Wastewater reuse in Mediterranean semi-arid areas: The impact of discharges of tertiary treated sewage on the load of polar micro pollutants in the Llobregat river (NE Spain)

The presence of sewage-borne micro contaminants in environmental waters is directly related to the discharge of treated effluents from wastewater treatment plants (WWTP) and the flow rate of the receiving river waters. Mediterranean rivers, in particular, are characterized by important fluctuations in the flow rates and heavy pollution pressures resulting from extensive urban, industrial and agricultural activities. This translates into contamination levels in these rivers often higher than those in other larger European basins. The present work provides an overview of the occurrence of five groups of organic contaminants (131 compounds) namely pharmaceuticals, illicit drugs, polar pesticides, estrogens, alkylphenols and related ethoxylates in WWTP tertiary treatment effluents. Data gathered during a period of water reuse carried out in the lower stretch of the Llobregat river (NE Spain), in the surroundings of the town of Barcelona as a consequence of the severe drought that took place along the years 2007-2008 are presented as illustrative example. In general, measured concentrations of the target compounds were in the low to mid ng L⁻¹ range. The total concentration of each compound class downstream to the discharge point was similar or slightly higher than that found upstream. Regarding the loads calculated for each compound, the relative contribution from the river upstream and the tertiary effluent were highly compound depending with no apparent trend. However, estimation of the overall bulk loads for each compound class determined in the Llobregat river showed the following rank order: pharmaceuticals > alkylphenols > pesticides > illicit drugs ? estrogens.     

The impact of environmental contamination with antibiotics on levels of resistance in soil bacteria

This study examined the effects of tetracycline and streptomycin on microorganisms in three different soil habitats: forest soil, agricultural soil, and compost. These antibiotics are commonly used in both medical and veterinary therapy as well as in the production of plant biomass and until quite recently, the production of animal biomass. Microcosms were used as model systems in which the number of microorganisms in environments containing different amounts of antibiotics was analyzed. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of tetracycline and streptomycin were determined. The MIC and MBC values of tetracycline against the tested strains were 20 to 180 microg/ mL and 30 to 300 microg/mL, respectively, and of streptomycin, 360 to 500 microg/mL and > or =500 microg/mL, respectively. Resistant bacterial strains were identified and their physiological profiles assessed. Streptomycin and tetracycline were found to reduce the number of bacteria in the studied soils by between 50 and 80%. Soil bacteria were found to be more resistant to streptomycin than to tetracycline. The bacterial species showing the highest resistance to tetracycline were Rhizobium radiobacter, Burkholderia cepacia, Brevundimonas vesicularis, and Pasteurella multocida. Most soils with high concentrations of streptomycin (5 mg/kg) contained Rhizobium radiobacter, Burkholderia cepacia, and Sphingomonas multivorum, among others. The strains most resistant to tetracycline were isolated from agricultural soil that is constantly subjected to tetracycline pressure from animal manures and biosolids. Among resistant strains, opportunistic pathogens were identified.     

Fast preparation of the seawater accommodated fraction of heavy fuel oil by sonication

The seawater accommodated fraction (SWAF) of oil is widely used for the assessment of its toxicity. However, its preparation in the laboratory is time consuming, and results from different authors are difficult to compare as preparation methods vary. Here we describe a simple and fast set up, using sonication, to produce reproducible SWAF in the laboratory. The system was tested on heavy fuel oil placed on seawater at different salinity and temperature conditions. Maximum dissolution of the oil was achieved after 24 h, independently of both seawater salinity and temperature. Our findings are discussed in relation to the fate of the oil from the deep spill of the Prestige tanker. Changes in temperature in the open ocean are bound to have larger impact in the concentration of the SWAF than the corresponding values of sea water salinity. We anticipate that in this type of incident the highest SWAF, as the oil reaches the sea surface, should be expected in the warmest and less saline waters of the water column.