Stripping of VOC`s from dissolved air flotation
- Carleton Univ., Ottawa, Ontario (Canada)
- Enviromega Ltd., Hamilton, Ontario (Canada)
A pilot scale study was performed to assess gas phase emissions of volatile organic compounds (VOCs) from the dissolved air flotation process. A high degree of mass closure was observed in experiments using tapwater dosed with a cocktail of VOCs, indicating that techniques employed to characterize the pilot plant were valid. Subsequent dosed wastewater experiments examined volatilization from a wastewater matrix that contained oils and suspended solids as well as investigating the impacts of hydraulic loading and recycle rate on the fate of the VOCs in the dissolved air flotation unit. Emissions of the dosed candidate compounds, calculated as a percentage of the influent mass flow, ranged from 0.2% of 1,1,2,2-tetrachloroethane to 9.9% of tetrachloroethylene. Hydraulic loading and compounding type had a statistically significant effect on the emissions of VOCs, however, a high degree of interaction between parameters was observed. Effluent recycle had a greater effect on emissions at the higher hydraulic loading than at the lower loading. A model which incorporated stripping by bubbles, volatilization from a quiescent oil-free surface and equilibrium partitioning to oil was developed. The model was able to simulate the candidate compound response under all experimental conditions except the case with low hydraulic loading and low recycle rate. The results suggest that the surface volatilization model may underestimate emissions. It is hypothesized that the presence of a float in the form of a foamy layer with a high surface area tends to increase liquid-gas mass transfer of the candidate compounds over that assumed in the surface volatilization model. 13 refs., 6 figs., 8 tabs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 476814
- Journal Information:
- Environmental Progress, Journal Name: Environmental Progress Journal Issue: 2 Vol. 15; ISSN 0278-4491; ISSN ENVPDI
- Country of Publication:
- United States
- Language:
- English
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