Agro-Industrial Wastewater Pollution in Greek River Ecosystems

In this chapter, the characteristics and environmental impacts of wastewaters from the major agricultural industries on the river ecosystems of Greece are reviewed and discussed, focusing especially on olive mills, orange juice processing factories and cheese processing factories. The high organic load, suspended solids and nutrients of these wastewaters, as well as their toxicity, have deteriorated river water quality and the ecological status of many running waters of Greece. Among the most common effects are eutrophication, the decline of fish and invertebrate populations, species richness loss and the consequent reduction of the river capacity for moderating the effects of polluting substances through internal mechanisms of self-purification. The organic load of the wastewaters, substrate contamination (sewage bacteria) and distance from the wastewater discharge outlet appear to be the most important factors affecting macroinvertebrate assemblages, while typology (i.e. slope, altitude), hydrology (i.e. permanent, intermittent), intensity and volume of the wastewater are the most important determinants of self-purification processes. As these industries are usually located near small-sized streams that are not significantly considered in the Water Framework Directive 2000/60/EC, there is a need for including them in monitoring and assessment schemes as they may considerably contribute to the pollution load of the river basin. Finally, guidelines to manage these wastes through technologies that minimise their environmental impact and lead to a sustainable use of resources are also critical.