Observation of a P/M interconversion of a gold-phosphine helicate via 31P NMR

Ligands containing P-CH2-CH2-P elements have been shown to form double-stranded helicates whose axis consists of gold atoms with Au...Au contacts; the interconversion of the P and M forms of the helicate [Au3(mu-pp2)2](OTf)3 (pp2 = PhP(CH2CH2PPh2)2) is monitored via 31P NMR.

A procedure for production of adapted bacteria to degrade chlorinated aromatics

Production of biomass adapted to the degradation of a mixture of chlorobenzene (CB) and 1,2-dichlorobenzene (DCB) was investigated in a batch culture with substrates supplied by pulses. CB and o-DCB concentrations which gave the best adapted biomass productivity were determined and found to be 150 and 30 microl l(-1), respectively. The biomass productivity was 51 mg l(-1) h(-1). The biomass yield was 0.38 g of biomass dry weight per gram of substrate. The pulses of 200 microl CB and 40 microl o-DCB, were inhibitory to the bacterial culture. Among the metabolites, muconic acid was found in large quantities in the medium and in the cells. At a time between two pulses of 60 min, adding 150 microl CB and 30 microl o-DCB per each pulse, 7.6g l(-1) of biomass was obtained. The produced biomass served as an inoculum for the biotrickling filter which treated industrial waste gases contaminated by CBs. The method of adapted biomass production was described using CBs, but the degradation of any other toxic volatile pollutant can be improved using this technique.

Photochemical-biological treatment of a real industrial biorecalcitrant wastewater containing 5-amino-6-methyl-2-benzimidazolone

5-amino-6-methyl-2-benzimidazolone (AMBI), used in the manufacture of dyes, was characterised as a biorecalcitrant compound by means of different biodegradability tests. In order to enhance the biodegradability of this important pollutant, the application of Advanced Oxidation Process (AOPs) as a pretreatment was explored. Some experiments were addressed to find the most efficient AOP. The systems H2O2/hv, TiO2/H2O2/hv, Fe3+/hv, Fe3+/H2O2 and Fe3+/H2O2/hv were compared. The photo-Fenton system was the most efficient and the optimal conditions (AMBI, Fe3+, H2O2 concentrations) for the degradation of AMBI were found. During the photo-Fenton degradation, experiments were also made to obtain information concerning the evolution of: (a) organic carbon and initial compound concentration; (b) the oxidation state; (c) the toxicity; (d) the biodegradability; and (e) the chemical nature of the intermediates. These analyses show that the solution resulting from the treatment of AMBI is biologically compatible and complete mineralisation can be performed by biological means. A combined photochemical (Fenton) and biological flow reactor for the degradation of AMBI was successfully operated in continuous mode at laboratory scale. 100% of the initial concentration of AMBI and 80.3% of Dissolved Organic Carbon (DOC) were removed in 3.5 hours of total residence time. Finally, some field experiments under direct sunlight carried out at the Plataforma Solar de Almeria, Spain, demonstrated that this solar catalytic system is an effective treatment for this kind of industrial wastewater.

Growth inhibition of biomass adapted to the degradation of toluene and xylenes in mixture in a batch reactor with substrates supplied by pulses

A biomass adapted to degrade toluene and xylenes in mixture was grown in a batch reactor with substrates supplied by pulses. The inhibition of biomass growth in the course of substrate degradation was investigated. The maximal biomass concentration of 7 g l-1 was obtained using 150 microliters of toluene and 15 microliters of a mixture of xylenes in one litre of liquid medium, and the maximal biomass productivity and yield were 53 mg l-1 h-1 and 0.32 gDW gs-1, respectively. Higher quantities of substrate added by pulses, that is 200 microliters of toluene with 20 microliters of xylenes and 300 microliters of toluene with 30 microliters of xylenes, caused an accumulation of metabolites. These higher quantities of substrates caused inhibition of microbial growth. Among the metabolites produced, 4-methyl catechol was found in large quantities in the culture medium and in the cells.

Escherichia hermanii--a new bacterial strain for chlorobenzene degradation

A new bacterial strain capable of chlorobenzene degradation has been isolated from sludge of an industrial wastewater treatment plant. The micro-organism is short, rod-shaped, Gram-negative, yellow-pigmented and has been identified as Escherichia hermanii. It was observed that high chlorobenzene concentrations (up to 394 mg l-1) had low toxic effects towards this strain, which was able to degrade chlorobenzene without any previous adaptation.

Biomass growth monitoring using pressure drop in a cocurrent biofilter

The possibility of following the biomass growth by pressure drop measurement was investigated in an aerated cocurrent upflow fixed-bed bioreactor continuously fed with wastewater containing industrial organic pollutants. The experiments were carried out in a biological filtration oxygenated reactor (Biofor) pilot plant packed with expanded clay balls (Biolite) of 2.7-mm diameter, which served as biomass carriers. The column was equipped for on-line pressure drop measurements. Correlation between pressure drop measurements and Reynolds numbers of air and water were determined in experiments carried out without biomass. Under operating conditions with biomass, it was demonstrated that column clogging and the operating time between washing cycles can be predicted depending on the volumetric organic load for a given total organic carbon inlet concentration. The biological activity of the fixed biomass was estimated from the oxygen consumption rate per unit time and carrier area. The oxygen consumption rate measurements demonstrated that the biological activity depends on the inlet substrate concentration, and that the Biofor column was most efficient between 75 and 100 g m-3 of total organic carbon inlet concentration. In the course of the wastewater treatment, using pressure drop measurements, the equivalent diameter of the Biolite particles, the reduced column macroporosity, and the biofilm thickness were calculated. An expression correlating biofilm density and biofilm thickness, as determined from the pressure drop measurements, was proposed. Good agreement was found between the fixed biomass in the reactor, determined as volatile suspended solids, and the biologically active biomass, estimated by respirometry. Copyright 1998 John Wiley & Sons, Inc.