Quantification of pathogenic microorganisms and microbial indicators in three wastewater reclamation and managed aquifer recharge facilities in Europe.

Managed Aquifer Recharge (MAR) is becoming an attractive option for water storage in water reuse processes as it provides an additional treatment barrier to improve recharged water quality and buffers seasonal variations of water supply and demand. To achieve a better understanding about the level of pathogenic microorganisms and their relation with microbial indicators in these systems, five waterborne pathogens and four microbial indicators were monitored over one year in three European MAR sites operated with reclaimed wastewater. Giardia and Cryptosporidium (oo)cysts were found in 63.2 and 36.7% of the samples respectively. Salmonella spp. and helminth eggs were more rarely detected (16.3% and 12.5% of the samples respectively) and Campylobacter cells were only found in 2% of samples. At the Belgian site advanced tertiary treatment technology prior to soil aquifer treatment (SAT) produced effluent of drinking water quality, with no presence of the analysed pathogens. At the Spanish and Italian sites amelioration of microbiological water quality was observed between the MAR injectant and the recovered water. In particular Giardia levels decreased from 0.24-6.14 cysts/L to 0-0.01 cysts/L and from 0.4-6.2 cysts/L to 0-0.07 cysts/L in the Spanish and Italian sites respectively. Salmonella gene copies and Giardia cysts were however found in the water for final use and/or the recovered groundwater water at the two sites. Significant positive Spearman correlations (p<0.05, r(s) range: 0.45-0.95) were obtained, in all the three sites, between Giardia cysts and the most resistant microbial markers, Clostridium spores and bacteriophages.

Quantitative PCR monitoring of antibiotic resistance genes and bacterial pathogens in three European artificial groundwater recharge systems.

Aquifer recharge presents advantages for integrated water management in the anthropic cycle, namely, advanced treatment of reclaimed water and additional dilution of pollutants due to mixing with natural groundwater. Nevertheless, this practice represents a health and environmental hazard because of the presence of pathogenic microorganisms and chemical contaminants. To assess the quality of water extracted from recharged aquifers, the groundwater recharge systems in Torreele, Belgium, Sabadell, Spain, and Nardò, Italy, were investigated for fecal-contamination indicators, bacterial pathogens, and antibiotic resistance genes over the period of 1 year. Real-time quantitative PCR assays for Helicobacter pylori, Yersinia enterocolitica, and Mycobacterium avium subsp. paratuberculosis, human pathogens with long-time survival capacity in water, and for the resistance genes ermB, mecA, blaSHV-5, ampC, tetO, and vanA were adapted or developed for water samples differing in pollutant content. The resistance genes and pathogen concentrations were determined at five or six sampling points for each recharge system. In drinking and irrigation water, none of the pathogens were detected. tetO and ermB were found frequently in reclaimed water from Sabadell and Nardò. mecA was detected only once in reclaimed water from Sabadell. The three aquifer recharge systems demonstrated different capacities for removal of fecal contaminators and antibiotic resistance genes. Ultrafiltration and reverse osmosis in the Torreele plant proved to be very efficient barriers for the elimination of both contaminant types, whereas aquifer passage followed by UV treatment and chlorination at Sabadell and the fractured and permeable aquifer at Nardò posed only partial barriers for bacterial contaminants.

Retrieval of aerosol profile variations from reflected radiation in the oxygen absorption a band.

Through a Fredholm integral equation of the first kind, aerosol kernel functions relate the variations in radiance measured by satellites to the variations in the aerosol extinction profile and thus permit profile retrieval from radiance measurements by inversion of the set of radiative transfer equations for various spectral intervals. Previously [Appl. Opt. 36, 1328 (1997)] the kernel functions were evaluated for the red and near-infrared spectral regions outside molecular absorption bands. Here they are computed within the oxygen A band with 20-cm(-1) spectral resolution. It is shown that, even with such a relatively low spectral resolution, the new set of kernels is able to provide better information on and improved accuracy of the retrieved profile.

Inferring aerosol layer properties from the spatial structure of satellite images.

Scattering from atmospheric aerosols causes blurring of satellite images. A study of this effect suggests that it might be possible to evaluate aerosol properties from these images. We consider an aerosol layer superimposed on a surface with a one-dimensional sinusoidal variation in reflectivity and with a half-plane reflectivity variation. A single scattering approximation is used to show that information about the aerosol layer height and optical depth can be extracted provided the variation in ground reflectivity is known.

Retrieval of aerosol profile variations in the visible and near infrared: theory and application of the single-scattering approach.

A linear relationship between the variations in radiance measured in the visible and near infrared by satellites and variations of aerosol-extinction profile has been derived, hence reducing the problem to that of solving a Fredholm integral equation of the first kind. The retrieved profiles, by the linear constrained-inversion method, have proved to be accurate in the lower atmosphere, even if simultaneous changes are taking place in the stratosphere. Variations in the stratosphere, however, are retrieved with a lesser degree of accuracy and only as long as no variations occur in the tropospheric haze.