Volatilization and Biodegradation of VOCs in Membrane Bioreactors (MBR)

Abstract

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...

Membrane bioreactor for the treatment of voc laden pharmaceutical wastewater: Effect of biological treatment systems on membrane performance

“…Similar result has been reported by Min and Ergas [37]. They reported that higher biodegradation of vinyl acetate reduced the volatilization loss to less than 0.59%, while treating synthetic wastewater containing VOC using an MBR at an OLR of 2.0 kg COD/m 3 days.…”

Long-term operation of submerged membrane bioreactor (MBR) for the treatment of synthetic wastewater containing styrene as volatile organic compound (VOC): Effect of hydraulic retention time (HRT)

“…Min and Ergas [15] have developed a mathematical model for treatment of VOC-containing wastewaters in MBRs which is a modified version of the model developed for CASPs by Hsieh [4]. This model, together with limited experimental data obtained for treatment of vinyl acetate synthetic wastewater in a laboratory side-stream MBR, predicts that unlike CASP processes, in MBRs, with increase in OLR (e.g.…”

“…For this reason, the air rates, reportedly used in MBR processes, are usually higher than those of CASPs [13,14]. However, according to the CASP model developed by Hsieh [4] and the MBR model developed by Min and Ergas [15], increase in air rate can lead to significant increase in the removal rate of VOCs by stripping mechanism.…”

Bibliometrics and Knowledge Map Analysis of Research Progress on Biological Treatments for Volatile Organic Compounds

“…Based on this, a model was developed for the treatment of mixed gas streams of VOCs in biofilters. Kyungnan et al [68] utilized mathematical models to determine the results of vinyl acetate removal at different organic loading rates, solid residence times, and dissolved oxygen concentrations. Currently, the method of predicting and evaluating bioreactor operating parameters and effectiveness by constructing models needs further exploration and investigation.…”