Sanafoam Vaporooter II is a trademark name for a
process which uses metham sodium and dichlobenil to remove
tree roots from municipal sewer and storm drain lines. One
or more of the chemicals in this process, or their
degradation products, have been suspected of disrupting the
nitrification process in waste treatment plants downstream
of the points of application. This work was undertaken to
identify the chemical responsible for the disruption, and to
recommend means for assuaging the problem.
The impacts of the herbicides used in the Vaporooter II
process were separately tested in bench scale reactors.
Metham sodium was found to be the herbicide responsible for
disrupting nitrification. It did so at concentrations of 4
mg/L or higher in systems which have a mixed liquor volatile
suspended solids concentrations of 1800 mg/L. This
corresponds to a herbicide to biomass ratio of 0.017
moles/gram.
The stability of metham sodium was also tested in bench
scale experiments. The compound was found to be fairly
stable at the pH values, temperatures and oxygen
concentrations typically found in sewage collection systems and so undergoes little degradation after application.
Powdered activated carbon (PAC) is effective in
absorbing metham sodium from raw sewage. In bench scale
reactors, application rates of 10 mg PAC per 1 mg metham
sodium reduced metham sodium concentrations to levels which
did not disrupt the nitrification process.
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