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.

-This paper investigated the influence of organic loading on BOD and COD removal in primary facultative ponds. The study was based on six full-scale pond plants in which average removals of unfiltered biochemical oxygen demand (BOD) and chemical oxygen demand (COD) were 72 and 50%, respectively. For filtered samples, the removals were 89 and 83%, respectively. First-order removal rates assuming ideal hydraulic patterns (completely mixed and plug-flow) decreased with increments in the mean hydraulic retention time (HRT). Reduction in organic loading also caused a decrease in removal rates. The results emphasized that HRT and surface organic loading are more reliable to estimate first-order removal rates than traditional Arrhenius-style equations. Thus, HRT and surface organic loading can be used to compute more realistic first-order removal rates and surface removal rates. An alternative design procedure based on HRT and surface organic loading was proposed and demonstrated.

RESUMO.A avaliação dos dados agrupados da monitoração de 16 ETEs do tipo tanque séptico (T SEP ) seguido por filtro anaeróbio (F AN ) mostrou remoção média global de 55% para DQO e SST. O desempenho alcançado foi abaixo do sugerido pela literatura, porém compatível com o de estudos recentes sobre sistemas em escala real no país. A remoção média global de bactérias do grupo coliforme, após desinfecção com solução de hipoclorito de sódio, foi de 3,0 unidades de log. Remoção mais elevada ocorreu com Escherichia coli como indicador (3,5 logs). Em geral, as maiores remoções de coliformes foram alcançadas com concentrações de cloro residual livre (CRL) variando de 2,0 a 2,5 mg L -1. Os resultados mostraram a aplicabilidade da turbidez para estimar concentrações de SST e DQO no efluente tratado. Observou-se também que a concentração de CRL é útil para estimar as concentrações de bactérias do grupo coliforme.Palavras-chave: sistemas anaeróbios, controle de efluente, turbidez, cloro residual livre.ABSTRACT. Turbidity and free residual chlorine for monitoring plants comprised by septic tank followed by anaerobic filter. Grouped monitoring data of 16 wastewater treatment plants was investigated. The plants were comprised by septic tanks followed by anaerobic filters and effluent disinfection with sodium hypochlorite. Removal of COD and total suspended solids was about 55%. This number was below values observed by the literature. However, the results were in accordance with recent findings in Brazilian full-scale plants. Coliform removal was about 3.0 log units with better results for Escherichia coli (3.5 logs). Best results were achieved with free residual chorine concentrations ranging from 2.0 to 2.5 mg L -1 . Findings showed that turbidity is a useful parameter to estimate COD and TSS concentrations in the treated effluent. Free residual chlorine may also be applied to estimate coliform numbers.

WSP technology has been used in Ceará, Northeast Brazil, since middle 1970s. There are presently 96 ponds plants and most of them are comprised by single cells (40%) and series of 3 ponds (35%). They were under loaded due to incomplete house connections to the sewerage network and low per capita wastewater contributions. Highest removal rates of organic material, ammonia and faecal coliform were found in 3 pond series. Faecal coliform removal was in accordance with the literature and series of ponds reached numbers ≤10(5) cells/100 ml. In series with 4 and 5 ponds FC was below 10(3) cells/100 ml. Ammonia removal varied from 30 to 80% and total phosphorus the removal was not significant. An increase in the number of maturation ponds enhances nutrient and coliform removal. Up-grading schemes should be investigated as well as effluent reuse potential.

RESUMO: Esta pesquisa tem como principal objetivo desenvolver uma metodologia para calcular o risco de eutrofização em um reservatório, baseado na teoria dos conjuntos difusos e nos mecanismos usados para a determinação do índice de estado trófico modificado. Para tal, foram usados os dados de um reservatório no estado de Ceará, Brasil, obtidos nos anos de 2001 a 2006. Estes dados foram cedidos pela Companhia de Gestão de Recursos Hídricos -COGERH. Para o cálculo do risco, o índice de estado trófico modificado (IET M ) foi transformado em funções de pertinências, com base na teoria dos conjuntos difusos. Os resultados mostraram que o uso da teoria dos conjuntos difusos pode ser uma ferramenta importante para calcular o risco de eutrofização para reservatórios e, com isso, fornecer subsídios aos gestores dos recursos hídricos, na formulação de politicas públicas para o planejamento dos recursos hídricos, no que diz respeito à qualidade de água em reservatórios.PALAVRAS-CHAVE: Eutrofização, índice de estado trófico modificado, teoria dos conjuntos difusos.