Genotoxicity and toxicity evaluations of ECF cellulose bleaching effluents using the Allium cepa L. Test

Toxicity and genotoxicity tests were performed on root cells of Allium cepa in order to evaluate wastewater quality following an ECF cellulose bleaching process. The results revealed a toxic effect of the effluent, with inhibition of meristem growth and generally lower values of metaphase, anaphase and telophase indices at pH 10.5 than pH 7 for all effluent concentrations. The genotoxicity effect was different from the toxic effect given that the micronucleus and the chromosomal aberration tests in anaphase-telophase cells were low over all ranges of the studied effluent concentrations

Advanced oxidation of a pulp mill bleaching wastewater

The degradation, by several advanced oxidation reactions, of a pulp mill ECF bleaching effluent, was studied. The initial biodegradability of the organic matter present in the effluent, estimated as the BOD(5)/COD, was low (0.3). When the effluent was submitted to ozonation and to five different advanced oxidation systems (O(3)/UV, O(3)/UV/ZnO, O(3)/UV/TiO(2), O(2)/UV/ZnO, O(2)/UV/TiO(2)), the biodegradability increase significantly. After five minutes of reaction, the O(3)/UV system, appears as the most efficient in to transform the organic matter to more biodegradable forms. A similar effect was observed when the effluent was submitted to an activated sludge treatment. The GOD, TOC and toxicity reduction correlated well with the biodegradability enhancement after AOPs treatments. (C) 1999 Elsevier Science Ltd. All rights reserved.39101679168

Interactions between photodegradation components

<p>Abstract</p> <p>Background</p> <p>The interactions of <it>p</it>-cresol photocatalytic degradation components were studied by response surface methodology. The study was designed by central composite design using the irradiation time, pH, the amount of photocatalyst and the <it>p</it>-cresol concentration as variables. The design was performed to obtain photodegradation % as actual responses. The actual responses were fitted with linear, two factor interactions, cubic and quadratic model to select an appropriate model. The selected model was validated by analysis of variance which provided evidences such as high F-value (845.09), very low P-value (<.0.0001), non-significant lack of fit, the coefficient of R-squared (R² = 0.999), adjusted R-squared (R_adj² = 0.998), predicted R-squared (R_pred² = 0.994) and the adequate precision (95.94).</p> <p>Results</p> <p>From the validated model demonstrated that the component had interaction with irradiation time under 180 min of the time while the interaction with pH was above pH 9. Moreover, photocatalyst and <it>p</it>-cresol had interaction at minimal amount of photocatalyst (< 0.8 g/L) and 100 mg/L <it>p</it>-cresol.</p> <p>Conclusion</p> <p>These variables are interdependent and should be simultaneously considered during the photodegradation process, which is one of the advantages of the response surface methodology over the traditional laboratory method.</p