Comparing Mixed-Media and Conventional Slow-Sand Filters for Arsenic Removal from Groundwater

Śmiech, Karolina M.; Tolsma, Aize; Kovács, T.; Dalbosco, Vlade; Yasadi, Kamuran; Groendijk, L.; Agostinho, L.L.F.

doi:10.3390/w10020119

Cited by 9 publications

(5 citation statements)

References 23 publications

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“…The applied upper layer of sand is capable of preventing the nails from moving while filling the filter with water. In order to facilitate cleaning of the filter, the upper sand layer was separated by a cloth from the nails [21,22]. As a consequence, it is imperative to instruct users of the filters correctly and carefully.…”

Section: Discussionmentioning

confidence: 99%

Results of the First Improvement Step Regarding Removal Efficiency of Kanchan Arsenic Filters in the Lowlands of Nepal—A Case Study

Mueller¹

2021

Water

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In Nepal as well as in other countries in Southeast Asia, the World Health Organization drinking water guideline of 10 µg/L concerning arsenic concentrations in ground water hosted in Quaternary alluvial sediments is often regionally exceeded. The commonly accepted theories include that arsenic in ground water stems from reductive dissolution of As-rich Fe(III)hydr(oxides) including microbial degradation of sedimentary organic matter. On the contrary, the influence of clay minerals in the sediments as hosts for As was clearly underestimated, as geochemical analysis depicted that As was generally associated with specific elements such as Na, K, Al, and Li. Moreover, there was a very weak correlation or decoupling between As and Fe in the ground water in Nepal, and this fact points to consequences for water treatment. The so-called Kanchan filters, used for the removal of As, installed in the lowlands of Nepal often exhibited effluent As concentrations well above Nepal’s drinking water quality standard value (i.e., 50 μg/L). Ground water concentrations of Fe and As proved to be the most important geochemical factors regarding the performance of the filters. Moreover, the flow rate as well as the contact time to the rusty nails in the filter, intended to adsorb As on their surface, influenced the removal efficiency. The removal rate was severely influenced by the handling of the filters, too. This short communication provides an overview of the removal efficiency of 30 filters, their drawbacks, the influence of the aging material in the filters as well as measures of improvements to enhance the efficiency of the filters. Proper instruction for users of Kanchan filters is a major point that needs to be addressed in the future.

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Section: Discussionmentioning

confidence: 99%

Results of the First Improvement Step Regarding Removal Efficiency of Kanchan Arsenic Filters in the Lowlands of Nepal—A Case Study

Mueller¹

2021

Water

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“…The concentration of arsenic in polluted areas is generally higher than 50 µg•L −1 , and in some areas the concentration of arsenic in water is above 1000 µg•L −1 [2][3][4][5][6]. A variety of arsenic pollution control methods have been developed, such as filtration [7,8], phytoremediation [9,10], coagulation [11][12][13], membrane [14,15], ion exchange [16,17], and adsorption [18][19][20].One of the most convenient methods to apply is adsorption [21,22].…”

Section: Introductionmentioning

confidence: 99%

Decontamination of Arsenic in Actual Water Samples by Calcium Containing Layered Double Hydroxides from a Convenient Synthesis Method

Liu

Zhang

et al. 2018

Water

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A series of calcium-containing layered double hydroxides (LDHs) and calcined product (CLDH) were synthesized using a comparative simple synthesis method (without using organic solvents and with a shortened reaction time) and applied in the adsorption of arsenic in water. The adsorption performance of arsenate on these LDHs and CLDH were studied using batch tests. The effects of various factors during the adsorption process, such as pH of the solution, dosage of materials, coexisting ions, contact time, and initial arsenate concentration, were evaluated. The maximum adsorption capacity of arsenate on three materials (CaFe-CLDH, CaFe-Cl-LDH, CaFe-NO3-LDH) were 156.0 mg·g−1, 150.5 mg·g−1, and 148.0 mg·g−1, respectively. When the concentration of CaFe-CLDH was 0.5 g·L−1, the concentration of arsenate was reduced from 5000 μg·L−1 to 10 μg·L−1 after adsorption. Moreover, when the CaFe-NO3-LDH or CaFe-Cl-LDH dosage was 1.0 g·L−1, a similar decontamination result could be achieved. The synthesized CaFe-CLDH was used to treat actual contaminated water samples from a river in a mining area north of Lengshuijiang City in Hunan Province, China. After treating using CaFe-CLDH, the residual arsenic concentration of actual water samples can fully meet the requirements for arsenic in the drinking water standards of the World Health Organization and China. This indicates that synthetic CaFe-CLDH has the potential to serve as an effective adsorbent for the removal of arsenic contamination.

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“…The KAF containing iron nails is such a promising solution [22,23]. However, available reports on As removal by KAFs seem rather univocal and overly generalized on their As removal efficiency [2,3,[24][25][26][27][28]. In particular, Smith et al [27] demonstrated that iron nails placed in biosand filter (BSF) were more effective than those placed above.…”

Section: Introductionmentioning

confidence: 99%

Kanchan Arsenic Filters and the Future of Fe0-Based Filtration Systems for Single Household Drinking Water Supply

Huang

Cao²,

Nya

et al. 2020

Processes

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Biological and chemical contamination of natural water bodies is a global health risk for more than one billion people, mostly living in low-income countries. Innovative, affordable, and efficient decentralized solutions for safe drinking water supply are urgently needed. Metallic iron (Fe0)-based filtration systems have been described as such an appropriate solution. This communication focuses on the Kanchan arsenic filter (KAF), presented in the early 2000s and widely assessed during the past decade. The KAF contains iron nails as the Fe0 source and is primarily designed to remove As from polluted tube well waters. Recent independent works assessing their performance have all reported on a high degree of variability in efficiency depending mostly on the following factors: (1) the current operating conditions, (2) the design, and (3) the groundwater chemistry. This communication shows that the major problems of the KAF are two-fold: (1) a design mistake as the Fe0 units disturb the operation and functionality of the biosand filter, and (2) the use of poorly characterized iron nails of unknown reactivity. This assertion is supported by the evidence that the very successful community filter designed by the Indian Institute of Technology Bombay works with iron nails and has been efficient for many years. Replacing iron nails by more reactive Fe0 materials (e.g., iron fillings and steel wool) should be tested in a new generation KAF. It is concluded that a methodological or systematic approach in introducing and monitoring the efficiency of KAF should be used to test and disseminate the next generation KAF worldwide. Moreover, better characterization of the Fe0 materials including their intrinsic reactivity is required.

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Comparing Mixed-Media and Conventional Slow-Sand Filters for Arsenic Removal from Groundwater

Cited by 9 publications

References 23 publications

Results of the First Improvement Step Regarding Removal Efficiency of Kanchan Arsenic Filters in the Lowlands of Nepal—A Case Study

Results of the First Improvement Step Regarding Removal Efficiency of Kanchan Arsenic Filters in the Lowlands of Nepal—A Case Study

Decontamination of Arsenic in Actual Water Samples by Calcium Containing Layered Double Hydroxides from a Convenient Synthesis Method

Kanchan Arsenic Filters and the Future of Fe0-Based Filtration Systems for Single Household Drinking Water Supply

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