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Writer's pictureMauro Gandola

ARSENIC REMOVAL WITH ION EXCHANGING RESINS TO TREAT WATER FOR DRINKING USE

Ion Exchange Technology is the ideal and most technologically advanced solution for the removal of arsenic from water intended for drinking use.


This Special Application is the result of intense research and experimentation conducted in recent years on the topic of the selective removal of arsenic from water for human consumption. Arsenic is in fact recognized as a class A carcinogen, and the most recent American and European regulations to protect the quality of drinking water have lowered the limit value for this contaminant to 10 ppb.


The Special Ion Exchange Application represents the perfect synthesis of the advantages of two proven technologies for the removal of arsenic, namely ion exchange on polymer resins and adsorption on granular iron oxides, and allows the disadvantages of both processes to be eliminated.


The Ion Exchange Polymer is in fact made by depositing and uniformly dispersing nanoparticles of hydrated iron oxides on the porous support provided by the resin, thus exploiting the high affinity and selectivity of the ferrous-based products towards arsenic and the proven mechanical and hydraulics of the macroporous beads of an ion exchange resin.


With this innovative product it is finally possible to obtain the very high arsenic retention capacity typical of granular iron oxides, while obviating the crushing and structural deterioration of these materials, which are by their nature fragile and friable. The flaking of iron oxides leads to the production of fines, which cause the clogging of the filter beds and the decay of the performance of the entire system, which therefore imperatively requires frequent backwashing at high flow rates. These backwashing generate a slurry containing iron and arsenic, which cannot simply be initiated at the exhaust, but it must be suitably treated and disposed of.

In the case of the Special De-Arsenic Resin, the mechanical strength of the support provided by the ion exchange resin definitively eliminates this problem, allowing constant performance for a long time without the need for backwashing, sometimes for the entire useful life of the product.


With the Special Resin it is possible to obtain an excellent quality of treated water, reducing the concentration of arsenic to a level well below the limit of 10 ppb for long periods of time;


the installation of two filters in series (plus possibly a third in stand-by to be inserted online when the first is exhausted) also allows a particularly simple management of the entire system, minimizing the need for presence and supervision by the plant operators and operating costs.


The production capacity of the system, which is a function of a certain number of parameters related to the characteristics of the feed water and the hydraulic operating conditions, can be estimated with good precision on the basis not only of theoretical knowledge, but also and above all on the basis to the data in our possession relating to the long-term operation of numerous plants already in service. At this point it is necessary to specify that, in order to make a correct estimate of the production capacity of the system, an accurate analysis of the influencing water is of vital importance, with particular reference to the parameters that directly or indirectly influence the operational capacity of the product. Among these parameters, we remember:


  • Arsenic Total

  • Arsenic III Trivalent

  • Arsenic V Pentavalent

  • pH

  • Phosphates

  • Silica

  • Vanadium

  • Oxyanios of Chromium, Molybdenum, Selenium e Antimony.


Only a precise knowledge of these parameters allows an accurate forecast of the plant's production capacity.


We also recommend a preliminary filtration of the feed water in order to avoid the accumulation of suspended solids inside the desiccant filters. The filters must in any case be equipped with the necessary valves to be able to carry out the backwashing of the resin upon loading and the connections useful for the hydraulic loading and unloading of the resin, respectively new and exhausted.


Special SBA Resin is an iron-infused anion resin that uses iron oxide to complex and remove pentavalent and trivalent arsenic from water. Special SBA Resin reduces arsenic levels to < 2 ppb and is ideal for municipal treatment plants, point-of-entry (POE) and point-of-use (POU) systems. It is compatible with most existing lead-lag or parallel design configurations and is recommended for either single use or for applications needing off-site regeneration.


Regeneration: Consult with EGMA Technical Dept. on further design details, which are evaluated case by case.


EGMA - Studio Associato remains available for any further information on the subject, as well as to provide adequate support for the development of a specific project and the definition of basic or detailed engineering entrusted to plant specialists appointed by the 'user. As of now, we remain available for the definition of the operating parameters and for the sharing of the plant layout of the executive project, as well as for the discussion / definition of the technical guarantees that can be requested and signed by the plant manufacturer in relation to expected performances suitable for the production of pure water.

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