Use of Ceramic Pot Filters for Drinking Water Disinfection in Guatemala

Researchers at Missouri University of Science &Technology have conducted studies indicating that arsenic exists in drinking water treated by ceramic pot filters (CPFs) used for point of use (POU) water filtration in developing countries. CPFs are formed from clay, sawdust, water, and colloidal silver. Van Halem et al. (2007) also showed that CPFs also leach arsenic into treated water above the World Health Organization (WHO) standard of 0.01 mg/L. The objective of this work was to field-determine the source of arsenic in CP- treated water, the form of arsenic (suspended or dissolved) in treated water, and whether arsenic concentration levels changed after prolonged use. This study focused on looking at the individual components of CPFs and to determine the source of this contamination. By isolating each component we were able to discern between those that influenced arsenic concentrations in treated water and those that did not. Field testing kits and a filtration device were used to determine the form and concentration of arsenic present in treated waters. A multi-day CPF volumetric sampling experiment was devised, where samples of new CPFs manufactured by a company in Guatemala were collected and analyzed to determine arsenic concentrations. After testing the individual components of CPFs, the data has shown that the source of arsenic contamination is the clay itself. Some clay sources have been excluded from use by the Guatemala manufacturing site because these sources were believed to contain levels of arsenic above WHO standard for arsenic exposure of 0.01 mg/L. While our testing points strongly to the likelihood that all current clay sources are contaminated with arsenic above 0.01 mg/L. The inherent variability of geologic materials makes it difficult to quantify these conclusions; it is believed that more testing may be required. This field study was conducted in and around Antigua, Guatemala where not unlike other makers of CPFs no onsite laboratory testing in existence, nor is there testing for arsenic contamination at established off site laboratories. The goal of the field testing component of this work was to prove that arsenic can be identified in the field using rather inexpensive procedures, and to lay the ground work for the design of a standard testing procedure for on-site by scientifically unskilled personnel or with help from Guatemalan University students. The ultimate goal of the this research is to develop a reliable standard testing procedures for both raw materials and finished CPF's, which would verify continued compliance/non-compliance with current WHO standards of 0.01 mg/L.