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Water Filtration - Contaminants in Water

Protozoans
General Information: Protozoans are single-celled, free-living, animal-like organisms ranging in size from 0.005 mm to 5 mm. All life-sustaining processes occur in one cell. Except for some in wet soil, all protozoans occur in the aquatic environment. Pathogenic protozoans comprise approximately 10,000 of the 35,000 species of protozoans known, and cause some of the worst diseases (Mitchell et al., 1988). Pathogens posing problems in drinking water are Giardia lamblia, Entamoeba hystolytica, Cryptosporidium, and Naegleria fowleri (AWWA, 1990). 
Giardia lamblia: Causes Giardiasis, a gastrointestinal disease.

Giardia can exist as a trophozite (9 to 21 um long) or as an ovoid cyst (10 um long and 6 m wide). Ovoid cysts can survive in water for one to three months. Humans become infected after ingesting as few as 10 cysts

Analytical Techniques: Current methods for protozoan detection are poorly standardized.
Isolation and identification of protozoa is difficult because they are relatively few in number, even in polluted water. Instead, other more plentiful organisms such as total coliforms, fecal coliform, and fecal streptococci are often used as indicator organisms. Detection of the indicator organism suggests that protozoa might also be present. Standard tests for coliforms are performed to assess probable presence of protozoa (Tchobanoglous 1991).

Leptospirosis
Leptospirosis is a bacterial disease that affects humans and animals. It is caused by bacteria of the genus Leptospira. Leptospirosis is treated with antibiotics, such as doxycycline or penicillin, which should be given early in the course of the disease. Leptospires are long, thin motile spirochetes. They may be free-living or associated with animal hosts and survive well in fresh water, soil, and mud in tropical areas. Organisms are antigenically complex, with over 200 known pathogenic serologic variants.

As the name implies, Leptospira are spiral shape organisms. Leptospirosis is a zoonosis; man is an accidental host via contaminated animal urine.

The Leptospires are thin, coiled, gram-negative, aerobic organisms 6-20 mm in length.

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