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An important tool in environmental management projects and studies due to the complexity of environmental systems, environmental modeling makes it possible to integrate many variables and processes, thereby providing a dynamic view of systems. In this study the bacteriological quality of the coastal waters of Fortaleza (a state capital in Northeastern Brazil) was modeled considering multiple contamination sources. Using the software SisBaHiA, the dispersion of thermotolerant coliforms and Escherichia coli from three sources of contamination (local rivers, storm drains and submarine outfall) was analyzed. The models took into account variations in bacterial decay due to solar radiation and other environmental factors. Fecal pollution discharged from rivers and storm drains is transported westward by coastal currents, contaminating strips of beach water to the left of each storm drain or river. Exception to this condition only occurs on beaches protected by the breakwater of the harbor, where counterclockwise vortexes reverse this behavior. The results of the models were consistent with field measurements taken during the dry and the rainy season. Our results show that the submarine outfall plume was over 2 km from the nearest beach. The storm drains and the Maceió stream are the main factors responsible for the poor water quality on the waterfront of Fortaleza. The depollution of these sources would generate considerable social, health and economic gains for the region.

Urban drainage systems can represent sources of pollutants input to the receiving bodies for which they are intended. Therefore, the present work aims to propose a tool for modeling the urban drainage system of the Vertente Marítima basin of Fortaleza, Ceará, aiming at the evaluation of bacteriological loads. For this purpose, the Stormwater Management Model (SWMM) was selected for the hydrological and hydraulic simulations; a methodology for the calculation of bacteriological loads was proposed by estimating the diffuse load [DL] (MPN, day -1 .ha -1 ) and its correlation with a series of hydro-environmental variables and scenarios for different pluviometry precipitation conditions were analyzed, as well as sewage collection and inadequately disposed solid waste (IDSW). The resultsshow that SWMM gives representative results and that the rainy season is responsible for the greater contribution of the bacteriological load to the seafront. Regarding the predictive model, a second-order potential function was adjusted by correlating DL with the average monthly precipitation (mm. day -1 ) for the three sub-basins analyzed. Subsequently, the coefficients of the equations found were correlated to IDSW (kg.day -1 ), obtaining a logarithmic adjustment (R 2 = 0.99), with which it is possible to obtain a DL estimation equation for any sub-basin of Vertente Marítima. An analysis of the scenarios showed a significant increase of the load in extreme precipitations (twice) and a considerable decrease with the increase of the fraction of the population connected to the sewage network and the decrease of IDSW production (0.28 and 0.38 times the initial value in the Jacarecanga and Maceió Stream, respectively).

Potential problems arising from the presence of cyanobacteria in water intended for human consumption have been reported by several researchers. Regarding water treatment plants, intact cells of cyanobacteria should be removed to avoid the release of cyanotoxins due to cell lysis. Water treatment techniques with different degrees of complexity can be employed but, whenever possible, the method of easiest installation, operation and maintenance should be selected, especially for non-industrialized countries and rural communities. In this context, research was carried out to evaluate the efficiency of slow sand filtration to treat water from Gavião reservoir in the city of Pacatuba, Ceara, Brazil, which has exhibited phytoplankton density of approximately 105 cells/mL with a prevalence of cyanobacteria representing over 90% of total cells. The results have demonstrated that slow sand filtration can be used to achieve water purification that meets federal standards. However, it was established that filtration through beds of gravel (prefilter) before the slow sand filtration is essential. The removal of phytoplankton reached values of approximately 97% and the filter run duration was more than 70 days. Furthermore, the slow sand filter was very efficient in removing total coliforms, with removal of up to 99.98%.