The Effect of Precipitation on the Microbiological Quality of Bathing Water in Areas under Anthropogenic Impact

Marin Ordulj,Mateja Baranović,Maja Krželj,Slaven Jozić

doi:10.3390/w14040527

Marin Ordulj, Mateja Baranović + Show 2 more

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https://doi.org/10.3390/w14040527

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Abstract

Intense rainfall can affect bathing water quality, especially in areas with poorly developed sewage systems or combined sewer overflows (CSOs). The aim of this study was to assess the impact of precipitation on coastal bathing water quality in the area of Split and Kaštela (Adriatic Sea), the urban areas where CSOs were applied. The study was conducted during two bathing seasons, 2020 and 2021. The sampling of coastal waters and measurement of physical/chemical parameters was performed every two weeks and after a precipitation event of more than 2 mm. The impact of precipitation on the quality of coastal bathing waters was not noted in the Split area nor in Kaštela, probably due to the low amount of precipitation. The quality of bathing waters in the Kaštela area was significantly worse than in the Split area, which is due to the condition of the sewage system in these areas and not the precipitation effect. It was also revealed that bathing water quality depends on the timing of sampling and the indicator against which it is assessed. Escherichia coli (E. coli) proved to be a better indicator for early morning sampling, while intestinal enterococci were better for late morning sampling.

Highlights

Monitoring the quality of coastal bathing waters is very important for the protection of human health and for preserving, protecting and improving the quality of the marine environment
The main goal of this study is to examine whether precipitation affects the bathing water quality in urban and suburban areas, which are exposed to the anthropogenic impact
From the results of the present study, it can be concluded either that precipitation in the studied area had no effect on fecal indicator bacteria (FIB) concentration in bathing water or that the precipitation was not sufficient to cause a higher FIB input because the lower precipitation that carry FIBs was probably quickly absorbed by the karstic terrain before reaching the bathing waters [14]

Summary

Introduction

Monitoring the quality of coastal bathing waters is very important for the protection of human health and for preserving, protecting and improving the quality of the marine environment. According to the BWD, bathing water quality monitoring must be carried out in accordance with the monitoring calendar, which shall be established before the beginning of each bathing season. The monitoring calendar may be suspended during ‘abnormal situations’ and shall be resumed as soon as possible after the end of the abnormal situation [3,4]. Croatian Regulation on sea bathing water quality [4] specifies abnormal situations as heavy rain, strong wind, large waves or the occurrence of macroalgae/phytoplankton proliferation. Some of these situations are among the main factors leading to microbiological pollution of coastal bathing waters and high levels of fecal indicator bacteria (FIB) used to assess bathing water quality

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