DEVELOPING A PROTOTYPE FILTER SYSTEM FOR THE REMOVAL OF HUMAN PATHOGENS FROM DRINKING WATER

Microbial contamination of groundwater is a serious concern worldwide. For many countries, groundwater provides approximately 40 % of the potable water used for human consumption. Cyst-forming protozoans such as Giardia intestinales and Cryptosporidium parvum, viruses such as Hepatitis A, and even pathogenic bacteria such as certain E. coli strains can survive for extended periods of time in ground water, migrate significant distances, and some of the pathogens (e.g. the protozoa mentioned above) are resistant to standard municipal water system chlorination practices.

Pathogenic bacteria, viruses, and protozoans tend to be negatively charged in the pH range of most ground waters. Thus, 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. In our experiments SMZ has been used to remove E. coli and the bacteriophage MS-2 from sewage water with a high success rate. E coli removal rates were 100% for at least five months when the material was installed as a well filter pack. Removal rates for the bacteriophage MS-2, which was used as an analog for the Hepatitis virus, were above 99%, when the barrier material was fresh and dropped to about 90 % after five months. Testing was conducted both in the laboratory and in the field. Microspheres and Bacillus subtilis spores were used as analogs for Giardia intestinales and Cryptosporidium parvum. Our most recent experiments focused on testing the removal efficiency of SMZ for Giardia intestinales using the actual Giardia cysts plus microsphere analogs for the field tests. Results from these tests indicate that none of the analogs commonly used truly matches the behavior of Giardia intestinales in the ground-water environment with a reactive barrier. The SMZ was effective at removing Giardia intestinales cysts from the groundwater, but not at as high rates as for bacteria and viruses. The removal efficiency varies with the exact formulation of the SMZ used. Our tests are targeted to develop a prototype filter system for removing a multitude of human pathogens in drinking water.