Sewage treatment by a low energy membrane bioreactor.

A new membrane bioreactor (MBR) was developed for treatment of municipal wastewater. The MBR was mainly made up of an activated sludge reactor and a transverse flow membrane module, with an innovative configuration being in application between them. As a result, the transverse flow membrane module and low recirculation flow rate created advantages, such as lower energy consumption and more resistance to membrane fouling.

Addition of anaerobic tanks to an oxidation ditch system to enhance removal of phosphorus from wastewater.

The oxidation ditch has been used for many years all over the world as an economic and efficient wastewater treatment technology. It can remove COD, nitrogen and a part of phosphorus efficiently. In the experiment described, a pilot scale Pasveer oxidation ditch system has been tested to investigate the removal of phosphorus from wastewater.

Transformation of carbon tetrachloride in an anaerobic packed-bed reactor without addition of another electron donor.

Carbon tetrachloride (52 microM) was biodegraded for more than 72% in an anaerobic packed-bed reactor without addition of an external electron donor. The chloride mass balance demonstrated that all carbon tetrachloride transformed was completely dechlorinated. Chloroform and dichloromethane were sometimes also found as transformation products, but neither accumulated to significant levels in comparison to the amount of carbon tetrachloride transformed.

Partially oxidized polycyclic aromatic hydrocarbons show an increased bioavailability and biodegradability.

Polycyclic aromatic hydrocarbons have a low water solubility and tend to adsorb on soil particles, which both result in slow bioremediation processes. Many microorganisms, known for their ability to degrade polycyclic aromatic hydrocarbons, only partially oxidize these compounds. White rot fungi, for instance, convert polycyclic aromatic hydrocarbons to more water soluble and bioavailable products.

Performance of a styrene-degrading biofilter containing the yeast Exophiala jeanselmei.

A general mathematical model developed for a description of pollutant degradation in a biofilm was used to evaluate the performance of a biofilter for the purification of styrene-containing gas. The biofilter contained perlite as an inert support on which a biofilm was present composed of a mixed microbial population containing the fungus Exophiala jeanselmei as a major styrene-degrading microorganism. Although styrene is a moderately hydrophobic compound, the biofilter was reaction limited at a styrene gas phase concentration of 0.

Transformation of carbon tetrachloride under sulfate reducing conditions.

The removal of carbon tetrachloride under sulfate reducing conditions was studied in an anaerobic packed-bed reactor. Carbon tetrachloride, up to a concentration of 30 microM, was completely converted. Chloroform and dichloromethane were the main transformation products, but part of the carbon tetrachloride was also completely dechlorinated to unknown products.

Styrene metabolism in Exophiala jeanselmei and involvement of a cytochrome P-450-dependent styrene monooxygenase.

The yeast-like fungus Exophiala jeanselmei degrades styrene via initial oxidation of the vinyl side chain to phenylacetic acid, which is subsequently hydroxylated to homogentisic acid. The initial reactions are catalyzed by a NADPH- and flavin adenine dinucleotide-dependent styrene monooxygenase, a styrene oxide isomerase, and a NAD(+)-dependent phenylacetaldehyde dehydrogenase. The reduced CO-difference spectrum of microsomal preparations of styrene-grown cells shows a characteristic absorption maximum at 450 nm, which strongly suggests the involvement of a cytochrome P-450-dependent styrene monooxygenase.

Metabolism of allantoin in Hyphomicrobium species.

Hyphomicrobium species are able to use allantoin as a nitrogen source for growth. Allantoin is broken down to glyoxylate and ammonia by the consecutive action of allantoinase, allantoicase, ureidoglycolase and urease.

Chemiosmotic coupling in Methanobacterium thermoautotrophicum: hydrogen-dependent adenosine 5'-triphosphate synthesis by subcellular particles.

Hydrogenase and the adenosine 5'-triphosphate (ATP) synthetase complex, two enzymes essential in ATP generation in Methanobacterium thermoautotrophicum, were localized in internal membrane systems as shown by cytochemical techniques. Membrane vesicles from this organism possessed hydrogenase and adenosine triphosphatase (ATPase) activity and synthesized ATP driven by hydrogen oxidation or a potassium gradient. ATP synthesis depended on anaerobic conditions and could be inhibited in membrane vesicles by uncouplers, nigericin, or the ATPase inhibitor N,N'-dicyclohexylcarbodiimide.

Improved identification of methanogenic bacteria by fluorescence microscopy.

Methanogenic bacteria can be tentatively identified by fluorescence microscopy. This technique was improved by carefully selecting a series of excitation and barrier filters that matched the excitation and emission spectra of some unique coenzymes viz., F420 and F350, in methanogenic bacteria.

ATP hydrolysis and synthesis by the membrane-bound ATP synthetase complex of Methanobacterium thermoautotrophicum.

The membrane-bound ATP synthetase complex of Methanobacterium thermoautotrophicum showed maximum activity for ATP hydrolysis at pH 8, at temperatures between 65 and 70 degrees C, and at an ATP-Mg2+ ratio of 0.5. Anaerobic conditions were not prerequisite for enzyme activity.

Dicarboxylic acid transport in membrane vesicles from Bacillus subtilis.

Membrane vesicles isolated from Bacillus subtilis W23 catalyze active transport of the C4 dicarboxylic acids L-malate, fumarate, and succinate under aerobic conditions in the presence of the electron donor reduced beta-nicotinamide adenine dinucleotide or the non-physiological electron donor system ascorbate-phenazine methosulfate. The dicarboxylic acids are accumulated in unmodified form. Inhibitors of the respiratory chain, sulfhydryl reagents, and uncoupling agents inhibit the accumulation of the dicarboxylic acids.