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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

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Guideline Value in Drinking WaterWHO 10 ug/L(ppb) = 0.01 mg/L (ppm)

Australia 7 ug/LCanada 25 ug/LEU 10 ug/LJapan 10 ug/LUSA 10 ug/L

Bangladesh 50 ug/LCambodia 50 ug/LChina 50 ug/LIndia 50 ug/LLao 50 ug/LMyanmar 50 ug/LNepal 50 ug/LPakistan 50 ug/LVietnam 10 ug/L urban, 50 ug/L rural

Source: World Bank. Towards a More Effective Operational Response. Volume 1. 2005

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Overview of Mitigation Options

Alternative Arsenic-Free Sources

Arsenic Removal Technologies

• Safe tube wells• Improved Dug wells• Deep wells• Rainwater harvesting• Surface water treatment

Arsenic Mitigation

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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Advantages:• Simple • Excellent microbial removal

Pass water through a porous, colloidal silver soaked ceramic container. Small pores and silver traps and inactivates pathogens.

Limitations:• Fragile• Low flow (1-2L/hr)• Requires frequent cleaning for turbid water

Surface Water TreatmentExample: Potter for Peace Filter

Developed in South America

Cost • US$10-15 initial• Minimal maintenance cost

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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 Removal• 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.

• Chemical: By chemical reaction with fluoride, the fluoride is bound in the solution, it would then require removal from solution.

• Precipitation/Sedimentation: Employed along with chemical reaction to remove particles, such as flocculants, from solution.

• Filtration: This method can be used in to remove particles, such as flocculants or bacteria from solution