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Indicator bacteria concentrations in microenvironments
of the Gulf of Elefsis (Greece)
Sotirios Karavoltsos, Ioulia Petraki, Aikaterini Sakellari, Manos Dassenakis,
Michael Scoullos
National and Kapodistrian University of Athens, Department of Chemistry, Laboratory of
Environmental Chemistry, Zografou, Panepistimiopolis 157 84, Athens, Greece
Abstract
This preliminary study demonstrates the water profile of the coastal area of the Gulf of
Elefsis, with reference to microbiological parameters required by Directive 2006/7/EC,
concerning the management of bathing water quality. In a grid of 14 coastal sampling sites,
high mean levels of faecal contamination were found at the discharge of the lake
Koumoundouros. Faecal contamination around the outfall of the Psyttalia wastewater
treatment plant was evaluated.
Keywords: Escherichia coli; Enterococci; marine water quality
1. Introduction
Microbial contamination by pathogens of the surface waters of coastal areas has a significant
impact on their commercial and recreational exploitation. Total coliforms, faecal coliforms
and Enterococci are universally used as indicators of enteric pathogens in aquatic
environments. Among the most important sources of surface waters contamination untreated
urban waste waters, industrial, agricultural and livestock farming wastes are included.
General degradation of water quality due to faecal contamination potentially results in
increased hazards for the public health (Kacar and Gungor, 2010). In bathing waters bacterial
levels, considered as microbial indicators, are often found to be associated with health risks
(Noble et al., 2003).
Directive 2006/7/EC (European Community 2006) on the management of bathing water
quality, resulted in a drastic reduction in the number of parameters employed: from 19 initial
parameters (Directive 76/160/EEC on bathing waters) to only 2 key microbiological
parameters (Intestinal Enterococci and Escherichia coli), providing the best match between
faecal pollution and health impacts in recreational waters, according to available scientific
evidence provided by epidemiological studies. Following contemporary patterns of bathing
water use and of the state of scientific and technical knowledge, the purpose of the Directive
is to preserve, protect and improve the quality of the environment and to protect human health
by complementing Directive 2000/60/EC.
Studies have shown a reduction of total coliforms concentration in seawater, which may
exceed 97% within 24-96 hours of their release, depending on water temperature, salinity and
exposure to sunlight (Rovirosa et al., 2004). Since treated sewage is often discharged to the
marine environment without being subjected to disinfection, questions may emerge on
whether elapsing a distance of few kilometers by the discharged sewage is sufficient for the
protection of bathing areas against contamination (Christoulas and Andreadakis, 1995).
The fate of indicator microorganisms of the Directive 2006/7/EC was studied in 14 coastal
areas of the Gulf of Elefsis, characterized by various environmental pressures particularly
near the discharges of runoff combined with fresh water streams, wastewater treatment plants
(WWTPs), harbours/marinas, various discharges from industrial and commercial activities
and bathing beaches. Furthermore preliminary field study was carried out examining the
faecal contamination attributted to the outfall system of the central waste water treatment
plant of Athens located at Psyttalia, where the treated effluents are discharged without
disinfection.
2. Materials and Methods
2.1 Sampling
Regarding the 14 coastal sampling sites (Fig. 1; Schlitzer, R., Oean Data View,
http://odv.awi.de, 2012), a total of 2 samplings were carried out at the coasts of Attica and
Salamis island within the Gulf of Elefsis (28/9/2009; 23/11/2009). In order to evaluate the
impact of the wastewater treatment plant of Psyttalia an additional sampling was realized on
7/12/2009 outside the Gulf of Elefsis and at the inner part of the gulf by the R/V Aegaeo, of
the HCMR (Hellenic Center for Marine Research), at stations S1, S2 (inner part of the gulf),
at S3 station (Keratsini Bay) and at S7 station where the Psyttalia treated sewage outfall is
located (Fig.1). In all cases surface samples were collected. During the first sampling
moderately strong winds prevailed, leading to waving and water mixing. The second and third
samplings were carried out under calm conditions without wave action.
Fig.1 Sampling sites within the Elefsis Gulf and around the WWT of Psyttalia
Immediately after their collection the samples were transported to the laboratory where the
determinations of the examined microbiological parameters were directly carried out.
2.2 Analysis
For the determination of Enterococci the method ISO 7899-2 was employed and for
Escherichia coli the method of membrane filtration with the use of the chromogen Hi Crome
E. Coli Agar.
3. Results
The concentrations of faecal bacteria determined in the coastal zone of the Gulf of Elefsis are
presented in Fig.2. The concentrations of Enterococci ranged from 3cfu/100mL to
1231cfu/100mL and their mean values from 15cfu/100mL to 632cfu/100mL. The highest
concentration was detected at “Blue lagoon” site (no.13) at the northern coast of the Salamis
island followed by that recorded at the site where the water of the shallow coastal
Koumoundouros lake discharges into the sea (no.1). Regarding Escherichia coli 3 and 9
positive samples were respectively determined during the first and second samplings. The
highest concentrations of Escherichia coli were determined at lake Koumoundouros in both
samplings, and at Aspropyrgos (no.2) and Neraki (no.9) beaches only during the second
sampling.
Fig. 2 Faecal bacteria concentrations in the coastline of the Elefsis Gulf
At all near shore sampling sites (S1, S2, S3, S7) Εnterococci were detected, with the highest
concentration measured at station S7 (188 cfu/100mL), located close to the Psyttalia treated
wastewater outfall (Table 1). In relation to E. coli the highest concentration was also
determined at station S7 (37 cfu/100mL), whereas at the rest of the examined sampling sites,
excluding station S3 (1 cfu/100mL), zero concentrations were measured.
Table 1 Faecal bacteria concentrations (cfu/100mL) in near shore sampling sites
Sampling station
Enterococci
E.coli
S1
71
0
S2
1
0
S3
84
1
S7
188
37
4. Conclusions
In accordance with the Directive 2006/7/EC, a few only of the coastal areas studied within the
Gulf of Elefsis are characterized as “poor” regarding the concentrations of Enterococci. These
are areas where apparently contaminated fresh water enters the sea. The Koumoundouros
lake/lagoon which constitutes wetland for many bird species apparently receives poorly
treated water from neighboring installations. This site should be considered as a significant
hot spot. High concentrations of faecal contamination were measured at the sampling station
near the outfall of the treated wastewaters released from the Psyttalia WWTP which,
however, is located far from the coast. For robust conclusions in relation to the impact of the
WWTP of Psyttalia on the inner Gulf of Elefsis, additionnal samplings are required, mainly in
terms of Enterococci.
5. Acknowledgment
The co-authors cordially dedicate this work to Prof. Michael Scoullos who had
initially inspired and encouraged them to devote a significant part of their research
activities to the Gulf of Elefsis.
6. References
Kacar, A. and Gungor, F., 2010. Comparison of feacal coliform bacteria before and after
wastewater treatment plant in the Izmir Bay. Environmental Monitoring and Assessment,
162, 355-363.
Noble, R.T., Moore, D.F., Leecaster, M.K., McGee, C.D., Weisberg, S.B., 2003. Comparison
of total coliform, fecal coliform and enterococcus bacterial indicator response for ocean
recreational water quality testing. Water Research, 37, 1637-1643.
Rovirosa, N., Sanchez, E., Cruz, M., Veiga, M.C., Borja, R., 2004. Coliform concentration
reduction and related performance evaluation of a down-flow anaerobic fixed bed reactor
treating low-strength saline wastewater. Bioresource Technology, 94, 119-127.
Christoulas, D.G. and Andreadakis, A.D., 1995. Application of the EU bathing water
directive to the design of marine sewage disposal systems. Water Science and Technology,
32, 53-60.