Arsenic Removal Technologies Research Articles

Testing of Chemically Activated Cellulose Fibers as Adsorbents for Treatment of Arsenic Contaminated Water.

Exposure to different arsenic concentrations (higher than 10 μg/L), either due to the direct consumption of contaminated drinking water or indirectly by using contaminated food is harmful for human health. Therefore, it is important to remove arsenic from aqueous solutions. Among many arsenic removal technologies, adsorption offers a promising solution with a good efficiency, however the material used as adsorbent play a very vital role. The present investigation evaluated the behavior of two cellulose-based adsorbent materials, i.e., viscose fibers (V) and its TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) derivative, obtained by using the well-established TEMPO-mediated protocol (VF). Due to the known arsenic affinity for Fe ions the two materials were later doped with it. This was done after a preliminary functionalization with di-2-ethylhexyl phosphoric acid (DEHPA), to obtain two materials: V-DEHPA-Fe and VF-DEHPA-Fe. Arsenic adsorption is known to be pH dependent (between 6 and 8); therefore, the optimal pH range for As(V) adsorption has been established. In order to evaluate the adsorption mechanism for both the synthesized materials, the influence of contact time, temperature and initial concentration was evaluated. Langmuir, Freundlich and Sips equilibrium isotherm models were used in order to determine the ability of the model to describe As(V) adsorption process. The maximum adsorption capacity of the material V-DEHPA-Fe was 247.5 µg As(V)/g with an As(V) initial concentration of 5 mg/L and for the material VF-DEHPA-Fe it was 171.2 µg As(V)/g with initial concentration of 5 mg/L.

Effect of pre-aeration on the removal of arsenic and iron from natural groundwater in household based ceramic filters

Maintenance of existing household arsenic (As) removal technologies are comparatively difficult due to the use of the sand beds as a filter. Moreover, pre-aeration of groundwater is avoided during filter operation that may affect the removal efficiency. This study investigated the effect of pre-aeration on the efficacy of simple iron nested ceramic filter (CF) for the removal of As and Fe from the natural groundwater. Five CFs at 5 households in the Bagerhat district of Bangladesh were tested for 31 days with pre-aerated groundwater (AGW system) and non-aerated groundwater (NAGW system). Pe-aeration of groundwater significantly improved (p > 0.5) the removal efficiency of As and Fe in the CFs. The filters effectively removed As in the groundwater from 203 - 231 μg/L to 29–40 μg/L in the AGW system whereas the effluent As were >50 μg/L in the NAGW system. Iron (Fe) was also removed effectively and the overall As and Fe removal efficiency were more than 82% and 99%, respectively in the AGW system. Removal of Mn and PO4–P were significantly enhanced achieving more than 56% and 99% removal, respectively in the AGW system. X-ray absorption fine structure (XAFS) analysis indicated that the oxidation of Fe2+ and As(III) and subsequent adoption/precipitation are the main processes controlling the removals of As and Fe in the CFs. Two stages oxidation of Fe2+ and As(III) in the AGW system facilitated to increase As and Fe removal efficiency. The findings of this study suggest that the iron net nested ceramic filters with pre-aeration step is an effective method and can be employed at the household level in As contaminated region.

Research Progress on the treatment of arsenic pollution by manganese oxide

Arsenic is a kind of protoplasmic poison, which exists widely in the natural environment. Consuming too much arsenic can cause a number of health problems. Manganese oxide plays an important role in arsenic pollution removal technology. In this paper, arsenic hazard and its treatment methods and the application of manganese oxides in arsenic pollution treatment are summarized, and the prospect of research on arsenic pollution treatment by manganese oxides is put forward.

Electrocoagulation for Arsenic Removal: Field Trials in Rural West Bengal.

Arsenic contamination in drinking water is a great concern in different regions of the world as well as in India. Several technologies have been investigated to remove arsenic from water, such as coagulation and co-precipitation, ion exchange, adsorption, and reverse osmosis. In the present research, electrocoagulation with iron electrodes has been assessed as a treatment technology for arsenic removal from groundwater to reach concentrations below 0.01mg/L (WHO limit) and which is technically effective, affordable for the local area, and easy to operate and maintain. Electrochemically generated iron is converted to hydrated ferric oxide within the contaminated water, which takes up the arsenic from water. A downstream filtration unit (sand or activated alumina) is applied to remove ferric hydroxide flocs produced during the process. The laboratory experiments were conducted in a batch reactor using iron plates as electrodes with monopolar configuration to study the effects of initial pH and electro-charge loading (ECL) on arsenic removal. The optimum operating condition was observed for an electro-charge loading of 25-30 Coulombs/L at pH 7.0 and an initial arsenic concentration of 0.2mg/L. Two field trials were implemented in West Bengal after suitably designing the electrocoagulation system. Arsenic removal was significant (75-80%) delivering safe water with arsenic below 0.01mg/L (acceptable limit). Passivation of the electrodes occurred during the operation and calcium-based (including iron) deposition was observed on the cathodes. Passivation is avoidable after running regular polarity reversal of the electrodes.

High-efficient removal of arsenite by coagulation with titanium xerogel coagulant

Coagulation with inorganic titanium (Ti) salts is a low-cost and high-efficiency technology for arsenic removal. However, the drastic decline of solution pH, which is caused by coagulation process, usually greatly reduces the removal efficiency of arsenite (As(III)). In this study, titanium xerogel coagulant (TXC) was employed for enhanced As(III) removal, and two common Ti-based coagulants, titanium sulfate (TS) and titanium tetrachloride (TC), were used as references. TXC outperformed TS and TC over the initial pH range of 5.0–10.0, especially under acidic condition, which was attributable to the moderate pH decline during TXC coagulation. TXC with dose of 10 mg Ti/L could eliminate above 90% of As(III) at pH 7.0 and 8.0. The maximum coagulation efficiency of the three Ti salts (10 mg Ti/L) at pH 8.0 followed an order of 625 mg/g Ti (TXC) > 588 mg/g Ti (TS) > 526 mg/g Ti (TC). The enhanced mechanisms involved in TXC coagulation were the strong adsorption ability of the in-situ formed flocs and binding affinity between As(III) and hydrolysates. TXC coagulation dominated by the unique network-like hydrolysates would generate in-situ flocs with more binding sites, and thus improved coagulation efficiency. Except for phosphate and silicate ions, the common water matrices did not greatly inhibit As(III) removal efficiency. In addition, TXC performed the highest As(III) removal efficiency in actual arsenic-containing wastewater. This study provided a high-efficient coagulant for As(III) pollution control, and shed light on the application potential of TXC in removing metalloid pollutants.

Review: Efficiently performing periodic elements with modern adsorption technologies for arsenic removal

Arsenic (As) toxicity is a global phenomenon, and it is continuously threatening human life. Arsenic remains in the Earth's crust in the forms of rocks and minerals, which can be released into water. In addition, anthropogenic activity also contributes to increase of As concentration in water. Arsenic-contaminated water is used as a raw water for drinking water treatment plants in many parts of the world especially Bangladesh and India. Based on extensive literature study, adsorption is the superior method of arsenic removal from water and Fe is the most researched periodic element in different adsorbent. Oxides and hydroxides of Fe-based adsorbents have been reported to have excellent adsorptive capacity to reduce As concentration to below recommended level. In addition, Fe-based adsorbents were found less expensive and not to have any toxicity after treatment. Most of the available commercial adsorbents were also found to be Fe based. Nanoparticles of Fe-, Ti-, Cu-, and Zr-based adsorbents have been found superior As removal capacity. Mixed element-based adsorbents (Fe-Mn, Fe-Ti, Fe-Cu, Fe-Zr, Fe-Cu-Y, Fe-Mg, etc.) removed As efficiently from water. Oxidation of AsO33- to AsO43-and adsorption of oxidized As on the mixed element-based adsorbent occurred by different adsorbents. Metal organic frameworks have also been confirmed as good performance adsorbents for As but had a limited application due to nano-crystallinity. However, using porous materials having extended surface area as carrier for nano-sized adsorbents could alleviate the separation problem of the used adsorbent after treatment and displayed outstanding removal performances.

Comparison between experimental results of different technologies for arsenic removal from water intended for human consumption

Abstract Arsenic contamination in drinking water is a major issue in the present world. Techniques such as oxidation, precipitation and adsorption have been widely used for arsenic removal. The goal of this work is to analyze four case studies where the problem of arsenic contamination in groundwater is faced with an approach that includes experimental activities at laboratory scale and/or pilot scale. The first case study investigates the mechanisms for enhancing arsenic removal with naturally occurring Fe by the addition of an oxidizing agent (KMnO4) or a concentrated basic solution of MnO4− and AlO2−. In the second case study, different experimental tests are carried out at laboratory scale in order to identify the best combination of treatments to be applied at full scale. The third case study shows the results of experimental studies followed by a full-scale upgrading for a drinking water treatment plant (DWTP) with no specific arsenic treatment in the first configuration. Last, the fourth case study investigates the performance of granular ferric oxide (GFO) with arsenic concentrations close to the Italian regulatory limit. A pilot GFO filter was installed in a DWTP. The monitoring results led to the implementation of the GFO filter at full scale.

Local innovation for application of membrane system for supply of arsenic-safe water in rural Bangladesh

Over seventy million people in Bangladesh are drinking arsenic contaminated water. There is a lack of available sustainable arsenic removal technologies in the rural Bangladesh. This paper reports on a successful retrofit that allows for readily available, cost effective and dependable membrane system application for arsenic removal in rural Bangladesh. The retrofit is very simple, overcoming the limitation of a hydraulic pressure by a low cost pump placement in line to the membrane system. The system was field tested in a well with high arsenic concentration 0.1 mg/L (Government of Bangladesh Limit is 0.05 mg/L), along with high iron and hardness. In the field trial, the retrofitted technology was successful and produced water that does not contain any arsenic (0.0 mg/L), low in iron, and low in hardness. The system cost, along with the retrofitting, is only a hundred and seventy US dollars, a sum within the reach of many in Bangladesh. It is also important to note that we are using an existing technology available off the shelf and retrofitting it using locally available materials. The work reported in the paper will create a significant impact relief to the people in the arsenic affected regions of Bangladesh.

Emerging technologies for arsenic removal from drinking water in rural and peri-urban areas: Methods, experience from, and options for Latin America

Providing drinking water with safe arsenic levels in Latin American (LA) countries (a total of 22 countries) is a major current challenge. Arsenic's presence in water has been neglected for many decades since it was first reported ~100 years ago in Argentina. The major arsenic source in this region is geogenic. So far, arsenic has been reported in 15 LA countries. Arsenic concentrations in drinking water have been reported up to >200 fold (2000 μg/L) the WHO limit of 10 μg/L. About 14 million people in the arsenic affected LA countries depend on contaminated water characterized by >10 μg/L of arsenic. Low-cost, easy to use, efficient, and sustainable solutions are needed to supply arsenic safe water to the rural and peri-urban population in the affected areas. In the present study, >250 research articles published on various emerging technologies used for arsenic remediation in rural and peri-urban areas of LA countries are critically reviewed. Special attention has been given to arsenic adsorption methods. The manuscript focuses on providing insights into low cost emergent adsorbents with an implementation potential in Latin America. Natural, modified and synthetic adsorbents used for arsenic decontamination were reviewed and compared. Advantages and disadvantages of treatment methods are summarized. Adsorbent selection criteria are developed. Recommendations concerning emerging adsorbents for aqueous arsenic removal in LA countries have also been made.

Alginate-based biotechnology: a review on the arsenic removal technologies and future possibilities

Abstract The alginate-based adsorption technologies have emerged as potential methods for arsenic removal from drinking water. The adsorbents (iron oxide, hydroxide, nano zero valent iron (nZVI), industrial waste, minerals, magnetite, goethite, zirconium oxide, etc.) are impregnated into alginate beads to produce the media. The biocompatibility, rough surface with large area, and amorphous and high water permeable bead structure improve arsenic adsorption efficiency while the regeneration process is simpler than the conventional adsorbents. In recent years, studies have reported laboratory-scale applications of alginate beads, encapsulated and impregnated with adsorbents, for arsenic removal from drinking water. The arsenic removal efficiencies were reported to be over 95% with a wide range of concentrations (10–1,000 parts per billion) and pH (3.0–7.5). However, commercial- and/or mass-scale applications have not been reported yet, due possibly to overall cost, complexity, reusability, and arsenic waste-laden sludge management. In this paper, research achievement on arsenic removal using alginate-based adsorbents has been reviewed. The review was performed in context to alginate bead development, adsorbent encapsulation and impregnation, application, performance, and regeneration. The advantages and limitations of the methods were analyzed and the scopes of future research were identified for mass scale domestic and industrial applications.

Arsenic in Argentina: Technologies for arsenic removal from groundwater sources, investment costs and waste management practices

An overview about the presence of arsenic (As) in groundwaters of Argentina, made by a transdisciplinary group of experts is presented. In this second part, the conventional and emerging technologies for As removal, management of wastes, and the initial investment costs of the proposed technologies, with emphasis on developments of local groups are described. Successful examples of real application of conventional and emerging technologies for As removal in waters for human consumption, for medium, small and rural and periurban communities are reported. In the country, the two most applied technologies for arsenic removal at a real scale are reverse osmosis and coagulation-adsorption-filtration processes using iron or aluminum salts or polyelectrolytes as coagulants. A decision tree to evaluate the possible technologies to be applied, based on the population size, the quality of the water and its intended use, is presented, including preliminary and indicative investment costs. Finally, a section discussing the treatment and final disposal of the liquid, semiliquid and solid wastes, generated by the application of the most used technologies, is included. Conclusions and recommendations, especially for isolated rural and periurban regions, have been added.

Genomic Analysis of Shewanella sp. O23S-The Natural Host of the pSheB Plasmid Carrying Genes for Arsenic Resistance and Dissimilatory Reduction.

Shewanella sp. O23S is a dissimilatory arsenate reducing bacterial strain involved in arsenic transformations within the abandoned gold mine in Zloty Stok (SW Poland). Previous physiological studies revealed that O23S may not only release arsenic from minerals, but also facilitate its immobilization through co-precipitation with reduced sulfur species. Given these uncommon, complementary characteristics and the application potential of the strain in arsenic-removal technologies, its genome (~5.3 Mbp), consisting of a single chromosome, two large plasmids (pSheA and pSheB) and three small plasmid-like phages (pSheC-E) was sequenced and annotated. Genes encoding putative proteins involved in heavy metal transformations, antibiotic resistance and other phenotypic traits were identified. An in-depth comparative analysis of arsenic respiration (arr) and resistance (ars) genes and their genetic context was also performed, revealing that pSheB carries the only copy of the arr genes, and a complete ars operon. The plasmid pSheB is therefore a unique natural vector of these genes, providing the host cells arsenic respiration and resistance abilities. The functionality of the identified genes was determined based on the results of the previous and additional physiological studies, including: the assessment of heavy metal and antibiotic resistance under various conditions, adhesion-biofilm formation assay and BiologTM metabolic preferences test. This combined genetic and physiological approach shed a new light on the capabilities of O23S and their molecular basis, and helped to confirm the biosafety of the strain in relation to its application in bioremediation technologies.

Isolation and Characterization of Arsenic Tolerant Bacteria Collected from Arsenic Contaminated Site of West Bengal, India

In the present study, arsenic tolerant bacteria were isolated and characterized from rhizospheric soil of rice plant growing in the arsenic contaminated area of West Bengal, India. Among 31 bacterial isolates, nine isolates were showed tolerance at higher concentration of arsenate (As V; 20000 mg mL-1). Selected arsenic tolerance bacterial isolates were characterized based on biochemical analysis, partial 16S rDNA gene sequencing and phylogenetic analysis. Results revealed that selected arsenic tolerant bacterial strains were lavished at 370C and neutral pH 7 and showed a positive response for catalase and oxidase enzymes. Using partial 16S rDNA based identification and phylogenetic analysis, selected bacterial isolates were identified as Jeotgalicoccus nanhaiensis, Alcaligenes faecalis, Paenalcaligenes sp., Providencia sp., Kocuria sp. and Pseudomonas stutzeri. Further, the isolated As tolerant bacterial strains may be tested for their possible utilization in arsenic mobilization in the rhizosphere for enhancing phytoremediation potential to remediate arsenic from contaminated sites. However, efficient arsenic accumulator strain like Pseudomonas stutzeri can be employed as bioresource to develop low-cost bioremediation technology for arsenic removal.

Sustaining efficient production of aqueous iron during repeated operation of Fe(0)-electrocoagulation

Iron-electrocoagulation is a promising contaminant (e.g. arsenic) removal technology that is based on electrochemical Fe(II) production from steel electrodes and subsequent transport of Fe(II) to the bulk solution, where contaminant removal occurs. Although Fe-electrocoagulation systems have been shown to effectively remove contaminants in extended field trials, the efficiency of field systems can be lower than in laboratory studies. One hypothesis for this disparity is that the Faradaic efficiency of short-term laboratory experiments is higher than field systems operated over extended periods. The Faradaic efficiency is a pivotal performance indicator that we define as the measured Fe dosage normalized by the theoretical Fe dosage calculated by Faraday's law. In this work, we investigated the Faradaic efficiency in laboratory experiments for up to 35 operating cycles (>2 months) with varied Fe(0) anode purity, charge dosage rate, and electrolyte composition. Our results showed that the Faradaic efficiency decreased continuously during repeated operation under typical field conditions (charge dosage rate = 4 C/L/min, synthetic groundwater) regardless of the Fe(0) anode purity, leading to a Faradaic efficiency ≈ 0.6 after 2 months. By contrast, increasing the charge dosage rate to ≥15 C/L/min produced a Faradaic efficiency >0.85 over the entire experiment for both Fe(0) anode purities. Electrolyte solutions free of oxyanions also resulted in sustained Faradaic efficiency >0.85, regardless of the charge dosage rate. Our results confirm a previously proposed relationship between low Faradaic efficiency and the formation of macroscopic electrode surface layers, which consist of Fe (oxyhydr)oxides on the anode and a mixture of Fe (oxyhydr)oxides and calcite on the cathode. Based on these results, we discuss potential strategies to maintain a high Faradaic efficiency during Fe-electrocoagulation field treatment.

An overview of main arsenic removal technologies

Abstract Arsenic (As) is metalloid, naturally present in the environment but also introduced by human activities. It is toxic and carcinogenic and its exposure to low or high concentrations can be fatal to human health. Arsenic contamination in drinking water threatens more than 150 million peoples all over the world. Therefore, treatment of As contaminated water is of unquestionable importance. The present review begins with an overview of As chemistry, distribution and toxicity, which are relevant aspects to understand and develop remediation techniques. The most common As removal processes (chemical precipitation, adsorption, ion exchange, membrane filtration, phytoremediation and electrocoagulation) are presented with discussion of their advantages, drawbacks and the main recent achievements.

Arsenic removal from drinking water using wood charcoal

Arsenic contamination of drinking water is threating the health of millions of people of Bangladesh. Lack of appropriate arsenic removal technology has complicated and inhibited mitigation initiatives. The effectiveness of wood charcoal for removal of arsenic from tubewell water was evaluated in this study. Arsenic contaminated water sample was passed through a pitcher having a small hole at its bottom contained wood charcoal at a controlled flow rate of 30 ml/min with different thickness of wood charcoal (7.5 cm, 10 cm, 12.5 cm, 15 cm, 17.5 cm, 20 cm and 22.5) and at different flow rates (10 ml/min, 30 ml/min, 50 ml/min, 70 ml/min, 90 ml/min, 110 ml/min and 130 ml/min) with 20 cm fixed thickness of wood charcoal. Results revealed that with the increased of flow rate the removal of arsenic percentage decreased. Maximum arsenic removal efficiency was obtained at a flow rate of 10 ml/min with 20 cm of charcoal thickness. In addition, it also observed that both flow rate and charcoal thickness are critically important in achieving higher arsenic removal efficiency. Therefore, water flow rate of 50 ml/min with charcoal thickness of 15 cm could be used to remove arsenic from contaminated tube well water (arsenic concentration after filtration is 30 μg/L which is below the allowable arsenic concentration standard i.e. 50 μg/L). [Fundam Appl Agric 2018; 3(3.000): 591-595]

Assessment of pilot-scale water purification module with electrodialysis technology and solar energy

In this research, an autonomous power module for the purification of brackish water (TDS=5482mg/L) with high concentration of arsenic (2.04mg/L) was successfully designed, constructed and tested. The energy supply for the module is provided by solar power and includes an electrical energy storage system composed of lithium ion batteries. The purification process combines ion exchange and adsorption technologies (column filtration system) with an electrodialysis (ED) system. Different configurations or process sequences were studied to determine the best operating conditions of the system. The salt removal efficiency and specific electricity consumption (SEC) were determined at each stage. It was found that the process that combines all technologies is more efficient than just using ED for the removal of arsenic and salts. The ion exchange step removes the divalent cations, whereas most of the arsenic is adsorbed in the adsorption column system increasing the removal efficiency in the electrodialysis stage. This combined process reduces the time of desalination and the consumption of electricity during the ED. The lowest specific electricity consumption was 2.16kWh/m3 for the ED and 5.46kWh/m3 for the global system. Salt removal exceeded 95% and in the majority of tests, the arsenic removal was more than 99.9%. The power module with the water purification system has a versatile design that allows working with different salts concentration either for the treatment of water from river or underground, effectively removing arsenic. Our proposed solution is an alternative to the conventional technologies for arsenic removal and the results of this study should be useful for the design of other large-scale water desalination systems.

Arsenic removal methods for drinking water in the developing countries: technological developments and research needs.

Arsenic pollution of drinking water is a concern, particularly in the developing countries. Removal of arsenic from drinking water is strongly recommended. Despite the availability of efficient technologies for arsenic removal, the small and rural communities in the developing countries are not capable of employing most of these technologies due to their high cost and technical complexity. There is a need for the "low-cost" and "easy to use" technologies to protect the humans in the arsenic affected developing countries. In this study, arsenic removal technologies were summarized and the low-cost technologies were reviewed. The advantages and disadvantages of these technologies were identified and their scopes of applications and improvements were investigated. The costs were compared in context to the capacity of the low-income populations in the developing countries. Finally, future research directions were proposed to protect the low-income populations in the developing countries.

Conventional as well as Emerging Arsenic Removal Technologies—a Critical Review

Arsenic poisoning from contaminated drinking water has evolved as one of the major health hazards in recent times. High concentrations of arsenic in water and soil have been found in many parts of the world. Developing countries like Taiwan, Chile, Argentina, Bangladesh, Nepal and Vietnam are most affected by the contamination of groundwater with arsenic. These countries also cannot afford expensive and large-scale treatments to remove arsenic from drinking waters to acceptable limits (10 ppb, as recommended by WHO and US EPA). The aim of this review is to summarize low-cost, effective conventional technologies currently described in the literature for arsenic removal that can be used in the third world and developing countries, compare them with the emerging technologies and discuss their advantages and disadvantages along with a brief analysis of arsenic chemistry.

Coagulation-Flocculation Technologies for Arsenic removal -A Review

This review article presents in brief an overview of various technologies available based on coagulationflocculation methods. Coagulation and flocculation are among the most employed and documented techniques for arsenic removal from water. Arsenic is a human carcinogen in drinking water, having harmful effects on both human health and environment, even at low concentration. A limit of 0.01ppm (10 μg/L) has been set by WHO as the safe limit in drinking water, above which it shows health hazards. In coagulation method the, positively charged ion of coagulants {e.g., aluminum sulphate (Al 2 (SO 4 ) 3 ), ferric chloride (FeCl 3 )} neutralize or reduce the negative charge of colloids, thereby causing coagulation of particles. On the other hand in Flocculation the addition of an anionic flocculants leads to charge neutralization between the formed larger particles which ultimately change in to big flocs. As a result the dissolved arsenic is transformed into an insoluble solid. The precipitation or co precipitation with certain metal hydroxides can be done to remove arsenic from drinking water through sedimentation or filtration. The pH of the medium plays an important role in deciding the suitability of a coagulant for the removal of Arsenic. Below pH 7.5, Al 2 (SO 4 ) 3 , and FeCl 3 are equally effective in removing arsenic from water Between the two inorganic arsenic species, most researchers suggested that arsenate is more efficiently removed compared to arsenite and that FeCl 3 is a better coagulant than Al 2 (SO 4 ) 3 at pH higher than 7.5.There is no effective treatment for arsenic toxicity. Removal of arsenic from water is the one and only method of preventing its toxicity. A great deal of research over recent decades has been done to lower the concentration of arsenic in drinking water and still there is a need to develop low cost viable techniques. Existing major arsenic removal technologies include oxidation, adsorption, precipitation, coagulation and membrane separation. This paper presents the review of current status of research in the area of arsenic removal from contaminated water with coagulation and flocculation methods.