Rodríguez-Suárez, Joann M.

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    Treatability study of an intermittent biosand filter for reduction of Escherichia coli and Enterococcus
    (2015) Rodríguez-Suárez, Joann M.; Tarafa-Vélez, Pedro J.; College of Engineering; Papadopoulos, Christopher; Hwang, Sangchul; Montalvo Rodríguez, Rafael; Department of Civil Engineering; Latorre Esteves, Magda
    According to the United Nations, although access to safe drinking water is improving worldwide, still over 1 billion people lack access to such. The intermittent biosand filter (IBSF), which is an adaptation of a slow sand filter, is an appropriate technology for removal of pathogens and suspended solids from water at the household level in developing communities due to its low cost and operational simplicity. In particular, pathogens are removed through a combination of adsorption, microbial activity, mechanical trapping, and natural death due to deprivation of oxygen and nutrients. However, the details of these mechanisms are not completely understood. This study measured particularly the Escherichia coli, Enterococcus populations and dissolved oxygen (DO) concentration in the water throughout the IBSF sand bed depth over time in order to understand the impact and contribution of the microbial and oxygen deprivation mechanisms in the Escherichia coli and Enterococcus removal by the IBSF. In addition the phosphate removal by the IBSF and a visualization of the biofilm developed over the sand grains over time were accessed. During this study, the E. coli population removal percent by the IBSF was up to 98%. According to the obtained results this high removal percent could not be only an effect of the biolayer, it could be also caused by other mechanisms, such as the lack of DO concentration inside the IBSF. After 30 days of filter use, the removal percent of E. coli increased with time and depth. In terms of the Enterococcus population, the IBSF remove up to 98.7 %, having the higher reduction at the biolayer. It seems that there was no difference between the Enterococcus reductions at the middle and the end of the IBSF sand bed depth and it was not influenced by the lack of DO concentration. Since the first week of the IBSF use, the development of the biofilm over the sand grains was observed until 29.7 cm of the sand bed depth and had a high diversity that increase over time. The results demonstrated the IBSF could remove up to 86.4 % of the phosphate present in the feeding water. One of the possible capture mechanisms for the phosphate removal in the IBSF could be adsorption to the iron particles that were present in the sand bed.