Comment on “Landfill-Stimulated Iron Reduction and Arsenic Release at the Coakley Superfund Site (NH)”

Abstract

Jamie deLemos et al. conclude in their recent article, "Landfill-stimulated iron reduction and arsenic release at the Coakley superfund site (NH)" (1), that the reducing environment present in the Coakley Superfund Site mobilizes arsenic. Such an environment is produced by microbial activity that essentially reduces insoluble Fe(III) to dissolved Fe(II), causing the desorption of arsenic from ferrihydrites present in glaciomarine clays. The active flushing of arsenic from the soil produces levels greater than naturally occurring concentrations, instigating health and safety concerns (1). The findings of the study raise legitimate concerns about the effectiveness of USEPA's toxicity characteristic leaching procedure (TCLP) (2), the primary criterion for determining the suitability of a material for landfill disposal. The current TCLP protocol fails to take into consideration the redox environment in the vicinity of the disposed material. Thus, any toxic substance whose stability or sorption affinity significantly diminishes under reducing environments may appear in the landfill leachate at significantly higher concentrations.

Evidence of Economically Sustainable Village-Scale Microenterprises for Arsenic Remediation in Developing Countries

“…HIX-Nano has demonstrated regenerability for at least five cycles versus 1–2 cycles for activated alumina. The spent regenerant was treated for environmentally safe containment of the resulting sludge; details have previously been provided in the open literature regarding the influence of pH on arsenic removal by HIX-Nano and regeneration technique (a. pH neutralization, b. ferric oxide sorption-precipitation, c. safe storage on aerated sludge). ,,− ,− …”

“…The eighty-eight existing plants, including the three plants specifically investigated in detail for their differences in ethnicity, provide evidence that plants once installed can be operationally self-sustainable without subsidy and earnings may be reinvested to install new plants in affected areas. Regenerable and reusable HIX-Nano sorbents , used in systems enable environmentally benign, low-cost waste management. − Local jobs were created in affected communities where the average per capita income was less than $1.50 per day, across regions diverse in ethnicity, language and religion. − Besides Bangladesh and India, similar success in mitigating the arsenic crisis was also observed in Nepal and Cambodia, the latter being a predominantly Buddhist country. , …”

“…Hybrid ion exchangers or HIX-Nano materials are comprised of a polymeric anion exchange resin support that is dispersed with metal oxide nanoparticles (e.g., iron, zirconium) both within the macropores and the gel phase. − HIX-Nano was commercialized over a decade ago because of its synergy of high capacity, high reusability and consequent reduction in the cost of treated water for arsenic, fluoride, and phosphate removal. ,,− Arsenic removed from groundwater is converted into solids (sludge) of ferric hydroxide that are contained over an aerated coarse filter under an oxidizing environment. Continued research and field-scale applications in India, Cambodia, Bangladesh, and Nepal have created robust and simple-to-apply sludge containment protocols in rural communities to ensure environmental compatibility and public safety. − In addition to robustness and high capacity, the reusability of HIX-Nano makes the process conducive to long-term application in developing countries due to lesser dependence on supply of the adsorbent material. Several community-based systems are in operation for more than a decade and HIX-Nano materials are now produced in India.…”

Use of ArsenXnp, a hybrid anion exchanger, for arsenic removal in remote villages in the Indian subcontinent

“…TCLP (Toxicity Characteristic Leaching Procedure) may indicate minimal leaching of arsenic from the sludge, as it is performed under oxidizing environment [34]. However, under reducing condition, such as that inside landfills there will be enhanced leaching of arsenic [35,36]. Also, there is evidence of research findings that TCLP underestimates leaching of arsenic as the protocol essentially proposes to carry out tests with a headspace of air in the bottles [37].…”

Response to Comment on “Landfill-Stimulated Iron Reduction and Arsenic Release at the Coakley Superfund Site (NH)”

“…Several types of arsenic-bearing wastes may be affected by geochemical reduction. In particular, water treatment residuals often contain high levels of arsenic bound to iron oxides ( , ) and may be destabilized when stored in landfills that undergo geochemical reduction. Given the increased need for arsenic water treatment to meet the new 10 μg/L water standard, the use and disposal of these wastes is likely to increase in the future.…”