Microbiological Quality of River Sediments and Primary Prevention

Abstract

The preservation of aquatic ecosystems is fundamental because water quality, plant and animal biodiversity, industrial activities and human health rely on it. During recent centuries, the condition of aquatic ecosystems has become worse due to the increasing their use for irrigation and drinking, excessive land use and deforestation, hydro morphology alteration, riparian zone reduction and not least, climate change. A strong interdependence between the health of the ecosystem and human health can be demonstrated. Microbiological risks for human health can occur through direct or indirect (fish, molluscs, recreational activities, algal bloom, vegetables, fruits) consumption of contaminated water (Tauxe, 1997; UNEP 1997, 1998; Noji, 1997; Ahem et al., 2005). It is a priority to know the quality of the water and manage the data, in this sense it is necessary to identify the main variables that negatively impact human health. Indicator organisms are commonly used to evaluate the microbiological quality of aquatic ecosystems (Berg 1978; Grabow 1996; EU 2006; Tyagi et al. 2006). Standard-based water quality assessment is an essential component of monitoring programs and also works to protect human health. As a rule, microbiological indicator detection ( i.e. Enterococci and Escherichia coli) take place in the water column as necessitated by national and international laws. In this context, it is appropriate underline the important role of sediment on aquatic ecosystems. This matrix is an extremely heterogeneous habitat characterised by a high microbial biodiversity due to the wide range of functional roles that they perform. Its origin is in the weathering and erosion of minerals, organic material, and soils in upstream areas usually after rainfall or the melting of snow. Transported downstream, it settles along the river bed and banks as sedimentation. Sediments consist of particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of water bodies. The suspended particle matter (SPM) which settle by sedimentation, include sediments whose diameter falls between 0.1 and 100 μm. Sediment heterogeneity (e.g. grain-size) in fresh and salt water, creates favorable conditions for biodiversity and is a source of life for a healthy river. The particulate matter that plays a specific role in the aquatic ecosystems is the remaining material on a filter with a nominal porosity between 0.4 …