Q&A: Other Considerations for Arsenic Removal

Phosphates, iron, manganese and more can have an affect on arsenic removal

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This Q&A concludes the discussion of arsenic treatment options with AdEdge Water Technologies.

How does pH affect arsenic removal?
The pH of the water impacts the life of the arsenic removal media. The Bayoxide E33 media itself is stable between pH 4 and pH 11. Arsenic changes its behavior, both the ionic charge and the molecular shape, depending on the pH value. These changes affect how the reactions occur and the mechanisms to bond the arsenic to the Bayoxide E33 media. The best operating range is a pH of 6.0 to 8.0 with an optimum range of 6.5 to 7.5. Adjusting pH may help media performance.

How do phosphates affect arsenic removal?
Chemically, phosphorus in water behaves very similar to arsenic. Phosphorus and arsenic are very close on the periodic table of elements and so molecular shapes and ionic charges are similar in the same conditions. As such, phosphorus is adsorbed onto the Bayoxide E33 media filling the active adsorption sites. Phosphorus is more common than arsenic and generally appears at higher concentrations and can therefore fill these active adsorption sites faster, limiting the amount of arsenic that can be adsorbed. Best operating conditions are when phosphate is below 0.5 ppm.

How does silica affect arsenic removal?
Under some conditions, the Bayoxide E33 media can act as the nucleation point for the silica in the water to start to polymerize. When this happens, the polymerized silica physically blocks some of the pores into the porous media, making these active sites unusable. As a result, the capacity of the Bayoxide E33 will be reduced. It is possible to alter the water chemistry to negate this effect if the analysis is provided at design stage.

How do iron and manganese affect arsenic removal using E33?
Any iron and manganese in the water have the potential to precipitate out during the vessel. The solids generated will be removed by the Bayoxide E33 media, creating an increased pressure drop through the media bed. It can affect the chemistry and capacity of the Bayoxide E33 media so more frequent backwashing is required. It is therefore recommended to have iron or manganese levels above their MCLs be reduced prior to E33 media.

Is there a simple test for testing arsenic in your water?
Arsenic Quick Test was designed to give the user accurate results without sacrificing cost and time, EPA/ETV test verified performance. Designed using cutting-edge chemistry, Arsenic Quick Test reports results in only 12 minutes. Ideally suited for homeowners, water treatment salespeople and field technicians with only three simple test procedures and a simple color chart. Results indicate the total arsenic present including Arsenic III and Arsenic V.

Why should you choose a lead lag series design vs. a parallel design?
Treatment through two adsorbers in series flow configuration (“lead/lag”) is recommended for waters with high arsenic levels (>30 µg/L). This media’s arsenic adsorption capacity can be optimized by allowing the first “lead” bed of media to continue to adsorb arsenic past the 10 µg/L MCL while the second bed acts as a polishing, or “lag,” adsorber. This is possible because the arsenic breakthrough curve is gradual even when the treated water exceeds 10 µg/L of arsenic. When media is changed out in the first adsorber, the second one becomes the lead adsorber while the first one is placed in lag position. The media can adsorb up to 40 percent additional arsenic in this configuration when compared with proportional operating costs for parallel flow.


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