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For research purposes, three different liquid manure treatment plants were hygienically and microbiologically tested. The first examination, that was financed by the Agricultural Ministry of Baden-Würtemberg, centred around a two-stage unit for the aerobic-thermophilic stabilisation of liquid manure (ATS-unit) and a single-stage unit for the anaerobicthermophilic fermentation of liquid manure (biogas-unit). In the second project, which was financed by the Nordrhein-Westfalen Ministry of Environment & Agriculture, a unit for the pre-pasteurising of liquid manure (pasteurisation-unit) was examined.The ATS-unit can be operated in a batch mode of operation (heating method) or in a semicontinual mode (uninterrupted method). For the batch mode, both containers of the ATSunit are filled with manure. Ventilation motors mix the substrate and enrich it with air. The microorganisms give off heat during their aerobic metabolism, which can cause the manure substrate to heat up to a temperature of approximately WC. The bacteriological examination (substrate specimens and bacteria germ carrier samples) showed hat, if an operational temperature of WC is achieved, this is sufficient to reduce the number of Escherichia coli, Salmonella senftenberg and also the faecal streptococci by 5 log10 units. Thus, the set aim which was to obtain a reduction of 5 log10 units, for these germs - and therefore obtain a sufficient degree of hygiene, has been met. The continual application of an initial temperature scale of 35-45°C and a final high temperature scale of 50-55°C reduces the viability of the Cryptosporidium oocysts. During the "warming up" phase of 35-45°C it would seem that Cryptosporidium oocysts are activated. During this process they give off their infectious forms (Sporozoites) into the manure, which then disintegrate due to the lack of target cells. The application of the high temperature phase of 50-55°C then damages the rest of the Cryptosporidium oocysts which, up until this point of time, have remained morphologically unchanged. The parasite examination (parasite germ carrier samples) came to the conclusion that a batch mode, conducted in an alkali environment, whereby an initial temperature phase of 35-45°C for a period of 24 hours is applied, followed by a final temperature phase of at least WC, eliminates Cryptosporidium oocysts.During the semi-continual mode of the ATS-unit the manure remains in each of both containers for a period of at least 24 hours. On a daily basis untreated manure (approx. temperature of 10-15°C) is added to the substrate in the first container. This means that the manure in container 1 is relatively cool in comparison to the manure in container 2. Hereby container 1 (at 35-45°C) acts as a kind of pre-heating stage for container 2. The latter reaches a temperature level of about WC and can hold this in the plant for a long period of time. This two stage method has a similar good effect on the Cryptosporidium oocysts as the two stages of the batch mode, described before. A considerable reduction takes place. If the manure has been processed in the regular semi-continual mode, viabel Cryptosporidium oocysts are no longer in evidence. The bacteriological examination (substrate specimens and bacteria germ carrier samples) show that in container 1 a small reduction of the indicator organism was achieved. The actual hygienic effect was accomplished during the process that took place in container 2. The semi-continual mode of the ATS-unit also led to a reliable reduction of the indicator organisms by more than 5 log10 units.In the single-stage biogas-unit manure treatment takes place within the mesophilic range (3842°C) as well as in the thermophilic range (43-58°C). The maximum possible duration is limited to 24 hours due to the regulated single-stage operational method. This one-day treatment of manure in the mesophilic mode reduces the germ count of Escherichia coli and Salmonella senftenberg by 2 or 3 log10 units. Faecal streptococci are not, or are only partly eliminated. Cryptosporidium oocysts excyst in a similar form as in the two operational modes of the ATS-unit (at the corresponding temperatures described). However most of the Oocysts remain viabel and therefore the intended satisfactory hygienic state cannot be maintained within the given time. The one-day treatment of manure in the thermophilic mode reduces Escherichia coli, Salmonella senftenberg and the faecal streptococci by more than 5 log10 units. The single phase 24 hour high temperature (49°C-58°C) treatment of the Cryptosporidium oocysts does not seem to lead to their complete extermination. In all the three research methods applied there were always occasional signs that some Oocysts had remained viabel. However, the research methods used do prove, that a reduction of at least 2 or 3 log10 units. can be achieved. If the treatment duration is extended to 48 hours the reliability and safety of the thermophilic mode can be increased accordingly. Generally speaking, for technical reasons, this practice of extended operation is not usually applied. This doesn"t mean, that the anaerobic process is basically an ineffectual method and not suitable for the intended project target. It is most probably he case, that a two-stage biogas-unit with similar operational modes to the ATS-unit could also be successful. However, due to external limitations, this could not be examined.The operational mode of the one-stage, semi-technical unit for he pre-pasteurisation has two hygienic phases in sequence that complement each other. The "warming up" phase (WC to 65°C resp. 75°C) and in combination a 60min holding phase (WC resp. 70°C) lead to a reliable elimination of all bacterial indicator organisms (substrate specimens and bacteria germ carrier samples) as well as a complete extermination of viabel Cryptosporidium oocysts. All of the three testing methods used showed that if the Cryptosporidium oocysts are only treated to 70°C for a period of one hour, a rest population of Oocysts remains viabel. A reduction of only 2 log10 units are in evidence.The examinations carried out show that if liquid manure is treated correctly, it can certainly be processed in such a way to become a hygienic economic fertiliser. For this reason stringent stipulations regarding the protection of ground water in chalky formation, which forbid the spreading of liquid manure for hygiene reasons, are unnecessary.