Quantifying the Potential for Re-infection of CPF Filtered Water and Developing Techniques for Contaminated CPF Reactivation

摘要

It has been suggested that ceramic pot filter systems which are used for water disinfection in developing countries, can be subjected to recontamination due to improper use and maintenance. Two phases of experiments to evaluate recontamination potential were conducted in the laboratory and in the field and a third phase was conducted only in the field in Guatemala. Phase One identified the potential for recontamination which tested three different mechanisms: placement of the filter unit on a contaminated surface, unsanitary handling of the spigot, and faulty cleaning of the entire system. The results suggest that only concentrations of fecal coliforms which exceeded typical Guatemalan source water concentrations by several magnitudes resulted in recontamination. Experiments were repeated in Guatemala during a total of four weeks. Phase Two consisted of field studies during the four weeks in Guatemala in which five communities were visited to gather CPF users' testimonials and to collect CPF-treated water quality data. Of the 44 CPFs tested in the villages, 33 percent showed signs of recontamination. These results indicate that recontamination is possible but more likely develops from human error than equipment malfunction. Phase Three investigated the potential of two filter reactivation techniques to remove bacteria from the unit in the event that recontamination does occur. The first method was to quantify fecal coliform die-off of two separate Guatemalan rivers. This produced evidence that fecal coliforms die-off over time periods exceeding 12 days. The second method of pot reactivation was to flush eight liters of disinfected water through the CPFs. This found that the bucket and spigot components were free of bacteria but that fecal coliforms were still present in the treated water. These results indicate that disinfection of a contaminated CPF system requires an intervention beyond simple flushing to restore a contaminated CPF system.