates.
• Full-scale operation was monitored over four months, analyzing influent and effluent concentrations.

Main Results:

• The air stripper achieved over 99% DCB removal efficiency.
• Full-scale biofilters maintained DCB concentrations below 1 ppmv in the outlet air.
• Biofilter removal efficiency varied (0-79%) due to lower-than-expected DCB loads, operational fluctuations, and naphthalene presence.
• Naphthalene co-contamination was observed to slow down DCB degradation.

Conclusions:

• Air biofiltration is a suitable technology for degrading dichlorobenzenes in industrial air streams.
• The combined stripping and biofiltration system effectively reduces DCB emissions from contaminated groundwater.
• Optimizing biofilter performance requires stable operating conditions and consideration of co-contaminants like naphthalene.