Selected water quality data from La Plata River Basin shared by 5 SouthAmerican countries (Argentina, Bolivia, Brazil, Paraguay and Uruguay) was employed to evaluate advantages and constraints for global water quality indicators development. Water quality state indicators from UNSD/UNEP Questionnaire (2004) were considered at 5 sampling stations located on the Paraná (3), Pilcomayo and La Plata Rivers. Water pollution pressure indicators, also called driving forces, were estimated for the main emissions from the Metropolitan Area of Buenos Aires into the La Plata River. Multiple and different monitoring programs and operating agencies limited the availability of continuous time series of water quality indicators for this large river basin. Further development of water pollution pressure and technological indicators is required to improve cause-effect water quality follow up. Attention was given to the need to develop criteria for censored data statistics (mostly related with toxics constituents), and to establish tools to assess, periodically, the state of water environments through water quality guidelines, standards and risks to the biota through the usage of potency factors.
We studied the degradation of mixtures of o-cresol, m-cresol, and p-cresol, by Pseudomonas putida isolated from natural sources, and the application of this degradation to the depuration and detoxification of synthetic and industrial wastewater. Biodegradation assays were performed in batch and continuous-flow fixed-bed aerobic reactors. Biodegradation was evaluated by cresol determination using micellar electrokinetic capillary chromatography, UV spectrophotometry, and chemical oxygen demand (COD). Mineralization of cresols was assessed by gas chromatography performed both at the end of the batch process and in the continuous flow reactor effluent. Microbial growth was measured by the plate count method. Scanning electronic microscopy was employed to observe bacterial cells adsorbed on polyvinyl chloride cylinders in the reactor. Detoxification was evaluated by Vibrio fischeri, Pseudokirchneriella subcapitata, and Daphnia magna toxicity tests. Results obtained show that under batch conditions the strain grew exponentially with 100, 200, and 300 mg/L of each of the isomers in synthetic minimal medium within 48 h; in industrial wastewater with 540 mg/L of cresols similar results were obtained. Removal of cresols and COD was higher than 99.9% and 95.0%, respectively. When assays were performed in continuous flow reactor in synthetic wastewater under operating conditions a removal of total cresols and COD of 99.9% and 96.4%, respectively, was achieved. Results of capillary electrophoresis may suggest a concurrent isomers utilization and simultaneous growth on the substrates. Toxicity was neither detected at the end of the batch process nor in the continuous flow reactor effluent.
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