Enabling Marginalized Communities to Monitor and Treat Chromium-Polluted Groundwater with Decentralized and Affordable Technologies

Chromium (Cr) contamination of groundwater from legacy industrial solid waste is a severe environmental problem, especially for marginalized communities dependent on groundwater as their only potable and irrigational resource. At one such site in Rania, India, alarming Cr concentrations (1-10 mg/L) relative to the World Health Organization (WHO) recommended 0.05 mg/L have been persistent for more than a decade. To mitigate this problem, sustained laboratory- to field-based interventions in the past led to the development of affordable methods for (1) rapid and accurate on-site measurement of Cr(VI) using a smartphone-based monitoring tool and (2) treatment of Cr(VI)-containing groundwater with ferrous sulfate amendment followed by slow sand filtration. In this contribution, these methods were scaled-up to a & SIM;14 L household filtration unit where Cr(VI) was first reductively precipitated as Fe(III)-Cr(III) oxyhydroxide particles in a specifically designed reactor. The particles were then removed by passing the suspension through an existing biosand filter (JalKalp), which also removed microbial contamination. The developed filter unit treated Cr-free groundwater spiked with variable Cr(VI) concentrations and Cr(VI)-contaminated groundwater sampled from the site with >99% efficiency. The toxicity characteristic leaching procedure confirmed that the generated sludge from these operations was nonhazardous. Subsequently, this filter and the smartphone-based monitoring tool were provided to an affected household to assess their performance and acceptability to the end user. With minimal training, the residents were able to operate the filter and systematically record Cr(VI) concentrations before and after filtration over 65 days of operation. JalKalp was able to limit Cr(VI) concentrations and other water quality parameters, except hardness and alkalinity, below the drinking water limit, and was operable without any electricity at a low cost of USD 0.057/100 L of purified water. This study serves as an example of how research outreach could not only provide translatable technical solutions to marginalized sections but also benefit from citizen science.