Abstract
Submarine outfalls are proposed as an efficient alternative for the final destination of wastewater in densely populated coastal areas, due to the high dispersal capacity and the clearance of organic matter in the marine environment, and because they require small areas for implementation. This paper evaluates the probability of unsuitable bathing conditions in coastal areas nearby to the Ipanema, Barra da Tijuca and Icaraí outfalls based on a computational methodology gathering hydrodynamic, pollutant transport, and bacterial decay modelling. The results show a strong influence of solar radiation and all factors that mitigate its levels in the marine environment on coliform concentration. The aforementioned outfalls do not pollute the coastal areas, and unsuitable bathing conditions are restricted to nearby effluent launching points. The pollution observed at the beaches indicates that the contamination occurs due to the polluted estuarine systems, rivers and canals that flow to the coast.
Highlights
The coastal occupation of major Brazilian cities has been steadily increasing in recent years
In the present work the water quality assessment is based on coliform bacteria concentration in coastal waters
All meteorological and oceanographic parameters that affect directly or indirectly the solar radiation are extremely relevant in determining the fecal coliform concentration in seawater
Summary
The coastal occupation of major Brazilian cities has been steadily increasing in recent years. Increased urbanization in coastal areas has not been followed by appropriate sewage networks. In recent decades the water quality in coastal areas has suffered an intense process of degradation due to domestic sewage that flows to the beaches without any treatment, either by direct dumps or through rainwater drainage networks. Beach contamination occurs from point sources along the coastline, or indirectly through its connection with polluted rivers and tidal channels. This fact leads to the constant contamination of the beaches, which, in turn, compromise the water quality standards and increase the risk of diseases through primary or secondary contact with polluted waters. In coastal areas the increased urbanization leads to an unavailability of space for sewage treatment
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