Protozoan parasites are responsible for the majority of gastrointestinal infections and even drinking treated tap water was reported risk factor for sporadic giardiasis. Variety of technologies has been used for elimination of Giardia cysts as well as removing other microbial contaminants and particles. The cysts are usually identified by their indistinguishable morphology. We applied direct current (DC) electrical charges for 1 to 4 min, 10 mA or 12 V, and 15 mA or 18 V in a handmade electrolytic cell filled with a prepared 105 cysts per ml emulsion, to examine its effectiveness as cysticide. Fresh human stools with Giardia, stained with Eosin Gelblich, were used to prepare wet mounts. Samples were examined by conventional light microscopy for the presence of cysts. Temperature and pH of the emulsions were measured in all stages. DC electrical charges equal or more than 15 mA (18 V in our circuit), in 2 min are practically lethal for Giardia cysts found in human stools, in a watery base with this concentration. pH of the emulsions varied between 3.5 to 8.8 in 22-24.4°C, when the currents were applied. 5 min after closing the DC electrical circuit, the tank water was treated and could be used.
Key words: Giardia lamblia, water treatment, direct electrical currents, cysticides.