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Arsenic Removal

Papers
  1. Arsenic Removal Methods (UNU.edu)
      "In the context of prevalence of high concentrations of arsenic in tubewell water, a wide range technologies 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. 11-07

  2. Arsenic Removal Using Iron and Manganese (Eng-Consult.com)
      "Iron coagulation/filtration and iron addition with direct filtration methods are effective for arsenic (V) removal. Source waters containing naturally occurring iron and/or manganese and arsenic can be treated for arsenic removal by using conventional Fe/Mn removal processes. These processes can significantly reduce the arsenic by removing the iron and manganese from the source water based upon the same mechanisms that occur with the iron addition methods. The addition of iron may be required if the concentration of naturally occurring iron/manganese is not sufficient to achieved the required arsenic removal level." 10-07

  3. Arsenic Waste Disposal (Eng-Consult.com)
      "Regeneration of AA columns results in a toxic waste containing very high concentration of soluble arsenic. The effluent of acid rinses is mixed with the caustic rinses and this mixed arsenic waste can then be disposed on a prepared bed of cowdung in a shallow hole dug in earth. The micro-organisms in cowdung transform the arsenic to gaseous arsine and arsenic is thus released into the surrounding air." 10-07

  4. Massive Arsenic Poisoning in Bangladesh (CNN News)
      "A new study published Saturday in the British medical journal the Lancet found that tens of millions of people in Bangladesh have been exposed to poisonous levels of arsenic from contaminated groundwater." See Arsenic Removal 06-10

  5. Microbes Change Arsenic Concentrations in Water (ScienceDaily.com)
      "To see if bacteria affect arsenic concentration, groundwater samples were taken from two high-arsenic areas in Maine, and water chemistry and two bacterial populations were measured. Wells with high total arsenic concentrations had a higher proportion of iron-reducing bacteria than wells with lower arsenic." 09-08

  6. Microbes as a Cure for Arsenic in Water (ScienceDaily.com) star
      "Microbial processes ultimately determine whether arsenic builds to dangerous levels in groundwater, say researchers at the University of Illinois at Urbana-Champaign. Remediation may be as simple as stimulating certain microbes to grow."

      "The concentration of arsenic varied inversely with the concentration of sulfate, the researchers found. Methane concentration also varied with the sulfate content. "We believe this reflects the distribution of microbial populations in the aquifer system," said graduate student Matthew Kirk. "Our analyses suggest the aquifer is divided into zones of mixed microbial activity, some dominated by sulfate-reducing bacteria, others by methanogens." Sulfate-reducing bacteria will consume sulfate and reduce it into sulfide. The sulfide then reacts to precipitate arsenic, leaving little in solution."

      "If the sulfate-reducing bacteria run out of sulfate, methanogenic bacteria take over as the dominant metabolic force, Kirk said. Because methanogenic bacteria don't produce sulfide, there is no precipitation pathway for the arsenic, which then accumulates to high levels in the groundwater." 11-07

  7. Safe Technology for Arsenic Removal (UNU.edu - Johnston and Heijnen)
      "This paper describes some safe water technologies for arsenic removal."

      "Coagulation is the most common arsenic removal technology. As many Bangladesh waters contain arsenite, oxidation with chlorine or permanganate is required first. Coagulation with ferric chloride works best at pH below 8." 10-07

  8. Two Simple Methods of Reducing Arsenic in Groundwater (Hussam) star
      "The first method is simply leaving the groundwater for a few hours in the container and collecting the water by decanting. This method can be used to remove 50-70% arsenic from drinking water containing soluble iron. The efficiency of this method is discussed in relation to water chemistry parameters and chemical equilibrium models. The second method consists of a simple three-pitcher (locally known as ‘3-kalshi’) filtration assembly made entirely from readily available local materials. In a 3- kalshi assembly, the first kalshi has iron chips and coarse sand, the second kalshi has wood charcoal and fine sand, and the third kalshi is the collector for filtered water. About 240 L of arsenic contaminated groundwater and groundwater spiked with high concentrations of both As(III) and As(V) were filtered. It has been shown that more toxic As(III) can be removed from 800 ppb to below the detection limit of 2 ppb. The As(total) can be removed to a level below 10 ppb for most samples even at the highest input concentration of 1000 ppb As(total). The dissolved iron concentration decreased from an average 6000 ppb to 200 ppb. Calculations based on compound formation and arsenic adsorption on hydrous ferric oxide show that, with a constant input of dissolved iron the arsenic removal capacity increases linearly with each kalshi of filtration. The decrease in conductivity by 35% of the original value indicates substantial removal of dissolved ions. The final water quality was comparable to that of the guideline values suggested by World Health Organization and Bangladesh."

      "In both series of experiments As(III) was nearly completely removed from a maximum value of 800 ppb to below the detection limit of the instrument (ca. 2 ppb) for all influx. It appears that most of the As(III) is oxidized into more stable As(V) and precipitated in A and B kalshis. It has been recognized that As(III) is more prevalent in groundwater than was previously believed which is a concern because As(III) is more toxic than As(V) (Korte, et. al., 1991; Knowles, et. al., 1983). In Bangladesh, the groundwater contains 43-98% of arsenic in the form of As(III). For direct consumption, this is possibly one of the most toxic groundwater known today. Therefore, the removal of As(III) by any filtration procedure is crucial. In contrast, negligible removal of As(III) from drinking water was achieved by coagulation with alum (Hering, et. al., 1996)."

      "The maximum desirable concentration of iron in water is 300 ppb and the maximum permissible concentration is 1000 ppb (see Table 2). Besides causing pots and pans to become brown, at high concentration it can be toxic to small infants (Miah, 1996). The concentration of soluble iron originally present in the well water has decreased significantly, form 6000 ppb to a range of 0 - 480 ppb with an average of 200 ppb which is below the permissible level for most cases. Dissolved iron, primarily present as Fe(II) in groundwater plays a very significant role in removing arsenic and other trace metals." 11-07

Research
  1. 10-23-07 Filtering Unit Costs $35 and Lasts Five Years (Time.com)
      "Abul Hussam calls the poisoning of drinking water with arsenic 'one of the worst natural disasters on earth,' and he is not the sort to stand idly by in the face of it. After decades of research, this associate professor of chemistry at George Mason University in Virginia has come up with a deceptively simple device to address the problem. It could save countless lives among the estimated 137 million people around the world whose water supply is contaminated with high levels of the colorless, odorless and tasteless metal, which accumulates in the body to cause sores, nerve damage, cancer and, too often, death."

      "Hussam set about working on an affordable, effective and environmentally sustainable way to make water arsenic-free. The result: his SONO filter, which uses a "composite iron matrix" that can be manufactured locally from cast-iron turnings, along with readily available river sand, wood charcoal and wet brick chips. The filter's humble housing in a stack of three buckets belies its power to change lives. It removes 98% of arsenic content as well as other mineral impurities that make water hard. A $35 unit serves two families and lasts at least five years." 10-07

   
   


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