The effect of carbon steel-wool in removal of arsenic from drinking water

. This paper attempts to prove that the removal of arsenic in drinking water is a combination of the granular activated carbon and carbon steel-wool. The steel-wool filter is the most important in residential applications. The single most important consideration is the empty bed contact time. Removal of inorganic arsenic to parts per million (ppm) or parts per billion (ppb) levels within 15 to 30 min is fairly common. Immobilization techniques are likely to continue to gain importance in the world.     

Encapsulation of limestone waste in concrete after arsenic removal from drinking water

Arsenic is one of the many naturally occurring contaminants in drinking water. Although various treatment technologies can remove arsenic, most suffer from a common problem of disposal of arsenic-enriched waste after treatment. This project focused on improving a limestone-based disposal technique by encapsulating the arsenic-enriched limestone waste in concrete. The research work determined the compressive strengths of the concrete cubes prepared using treated limestone after arsenic removal and determined the amount of leaching from the arsenic-encapsulated concrete. The removal of arsenic was done with batch experiments using 0.5–1 mm sized Minnekahta Limestone. The efficiency of the limestone in removing arsenic ranged from 85.9 to 95.5%. The amount of arsenic adsorbed onto the surface of each gram of limestone ranged from 0.8 to 3.9 μg. Compressive strength results of concrete cubes prepared by incorporating arsenic-enriched limestone showed typical strength curves at 1, 3, 7 and 28 days. Leaching of arsenic was less than 0.05 mg/L, which is 1/100 of the US Environmental Protection Agency’s standard for disposal of arsenic in a landfill. Hence, encapsulating the arsenic-enriched limestone in concrete has potential for recycling the waste material, thereby reducing disposal costs of the limestone-based removal method.     

Effect of source water quality on arsenic (V) removal from drinking water by coagulation/microfiltration

The effect of the source water quality on As(V) removal by coagulation/microfiltration (C/MF) was investigated systematically using a jar test and a lab-scale test; the results of the lab-scale test coincide with those of the jar test. It showed that the increase of dissolved organic carbon (DOC), HPO₄ ²⁻ and HCO₃ ⁻ concentrations would moderately decrease As(V) removal, and the residual As(V) concentration in treated water is no more than 10 μg L⁻¹ when the concentration of DOC, HPO₄ ²⁻ and HCO₃ ⁻ in raw water is not beyond 9.22 mg L⁻¹, 1.6 mg L⁻¹ and 300 mg L⁻¹, respectively. Other co-ions, such as Cl⁻, NO₃ ⁻, F⁻, SO₄ ²⁻, and counter-ions including K⁺, Ca²⁺ and Mg²⁺, have little effect on As(V) removal. Both results of the jar test and the lab-scale test demonstrate that Fe³⁺ dose of 6 mg L⁻¹ is enough to eliminate the influence of HCO₃ ⁻ whose concentration changes from 350 mg L⁻¹ to 450 mg L⁻¹. In the lab-scale test, As(V) removal ranged from 92.8 to 98.2% at Fe³⁺ dose of 4 mg L⁻¹ and 5 mg L⁻¹ when As(V) concentration in raw water was about 100 μg L⁻¹. The results obtained in this study suggest that As(V) removal by C/MF process is sensitive to the quality of raw water, and a jar test needs to be done before C/MF process is used for arsenic removal from drinking water.     

Application of zeolitic volcanic rocks for arsenic removal from water

Natural zeolitic rocks consisting mainly of chabazite-phillipsite, clinoptilolite, and volcanic glass have been evaluated by means of batch methods to remove arsenic from waters with different mineralization degree (from deionized water to natural water with a specific conductivity of 1,600 μS cm^− 1). Arsenic was previously spiked in the studied waters at concentrations of about 100 µg l^− 1 to simulate actual cases. The compositional range of natural waters is representative of large hydrogeochemical regions around the world. The experiments were focussed on the application of natural common zeolitic rocks to water treatment for human consumption. The removal efficiency observed rises, in the better cases, 60–80% for chabazite-phillipsite raw materials whereas is 40–60% for clinoptilolite-bearing ones. The arsenic removal tends to increase with water mineralization degree, independently of the zeolitic rock type. A large zeolitic content in the chabazite-phillipsite raw materials increase the removal. Instead, the inverse situation is observed in the clinoptilolite-bearing rocks. The relevance of the quantitative mineralogical analysis, determining also the content of volcanic glass, as well as the use of natural waters in the removal tests has been demonstrated.     

The Geogenic Contamination Handbook: Addressing arsenic and fluoride in drinking water

In some groundwaters, arsenic and fluoride can reach concentrations that are hazardous to human health if geological and geochemical conditions favour the release of these contaminants. This can especially pose a problem in developing countries where water service providers already struggle with the provision of clean water. The Geogenic Contamination Handbook, released in January 2015, aims to provide concise guidelines for practitioners faced with the problem of geogenically contaminated drinking water in low- and middle-income countries. The handbook is a digital resource, with the reader benefitting from numerous weblinks and embedded documents giving additional information where relevant. The necessary steps needed for sustainable mitigation of arsenic or fluoride-contaminated drinking water are outlined. This includes information on water quality testing (e.g. how to plan a field survey), different water treatment options as well as practical guidelines on the integration of technical, institutional and sociological aspects of arsenic and fluoride mitigation.     

Association between multi-level inorganic arsenic exposure from drinking water and skin lesions in Inner Mongolia, China

Arsenic is one of the most important single-substance toxicants in the environment. In Inner Mongolia of China, 300000 residents are believed to drink water containing 〉50 μg/L. Skin lesions have been known as the most common consequences resulting from chronic exposure to arsenic. To clarify the prevalence of arsenic-induced skin lesions, it is important to assess the impact of this problem on the target population, and to make future planning. We evaluated the association between multi-level inorganic arsenic exposure from drinking water and skin lesions in an arsenic-affected area in Inner Mongolia, China. 109 and 32 subjects fi＇om high-level arsenic-affected （〉5 μg/L） village and low-level （≤50 μg/L） village were recruited and had detailed physical examination with special emphasis on arsenic-related skin lesions. Arsenic exposure was measured for each participant with As concentration of primary well and the duration of using the well was recorded. Arsenic-induced skin lesions including keratosis, pigmentation, and/or leucomelanosis were diagnosed in 56 and 3 subjects in the two villages, respectively. Logistic regression was conducted to calculate prevalence-odd ratios of skin lesions by levels of arsenic exposure with adjustment of sex, age group, smoking and duration of exposure. A consistent dose-response relationship between arsenic exposure level and skin lesion risk was observed.     

Development of attapulgite composite ceramsite/quartz sand double-layer biofilter for micropolluted drinking source water purification

This study compared start-up and steady-state affecting factors of attapulgite composite ceramsite/quartz sand double-layer biofilter (ACC/QSDLBF) and quartz sand single-layer biofilter (QSSLBF) on micropolluted drinking source water treatment. Results showed that the ACC has suitable pore size distribution in the range of 5–850 nm which is conducive to biofiltration. Turbidity removal efficiency of ACC/QSDLBF was a little lower than QSSLBF, but organic matters and ammonia removal efficiencies of ACC/QSDLBF were much higher than QSSLBF due to biodegradation and nitrification by microorganisms colonizing on the ACC. At stable state, the growth of head loss for ACC/QSDLBF was lower than that of QSSLBF. The complete filtration cycle of ACC/QSDLBF was 52 h. The total COD_Mn removal rate of ACC/QSDLBF was 20.93 %, in which 90 % of removed total COD_Mn was achieved at the upper 60 cm of ACC filter layer. The removal of COD_Mn decreased from 35.89 to 13.16 % in ACC/QSDLBF when increasing hydraulic loading from 2 to 16 m/h. After analysis of efficient EBCT in ACC/QSDLBF, optimized hydraulic loading was 12 m/h. These conclusions would be helpful to practical application of ACC as functional material for new construction of waterworks, especially upgrading of existing waterworks treating micropolluted drinking source water.     

UTCHEM model application for prediction of crude oil removal from contaminated sand columns

Soil pollution by crude oil is a challenging environmental issue for oil producing countries. Several methods have been developed for remediation of the contaminated soil including washing with different detergents. In this work, we applied UTCHEM simulator model to the sand columns polluted by 10000 and 30000 ppm of crude oil which was treated with 0.05, 0.1 and 0.2 wt% of a biological detergent, saponin. The results showed a good agreement between simulated and pilot study. The maximum remediation was 61% with a pH of 9 when we utilized 0.2 wt% saponin for the column contaminated with 30000 ppm of crude oil. 47% remediation was achieved with a pH of 9 when 0.1wt% of detergent was applied to the same column. Sensitivity analysis indicated an increase in remediation by increasing the pH with the optimum pH of 11. The best possible concentrations of surfactant solutions were 0.1 and 0.2 wt% for 10000 and 30000 ppm pollution, respectively, resulting in crude oil removal efficiencies of 69% and 72%, respectively. Simulation results also indicated that an increase in the permeability of the sand columns would also result in an increased remediation.     

Modeling transport of arsenic through modified granular natural siderite filters for arsenic removal

Groundwater arsenic(As)contamination is a hot issue,which is severe health concern worldwide.Recently,many Fe-based adsorbents have been used for As removal from solutions.Modified granular natural siderite(MGNS),a special hybrid Fe(II)/Fe(III)system,had higher adsorption capacity for As(III)than As(V),but the feasibility of its application in treating high-As groundwater is still unclear.In combination with transport modeling,laboratory column studies and field pilot tests were performed to reveal both mechanisms and factors controlling As removal by MGNS-filled filters.Results show that weakly acid pH and discontinuous treatment enhanced As(Ⅲ)removal,with a throughput of 8700 bed volumes(BV)of 1.0 mg/L As(Ⅲ)water at breakthrough of 10 μg/L As at pH 6.Influent HCO_3~-inhibited As removal by the filters.Iron mineral species,SEM and XRD patterns of As-loading MGNS show that the important process contributing to high As(Ⅲ)removal was the mineral transformation from siderite to goethite in the filter.The homogeneous surface diffusion modeling(HSDM)shows that competition between As(III)and HCO_3~-with adsorption sites on MGNS was negligible.The inhibition of HCO_3~-on As(Ⅲ)removal was connected to inhibition of siderite dissolution and mineral transformation.Arsenic loadings were lower in field pilot tests than those in the laboratory experiments,showing that high concentrations of coexisting anions(especially HCO_3~-and SiO_4~(4-)),high pH,low EBCT,and low groundwater temperature decreased As removal.It was suggested that acidification and aeration of highAs groundwater and discontinuous treatment would improve the MGNS filter performance of As removal from real high-As groundwater.     

Application of nanoadsorbents for removal of lead from water

Enormous increase in the application of various heavy metals including lead for commercial and non-commercial purposes has also led to their enhanced occurrence in the effluents from industries and domestic discharge creating substantial environmental concerns. The existing techniques for removal of these contaminants such as reverse osmosis and ion exchange suffer a few disadvantages and hence, thrust to develop efficient techniques for the removal have been ever increasing. Adsorption based on the use of nanoadsorbents is promising being cost effective and based on the ease of operation. The present work furnishes a detailed overview on nanoadsorbents for removal of lead from water. The various nanoadsorbents covered in the analysis include alumina, anatase, carbon nanotubes, chitosan, copper, iron and zinc oxide, magnetite, nanoclay and zirconium nanoparticles. The review also gives an insight into the synthesis and characterization of nanoadsorbents followed by guidelines on optimum operating parameters to be used in the removal process for maximizing the extent of removal. The typical optimum conditions established based on the critical analysis of literature are pH ≤ 6, contact time ≥60 min and optimum adsorbent dose dependent on the nanomaterials. Comparison of different nanoparticles revealed that titanium oxide and hematite nanoparticles are the best, giving 100% removal efficiency for lead ions. The sequestration was mainly dependent on adsorbent dose that has to be kept optimum to yield adequate surface area and number of adsorption sites. Overall, nanoadsorbents have been established to yield efficient removal of lead from water.     

Biological nitrate removal from water resources

During the recent decades, the increasing trends in nitrate ion concentration in ground water sources have meant more research to find effective procedures for the prevention of even more water contamination by nitrogen sources. In this study a pilot was designed to examine the application of biological method for eliminating nitrate from the water of well No.903 of Mehrabad Airport, Tehran, Iran. Design, installation and running processes were done from April to November 2003. A fixed biological bed containing five-centimeter trunk pipes 16 mm in diameter were installed in the reactor and the system was operated with upflow current. Instead of Methanol, Acetic acid was used as the carbon source because of its easier acceptance by the public, lower price and availability as well as easier storage. The pilot was run in different hydraulic retention times from 48 h up to one hour. Considering economical, operational and maintenance factors, retention time of 2 h was determined to be optimum, in which 77% nitrate removal was achieved. Considering a ratio of 2 for COD/N, inlet COD of about 140 mg/L and the optimum retention time, COD removal of about 80% is also accomplished in this process. The amount of nitrite concentration, pH values, COD and turbidity is also evaluated versus different hydraulic retention times.     

Long-term interaction of wollastonite with acid mine water and effects on arsenic and metal removal

This paper reports the results of a laboratory experiment conducted to investigate the effects of wollastonite dissolution on removal of potentially toxic trace elements from stream waters affected by acid mine drainage (AMD). Nearly pure wollastonite was treated with natural acid mine water (pH 2.1) for different lengths of time (15, 30, 50 and 80 days). The compositional and textural characterization of the solid reaction products suggests that wollastonite was incongruently dissolved leaving a residual amorphous silica-rich phase that preserved the prismatic morphology of the parent wollastonite. The release of Ca into solution resulted in a pH increase from 2.1 to 3.5, and subsequent precipitation of gypsum as well as poorly crystallized Fe–Al oxy-hydroxides and oxy-hydroxysulfates whose components derived from the AMD solution. A geochemical modeling approach of the wollastonite–AMD interaction using the PHREEQC code indicated supersaturation with respect to schwertmannite (saturation index = 10.7–15.7), jarosite (SI = 8.7–10.2), alunite (SI = 5.1), goethite (SI = 4.7) and jurbanite (SI = 2.2). These secondary phases developed a thin coating on the reacted wollastonite surface, readily cracked and flaked off upon drying, that acted as a sink for trace elements, especially As, Cu and Zn, as indicated by their enrichment relative to the starting wollastonite. At such low pH values, adsorption of As oxyanions on the positively charged solid particles and coprecipitation of metals (mainly Cu and Zn) with the newly formed Fe oxy-hydroxides and oxy-hydroxysulfates seem to be the dominant processes controlling the removal of trace elements.     

Removal of arsenic from contaminated water utilizing tea waste

Activated carbon is the adsorbent commonly used to remove arsenic from contaminated water. However, the problem is that it is not always available everywhere and considered expensive in developing countries. An inexpensive alternative to activated carbon can therefore aid the adequate treatment of contaminated water. Tea waste, water hyacinth and banana peel are investigated extensively in this study as the inexpensive alternative. Tea waste treated with a right proportion of aqueous FeCl₃ reagent is found to have substantially higher arsenic removing capacity (which is quantified by arsenic concentrations measured employing Double Beam Atomic Absorption Spectrophotometer) than the other two. The comparison made subsequently between tea waste and activated carbon reveals the feasibility of the utilization of tea waste. The arsenic removing capacity of tea waste treated with the right proportion of aqueous FeCl₃ reagent is found to be equal to that of the activated carbon treated with the same reagent over the continuous operative time of 2 h. The tea waste treated rightly with the same reagent also removes arsenic at acceptable capacities over extended operative times such as 4–6 h. It is therefore proposed to consider tea waste as the inexpensive alternative to activated carbon in treating arsenic contaminated water.     

Carbon steel slag and stainless steel slag for removal of arsenic from stimulant and real groundwater

Arsenic in groundwater is a serious environmental problem. The contamination of groundwater with arsenic has been of utmost concern worldwide. Steel slag is a solid waste generated from steel production. Although steel slags have been used for arsenic removal from water, this process has not been systematically or integratively researched. In this study, the arsenic removal capacity and mechanism were investigated for carbon steel slag, stainless steel slag and Fe-modified stainless steel slag based on an in-depth study. The study also evaluated the potential utilization of different steel slag for regeneration. The maximum adsorption of arsenic on carbon steel slag, stainless steel slag and Fe-modified stainless steel slag was 12.20, 3.17 and 12.82 mg g^?1 at 25 °C, respectively. The modification of stainless steel slag by FeC1₃ can generate more pore structures and larger surface areas, and 300 °C treatment produces the best regeneration efficiency. The ΔG values were negative for all of the steel slags, indicating the spontaneous nature of the adsorption process. The solution pH was a critical parameter for the removal of arsenic for steel slags. Under highly alkaline solution conditions, the mechanism of arsenic removal by carbon steel slag and stainless steel slag can be attributed to chemisorption, including chemical precipitation and coordination reactions, and under weakly alkaline solution conditions, electrostatic interaction and specific adsorption are the arsenic removal mechanisms by Fe-modified stainless steel slag. Regeneration of the Fe-modified stainless steel slag was better achieved than that of the other steel slags in the application of high-temperature treatment.     

Laboratory testing of trace metals removal from mine drainage and arsenic removal from groundwater in the Black Hills of South Dakota

The Gilt Edge Superfund Site is a former heap-leach gold mine that currently is being remediated in the Black Hills of South Dakota. Mine runoff water is treated before release from the site. The field pH, before treatment, is about 3; the water contains arsenic at low levels and some trace metals at elevated levels, in addition to total dissolved solids concentrations of more than 1,900 mg/L. In the Keystone area of the Black Hills, naturally occurring arsenic has been detected at elevated concentrations in groundwater samples from wells. The City of Keystone’s Roy Street Well, which is not used currently, showed arsenic concentrations of 36 parts per billion and total dissolved solids of 320 mg/L. With field samples of water from the Gilt Edge site, a limestone-based method was successful in reducing trace metals concentrations to about 0.001 mg/L or less; at the Keystone site, the limestone method reduced arsenic levels to about 0.006 mg/L. The results are significant because previous research with the limestone-based method mainly had involved samples prepared with distilled water in the laboratory, in which interference of other ions such as sulfate did not occur. The research indicates the potential for broader applications of the limestone-based removal method, including scale-up work at field sites for water treatment.     

高岭土/菱铁矿杂化材料制备及除砷性能研究

采用KOH活化后的高岭土和菱铁矿为主要原材料,磷酸酸化过的花生壳为造孔剂,采用高温活化的方法,通过正交静态吸附试验,研究其在常温常压下对水中砷的吸附去除效果。结果表明,在高岭土、菱铁矿、花生壳用量之比为2∶2∶1,KOH浓度为0.3mol/L,浸泡时间为6h,活化温度为900℃时,制备得到的粉末状材料具有最好的除砷效果,可达到95%。利用直径40mm,长450mm的有机玻璃柱进行动态连续吸附试验,结果表明此材料可以连续有效除砷20h左右,除砷效果平均可达到84%。此材料吸附除砷符合Langmuir等温吸附模型。     

Removal of chromate from drinking water using powder carbon steel

This paper presents the possible alternative removal options for the development of safe drinking water supplies in areas affected by hexavalent chromium. Chromate is a matter of great environmental concern due to its extensive contamination and carcinogenic toxicity. In this study, the conventional adsorption with various types of adsorbent method were used for chromate removal, but only powder carbon steel was compatible with household water treatment and can be designated based on high removal efficiency and affordable cost. Home powder carbon steel with granular activated carbon (PCS–GAC) treatment systems are quite simple. Water needing treatment passes through the cartridge or filter candles contacting PCS–GAC on its way to the faucet. This method is based on the use of powder carbon steel, ML 90 Bombril S.A, as a cleaning agent. Granular activated carbon filters have been employed in home water purification systems essentially for the removal of taste, odor, and color. The effect of pH, redox potential, time, and adsorbate concentration on the uptake carbon steel were observed. The lack of desorption suggests that anion chromium is irreversibly sorbed by the powder carbon steel.     

Semivolatile organic compounds removal and health risk reduction in drinking water treatment biofilters applying different backwashing strategies

This study aimed to investigate the removal of 24 semivolatile organic compounds in Yangtze River (China) source water treated by six biofilters using different backwashing methods. Health risks induced by the pollutants in the influent and effluent water were also assessed based on the chemical detections. Comparatively, the biofilter backwashed with both air (15?m/h, 3?min) and water (8?m/h, 5?min) was most efficient in removing semivolatile organic compounds and reducing health risk. PCR-denatured gradient gel electrophoresis showed that backwashing alterations posed considerable influences on microbial community structure in the six biofilters. About 72.4?% of di-n-butyl phthalate and 81.8?% of bis(2-ethylhexyl)phthalate (two main semivolatile organic compounds in the river water) were removed under the optimal backwashing conditions. However, in the effluent of each biofilter, non-carcinogenetic risks of 2,6-dinitrotoluene and bis[2-ethylhexyl]phthalate and carcinogenetic risks of dibenz[a,h]anthracene and benzo[a]pyrene did not reach safety levels, revealing that these pollutants in the source water deserve more public health concerns. This study might serve as a basis for biofiltration process optimization and also as a benchmark for the authorities to reduce the health risk induced by exposure to the hazardous pollutants.     

Geochemical thermodynamics of cadmium removal from water with limestone

Limestone-based material can reduce concentrations of cadmium below 0.001 mg/L (1 ppb) in water, resulting in > 99% removal efficiency. Thermodynamic constraints appear to be favorable for reactions involving the formation of otavite during cadmium removal. Thermodynamic values for these reactions yield a theoretical removal limit of 0.0015 mg/L or better for cadmium, in reasonable agreement with tests on laboratory and field samples that show cadmium removal at levels less than 0.001 mg/L.