High arsenic concentrations in ground water have been documented in many areas of the United States. Within the last decade investigations of ground water in Maine, Michigan, Minnesota, South Dakota, Oklahoma, and Wisconsin suggest that arsenic concentrations exceeding 10 mg/L are more widespread and common than previously recognized.

Severe health effects have been observed in populations drinking arsenic-rich water over long periods in countries worldwide. Low arsenic water is only needed for drinking and cooking. Arsenic-rich water can be used safely for laundry and bathing.

Source of Arsenic

Arsenic is widely distributed throughout the earth's crust. Arsenic may be found in water, which has flowed through arsenic-rich rocks. Concentrations in groundwater in some areas are elevated as a result of erosion from local rocks

Arsenic is also used commercially e.g. in alloying agents and wood preservatives. Combustion of fossil fuels is a source of arsenic in the environment through disperse atmospheric deposition.

Inorganic arsenic can occur in the environment in several forms but in natural waters, and in drinking water, it is mostly found as trivalent arsenite (As(III)) or pentavalent arsenate (As (V)).

Organic arsenic species, abundant in seafood, are very much less harmful to health, and are readily eliminated by the body.

Arsenic in drinking water poses the greatest threat to public health.

Arsenic in Ground Water

Arsenic is introduced into water through the dissolution of minerals and ores. Arsenic release from iron oxide appears to be the most common cause of widespread arsenic concentrations exceeding 10 mg/L in ground water. Iron oxide also can release arsenic to alkaline ground water, such as that found in the western U.S. Within the conterminous United States, widespread high arsenic concentrations in ground water most commonly result from: (1.) Upflow of geothermal water, (2.) dissolution of, or desorption from, iron oxide, (3.) dissolution of sulfide minerals, and (4.) evaporative concentration. Concentrations of naturally occurring arsenic in ground water vary regionally due to a combination of climate and geology. At a broad regional scale, arsenic concentrations exceeding 10 mg/L appear to be more frequently observed in the western U.S. than in the east (Welch et al., 2000). As state previously investigations of ground water in Maine, Michigan, Minnesota, South Dakota, Oklahoma, and Wisconsin within the last decade suggest that arsenic concentrations exceeding 10 mg/L are more widespread and common than previously recognized. Industrial effluents also contribute arsenic to water in some areas.

What are the Health Effects?

Chronic arsenic poisoning, as occurs after long-term exposure through drinking water is very different from acute poisoning. Long-term exposure to arsenic via drinking water causes cancer of the skin, lungs, urinary bladder, and kidney, as well as other skin changes such as pigmentation changes and thickening (hyperkeratosis). Increased risks of lung and bladder cancer and of arsenic-associated skin lesions have been observed at drinking-water arsenic concentrations of less than 0.05 mg/L. Cancer is a late phenomenon, and usually takes more than 10 years to develop.

Immediate symptoms on an acute poisoning typically include vomiting, esophageal and abdominal pain, and bloody diarrhea. The symptoms and signs that arsenic causes appear to differ between individuals, population groups and geographic areas. Thus, there is no universal definition of the disease caused by arsenic. This complicates the assessment of the burden on health of arsenic. Similarly, there is no method to identify those cases of internal cancer that were caused by arsenic from cancers induced by other factors.

Absorption of arsenic through the skin is minimal and thus hand-washing, bathing, laundry, etc. with water containing arsenic do not pose human health risk.

Treatment and removal

In water, the most common valence states of arsenic are As+5 (or arsenate) which is more prevalent in aerobic surface waters, and As+3 (or arsenite) which is more likely to occur in anaerobic ground waters. As+3 may be easily converted by oxidation to As+5. In the arsenate state, arsenic tends to adhere to ferric hydroxide, a common precipitate produced in the filtration process.

Control of arsenic is more complex where both As+3 and As+5 are present. However, As+3 is easily oxidized by chlorine, potassium permanganate, or ozone.

The technology for arsenic removal from the water supply is moderately costly and requires technical expertise. New types of treatment technologies, including co-precipitation, ion exchange and activated alumina filtration can offer answers to treatment and have been used with good success in many part of the U.S. during the last few years.

Any system however requires detailed analysis of the water and regular maintenance and testing.

One of the simplest technologies for household removal of arsenic from water is the GFH (Granular Ferric Hydroxide) media system, and has a much greater removal capacity than previously used technologies, utilizes only simple equipment, and is easily installed.

The GFH Arsenic Removal System for drinking water from a variety of sources is a media adsorption process capable of removing arsenic and other heavy metals from raw water supplies. The process is simple and utilizes a ferric-based, non-regenerative media to absorb arsenic, selenium, uranium, chromium and other heavy metals from drinking water. Like other adsorption processes, the water is simply passed through the media to remove the contaminants. Once the media has depleted its adsorption capacity it is removed from the vessel and additional media is installed. In many cases the exhausted media can be discarded in landfills and classified as non-hazardous waste. On-site storage of regeneration chemicals and concentrated waste disposal issues are eliminated with the single use media.

The adsorption life of the media depends on raw water pH, arsenic concentration levels, and volume of water treated. GFH does not require preconditioning or pre-oxidation procedures, and the use of non-regenerative media are design features that are ideal for small and wellhead applications, particularly where no treatment currently exists.

The GFH system is available in a parallel or series operation depending on the required removal concentrations. In most residential systems a dual series tank system is used. Water flows through the first tank where the Arsenic is removed then into the second tank. If there is any fault in the first tank, or if it runs out of capacity, the second tank provides additional removal capacity. If a consistent 90% reduction is needed across the system, the series design is used. However, if the percentage is less than 90%, then the parallel design is typically applied.

Parallel Systems

Three in-service vertical pressure vessels in a parallel system are each designed to treat 1/3 of the incoming flow at a hydraulic loading rate to treat Arsenic of 5gpm/sq.ft. (12.2 m/hr). A five minute Empty Bed Contact Time (EBCT) for Arsenic removal is provided through the parallel system, plus backwash water is supplied solely from the in-service vessels where they are backwashed during the same event. During the initial start-up of the plant, one vessel is placed on-line where it begins the exhaustion curve. Subsequently, the second vessel is started and later the third one is activated. This process causes all the vessels to operate at varying degrees of exhaustion, and the blended effluent concentration is below the desired level. The blended effluent concentration eventually approaches the acceptable limit, however, and when the media in the longest running vessel is replaced, the overall blended effluent is reduced. Overall media life is extended when operated in this fashion.

Advantages of GFH Filtration:

• Up to 95% removal of total arsenic through a simple, single stage filtration process alone.
• Simple control requirements, can be fully automated for minimal operator intervention.
• Efficient operation, minimal waste product with no need for neutralization.
• No need for expensive, consumable ion exchange resins or regeneration equipment.
• Non-hazardous requirement for spent media disposal.
• No handling of dangerous chemicals.

POU treatment systems.

Reverse Osmosis does an excellent job of removing As+5 but may have little capability to remove As+3. Therefore, raw water must be pre treated with chlorination, or manganese greensand oxidation with potassium permanganate.

Questions and additional information about your water.

The above is probably more than you ever wanted to know about Arsenic, and may appear very frightening. However, many GFH systems have been installed all over the US, and have performed almost perfectly when properly maintained. You can drink and enjoy your treated water without worry. If you have any other questions about your water, or water treatment needs, please feel free to contact us. We have installed literally thousands of water treatment systems ranging from iron filters, taste and odor filters, reverse osmosis drinking water systems, water softeners as well as organic removal systems and, nitrate removal systems. Please...Enjoy your water!