Search

The objective of this research was to assess the mechanism and effectiveness of the zerovalent iron (ZVI) to remediate the Cr(VI) contaminated water. The mechanism of Cr(VI) reduction by ZVI was evaluated by characterising surface properties and chemical compositions of Fe and Cr products using SEM-EDS, XRD and XPS analyses. The effectiveness of ZVI in Cr(VI) reduction was assessed by the luminescent bacteria (Photobacterium Phosphoreum). The Cr(VI) was reduced to Cr(III), when the reactive Fe0 was oxidised to Fe(II,III), showing the presence of Fe2O3, (Fe-Cr)2O3 and FeOOH. The SEM-EDS analysis showed that ZVI with a higher reducing capacity was more subject to changes of surface and morphological properties due to ionisation of ZVI. The Cr and Fe in precipitates subsisted exclusively in the Cr(III) or Fe(III) states with the respective forms of Cr(OH)3 or Cr2O3 and FeOOH or Fe2O3. Electrons produced from ZVI oxidation reduced Cr(VI) to Cr(III), thus resultantly Cr(III) precipitated or co-precipitated with Fe(III) to form Fe(III)-Cr(III) hydroxide or Fe(III)-Cr(III) oxyhydroxide. Toxicity of water reacted with ZVI was significantly lower than that of the untreated water.

A reliable wastewater characterization is an integral part of treatment and management strategies for industrial effluents. This is especially true for the pharmaceutical industry, which exhibits significant differences in its line of activity, generating effluents of very specific and complex natures. Any hazard or risk assessment of wastewater and/or determination of its treatability must include an evaluation of its degradability. Usually various non-standardized laboratory or pilot-scale long-term tests are run by measuring summary parameters for several days to determine the biodegradation potential of the effluent. A complex approach, based on stabilization studies, was proposed to determine the hazardous impact of wastewaters in terms of biodegradable and persistent toxicity. The objective of our work was to carry out complex hazard evaluation of pharmaceutical wastewaters. Whole effluent toxicity was determined using two different toxicity tests. First, we measured the inhibition of oxygen consumption by activated sludge. The test indicated toxicity of the wastewater and thus we performed an additional acute toxicity test with luminescent bacteria Vibrio fisheri. The next step was the determination of whole effluent ready biodegradability. It was determined with simultaneous measurement of oxygen consumption (ISO 9804) and carbon dioxide production (ISO 9439) in a closed respirometer, accompanied by DOC/IC measurements. The pharmaceutical wastewater degraded readily (83%, lag phase was 2 days, biodegradation rate was 0.339 day−1) on the basis of O2 measurements. The biodegradation, calculated from the CO2 measurements, was comparable. We also applied mass balances of DOC/IC at the beginning and at the end of biodegradation experiments to confirm the extent and rate of biodegradation. The determination of hazardous impact and treatability of the effluent was concluded with aerobic stabilization studies. Biodegradation of the wastewater during the study was followed by relevant biochemical analysis and DOC/IC mass balance.

The purpose of our investigation was the acute and chronic toxicity evaluation of the wastewater from the chemical industry, while the previous study had indicated high toxicity of the receiving streams far away from the point of wastewater inflow. The luminescent bacteria Photobacterium phosphoreum and invertebrate Daphnia magna were used for toxicity tests. The results of the toxicity tests showed that the investigated wastewater contained toxic substances, which caused acute and chronic toxicity to test organisms. Daphnia magna were more sensitive than Photobacterium phosphoreum. The acute toxicity of the wastewater on daphnids disappeared after dilution to 1:420, but the chronic toxicity did not disappear earlier than 1:1350.

Organic concentrates of River Meuse water were tested for toxicity with a five minutes test (Microtox*) on luminescent bacteria (Photobacterium phosphoreum). Over the year 1992, the surface water was sampled six times at seven stations in the stretch between Remilly (France) and Keizersveer (The Netherlands). Unfiltrated water samples were concentrated by neutral adsorption on XAD resin followed by elution with acetone. The measured toxicity is expressed as the concentration factor causing 20% reduction in bacterial luminescence after five minutes of exposure (EC20,5). The observed toxicity is transformed into a so called pT-value, pT=10log(EC20,5/100), relating toxicity to acceptability criteria. Along the river, the toxicity attributable to organic pollution did not reach environmentally acceptable levels. The toxicity in the French and Belgian parts of the river increased gradually to a maximum toxicity generally observed near the industrial centre Liège. In the Dutch stretch, the organic toxicity generally decreased as a consequence of lower pollutant input, pollutant degradation, or pollutant adsorption to newly formed particulates.

Aquatic toxicity of point-source discharges are examined with the MICROTOX system using luminescent bacteria, Photobacterium phosphoreum . Samples include treated wastewaters from industrial dischargers, municipal sewage treatment plants and community sewage treatment plants, all of which eventually flow into Tokyo Bay. Among 34 samples from industry, 11.7% exhibit high toxicity (EC50 =

Ash-heap water (AHW - phenolic wastewater of local oil-shale industry) was analyzed for its phenolic composition using HPLC and for its relative toxicity using MicrotoxTM and BiotoxTM tests where inhibition of natural luminescence of photobacteria is used as toxicity endpoint. Most abundant components in AHW were phenol (84 mg/L) and p -cresol (70 mg/L). The 5-min EC50 values for AHW (the concentration of AHW, %, which reduces the light output of bacteria by 50% after being in contact with bacteria for 5 minutes) for BiotoxTM and MicrotoxTM tests were 1.5% and 0.6%, respectively. Also, the toxicity of AHW towards two different activated sludges (acclimatized and not acclimatized to phenolic wastewater) was evaluated using decrease of adenosine triphosphate (ATP) content of the sludge as toxicity endpoint. AHW was relatively non-toxic to activated sludges, especially to the acclimatized sludge. The respective 60-min EC50 value for AHW (the concentration of AHW, %, which decreases the ATP level of activated sludge compared to the non-exposed control by 50% after being in contact with sludge for 60 minutes) was 20-30% for non acclimatized sludge and 50-60% for acclimatized sludge. Therefore, the biopurification of AHW using an adapted activated sludge process could be considered feasible.

The relative toxicity (expressed as 5-min EC50 value - the concentration of chemical which reduces the light output of bacteria by 50% after contact for 5 minutes) of 13 pesticides ( e.g. , 2,4-dichlorophenoxyacetic acid, atrazine, coumarin, glyphosate, paraquat, pentachlorophenol, lindane, malathion) and 14 solvents was evaluated using Biotox TM test that is based on reconstituted freeze-dried viable Photobacterium phosphoreum . The most toxic of the 13 pesticides analyzed using Biotox TM was pentachlorophenol (5-min EC50=0.55 mg/L) and the less toxic was paraquat (5-min EC50=14800 mg/L). The 5-min EC50 data for Biotox TM were compared to the respective data for Microtox TM test (also based on freeze-dried P. phosphoreum ) and rodent oral LD50 values. For Biotox TM vs Microtox TM the log-log correlation coefficients for the whole data set (pesticides+solvents, pesticides, solvents) were 078, 0.37 and 0.95, respectively. The less toxic solvents to Biotox TM were ethylene glycol, DMSO, methanol, ethanol, acetone and acetonitrile and, therefore, these solvents could be used for increasing the solubility of lipophilic compounds, e.g. , for testing the toxicity of pesticides. In order to analyze toxic effects of pesticides in complex mixtures the EC50 values of pentachlorophenol, coumarin and glyphosate as pure substances and in their mixtures were compared: the toxic effects of the above-mentioned pesticides in their mixtures were not additive.