LARGE-VOLUME SAMPLES FOR CRYPTOSPORIDIUM AND GIARDIA FROM SMALL STREAMS

Sampling the headwaters of tributaries for the parasitic protozoa Giar dia and Cryptosporidium presents challenges, especially because calcul ated limits of detection are dependent on volumes of water filtered wi th a sampling apparatus. The design for sampling equipment analyzed he re is useful for sampling waters of low to moderate sediment-generated turbidity and has been tested in the Catskill Mountains of New York S tate. It is highly portable and operates under gravity head, It can be left unattended, provided that conditions at sampled sites are favora ble for completing collection of a sample. In all field applications, it met or exceeded federally recommended sample volumes. Tests with su spended sediment indicate that the sampler will filter at least 140 L (35 gal.) if sediment-generated turbidities are less than 140 NTU and elevation head is between 1-4 m. If turbidity at sites of interest is related primarily to suspended sediments, this testing method may be u seful for raw water sampling.