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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.

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Drinking water treatment, outbreaks and methods of detection and viability

Surface water bodies are more vulnerable to contamination of (oo)cysts than groundwater, although (oo)cysts have been identified in both types of water sources as previously described in this report. Prevention of the transmission of protozoan parasites through drinking water requires a multiple barrier approach; protection of watersheds and adequate treatment steps for the reduction. Hydraulic models of the catchment may be helpful for predicting the (oo)cyst concentration as well as to identify important sources of contamination or environmental events when a spread is more likely to occur. One important aspect of watershed protection is to recognise the potential sources of contamination for the specific water catchment and to prevent the contamination as much as possible. Giardia cysts and Cryptosporidium oocysts may be introduced in a water source via insufficient treated sewage, though treatment of sewage is an important barrier against environmental transmission. Also treatment of slurry before land application will reduce the numbers of viable Cryptosporidium oocysts potentially contamination of water sheds via run-off. As described earlier vegetated strips between grazing pasture and watershed may be used as an additional barrier. Storage in reservoirs can also reduce the concentrations of (oo)cysts as shown by Ketelaars et al. (1995). In the Nordic countries the multiple barrier concept is usally adopted.

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