Abstract
The discharge of domestic sewage is one of the most common types of marine pollution, namely through submarine outfalls. In this study, water and sediments of the coastal submarine sewage outfall in Guarujá, São Paulo, Brazil were assessed during the high (January) and low (April) tourist seasons in 2018. The Canadian Council of Ministers of the Environmental Water Quality Index (CCMEWQI) showed a “marginal” water quality, in both seasons, where dissolved oxygen, biochemical oxygen demand, oil and greases, ammonia, surfactants, aluminium, lead, copper, nickel, Escherichia coli and Enterococci showed potential ecological risks. However, no mutagenic potential was detected in the complex mixture (Ames Salmonella/microsome test: MI<2), and no protozoa and Salmonella bacteria were found. In the sediment, a total of 25 benthic taxa were inventoried, suggesting that the macrofauna is not under contamination stress. Cadmium, lead, copper, chromium, nickel and zinc were below the Threshold Effect Level, and the Geoaccumulation Index was <0. Furthermore, the absence of acute toxicity to the test organism Kalliapseudes schubartii (EC50: 96h) and the Shannon-Wiener diversity index (H’: 2.5 to 3.5 bits/ind) suggests healthy or unpolluted environments. However, the deviation of some environmental indicators suggests the need of continuous monitoring based on field measurements.
Highlights
Worldwide population density increase in coastal areas has been highly responsible for the alteration of marine ecosystems (Pelling and Blackburn, 2013; Libhaber, 2016), for instance namely due to untreated municipal sewage discharges (Cesar et al, 2007; Soto-Jiménez et al, 2011; De La Ossa Carretero et al, 2012)
The 17 coastal states are served by 20 wastewater treatment plants (WWTP) with preliminary levels of treatment (Lamparelli and Ortiz, 2007; De Souza Abessa et al, 2012), including the WWTP of Guarujá city, in São Paulo State (Baptistelli and Marcellino, 2016)
The results demonstrate a predominance of NH3 (0.18 to 0.44 mg/L) in relation to NOx (NO2- + NO3-) in both seasons (Table 2)
Summary
Worldwide population density increase in coastal areas has been highly responsible for the alteration of marine ecosystems (Pelling and Blackburn, 2013; Libhaber, 2016), for instance namely due to untreated municipal sewage discharges (Cesar et al, 2007; Soto-Jiménez et al, 2011; De La Ossa Carretero et al, 2012). The average sewage composition is 99.9% water and only 0.1% contaminants (Libhaber, 2016), this former fraction represents a complex physical, chemical, and biological mixture, which may lead to the depletion of oxygen levels (Bleninger et al, 2016), eutrophication (N and P enrichment) (Heisler et al, 2008; Howarth, 2008), introduction of pathogenic organisms (Olalemi et al, 2016), and heavy metal contamination (Christophoridis et al, 2009) This complex mixture can cause severe changes in the environmental quality of waters (Christophoridis et al, 2009; Tabrez et al, 2011) and sediments (Gonzalez et al, 1999; Santi and Tavares, 2009) in areas adjacent to oceanic sewage disposals (Cesar et al, 2007; Soto-Jiménez et al, 2011; De La Ossa Carretero et al, 2012). These systems are chosen mainly due to their lower maintenance and operation costs (10 to 20 times lower than a secondary system) (Roberts, 2016) and minimum space requirements (Libhaber, 2016), which makes them an ideal alternative for developing countries such as Brazil (Bleninger et al, 2016)
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