Toxins in cyanobacteria are a recognized risk in the treatment of drinking-water treatment. Cyanotoxins can occur in two modifications: cell bound and dissolved in water. The process of toxin release may occur naturally, but it also may be induced through the processes of drinking-water treatment. Both causes of release are relevant to the safety of drinking water. This study investigated cyanotoxin release and elimination through different treatment trains in systematic pilot-scale studies with water from the Weida Reservoir, in Thuringia, Germany. The Weida Reservoir is a dimictic mesoeutrophic reservoir typical for a number of mountainous areas in Europe, with Planktothrix rubescens as the dominant phytoplankton species, and shows a characteristic seasonal pattern of population development and microcystin occurrence. To assess the risk of microcystin breakthrough, the pilot-scale results as well as results of laboratory-scale experiments were used for developing a kinetic model of toxin release in relation to elimination. By calculating removal efficiency of total microcystins (cell bound and dissolved) for different treatment trains, raw water quality was related to the quality targets for finished water, and breakthrough risks could be calculated for given treatment trains and varying cyanobacterial population densities in the reservoir.

This study developed a statistical approach to predicting the probability of the occurrence of phytoplankton species from the general properties of a water body and the specific conditions at the time of sampling. Here, we report the results for the two Dinophytes Gymnodinium uberrimum and Peridinium willei which frequently cause problems in drinking-water treatment. Our statistical approach addresses the problem of uneven distribution of samples across parameters. For this purpose, we used probability calculation to assess under which conditions the species' occurrence is a likely or an unlikely event. The ecological niches of both species turned out to be similar, as both occur in oligotrophic to mesotrophic, deep, stratified reservoirs at low phosphorus concentrations. However, their pH and temperature range differed: G. uberrimum occurred predominantly between pH 6 and 7 and at a temperature range up to 168C, whereas P. willei showed a wider pH range and a temperature range below 128C. With these results, the classification of P. willei within the functional group L o proposed by Reynolds et al. (Reynolds et al., 2002) is now underpinned with a substantial database. The results suggest G. uberrimum to fit into this association as well.

Human pathogenic viruses may end up in surface waters by fecal contamination. However, the German drinking water ordinance requests that pathogens in drinking water should not be present in concentrations constituting a potential danger to human health. Since many viruses do have a very low dose of infection, they have to be sufficiently eliminated in the process of drinking water purification. Waterborne virus outbreaks in Europe, over the last few decades, were mostly linked to noncompliance with the generally accepted codes of practice for drinking water production. The aimed level of protection of drinking water supplies in Germany, however, exceeds prevention of outbreaks by even protecting against sporadic virus infections. Documentation of such a high level of protection is not achieved by end product control alone but requires a process analysis with risk assessment. To do such an analysis, information regarding the presence of viruses in the raw water used for drinking water production, as well as data of virus elimination rates during purification processes, are of major importance. This paper presents suggestions for implementation of such a risk assessment, focusing on the evaluation of raw water quality.

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Natürliche und anthropogene Einflüsse verursachen in Talsperren erhebliche Variationen in der Wasserqualität und in der verfügbaren Wassermenge. Andererseits ist es Aufgabe von Trinkwassertalsperren eine möglichst hohe Kontinuität in Qualität und Quantität bereitzustellen. Wachsender Druck auf die Nutzung von Einzugsgebieten und Talsperren sowie witterungsbedingte Extremereignisse können diese Nutzungsziele in Frage stellen. Eine wichtige Strategie, diesem Problem zu begegnen, ist die Optimierung der Bewirtschaftung auf der Basis Online erfaßter Umweltkriterien und computergestützter Simulations-und Vorhersagewerkzeuge. In Zusammenarbeit zwischen dem Fraunhofer Anwendungszentrum Ilmenau (FhG-AST) und der Thüringer Talsperrenverwaltung (ThürTV) entstand in den vergangenen Jahren ein Entscheidungshilfesystem, welches für die Optimierung der Bewirtschaftung eines großen Trinkwassertalsperrensystems in Thüringen eingesetzt wird.The water quality and the available water quantity in reservoirs are being increasingly influenced by natural and antropogenie factors. On the other hand exists an great requirement on a high water quality and a constant provision of water quantity. An increasing demand for a multiple using of reservoirs and their catchment areas and extremely weather conditions, caused by climate changes procure of disturbs in the use of reservoirs. An important strategy to manage these problems is the optimization of reservoir management, based of Online monitoring and computer simulations. In cooperation between the Fraunhofer Application Center (FhG-AST) and the Thueringian Reservoir Administration (ThürTV) a management system is developed that helps in reaching decisions to improve the possibilities of reservoir management. Problemstellung Talsperren sind Ökosysteme, welche empfindlich auf Veränderungen in der Umwelt reagieren. Entscheidend sind einerseits Menge und Art der Stoff-und Energieeinträge in das Gewässer und andererseits auch Prozesse des Stoffund Energieumsatzes im Gewässer selbst. Die Gefährdung der Trinkwasserressourcen wächst mit der Intensität derEinzugsgebietsbewirtschaftung und der Nutzung des Gewässers selbst. Andererseits werden von den unterschiedlichsten Interessengruppen die Verfügbarkeit und die Nutzung der Flächen an den Gewässern (Landwirtschaft, Gewerbe, Kommunen) und der Ressource Oberflächengewäs-ser selbst gewünscht (Hochwasserschutz, Energiegewinnung, Naherholung, Fischerei, Naturschutz). Die externe Beeinflussung der Talsperren und die internen Umsatzprozesse im Gewässer werden aber auch erheblich durch meteorologische und hydrologische Einflußgrößen bestimmt Die Bedeutung dieser Einflußgrößen hat in den letzten Jahren zugenommen. Die inzwischen unbestrittenen globaler Klimaänderungen haben witterungsbedingte Extremwetterlagen, wie Rekordüberschwemmungen (Bangladesch. Nordamerika, China) und Dürreperioden (Afrika, Australien) zur Folge [1], Ungewöhnliche Wetterlagen führten in der jüngsten Vergangenheit auch in Mitteleuropa zu Situationen, in denen die kontinuierliche Berei...