Technologies for Decentralized Fluoride Removal: Testing Metallic Iron-based Filters

Abstract

Since the realization in the 1930s that elevated fluoride concentrations in drinking water can have detrimental effects on human health, new methods have been progressively developed in order to reduce fluoride to acceptable levels. In the developing world the necessity for filtration media that are both low-cost and sourced from locally available materials has resulted in the widespread use of bone char. Since the early 1990s metallic iron (Fe 0 ) has received widespread use as both an adsorbent and a reducing agent for the removal of a wide range of contaminant species from water. The ion-selectivity of Fe 0 is dictated by the positively charged surface of iron (hydr)oxides at circumneutral pH. This suggests that Fe 0 could potentially be applied as suitable filter media for the negatively charged fluoride ion. This communication seeks to demonstrate from a theoretical basis and using empirical data from the literature the suitability of Fe 0 filters for fluoride removal. The work concludes that Fe 0 -bearing materials, such as steel wool, hold good promise as low-cost, readily available and highly effective decentralized fluoride treatment materials.

Appropriate technology for domestic wastewater management in under-resourced regions of the world

“…In order to ensure compliance with the recommended guidelines and standards, information on discharge and reuse standards should be made available to the operators and the cost of laboratory analysis should be highly subsidized or borne by a third party. The importance of well-equipped laboratory in the developing world as a prelude to safe water delivery and improved environmental sanitation has been previously recognized (Tepong-Tsindé, et al, 2015, Ndé-Tchoupé, et al, 2015.…”

Predicting the Hydraulic Conductivity of Metallic Iron Filters: Modeling Gone Astray

“…Individual researchers already went down this path [10,119]. As an example, the author of this communication has published on reductive precipitation of U VI by Fe 0 [120], then on reduction as a removal mechanism, until 2010 [14], only with [121] and hints from anonymous reviewers did he realize that at concentrations relevant for safe drinking water, reduction cannot be a stand-alone removal mechanism for any contaminant [78,122]. For environmental remediation, chemical reduction (degradation) may be sufficient when reaction products are readily degradable, for instance when nitrobenzene is quantitatively reduced to aniline.…”

“…Considering this vacuity, the intention herein is to pave the way for the determination of k iron values useful for modeling purposes. Clearly, while determining k iron values useful for models, experiments should be designed to characterize as much parameters as possible in a systematic approach [77,78]. The major advantage of this approach is that the same set of experiments will generate data enabling the discussion of the appropriateness of current approaches, as well.…”

“…To optimize the efficiency of the filtration unit, the effluent should be clarified and deaerated before being introduced into the first column. A simple device for clarification and deaeration is a slow sand filter [78].…”

“…The presentation above demonstrates that the short-term rate constants of Fe 0 corrosion (k 0 iron) have been mistakenly used to interpret results To optimize the efficiency of the filtration unit, the effluent should be clarified and deaerated before being introduced into the first column. A simple device for clarification and deaeration is a slow sand filter [78].…”