Volatile Organic Compound Emission Rates from Mechanical Surface Aerators:  Mass-Transfer Modeling

Abstract

In wastewater treatment plants, many operation units such as equalization and aeration involve oxygen transfer between wastewater and air. While oxygen is transferred from air to wastewater, volatile organic compounds (VOCs) are stripped from wastewater to air. Because of increasingly stringent environmental regulations, wastewater treatment operators have to do VOC inventory of their facilities. A new mass-transfer model has been developed to predict the VOC emission rates from batch and continuous aeration tanks with mechanical surface aerators. The model takes into consideration that the VOC mass transfer occurs in two separate mass-transfer zones instead of lumping the overall VOC transfer in the whole aeration tank as is done in the conventional ASCE-based model. The predictive capabilities of the two-zone and the ASCE-based models were examined by calculating the emission rates of 10 priority pollutants from aeration tanks. The effects of the hydraulic retention time, the Henry's law constant, gas-phase resistance, and the water and air environmental conditions on the VOC emission rates were predicted by the two models.

Effect of volatile organic chemicals on surface-enhanced Raman scattering of 4-aminobenzenethiol on Ag: comparison with the potential dependence

“…In most cases, the effect would be negligibly small, but in some cases, especially for nanodevices operating under ambient conditions, this could be pivotal in running them under optimal conditions. [1][2][3][4][5][6][7][8] Unfortunately, no device is yet available to measure the effect directly, but we reported recently that the VOC effect, at least on nanostructured gold and silver, can be identified, although indirectly, by means of surface-enhanced Raman scattering (SERS) of isocyanides. [9][10][11] For instance, in the presence of acetone the NC stretching band of 2,6-dimethylphenylisocyanide (2,6-DMPI) on Au blue-shifted by as much as 6 cm À1 , while the same band red-shifted by as much as 20 cm À1 in the presence of ammonia.…”

Stripping of organic compounds from wastewater as an auxiliary fuel of regenerative thermal oxidizer

“…During aeration, oxygen is transferred into the wastewater while the pre-dissolved VOCs will emit to the atmospheric air from the wastewater simultaneously [9][10][11][12]. Aeration was viewed as a good method to remove VOC in wastewaters before, but emitted VOCs become air pollution problems of great concern now.…”

The effect of agitation on volatilization of naphthalene from solution containing surfactant

“…In natural waters, volatilization primarily controls the residence time of hydrophobic organic compounds that are resistant to physicochemical and biological degradation [1]. In municipal and industrial wastewater treatment plants, volatilization can lead to the emission of toxic compounds that must be controlled, particularly when regulations on the toxic emission become increasingly stringent in recent years [2][3][4]. The factors that affect the volatilization are well documented, including organic solute properties, such as diffusion coefficient, aqueous solubility, molecular weight and Henry's law constant [4][5][6][7][8].…”