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Arsenic and Fluoride
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Zheng Gong, MIT department of Civil and Environmental Engineering, August 2005
Over 30 countries in the world is affected by arsenic in drinking water
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• Naturally occurring metalloid element in the earth’s crust
• Released to the environment by natural pathways volcanic emissions biological activities weathering reactions
Arsenic in the Environment
Source: WHO Synthesis Report on Arsenic in Drinking Water 2002
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• Released to the environment by human activities burning high-arsenic coal arsenic mining CCA-treated wood (chromated copper arsenic) arsenic-containing pesticides and herbicides
• Arsenic is an element that CANNOT be destroyed. It can only change from one form to another
Arsenic in the Environment
Source:WHO Synthesis Report on Arsenic in Drinking Water 2002
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Baseline Arsenic in the Environment
Water Source Typical baseline concentrations
Atmospheric precipitation (rain and snow)
Usually < 0.03 ug/L
River water Usually < 2 ug/L
Lake water Usually < 1 ug/L
Seawater Usually about 1.5 ug/L
Groundwater Usually < 10 ug/L
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Ingestion • Drinking water• Eating food containing high arsenic
Dermal absorption• Bathing in high arsenic water• Handling arsenic contaminated substances
Inhalation• Breathing sawdust or burning smoke from
wood treated with arsenic• Living in areas with unusually high natural
levels of arsenic in rock
Exposure Pathways
Usually major
Usually minor
Sources:• US Agency for Toxic Substances and Diseases Registry (ATSDR) ToxFAQ for Arsenic. Accessed Sep 27, 05. http://atsdr1.atsdr.cdc.gov:8080/tfacts2.html• WHO Synthesis Report on Arsenic in Drinking Water 2002
Chronic Health Effects
Source: Harvard University. “Harvard Arsenic Project.” Internet. Accessed Sep 27, 05. http://phys4.harvard.edu/%7Ewilson/arsenic/arsenic_project_introduction.html
After melanosis, keratosis and other lesions may occur
Keratosis is the hardening skin bulges on palms and feet
The Removal of Arsenic
Modification to
The All Natural Biosand Water Filter
Diffuser Basin
Brick Chips / Iron Nails
Outlet Pipe
Filter Lid
Fine Sand Layer
Standing Water Layer
Separating Gravel
Under drain Gravel
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THE REMOVAL OF ARSENICBy adding 5 kg (11lbs) of small non-galvanized iron nails, covered by a layer of brick chips, the Biosand filter can remove a certain level of arsenic from water. This is accomplished by replacing the diffuser plate with a deep diffuser basin. The iron nails in the diffuser basin, after contact with water and air, will quickly rust. Iron rust (ferric hydroxide) is an excellent adsorbent for arsenic.
When arsenic-containing water is poured into the filter, surface reactions with iron occurs, and arsenic is rapidly adsorbed onto the surface of ferric hydroxide particles.
The arsenic loaded iron particles are then flushed down and trapped on top of fine sand. The purpose of the brick chips is to disperse the water over the nails to allow for further absorption.
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Slow sand filter adapted for intermittent use for a household Advantages:
• Removal of turbidity, colour, odour• Good microbial removal• High flow rate (15-30L/hr)
Limitations:• Not 100% microbial removal, may require post-disinfection• May not remove pesticides, fertilizers, and other chemicals
Cost:• US$30-50 initial• Minimal maintenance
Surface Water TreatmentExample: Biosand Filter
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Diffuser Basin
Lid
Container
Pipe
KanchanTM Arsenic Filter Components
Gravel
Coarse Sand
Water
Fine Sand
Iron Nails
Brick chips
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Arsenic Symptoms, Diagnosis and Treatment
UPdate Summer 2002
Diagnosis of arsenic poisoning, especially from low doses of inorganic arsenic, the type found in CCA lumber, is not easy. There is no one set of symptoms. Different people respond differently, depending on how much exposure they get, and by what means.
Arsenic can be inhaled, ingested (swallowed) or absorbed through contact. Arsenic poisoning is difficult to pin down because most of the arsenic leaves the body within three days of exposure. The arsenic which remains is stored in the brain, bones, and tissue and continues to do serious damage. Some people have no immediate symptoms, but the exposure can cause many types of cancer or diabetes later on. T
There is new evidence that arsenic may also lead to heart disease or strokes. It may cause long term liver, kidney, and central nervous system damage.
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Arsenic exposure, even at low levels, can result in a range of symptoms. Swallowing or inhaling low levels of inorganic arsenic can result in stomach ache, nausea, vomiting and diarrhea.
It can also result in decreased production of red and white blood cells which may cause fatigue, abnormal heart rhythm, blood-vessel damage resulting in bruising, and impaired nerve function.
One of the early warning signs of arsenic poisoning is a "pins and needles" sensation in hands and feet.
Long-term oral exposure to inorganic arsenic can result in skin changes including a darkening of the skin and the appearance of small "corns" or "warts" on the palms, soles, and torso.
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Other signs and symptoms include skin thickening, fluid accumulation (resulting in puffiness) especially around the lower eyelids, face and ankles, diarrhea, garlic breath, perspiration, excessive salivation, generalized itching, oral inflammation, sore throat, runny nose, excessive tearing, numbness, skin inflammation, hair loss, weakness, and loss of appetite.
Arsenic can also cause a range of neurological effects, including headaches and vision problems.
It can cause noticeable behavioral changes, most commonly aggression or depression.
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Because most arsenic leaves your body within a few days, analysis of urine cannot detect if a person was exposed to arsenic in the past.
Tests of hair or fingernails can determine exposure to high levels of arsenic over the past 6-12 months, but these tests are not very useful in detecting low-level exposures.
Early treatment of arsenic poisoning is critical. The longer arsenic remains in the body, the more damage is done.
If arsenic poisoning is determined, oxygen therapy, chelation therapy, saunas and other methods used for detoxification of heavy metals is the usual treatment.
There is some new information that selenium may help decrease the effects of arsenic. Naturopaths may be able to help with diagnosis and treatment with other methods.
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Defluoridation of Drinking Water
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Fluoride in Water• Naturally occurring fluorides are released from rocks
and minerals as they are eroded over time.• They are also released into the environment through
volcanic activity or marine aerosols. • Industrial activities such as mining, phosphate
fertilizer manufacturing, and coal fired power plants can also result in release of fluoride into the environment.
• Fluoride is usually tightly bound in the soil, but when this level is above what the soil can retain, inorganic fluorides can be leached into the groundwater or taken up by plants.
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Harmful Levels
• WHO guidelines specify that fluoride levels be no higher than 1.5 mg fluoride/L drinking water
• However, levels of 0.6 mg/L have been suggested as being a problematic in areas of hot dry climate
Source: (www.wrc.org.za)
Source:http://www.unicef.org/india/wes_1428.htm?q=printme
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Fluoride Guidelines
Dose Symptoms
< 0.5 mg/L Susceptibility to dental caries
0.5 - 1.0 mg/L Lower dental caries
1.5 - 4 mg/L Dental fluorosis
> 4 mg/L Dental and skeletal fluorosis
>10 mg/L Cripping fluorosis
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Health Effects
• Low levels of fluoride can prevent dental caries• Excess fluoride can cause fluorosis
– Dental fluorosis
– Skeletal fluorosis
– Acute fluorosis
Note: Fluorosis is further
aggravated by calcium and
vitamin D deficiencies. (Source: www.wateraid.org)
Source: http://www.fannz.org.nz/text/the_case.htm
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Theory of Fluoride Removal1. Adsorption/Ion Exchange: Through adsorption, fluoride
ions are collected on the surface of the adsorbant; in ion exchange, fluoride ions would be removed from solution onto the ion exchange resin in exchange for a less problematic ion.
2. Chemical: By chemical reaction with fluoride, the fluoride is bound in the solution, it would then require removal from solution.
3. Precipitation/Sedimentation: Employed along with chemical reaction to remove particles, such as flocculants, from solution.
4. Filtration: This method can be used in to remove particles, such as flocculants or bacteria from solution
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