Solution of coupled partial differential equations of a packed bed reactor for SO2 removal by lime using the finite element method

In the present work, the reaction of SO₂ with a single pellet and also a packed bed reactor of conventional and macropore lime was simulated by applying the random pore model.

Kinetics of styrene biodegradation in synthetic wastewaters using an industrial activated sludge

Kinetics of styrene biodegradation in synthetic wastewaters, containing either styrene or styrene together with ethanol, by an industrial activated sludge obtained from the wastewater treatment unit of a petrochemical complex was studied. The kinetic data could be fitted using the Haldane kinetic model. This model was previously used to predict kinetic data for biodegradation of styrene by pure or mixed microbial cultures isolated from biofilters, but the values of the model parameters reported in these studies was substantially different from that obtained for the industrial activated sludge. The presence of ethanol did not affect the kinetics of styrene biodegradation by the industrial activated sludge; however, it increased the rates of styrene biodegradation due to the resulting higher microbial growth rates. Styrene concentration was found to affect the specific growth rate in a manner similar to its effect on the styrene degradation rate. No lag phase was observed in styrene biodegradation by industrial activated sludge for styrene concentrations up to 100mg/L. Lag phase was observed for municipal activated sludge even at 50mg/L styrene concentration but the rate of styrene biodegradation after the lag phase was similar to that achieved by the industrial activated sludge.

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)

In this study, the membrane bioreactor (MBR) was utilized to remove styrene from a synthetic wastewater having a chemical oxygen demand (COD) and styrene concentration of 1500 mg/L and 50 mg/L, respectively. At two hydraulic retention times (HRTs) of 24 h and 18 h, the MBR was operated for a period in excess of 100 days. The HRT effects were studied and it was found out that the removal efficiency of COD and styrene for both HRTs was consistently higher than 99%. Unlike conventional activated sludge processes (CASPs), no styrene was detected in the exhaust air, which meant that biodegradation was the major styrene removal mechanism at both HRTs. The transmembrane pressure (TMP) profile during the operation of the MBR showed a fairly low and constant TMP up to day 70, after which, the TMP showed a dramatic rise, as a result of the occurrence of severe membrane fouling. It was thought that an increase in styrene loading rate, when HRT was reduced to 18 h, resulted in the release of extracellular polymeric substance (EPS) from the bacterial cells, which in turn was responsible for the rise in soluble microbial product (SMP) and sludge deflocculation. The severe fouling observed during operation of MBR at HRT of 18 h was attributed to the rise in SMP concentrations and decrease in mean floc size and increase in the proportion of small particles in the activated sludge.

Enzymatic degradation of anthracene by the white rot fungus Phanerochaete chrysosporium immobilized on sugarcane bagasse

Bagasse is a by-product of sugar milling and important fuel resource for that industry. It is a fibrous, low density material with a very wide range of particle sizes and high moisture content. The goal of this study is the development of a system based on the use of the ligninolytic enzyme manganese peroxidase (MnP) produced by Phanerochaete chrysosporium for the degradation of polycyclic aromatic hydrocarbons (PAHs), of which anthracene was selected as an example. The white rot fungus P. chrysosporium immobilized on bagasse was grown in both stationary and agitated cultures (rotary shaker, 80rpm) using nitrogen limited growth medium to study the ability of the fungus to degrade anthracene in aqueous media. Production of MnP occurred simultaneously in nitrogen limited culture medium with the added MnSO4 at 40ppm. The MnP activity was at relatively high level (76Ul(-1)) and in this condition, the residual anthracene concentration was 16%.

Copper biosorption from aqueous solutions by sour orange residue

In this study, copper uptake by sour orange residue (SOR) was investigated. Equilibrium isotherms and kinetics were obtained and the effects of solution pH, temperature, and particle size were studied in batch experiments. Equilibrium was well described by Langmuir and Freundlich isotherms and kinetics was found to be best-fit pseudo-second order equations. Maximum uptake was observed at pH 5. With an increase in temperature from 20 to 50 degrees C, copper removal decreased about 20%. Additional chemical treatment of the biosorbent by NaOH, increased the biosorption capacity. It was found that increase in biosorbent particle size had no significant effects on the final equilibrium concentration, but decreased biosorption rate.