Microbiological hazard identification in river waters used for recreational activities.

Pathogenic bacteria, viruses, and parasites can cause waterborne disease outbreaks. The study of coastal water quality contributes to identifying potential risks to human health and to improving water management practices. The Río de la Plata River, a wide estuary in South America, is used for recreational activities, as a water source for consumption and as a site for sewage discharges. In the present study, as the first step of a quantitative microbial risk assessment of the coastal water quality of this river, a descriptive study was performed to identify the microbial pathogens prevalent in its waters and in the sewage discharged into the river. Two sites, representing two different potential risk scenarios, were chosen: a heavily polluted beach and an apparently safe beach. Conductivity and fecal contamination indicators including enterococci, Escherichia coli, F + RNA bacteriophages, and human polyomaviruses showed high levels. Regarding enterococci, differences between sites were significant (p-values <0.001). 93.3% and 56.5% of the apparently safe beach exceeded the recreational water limits for E. coli and enterococci. Regarding pathogens, diarrheagenic E. coli, Salmonella, and noroviruses were detected with different frequencies between sites. The parasites Cryptosporidium spp. and Giardia duodenalis were frequently detected in both sites. The results regarding viral, bacterial, and parasitic pathogens, even without correlation with conventional indicators, showed the importance of monitoring a variety of microorganisms to determine water quality more reliably and accurately, and to facilitate further studies of health risk assessment. The taxonomic description of microbial pathogens in river waters allow identifying the microorganisms that infect the population living on its shores but also pathogens not previously reported by the clinical surveillance system.

Evaluation of bottled water quality by determining nitrate concentration.

The presence of nitrate in sources of drinking water is a matter of concern because of its potential risk for human health. In many countries like Argentina, an increasing proportion of the population chooses to consume bottled water, among other reasons, for lack of water access. The present study was conducted (a) to evaluate the quality of bottled waters by determining nitrate concentration, (b) to relate bottled water quality with water access, (c) to analyze public awareness about bottled water quality and consumption habits of the population in the urban area of Buenos Aires. Two locations were selected, Ciudad Autónoma de Buenos Aires (C.A.B.A.) and Malvinas Argentinas in Buenos Aires Province (PBA), with percentages of water access of 99.6% and 8.8%, respectively. Random samples from both locations (n = 100) were analyzed. A survey was conducted in order to inquire about perception of population on bottled water quality and their consumption habits. In C.A.B.A., no sample exceeded the 45 mg/L limit value in force in Argentina, while in Malvinas Argentinas, 34% of the brands analyzed showed values above it. The survey revealed that 71.7% of people consume bottled water. While people in C.A.B.A. do so mainly out of habit, safety is the priority in PBA.

Biotransformation of chromium (VI) in liquid effluents by resistant bacteria isolated from the Matanza-Riachuelo basin, in Argentina.

The aims of this investigation were to evaluate the bacterial resistance to zinc, copper, chromium (VI) and lead in surface water streams from Buenos Aires, Argentina; to select a chromium-resistant strain able to remove the metal in batch process and to evaluate the potential of this strain to remove chromium (VI) in liquid effluents. Bacterial resistance to the metals was evaluated by determining the minimal inhibitory concentration. The kinetic of chromium (VI) removal by one of the resistant strains was studied in nutrient broth with 50 and 100 mg L-1 of the metal, as well as an effluent from an electroplating industry. High resistance to all the metals under study was observed in the bacterial communities of the Matanza-Riachuelo basin. A chromium-resistant strain was isolated and identified as Microbacterium sp. It was able to remove 50 and 100 mg L-1 of Cr (VI) in 36 and 66 h respectively, with efficiency higher than 99%. Experiments with liquid effluents showed the ability of the strain to transform 150 mg L-1 of the metal in 84 h, with efficiency higher than 99%. These results show the potential of this native strain for the treatment of liquid effluents that contain chromium (VI).

Aerobic degradation of ibuprofen in batch and continuous reactors by an indigenous bacterial community.

Water from six points from the Riachuelo-Matanza basin was analyzed in order to assess ibuprofen biodegradability. In four of them biodegradation of ibuprofen was proved and degrading bacterial communities were isolated. Biodegradation in each point could not be correlated with sewage pollution. The indigenous bacterial community isolated from the point localized in the La Noria Bridge showed the highest degradative capacity and was selected to perform batch and continuous degradation assays. The partial 16S rRNA gene sequence showed that the community consisted of Comamonas aquatica and Bacillus sp. In batch assays the community was capable of degrading 100 mg L(-1) of ibuprofen in 33 h, with a specific growth rate (µ) of 0.21 h(-1). The removal of the compound, as determined by High performance liquid chromatography (HPLC), exceeded 99% of the initial concentration, with a 92.3% removal of Chemical Oxygen Demand (COD). In a down-flow fixed-bed continuous reactor, the community shows a removal efficiency of 95.9% of ibuprofen and 92.3% of COD for an average inlet concentration of 110.4 mg. The reactor was kept in operation for 70 days. The maximal removal rate for the compound was 17.4 g m(-3) d(-1). Scanning electron microscopy was employed to observe biofilm development in the reactor. The ability of the isolated indigenous community can be exploited to improve the treatment of wastewaters containing ibuprofen.