Simulating the Emission Rate of Volatile Organic Compounds From a Quiescent Water Surface: Model Development and Feasibility Evaluation

Organic solvents are commonly used in industrial manufacturing processes, resulting in large quantities of volatile organic compounds (VOCs) emitted from effluent wastewater treatment facilities. This work presents a novel stainless steel simulator designed for developing a model that estimates VOC emission rates from a quiescent water surface in an open/unaerated basin. The target pollutants were aqueous VOCs: alcohols (ethanol and iso-propanol) and methyl ethyl ketone. Two aromatic hydrocarbons, toluene and benzene, were also used and each mixed with ethanol. A formula, based on penetration theory and the concept of mass balance, was devised for simulating emission rates (N), with the following variables: wind velocity (W) above the air–water interface with a power number of β, the VOC concentration (C _g*) at equilibrium with aqueous concentration (C _L), and the emitted concentration (C _g). Restated, N = kW ^β A _s(C _g* − C _g), where k and β denote dimensionless constants, which were solved herein, and A _s represents the emission surface area. From the proposed formula, three parameters (C _L, water temperature, and W) were controlled during each simulation test to derive k and β values. To assess the feasibility of the simulation procedures for real water with multiple VOC compositions, a large open neutralization basin was used to measure the VOC emission rate. Comparing the calculated results, respectively using the proposed formula and emission model Water 8 developed by the U.S. EPA in 1985, confirmed that the proposed simulation method was a feasible alternative to Water 8.

Keywords:

• Volatile organic compound (VOC)
• Simulation
• Emission
• Quiescent water surface
• Water 8

ACKNOWLEDGMENT

We thank the National Science Council, Taiwan, Republic of China, for financially supporting this research under Contract No. 92-2211-E-242-004.

Notes

*RSTD are the relative standard deviations for b, a, and R ².

†Ethanol content (%) and water temperature are also described.

*kand β are averaged from each simulated result of a VOC.

†Ranges of C _L, W,T _w, and relative humidity are displayed for each simulation.

‡Toluene and benzene were mixed with approximately 6% ethanol in water.

* Data of Henry's law constant (H _c) of VOCs in pure water. ^[13]