Cost and Efficiency of Arsenic Removal from Groundwater: A Review

Abstract

Hundreds of millions of people worldwide are exposed to arsenic-contaminated drinking water, leading to significant health complications, and social and economic losses. Currently, a wide range of technologies exists to remove arsenic from water. However, despite ongoing research on such technologies, their widespread application remains limited. To bridge this gap, this review aims to compare the effectiveness and costs of various arsenic remediation technologies while considering their practical applicability. A search conducted using the Medline and Embase databases yielded 31 relevant articles published from 1996 to 2018, which were categorized into laboratory and field studies. Data on the effectiveness of technologies in removing arsenic and associated costs were extracted and standardized for comparison as much as was possible, given the diversity of ways that studies report their key results. The twenty-three (23) technologies tested in laboratory settings demonstrated efficiencies ranging from 50% to ~100%, with the majority reaching relatively high removal efficiencies (>90%). Approximately half achieved the WHO standard of 10 µg/L. Laboratory studies used groundwater samples from nine (9) different countries – Argentina, Bangladesh, Cambodia, China, Guatemala, India, Thailand, the United States, and Vietnam. The fourteen (14) technologies tested in the field achieved removal efficiency levels ranging between 60% and ~99%, with ten (10) attaining above 90% removal efficiency. Of these, only five (5) reached established the WHO standard. Some of the technologies under-performed when their influent water contained excessive concentrations of arsenic. Only six (6) countries (Argentina, Bangladesh, Chile, China, India, and Nicaragua) were represented among the studies that implemented and tested technologies in the field, either at household or community level. For technologies tested in the laboratory, the cost of treating one cubic meter of water ranged from near-zero to ~USD 93, except for one technology which cost USD 299/m³. For studies conducted in the field, the cost of treating one cubic meter of water ranged from near-zero to ~USD 70. Key factors influencing the removal efficiencies and their costs include the arsenic concentration of the influent water, pH of the influent water, materials used, the energy required, absorption capacity, labour used, regeneration period and geographical location. Technologies that demonstrate high removal efficiencies when treating moderately arsenic-contaminated water may not be as efficient when treating highly contaminated water. Also, the lifetime of the removal agents is a significant factor in determining their efficiency. It is suggested that remediation technologies that demonstrate high arsenic removal efficiencies in a laboratory setting need to be further assessed for their suitability for larger-scale application, considering their high production and operational costs. Costs can be reduced by using locally available materials and natural adsorbents, which provide near zero-cost options and can have high arsenic removal efficiencies. A notable feature of many arsenic removal approaches is that some countries with resource constraints or certain environmental circumstances – like typically high arsenic concentrations in groundwater –aim to reach resultant arsenic concentrations that are much higher than WHO’s recommended standard of 10 µg/L. This report maintains that – while this may be a pragmatic approach that helps progressively mitigate the arsenic-related health risks – it is unfortunately not a sustainable solution. Continuing exposure to higher levels of arsenic ingestion remains harmful for humans. Hence arsenic-removal technology should only be seen efficient if it can bring the water to the WHO standard. A less radical approach effectively shifts the attention from the origin of the problem in addressing the impacts and postpones achieving the best possible outcome for populations. The quantitative summary of costs and effectiveness of arsenic remediation technologies reviewed in this report can serve as a preliminary guideline for selecting the most cost-effective option. It may also be used as an initial guideline (minimum standard) for summarising the results of future studies describing arsenic remediation approaches. Looking ahead, this study identifies four priority areas that may assist in commercializing wide-scale implementation of arsenic removal technologies. These include: i) focusing efforts on determining market viability of technologies, ii) overcoming practical limitations of technologies, iii) determining technology contextual appropriateness and iv) concerted effort to increase knowledge sharing in and across regions to accelerate the implementation of research on the ground. Overall, the current science and knowledge on arsenic remediation technologies may be mature enough already to help significantly reduce the global numbers of affected populations. The missing link for today’s arsenic removal challenge is the ability to translate research evidence and laboratory-level successes into quantifiable and sustainable impacts on the ground. Achieving this requires a concerted and sustained effort from policymakers, engineers, healthcare providers, donors, and community leaders.