| Summary: | Eutrophication has become the primary water quality issue for most of the freshwater and coastal marine ecosystems in the world. It is one of the most visible examples of human changes to the biosphere, affecting aquatic ecosystems from the Arctic to the Antarctic. More than 40% of water bodies in many regions of the world are considered to have eutrophication problems. A recent study of over 14,000 lakes <1 ha in size in Great Britain found that 51% are likely to require P-decrease measures to meet the Water Framework Directive to achieve ‘good status’ by the year 2015. Many shallow eutrophic lakes will have difficulties meeting the EU Water Framework Directive (WFD) criteria in 2015 without restoration. Therefore, regional water action plans have been adopted to find possibilities for the lakes to meet the criteria of “moderate”, “high”, or “good” ecological condition. Restoration has been defined as the return of a disturbed system to some pre-disturbance state that is both self-regulating and integrated into the larger landscape. The chemical restoration methods mainly aim at reducing the P release from the sediment by improving the P binding capacity and thus creating P limitation of the phytoplankton. During the recent decade, scientific research has considered a number of different solid adsorbents to be used in reducing the P levels entering the water bodies. The main objective of the present PhD thesis was to develop physicochemical methods for restoring degraded and poor quality natural water bodies threatened by eutrophication. In the beginning of our research, a primarily in-depth review of restoration methods, emphasizing remediation methods of internal nutrient release budget as a basic factor to control eutrophication, was of major importance, as this knowledge was lacking from the scientific community. The use of phosphate inactivation agents as a restoration tool, their capacity and application methods, as well as the individual results (in water quality, algal blooms, flora and fauna) in a ...
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