Fecal pollution in coastal marine sediments from a semi-enclosed deep embayment subjected to anthropogenic activities: an issue to be considered in environmental quality management frameworks development.

Sewage discharge is a major source of pollution in marine environments. Urban wastewaters can directly enter marine environments carrying pathogen organisms, organic loads, and nutrients. Because marine sediments can act as the ultimate fate of a wide range of pollutants, environmental quality assessment in this compartment can help to identify pollution problems in coastal areas. In the present study, characterization of surficial marine sediments allowed assessment of fecal pollution in a semi-enclosed deep embayment that is subjected to anthropogenic activities. Physicochemical parameters and fecal indicators presented a great spatial heterogeneity. Fecal coliform and Clostridium perfringens showed accumulation in an extensive area, not only in proximity to sewage discharge points, but also in sediments at 100 meters depth. Results included herein demonstrated that, in coastal areas, urban wastewater discharge can affect the whole ecosystem through accumulation of fecal matter in bottom sediments. Application of multivariate techniques provided useful information with applicability for management of coastal areas in such complex systems. Environmental implications of wastewater discharge in coastal areas indicate the need to implement and include sediment quality control strategies in legislative frameworks.

Effect of the test media and toxicity of LAS on the growth of Isochrysis galbana.

In this paper, the toxicity of linear alkylbenzene sulfonate (LAS) was evaluated in the marine microalga Isochrysis galbana using data of growth inhibition toxicity tests at 96-h exposure time. Toxicity was examined in standard conditions and by means of the modification of two variables of the test media: (1) the dilution water and (2) the content of nutrients in the test medium. For this purpose, a total of 10 toxicity test were designed: five dilution waters, four natural marine waters and one synthetic seawater; each in two different nutritive conditions, saturated nutrient concentration (SC) by the addition of modified f/2 nutritive medium, and natural nutrient concentration (NC), i.e., without the addition of f/2. At threshold toxicity levels, the dilution waters used in the test and the nutrient concentrations did not affect the toxicity of LAS. At IC50 concentrations, the toxicity of LAS is influenced by both variables: under SC conditions, the toxic effect of LAS diminishes, obtaining in all the tests IC50 > 10 mg/L LAS. Under NC conditions, IC50 concentrations ranging between 3.15 and 9.26 mg/L LAS have been obtained.

Modelling of reactivation after UV disinfection: effect of UV-C dose on subsequent photoreactivation and dark repair.

The increased use of UV radiation as a wastewater treatment technology has stimulated studies of the repair potential of microorganisms following treatment. In this study, samples of unfiltered secondary effluent were irradiated with seven levels of UV-C doses (50-200 mW s/cm(2)) from six low-pressure lamps in an open-channel UV disinfection system. Following irradiation, samples were incubated at 20 degrees C under photoreactivating light or in darkness. Samples were analysed for 240 min following incubation. The logistic model is proposed to explain the relation between photoreactivation and the UV-C dose received by the microorganisms. That model accurately fitted the data obtained in photoreactivation experiments, permitting interpretation of the estimated kinetic parameters: S(m) and k(2). In the experiments carried out in darkness, a slight reactivation is observed (<0.1%), followed by a decay period in which survival decreases. In order to model this last period, a modification was made to the logistic model by including a term of mortality that assumes a zero-order kinetic. The parameters S(m) and k(2), in both photoreactivation and darkness, show an exponential dependence on the UV-C inactivating dose. It is possible to predict their values, and hence the reactivation curve, from the equations proposed in this work.

A set of marine microalgae bioassays for the evaluation of biological water quality in enclosure areas in south of Spain.

The aim of this study has been the identification of the nutritive status (oligotrophy end eutrophy) in four enclosure areas from Gulf of Cadiz (Southwest Iberian Peninsula-Europe) by means of a battery of water column toxicity tests. The test organisms were four marine microalgae which comprised a wide taxonomic range. Growth tests with receiving waters from the four study areas were carried out under two nutritive conditions; with and without additional nutrient-enriched medium. The results of both bioassays were used to define a new eutrophication index (I(E)). The I(E) index obtained presents a good correlation with the traditional physical-chemical parameters in the enclosure areas; nevertheless in open waters where the dilution processes are more important the results show less correlation.

Wet air oxidation of oily wastes generated aboard ships: kinetic modeling.

Ships are floating industrial plants which generate great amounts of toxic and hazardous wastes. Nevertheless, a feasible model for the management of such wastes has not been developed yet. This work studies the feasibility of treating those wastes aboard the ship by means of aqueous oxidation at high pressures and temperatures. Wet air oxidation has proved to be a very efficient technology for the treatment of those residual currents, resulting in destruction efficiencies of greater than 90% of initial COD and 99.9% of oil/greases content. A kinetic model for the oxidation process, based on a series-parallel reaction pathway, is proposed and is shown to fit the experimental results.