Millions of people worldwide are exposed to harmful levels of fluoride (F) by consuming groundwater (GW) exceeding the World Health Organization guideline value of 1.5 mg/L. Many affected live in low resource settings including dispersed rural settlements lacking infrastructure and rely on wells requiring point-of-use (POU) treatment as their main source of drinking water. One such region is Guanajuato state, central Mexico, where F levels in community wells can exceed 20 mg/L and values ranging from 2-8 mg/L are common. Cow bone-char (BC) produced locally utilizing waste material from beef processing has shown promise as a low-cost sorbent for uptake of F from GW. Traditionally, pilot tests have been conducted but are costly, time consuming, and require large amounts of water from water-scarce areas. Therefore, a bench scale method applying a rapid small-scale column test (RSSCT) approach was developed to be used in a field lab setting to quantify F removal by BC sorbents from GW specific to central Mexico. Isotherm batch and differential column batch reactor tests were conducted with different BC particle size to determine kinetic parameters following the homogeneous surface diffusion model (HSDM) informing the relative importance of external (film) diffusion to intraparticle diffusion. Results were used to design constant (CD) and proportional (PD) diffusivity RSSCTs with crushed BC for comparison with pilot columns using full size BC granules. CD and PD RSSCT breakthrough curves were fit with the HSDM to determine the best approach for predicting F breakthrough from actual treatment systems. Duplicate experiments were conducted using two different BC batches, and with GW collected in Mexico compared to a laboratory model GW with similar background chemistry. This RSSCT approach will save time, labor, and experimental resources, and support the implementation of affordable POU water treatment in low resource settings.

Rapid small-scale column test development for fluoride control using bone-char sorbents

2019 Fall National Meeting

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