Performance of field-installed groundwater arsenic remediation systems in Bihar, India: Role of source water chemistry, technology type and other factors

The impact of source water chemistry on the efficiency of groundwater arsenic (As) remediation systems in real-world conditions remains under-investigated. To contribute to addressing this gap, the aim was to systematically evaluate removal efficiency of field-installed As remediation systems (n = 98) in Bihar, India from locations with varying groundwater chemistry ( e.g. As: < 1 - 100 μg/L; Fe: < 1 - 1000 μg/L; P: 10 - 600 μg/L; molar ratio: -900 - 300). Sampled systems varied in type ( e.g. source switching, pump and treat), technology ( e.g. filter, sorption, membrane), ownership ( e.g. private, public) and implementation setting ( e.g. household, community). Removal of As and other contaminants (Mn, Fe, F - and NO 3 - ) varied widely (negative to ∼ 100 %). Notably, ∼ 90 % of the installed systems had inlet As below the 10 μg/L WHO provisional guideline, highlighting the need to install remediation systems where their need is more indicated. Relative As removal was negatively correlated (p < 0.01) with inlet As ( ρ = -0.37), Fe ( ρ = -0.51), [Fe]/[As] ( ρ = -0.41), [Fe]/[P] ( ρ = -0.51) and ( ρ = -0.54); but no significant relationships were observed with those parameters if split by technology (presence/absence of reverse osmosis (RO) membrane). Privately owned and RO-based remediation systems had higher As removal than other systems, noting however potential confounding factors of differing technical specifications and/or system operations. To ensure effective and sustainable interventions, remediation system selection in groundwater As affected regions should adequately consider factors including system operation and maintenance and technology type in addition to geochemical suitability.