Removal of the human pathogen Giardia intestinales from groundwater

Colleen Frances Rust

Cyst-forming protozoans such as Giardia intestinales can survive for extended periods of time in groundwater systems with temperatures of less than 10 °C, migrate significant distances, and are relatively resistant to standard municipal water system chlorination practices. Though dormant outside the host, as few as ten cysts can result in animal or human infection. Because pathogenic bacteria, viruses, and protozoans tend to be negatively charged in the pH range of most groundwaters, naturally occurring and modified materials such as surfactant-modified zeolites (SMZ) having net positive surface charges are suitable as barriers to impede pathogen migration in aquifer systems. Three different SMZ formulations were prepared and characterized using zeolite from the St. Cloud mine in Winston, NM. Five different experimental runs were conducted under varied conditions (including use of raw zeolite and sand only) with a 10-cm wide barrier of SMZ to test the removal efficiency of SMZ for G. intestinales cysts and microsphere analogs. The model aquifer was filled with coarse silica sand to mimic realistic natural field conditions and potassium chloride (KCl), microspheres (Giardia analogs) and Giardia intestinales cysts were used as tracers. The arrival of the tracers down gradient of the SMZ barrier was compared to the arrival in the absence of the barrier to evaluate the effectiveness of each SMZ formulation. The coarse-grained Cationic SMZ (1.4-2.4 mm) formulation was further tested in the field using water amended with microspheres to simulate Giardia cyst behavior. The field site was an existing multiple well site at the University of Idaho in Moscow. The wells were completed in the Lolo Basalt Formation, a highly heterogeneous and anisotropic fractured basalt aquifer system typical of the subsurface of most of eastern Washington and northeastern Oregon. The SMZ pathogen field filter was installed directly in the well bore and the concentration of microspheres were measured before and after filtration. Pumping was continued over an extended period of time to test the lifetime of our prototype filter system. The goal of the project was to develop a prototype filter system for removing a multitude of human pathogens in drinking water.

Removal of the human pathogen Giardia intestinales from groundwater

Files and links (1)

Abstract

Metrics

Details