The transport of low-pressure natural gas presents a host of environmental problems that must be addressed. Drip water is generated in natural gas service lines as a result of water infiltration through piping and fittings. Drip water from low pressure lines is different from high-pressure gas condensate, which is typically oilier, with PCB and flammability concerns. Low-pressure line drip water has its own toxicity, including the presence of benzene, which requires disposal as a hazardous waste.
Working under an environmental term contract for a major utility company, H2M conducted an evaluation of mobile drip water treatment systems (DWTS) designed to treat the drip water at the point of generation to remove benzene as well as total hydrocarbons and any other soluble natural gas contaminants. Systems are comprised of a truck-mounted 500-gallon holding tank, a vacuum pump, and a filtration system with ancillary piping and equipment.
The purpose of this DWTS evaluation was to develop and demonstrate the effectiveness of a treatment system for regulatory approval. H2M used actual drip water spiked with known benzene concentrations. We collected influent, intermediate, and effluent samples and evaluated the treatment system efficiency at varied benzene concentrations. We also considered different pumping alternatives, vacuum flow and pressurized flow, and different filtration options of solids filters, proprietary filtration media and granular activated carbon filters. The end product was a system design that provided benzene removal to less than 1 part per billion that could operate in both summer and winter field environments