Modeling of coastal water contamination in Fortaleza (Northeastern Brazil)

Abstract

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.

Modelagem da drenagem urbana e avaliação das cargas bacteriológicas na Vertente Marítima de Fortaleza, Ceará

“…A água, como solvente universal e veículo das diversas substâncias, pode ser um indicador das condições ambientais das bacias hidrográficas (BRITES & GASTALDINI, 2007;ZAFFANI, 2012), e os sistemas de drenagem podem representar fontes pontuais de poluição aos corpos receptores aos quais se destinam, como lagos, rios ou oceanos (PEREIRA et al, 2015;TOSIC et al, 2017;BATISTA & HARARI, 2017).…”

“…Dessa forma, os poluentes presentes nas bacias hidrográficas, originários de fontes pontuais ou difusas, poderão ser carreados aos corpos d'água superficiais, fato que pode ser potencializado em períodos chuvosos em decorrência da lixiviação sobre as bacias hidrográficas ocasionada pelo escoamento superficial, bem como pelo extravasamento oriundo das redes coletoras de esgoto (PEREIRA et al, 2015); há ainda o risco de serem agravados por fatores climáticos locais, como intensidade e distribuição espaçotemporal das chuvas (BUTLER & DAVIES, 2004;EGODAWATTA;THOMAS;GOONETILLEKE, 2007;TUCCI, 2008;ARORA & REDDY, 2013;LI et al, 2015).…”

“…Estudos de modelagem bacteriológica, previamente realizados visando à avaliação da balneabilidade na zona costeira de Fortaleza, constataram que as maiores fontes responsáveis pela alteração na qualidade da água são oriundas do sistema de drenagem, incluindo galerias, canais e rios (PEREIRA et al, 2015). Portanto, o uso da modelagem torna-se muito recomendado, pois possibilita a realização de análises de diagnósticos e prognósticos, interpolação e extrapolação de dados e estudo da dinâmica de determinados processos, permitindo a integração de informações espacial e temporalmente dispersas.…”

Quantifying the environmental impact of pollutant plumes from coastal rivers with remote sensing and river basin modelling

“…Based on their analysis, the initial dilution from a submerged outfall was observed to vary with currents, and ranged between 126 and 1047, with lower values during effluent discharge periods and higher values during strong winds and currents. Decay rates ranged with sunlight, and daytime T 90 decay ranged from 2 to 20 h and night-time T 90 decay ranged from 22.5 to 100 h [31]. However, other studies have concluded that coastal currents had little effect on pollutant plume dispersion in coastal waters [3].…”

“…Plume and coastal mixing impacts the concentrations of E. coli in the water, which was demonstrated by in Fortaleza, Brazil by a group that simulated initial dilution, dispersion, and solar-decay with a hydrodynamic model [31]. Based on their analysis, the initial dilution from a submerged outfall was observed to vary with currents, and ranged between 126 and 1047, with lower values during effluent discharge periods and higher values during strong winds and currents.…”