Estimating Emissions of 20 VOCs. II: Diffused Aeration

Hsieh, Chu‐Chin; Babcock, Roger W.; Stenstrom, Michael K.

doi:10.1061/(asce)0733-9372(1993)119:6(1099)

Cited by 33 publications

(35 citation statements)

References 6 publications

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“…The S d values become close to 1.0 with decreasing H, because the equilibrium gas-phase concentration is small and thus saturation is achieved rapidly for low-volatility compounds (Hsieh et al, 1993).…”

Section: Mean Oxygen Saturation Concentrationmentioning

confidence: 92%

“…Total resistance (R T ) is thus equal to liquid resistance (R L ). The exponent n equals 0.5 for diffused aeration systems (Hsieh et al, 1993).…”

Section: Degree Of Voc Saturation In Exit Bubblesmentioning

confidence: 99%

“…The VOC mass transfer coefficient ((K L a) V OC ) can be estimated from the oxygen transfer efficiency ((K L a) O2 ) and the ratio of the diffusion coefficients as shown in Equation 8 (Hsieh et al, 1993;Hsieh, 2000). Since oxygen is a slightly soluble gas, it is assumed that the liquid film resistance controls the rate of mass transfer.…”

Section: Degree Of Voc Saturation In Exit Bubblesmentioning

confidence: 99%

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Volatilization and Biodegradation of VOCs in Membrane Bioreactors (MBR)

Min

Ergas

2006

Water Air Soil Pollut: Focus

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Volatilization and biodegradation are major competitive volatile organic compound (VOC) removal mechanisms in biological wastewater treatment process, which depend on compound specific properties and system design/operational parameters. In this study, a mathematical model was used to determine major removal pathways at various organic loading rates (OLR), solids residence time (SRT) and dissolved oxygen (DO) concentrations in a biological process for vinyl acetate. Model results showed that biological treatment process should be designed with long SRT, high OLR and low DO concentrations to maximize biodegradation and minimize volatilization of VOCs. Unless a VOC is toxic to microorganisms under the given conditions, low VOC emission rates are an inherent advantage of MBRs, which operate at higher OLR and longer SRT compared to conventional activated sludge process.A lab scale membrane bioreactor (MBR) was operated at varying OLR to investigate the relative volatilization and biodegradation rates for acetaldehyde, butyraldehyde and vinyl acetate. Synthetic wastewater containing three VOCs was introduced to the MBR. The DO concentration and SRT was maintained at 2.0 mg L −1 and 100 days, respectively. The overall VOC removal rate was more than 99.7% for three VOCs at all the OLR. For vinyl acetate, the biodegradation rate increased from 93.87 to 99.40% and the volatilization removal rate decreased from 6.09 to 0.59% as OLR was increased from 1.1 to 2.0 kg COD m −3 d −1 . It was confirmed that a MBR can be a promising solution to reduce VOC emissions from wastewater. Notation C eEffluent VOC concentration (mg L −1 )Operating oxygen concentration in the aeration basin (mg L −1 )Oxygen saturation concentration for tap water at 20 • C (mg L −1 ) C smT Mean oxygen saturation concentration at T • C for tap water at field operating conditions (mg L −1 ) C ST Oxygen saturation concentration at T • C for tap water at field operating conditions (mg L −1 )Oxygen transfer efficiency in clean water (%) 84 KYUNGNAN MIN AND SARINA J. ERGAS F Diffuser fouling factor f oc Fraction of organic carbon in solids (g organic carbon/g VSS) = 0.53 for biological cells presented by C 5 H 7 NO 2 . H Henry's constant (dimensionless) K b Apparent first-order biological rate constant (Overall oxygen mass transfer coefficient (Concentration of oxygen in the air leaving the aeration tank (%) P a Absolute pressure at the depth of air release (atm) P bPartial pressure of oxygen in the gas phase (atm)Amount of oxygen required for biodegradation (mg d −1 ) R T Total resistance (dimensionless) S d Degree of VOC saturation in exit bubbles (dimensionless) TOperating temperature ( • C) V Bioreactor volume (L) X bMixed liquor volatile suspended solids (MLVSS) concentration (mg L −1 ) in the bioreactor X w Wasting sludge concentration (mg L −1 ) α Ratio of the oxygen mass transfer coefficient (K L a) in wastewater to K L a in tap water (dimensionless) βRatio of the oxygen saturation concentration (C s ) in wastewater to C s in tap water ρ air Density of...

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Section: Mean Oxygen Saturation Concentrationmentioning

confidence: 92%

“…Total resistance (R T ) is thus equal to liquid resistance (R L ). The exponent n equals 0.5 for diffused aeration systems (Hsieh et al, 1993).…”

Section: Degree Of Voc Saturation In Exit Bubblesmentioning

confidence: 99%

Section: Degree Of Voc Saturation In Exit Bubblesmentioning

confidence: 99%

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Volatilization and Biodegradation of VOCs in Membrane Bioreactors (MBR)

Min

Ergas

2006

Water Air Soil Pollut: Focus

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“…After rearranging Eq. (4a): A relationship between the oxygen transfer coefficient and the overall mass transfer coefficient for any other VOC (K L a) VOC can be established (Roberts et al, 1984;Hsieh et al, 1993b;Munz and Roberts 1989):…”

Section: Methodsmentioning

confidence: 99%

Modeling of air stripping from volatile organic compounds in biological treatment processes

Soltanali

Hagani

2008

Int. J. Environ. Sci. Technol.

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ABSTRACT:The removal of volatile organic compounds from biological treatment processes occurs through several mechanisms. These include biodegradation, adsorption onto solids, and air stripping or volatilization to the atmosphere. Volatilization results in fugitive emissions to the atmosphere, which is largely uncontrolled. Recent regulations have called for increased evaluation and control of inadvertent volatile organic compounds emissions from treatment processes. The use oxygen as a parallel volatile compound is extremely useful for prediction of volatile organic compounds removal by air stripping. In this study, the simultaneous biodegradation and air stripping of volatile organic compounds, based on steady state mass balance are examined and a general approach to estimating the dominant removal mechanism is developed. A Monte Carlo simulation technique was used to estimate air stripping over a wide range of operating conditions. Several volatile organic compounds were selected for this study. The results showed the values drived from the model correspond with the experimental data for benzene, toluene, methylene chloride, trichloroethylene, and methyl isobutyl ketone.

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“…The primary operational parameters of the scrubber are liquid/gas ratio and retention time that strongly affect the mass transfer coefficient and removal efficiency [21]. To evaluate the effects of the operating parameters on K L a of NMHC, the enhancement factor (E) was calculated using the following equation.…”

Section: Enhancement Factor Of K L Amentioning

confidence: 99%