干旱区生态环境知识资源中心

Cryptosporidium parvum and Giardia lamblia are protozoan parasites that cause major human infections through waterborne transmission. The presence of these two parasites is closely linked with effluent reuse. Since most of the effluent, primarily in arid and semi-arid regions is reused for agricultural irrigation, extra work was conducted in order to detect these parasites in wastewater, the applied effluent, soil and crops. Unrestricted irrigation of a variety of vegetables with low-quality effluents could lead to crop contamination with large amounts of Cryptosporidium oocysts and Giardia cysts. A special occurrence was observed with zucchini that will be discussed further. Sprinkle, surface and subsurface dripping irrigation revealed that the last two methods are much safer for unrestricted irrigation, using the soil as an efficient filter matrix. Nevertheless, from the obtained results (using a new method for parasite recovery from soil) both protozoan parasites were isolated from soil, revealing their migration to a depth of 60 and 90 cm below surface when subsurface dripping irrigation was applied. These results will be further discussed as linked to optimization of secondary wastewater reuse in order to minimize environmental risk.