Arsenic Removal Technologies Research Articles

An overview of arsenic removal technologies in India

In the context of prevalence of high concentrations of arsenic in tubewell water, a wide range technology has been tried for the removal of arsenic from drinking water. The most common technologies utilized the conventional processes of oxidation, co-precipitation and adsorption onto coagulated flocs, adsorption onto sorptive media, ion exchange and membrane techniques for arsenic removal. The conventional technologies have been scaled down to meet the requirements of households and communities and suit the rural environment. Some technologies utilized indigenous materials for arsenic removal. This paper presents a short review of the technologies used for arsenic removal in Bangladesh and India.

Arsenic removal from industrial wastewater

The article presents current research on the removal of arsenic in one of copper smelter in Legnica-Glogow Copper District. Arsenic removal technology applied in the results of previous author’s researches has been described. Also, the content of arsenic in wastewater discharged into the receiver in 2012–2016 was examined. Additionally, the concentration of heavy metals in these wastewater was checked.

Arsenic removal from drinking water by electrocoagulation using iron electrodes- an understanding of the process parameters

Various methods exist for arsenic removal from water, but most are not viable as they require addition of oxidants and use adsorbents which have limited adsorption capacities. Electrocoagulation using iron electrodes (ECFe) is a promising technology for arsenic removal. Efficiency of arsenic removal by ECFe may be affected by parameters such as pH, current intensity, initial arsenic concentration and co-occurring ions like phosphate, silicate, natural organic matter (NOM), bicarbonate, sulphate, nitrate and chloride but the causal action is not well understood. Thus experiments were designed and carried out to observe these effects and get a better understanding of ECFe. The results indicate that the oxidation of Fe(II) generated during ECFe is essential for high efficiency (with respect to iron dose) of arsenic removal. Lower current intensities and pH7 were found to be most efficient for arsenic removal per unit weight of iron dissolved. Observations indicate that arsenic reacts with ferric (hydr)oxides and phosphate complexes with Fe(II). With time these complexes and precipitates are reordered to give a much higher affinity of iron (hydr)oxides for phosphate. Silicate, upto 20mg/L, had negligible effect but at 30mg/L was seen to reduce arsenic removal by ECFe. Increasing NOM concentrations also reduced arsenic removal but bicarbonate, sulphate, nitrate and chloride had no effect on arsenic removal by ECFe. Presence of old ferric (hydr)oxides in the reactor led to lesser requirement of Fe(II) to achieve less than 10ppb concentration as it promoted interfacial reactions. Formation of FeAsO4 was observed by FTIR analysis of the precipitates.

Technologies for Arsenic Removal from Water: Current Status and Future Perspectives.

This review paper presents an overview of the available technologies used nowadays for the removal of arsenic species from water. Conventionally applied techniques to remove arsenic species include oxidation, coagulation-flocculation, and membrane techniques. Besides, progress has recently been made on the utility of various nanoparticles for the remediation of contaminated water. A critical analysis of the most widely investigated nanoparticles is presented and promising future research on novel porous materials, such as metal organic frameworks, is suggested.

Surface interactions of monomethylarsonic acid with hematite nanoparticles studied using ATR-FTIR: adsorption and desorption kinetics

Monomethylarsonic acid (MMA) is an organoarsenical compound which, along with dimethylarsinic acid (DMA), poses health and environmental concerns. Little is known about the surface chemistry of MMA at the molecular level with materials relevant to geochemical environments and industrial sectors. We report the structure of MMA surface complexes and the adsorption/desorption kinetics of MMA to and from hematite as a model for reactive iron-containing materials commonly found in geosorbents and arsenic-removal technologies. Attenuated total internal reflectance Fourier transform infrared (ATR-FTIR) spectroscopy was used to study the surface interactions at the molecular level. Spectra of adsorbed MMA (MMA(ads)) were collected as a function of time and aqueous-phase concentration. Values for the apparent rates of adsorption and desorption were extracted from experimental data at pH 7 as a function of spectral components during the initial times of surface interactions (0–5 min). Results showed that MMA adsorbs on hematite nanoparticles with rates 1.3 to 1.6 times slower than arsenate. The desorption of MMA(ads) by hydrogen phosphate from hematite surfaces is 2× faster than arsenate, and proceeds with an overall nonunity order, suggesting the existence of more than one type of surface complex at equilibrium. Also, hydrogen phosphate leads to the desorption of about 67% of MMA(ads) compared with 26% of surface arsenate. Adsorption kinetics for aqueous hydrogen phosphate were also investigated in the absence and presence of surface arsenic and followed this order: fresh hematite > MMA/hematite ≥ iAs(V)/hematite. From this study, it can be inferred that, on average, the presence of the methyl group in MMA results in weaker surface interactions with hematite relative to arsenate under neutral pH because of the simultaneous formation of mono- and bidentate MMA complexes compared with predominantly bidentate complexes for arsenate.

Arsenic removal from naturally contaminated waters: a review of methods combining chemical and biological treatments

The presence of arsenic (As) in aquatic environments is often attributable to geogenic processes occurring within aquifers. Arsenic exists in two prevalent oxidation states, with the trivalent arsenite [As(III)] exerting stronger toxicity effects on the aquatic biota than the pentavalent arsenate [As(V)]. The review evaluates the literature available on the main arsenic removal technologies and the application of combined chemical and biological treatments. We provide a synthetic outlook on the potential strategies of biological As(III) oxidation to As(V) by means of cell-detoxifying mechanisms or metabolic processes with the aim to enhance As removal efficiency. Furthermore, the role of microorganisms in the mobility of arsenic in natural systems as well as the distribution of As-resistant bacteria, potentially suitable for arsenic removal, is discussed in the context of a case study carried out in Latium region (Italy), which is known for arsenic contamination of waters.

Clean Water for Developing Countries.

Availability of safe drinking water, a vital natural resource, is still a distant dream to many around the world, especially in developing countries. Increasing human activity and industrialization have led to a wide range of physical, chemical, and biological pollutants entering water bodies and affecting human lives. Efforts to develop efficient, economical, and technologically sound methods to produce clean water for developing countries have increased worldwide. We focus on solar disinfection, filtration, hybrid filtration methods, treatment of harvested rainwater, herbal water disinfection, and arsenic removal technologies. Simple, yet innovative water treatment devices ranging from use of plant xylem as filters, terafilters, and hand pumps to tippy taps designed indigenously are methods mentioned here. By describing the technical aspects of major water disinfection methods relevant for developing countries on medium to small scales and emphasizing their merits, demerits, economics, and scalability, we highlight the current scenario and pave the way for further research and development and scaling up of these processes. This review focuses on clean drinking water, especially for rural populations in developing countries. It describes various water disinfection techniques that are not only economically viable and energy efficient but also employ simple methodologies that are effective in reducing the physical, chemical, and biological pollutants found in drinking water to acceptable limits.

In situ treatment of arsenic contaminated groundwater by aquifer iron coating: Experimental study

In situ arsenic removal from groundwater by an aquifer iron coating method has great potential to be a cost effective and simple groundwater remediation technology, especially in rural and remote areas where groundwater is used as the main water source for drinking. The in situ arsenic removal technology was first optimized by simulating arsenic removal in various quartz sand columns under anoxic conditions. The effectiveness was then evaluated in an actual high-arsenic groundwater environment. The arsenic removal mechanism by the coated iron oxide/hydroxide was investigated under different conditions using scanning electron microscopy (SEM)/X-ray absorption spectroscopy, electron probe microanalysis, and Fourier transformation infrared spectroscopy.Aquifer iron coating method was developed via a 4-step alternating injection of oxidant, iron salt and oxygen-free water. A continuous injection of 5.0mmol/L FeSO4 and 2.5mmol/L NaClO for 96h can form a uniform goethite coating on the surface of quartz sand without causing clogging. At a flow rate of 7.2mL/min of the injection reagents, arsenic (as Na2HAsO4) and tracer fluorescein sodium to pass through the iron-coated quartz sand column were approximately at 126 and 7 column pore volumes, respectively. The retardation factor of arsenic was 23.0, and the adsorption capacity was 0.11mol As per mol Fe. In situ arsenic removal from groundwater in an aquifer was achieved by simultaneous injections of As(V) and Fe(II) reagents. Arsenic fixation resulted from a process of adsorption/co-precipitation with fine goethite particles by way of bidentate binuclear complexes. Therefore, the study results indicate that the high arsenic removal efficiency of the in situ aquifer iron coating technology likely resulted from the expanded specific surface area of the small goethite particles, which enhanced arsenic sorption capability and/or from co-precipitation of arsenic on the surface of goethite particles.

Sustained Applications of Pesticides and Fertilizers in Sugarcane, Cotton and Wheat Cultivated Areas Causes Ground Water Arsenic Contamination - District Rahim Yar Khan, Pakistan

Due to over all water scarcity situation, more reliance is made on local groundwater sources for drinking and other human needs /purposes. Most of the boreholes or shallow wells are confined to upper aquifers which are exposed to contamination from all sorts of wastewaters and run-off from agricultural field etc. Water quality monitoring from these ground water sources remained irregular, as main focus was on surface water quality monitoring . Information on seasonal water quality changes in surface and ground water was generally lacking. Natural factors facilitating introduction of arsenic into water are related to geomorphology, tectonic activities and chemical components of water bearing formations (Tong, 2002; Htay, 2004, Fengthong, 2004). Keeping in view the prevalence of arsenic in district Rahim Yar khan , a confirmatory arsenic testing was carried out and it was revealed that out of 45 samples, tested for arsenic contamination, 57.78 % were having more than 100 ppb arsenic contamination and 35.56 % were having arsenic contamination more than 50 ppb, which were higher than the WHO limits. During 2006, UNICEF installed some kind of arsenic removal technologies in the area, which were not sustainable due to lack of technical know and resources essentially needed during post project periods . At the same time no endeavors were made to ascertain the causes of arsenic prevalence for having sustainable alternative arsenic free water sources. The areas was rich for agricultural activities, with sustained use of pesticides and fertilizers . A well planned soil investigation process was carried out upto the depth of 387 feet to find out the existence of arseno-pyrites, the major cause of arsenic contamination. All the soil samples were analyzed in the laboratory by using XRD & XRF equipment. The soil investigation analysis, clearly indicated the absence of arseno-pyrites which could have been responsible for ground water arsenic contamination in the area. This very fact indicates that arsenic contamination was due to leaching of pesticides and chemicals , as cotton, being a major cash crop of Pakistan, consumes more than 70 % pesticides being used in the country and at least a dozen spray sessions are made during a single harvesting season September to November. Therefore keeping in view the above findings, a deep bore hole was installed up to the depth of 387 feet and arsenic contamination at 240 feet depth, was 5-10 ppb, which is within the permissible limits. The deep bore hole was monitored for complete one year and arsenic contamination was found to be within the limits. Thus, deep bore holes are one of the safe alternative drinking water sources, provided soil strata in arsenic hit areas is investigated prior to installing any arsenic removal technologies.

Social Behavioural Change Communication (SBCC) Strategies for Community Awareness, Mobilization and Participation for Adoption of Arsenic Free Water Consumption Practices -Pakistan

Arsenic contamination has emerged as a serious public health concern in Pakistan. Arsenic is an emerging serious issue at least in two provinces Punjab and Sindh where about 3% and 16% of water sources are contaminated with levels of arsenic over 50 ppb. The percentage of water sources with concentrations above the WHO level of 10 ppb is 20% and 36% respectively in Punjab and Sindh. Both shallow and deep sources have arsenic contamination and therefore testing of every water sources is necessary. A recent study on prevalence of arsenicosis confirmed presence of 40 cases in the study population giving a prevalence 140/100,00 for established and borderline cases. Keeping in mind its adverse impacts on human health, government with financial support of UNICEF launched various arsenic mitigation programmes and installations of various arsenic removal technologies, i,e household levels water filters, community based arsenic removal tank units and deep boring interventions. Unfortunately, all these interventions proved to be un-sustainable primarily due to devoid of community ownership. Lack of awareness, illiteracy and unfavorable socio-economic conditions make the end users in villages/rural areas, the most vulnerable to the adverse effects of any type of contaminated water. The overall increase in illiteracy rates in Pakistan, particularly in rural environment are the contributing factors which magnifies the mind set of arsenic affected communities to adopt safe drinking water best practices. Hence, there is a dire need to develop a sustainable and effective mechanism for Social & Behavioral Change Communication (SBCC), including the development of communication support materials, within the government structure such as health, education, and social welfare, with the support from print & electronic media and civil society. Though lot of efforts were made yet the current level of awareness cannot be regarded as satisfactory. Thus keeping view the importance of behavioral change communications, comprehensive communication behavioral change strategies, based on Knowledge , Attitude & Practices ( KAP) were evolved and implemented in the arsenic hit areas to ensure community mobilization, participation and ownership which is an important aspect towards post arsenic mitigation projects sustainability.

Performance Assessment of Installed Arsenic Removal Technologies and Development of Protocol for Alternative Safe Drinking Water Supply Options for Arsenic Hit Areas of Pakistan

After identifications of arsenic contamination in Pakistan, lot of technological based arsenic mitigation interventions were carried out which could not last longer due to non-availability of filtration media and running spare parts of arsenic removal tanks units in the local market. The in-depth performance analysis of arsenic removal technology (ART) units, clay pitchers and PUR sachet was carried out which showed un-sustainability of these interventions. The main reasons are lack of awareness, illiteracy and unfavorable socio-economic conditions which make the end users in villages/rural areas the most vulnerable to the adverse impacts of any type of contaminated water and own the installed arsenic removal interventions. Therefore, before taking up any arsenic removal project, it is worthwhile to explore those interventions which are compatible to local socio-economic environments. Deeping boring options have been found best suited, as most of the agricultural practices are dependent on ground water- at shallow depths. The soil analysis at deeper depth will help in ascertaining the causes of arsenic contamination due to presence of arseno-pyrites or due to leaching of sustained applications of pesticides & fertilizers. Therefore, in case of absence of arseno-pyrite sediments at deeper depths. Then the best option for provisioning of arsenic free water is deep boring. The active participation of the communities who are the intended beneficiaries of arsenic mitigation is vital for the success of the programme. Lack of awareness and generally unfavorable conditions are also obstacles to mobilizing communities to get the best out of community-based programmes and projects. Therefore, a well designed protocol for alternative water supply has been evolved which will help in provisioning of sustainable arsenic free water.

Removal of arsenic from drinking water using dual treatment process

This paper focuses on determining an efficient and simple method to remove arsenic from groundwater. Arsenic is a naturally occurring element widely distributed in the earth’s crust. Arsenic is very toxic when found in large quantities in drinking water. This report documents the selected treatment method and laboratory experimentation of arsenic removal from drinking water in small water delivery systems and domestic water systems. The objective is to expand upon research of new and existing arsenic removal technologies or promote a new, alternative process. Several treatment technologies have been considered to perform this function, but cost and reliability concerns prompted the decision to analyze small-scale, community-based filtration units, specifically. Based upon initial test data, the use of dual treatment method comprising of oxidation-coagulation-filtration and adsorption by activated alumina has proven to be more economic having more capacity and superior reliability as compared to other arsenic removal processes using various other media.

Effect of some operational parameters on the arsenic removal by electrocoagulation using iron electrodes.

Arsenic contamination of drinking water is a global problem that will likely become more apparent in future years as scientists and engineers measure the true extent of the problem. Arsenic poisoning is preventable though as there are several methods for easily removing even trace amounts of arsenic from drinking water. In the present study, electrocoagulation was evaluated as a treatment technology for arsenic removal from aqueous solutions. The effects of parameters such as initial pH, current density, initial concentration, supporting electrolyte type and stirring speed on removal efficiency were investigated. It has been observed that initial pH was highly effective on the arsenic removal efficiency. The highest removal efficiency was observed at initial pH = 4. The obtained experimental results showed that the efficiency of arsenic removal increased with increasing current density and decreased with increasing arsenic concentration in the solution. Supporting electrolyte had not significant effects on removal, adding supporting electrolyte decreased energy consumption. The effect of stirring speed on removal efficiency was investigated and the best removal efficiency was at the 150 rpm. Under the optimum conditions of initial pH 4, current density of 0.54 mA/cm2, stirring speed of 150 rpm, electrolysis time of 30 minutes, removal was obtained as 99.50%. Energy consumption in the above conditions was calculated as 0.33 kWh/m3. Electrocoagulation with iron electrodes was able to bring down 50 mg/L arsenic concentration to less than 10 μg/L at the end of electrolysis time of 45 minutes with low electrical energy consumption as 0.52 kWh/m3.

Survey on full-scale drinking water treatment plants for arsenic removal in Italy

Arsenic in drinking water causes severe health effects and it is widely diffused in groundwater around the world. This paper presents the results of a survey about the main arsenic removal technologies employed in Italy and the main features in the management of real treatment plants. 19 drinking water treatment plans were involved in this study. The specific aspects analysed in this survey were: type of technologies applied in the drinking water treatment plants (water characteristics, ionic form of As in raw water, etc.), technical aspects (chemical dosage, treatment steps, hydraulic load, retention time, etc.), operational aspects (backwashing, media regeneration, management of residues, etc.) and costs of these technologies. In Italy, the main technologies employed are chemical precipitation (10 plants) and adsorption with granular ferric hydroxide (GFH) (six plants). Two of these plants employ both chemical precipitation and GFH. Moreover, there are some applications of adsorption on titanium dioxide (two plants), reverse osmosis (two plants) and ionic exchange (two plants).

Water purification of arsenic-contaminated drinking water via air gap membrane distillation (AGMD)

Arsenic contamination in shallow tubewell water is a serious health issue in Bangladesh and other Southeast Asian countries. Rural and remote areas in these locations continue to face tremendous challenges in providing access to affordable and safe arsenic-free drinking water. In recent years, intensive efforts have been undertaken to identify appropriate technologies for arsenic removal. This study examines one approach by investigating the application of suitable membrane technologies, specifically air gap membrane distillation (AGMD), as a promising method for small-scale, low cost deployment. The objective of this study was to test an AGMD commercial prototype (nominal capacity of 2 L/hr) with three different feedstocks: arsenic-containing groundwater (medium concentration) and arsenic-spiked tap water (medium and high concentrations). Results show that the tested AGMD prototype is capable of achieving excellent separation efficiency, as all product water samples showed arsenic levels well below WHO accepted limits (10 µg/L) even for initial concentrations over 1800 µg/L. Parametric studies with focus on variation of coolant temperature illustrate the possibility of integrating AGMD in various thermal systems.

CHALLENGING ANALYTICAL TASK: ANALYSIS AND MONITORING OF ARSENIC SPECIES IN WATER

Analysis and monitoring of arsenic is still a challenging analytical task. Due to its complex behaviour (different forms of arsenic that can be present depending on pH and oxidation states of arsenic) as well as demanding analytical procedures and instrumental tools for control of arsenic concentration in drinking water which is set to 10 µg L –1 , there are still some open questions and issues when arsenic is the scientific topic. In this paper the idea was to use a multivariate statistical approach to identify the key variables and their relation to high arsenic concentration in surface waters of Serbia. The main idea was to identify and connect the key water quality parameters with arsenic concentration and to suggest adequate treatment technologies for water purification and arsenic removal. The data set for multivariate statistical approach were water quality parameters of surface water samples from Serbia. The artificial neural network (ANN) was applied for data analysis. After applying ANN the results showed strong relation between arsenic concentration and Ptot, SO4 2– , COD, carbonate, Norg, DO, and SiO2 content. What could be concluded from the obtained results is that high concentration of organic matter, proportional to nutrients (nitrogen and phosphorus), silica (SiO2) and dissolved oxygen highly correlates with the dissolved arsenic which implies that the most adequate technology for the water treatment could be precipitation, which in general includes coagulation. What remains unquestioned and needs to be performed is arsenic speciation analysis.

Bioremediation of Arsenic-Contaminated Water: Recent Advances and Future Prospects

Arsenic contamination of groundwater and surface water is widespread throughout the world. Considering its carcinogenicity and toxicity to human and animal health, remediation of arsenic-contaminated water has become a high priority. There are several physicochemical-based conventional technologies available for removing arsenic from water. However, these technologies possess a number of limitations such as high cost and generation of toxic by-products, etc. Therefore, research on new sustainable and cost-effective arsenic removal technologies for water has recently become an area of intense research activity. Bioremediation technology offers great potential for possible future application in decontamination of pollutants from the natural environment. It is not only environmentally friendly but cost-effective as well. This review focuses on the state-of-art knowledge of currently available arsenic remediation methods, their prospects, and recent advances with particular emphasis on bioremediation strategies.

Arsenic Waste Management: A Critical Review of Testing and Disposal of Arsenic-Bearing Solid Wastes Generated during Arsenic Removal from Drinking Water

Water treatment technologies for arsenic removal from groundwater have been extensively studied due to widespread arsenic contamination of drinking water sources. Central to the successful application of arsenic water treatment systems is the consideration of appropriate disposal methods for arsenic-bearing wastes generated during treatment. However, specific recommendations for arsenic waste disposal are often lacking or mentioned as an area for future research and the proper disposal and stabilization of arsenic-bearing waste remains a barrier to the successful implementation of arsenic removal technologies. This review summarizes current disposal options for arsenic-bearing wastes, including landfilling, stabilization, cow dung mixing, passive aeration, pond disposal, and soil disposal. The findings from studies that simulate these disposal conditions are included and compared to results from shorter, regulatory tests. In many instances, short-term leaching tests do not adequately address the range of conditions encountered in disposal environments. Future research directions are highlighted and include establishing regulatory test conditions that align with actual disposal conditions and evaluating nonlandfill disposal options for developing countries.

Life cycle analysis of two Hungarian drinking water arsenic removal technologies

Determining a technology's merit as a solution to Hungarian drinking water arsenic contamination goes beyond technical concerns: environmental and economic aspects also play very important roles. In an effort to address the current arsenic drinking water requirements in Hungary, life cycle analysis (LCA) methodology was applied on two example arsenic removal technologies, coagulation-filtration and adsorption, from cradle to grave. A distribution of 500 m3/day was assumed, along with a range of possible operation boundary conditions modelled solely for As treatment. Nine out of 10 considered impact categories tended to favour coagulation-filtration, however realistic variations in water chemistry and product characteristics led to some overlap of their environmental impact. Unlike other studies on water systems, electricity did not have a large direct impact; this was due to the focussed nature of this study on individual treatment technologies rather than an entire water supply system. Regeneration of the adsorption technology filter material was also observed to require nearly the same mass of materials for one regeneration as what was needed to support the coagulation-filtration technology for an entire year. Hazardous waste was surprisingly not reduced for adsorption compared to coagulation-filtration due to prefiltration requirements and an extra regeneration, even though adsorption shifts some of the environmental burden to the production phase. Additionally, cost analysis observes that coagulation-filtration is the cheaper of the two technologies; its highest cost is that of waste disposal, while the highest single expense modelled is that of the adsorption media cost.

A cost-effective system for in-situ geological arsenic adsorption from groundwater

An effective and low-cost in-situ geological filtration system was developed to treat arsenic-contaminated groundwater in remote rural areas. Hangjinhouqi in western Hetao Plain of Inner Mongolia, China, where groundwater contains a high arsenic concentration, was selected as the study area. Fe-mineral and limestone widely distributed in the study area were used as filter materials. Batch and column experiments as well as field tests were performed to determine optimal filtration parameters and to evaluate the effectiveness of the technology for arsenic removal under different hydrogeochemical conditions. A mixture containing natural Fe-mineral (hematite and goethite) and limestone at a mass ratio of 2:1 was found to be the most effective for arsenic removal. The results indicated that Fe-mineral in the mixture played a major role for arsenic removal. Meanwhile, limestone buffered groundwater pH to be conducive for the optimal arsenic removal. As(III) adsorption and oxidation by iron mineral, and the formation of Ca-As(V) precipitation with Ca contributed from limestone dissolution were likely mechanisms leading to the As removal. Field demonstrations revealed that a geological filter bed filled with the proposed mineral mixture reduced groundwater arsenic concentration from 400 μg/L to below 10 μg/L. The filtration system was continuously operated for a total volume of 365,000L, which is sufficient for drinking water supplying a rural household of 5 persons for 5 years at a rate of 40 L per person per day.