Assessment of the Treatability of Toxic Organics by Overland Flow,
COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
Pagination or Media Count:
The removal efficiency for 13 trace organics in wastewater was studied on an outdoor, prototype overland flow land treatment system. The removal for each of these substances was greater than 94 at an application rate of 0.4 cmhr. The percent removals declined as application rates were increased. The rate of removal from solution was described by the sum of two mass- transport-limited, first-order rate coefficients representing volatilization and sorption. A model based on the two-film theory was developed the observed removal rate coefficients were regressed against three properties of each substance the Henrys constant, the octanol-water partition coefficient and the molecular weight. The dependence of the removal process on temperature was studied and is included along with average water depth in the model. The decrease in removal rate as temperature declined is supported by the known dependence of Henrys constant and diffusivity on temperature. The model was validated on a second overland flow system. The surface soil concentrations of the trace organics determined at the end of the experiment suggest that a secondary mechanism renews the surface rapidly enough so that contaminants do not build up on the surface, with the possible exception of PCB. Biodegradation is suggested as the predominant secondary mechanism rather than volatilization because substances less volatile than PCB were not found at the end of the experiment.
- Water Pollution and Control