Protozoan Parasites in Sewage Sludge

image of Protozoan Parasites in Sewage Sludge

A Nordic project was initiated as part of an evaluation of sludge treatment processes based on the suggested new EU legislation (EC 2000REF). This report covers the different parts of the project. The project focused on sewage and sludge treatment within a broader frame of background information regarding Giardia and Cryptosporidium, especially the relationship between the risk of transmission and the risk of aquiring infections from the environment. The objectives were further to exemplify the occurrence and viability of Giardia and Cryptosporidium through investigations in raw sewage and untreated or treated sludge from two sewage treatment plants. This report includes: 1. A literature review of Giardia and Cryptosporidium in the society and the environment. 2. A field study of occurrence and removal of the protozoa during wastewater and sludge treatment and,3. A laboratory study to further evaluate the efficiency of sludge treatment at various temperatures.



Material and Methods

The sewage treatment plants (STPs) in this investigation were chosen to reflect two different sewage sludge processes, either mesophilic as in Henriksdal, Stockholm, or thermophilic as in Tegelviken, Kalmar. The thermophilic treatment was run at 49.5°C for 14 days (mean retention time), while the corresponding mesophilic treatment was run at 35–37 °C for 21days (mean retention time). Henriksdals SWTP, connects 641,000 people and Tegelviken 52,000 people. The sewage sludge treatments were run with continously operation.


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