Arsenic challenge unites water teams in the Netherlands and Argentina

A naturally occurring substance present in the environment and soil, arsenic, has been found in high concentrations in several parts of Argentina.

Two pilot projects are underway between Argentina’s major water utility Agua y Saneamientos Argentinos S.A. (AySA) and partners Royal HaskoningDHV, TRAIDE, and KWR Water Research Institute (KWR) with support of the Embassy of the Kingdom of the Netherlands in Buenos Aires, according to KWR Project Manager Gerard van den Berg.

As part of the two-and-a-half-year LEAF (Low Energy Arsenic Free) project, the initiative took place over three months at the Ezeiza water treatment plant. KWR developed the project set up, designed the pilots, and defined the research. Work was carried out by the AySA research team, in close cooperation with KWR.

One pilot is based on co-precipitation followed by rapid sand filtration (C-RSF), and the other on co-precipitation followed by ultrafiltration (C-UF).

Going above WHO arsenic limits

World Health Organization (WHO) guidelines for arsenic stand at 50 micrograms per litre. Countries such as the Netherlands have gone further, mandating 10 micrograms per litre. In Argentina, current arsenic parameters settled by the WHO are accepted as valid and epidemiological studies are being carried out to verify if it is mandatory to be more demanding with the regulations.

The pilot projects in Argentina showed positive results during the first three months of implementation, reducing arsenic levels in the treated groundwater down to 10 micrograms per litre and lower, complying with the outlet concentration with Argentine regulations. Although the results obtained are encouraging, a longer period is required to draw conclusive conclusions. Furthermore, significant energy and chemical savings were achieved.

Ron Jong, a senior water treatment specialist and researcher from KWR, said: “Many of the existing technologies, such as reverse osmosis membranes or absorption processes use a lot of energy and chemicals, respectively, and operational costs can be high. The new solution developed by KWR, together with the Dutch drinking water companies, requires minimal energy. We apply this process in the Netherlands but as there’s already iron in the water, it works naturally. In Argentina, as the water is iron-free, this iron has to be added.”

By correctly dosing, the arsenic connects to the iron in the water as iron flocs, which can then be removed either using the sand filtration or ultrafiltration.

Jong believes the partnership will eventually help to disseminate knowledge and solutions to other parts of the world, with Argentina acting as a gateway into Latin America.

“Many other countries in Europe and the rest of the world have arsenic problems seriously affecting drinking water safety. For example, Bangladesh and Serbia, as well.”

Modifying existing processes 

Cost calculations to date have shown that if AySA’s current adsorption processes are modified to the co-precipitation rapid sand filtration set-up, these costs would be recuperated in relatively short time.

Jong added: “After proving that arsenic can be removed at the location, we’re looking at adapting the process circumstances to apply it at the bigger water treatment plants. This will further evaluate and test the ability to modify and operate the process, at a larger scale.”

He says that the challenge of processing the by-product remains with scaling the process in Argentina.

“Waste liquid streams from the current absorption processes can be disposed of into surface waters. However, the waste stream from this new process is an iron sludge containing arsenic. As questions remain over the potential and reuse options in Argentina, this will require further research.”

AySA considered the partnership with KWR to be very valuable, going beyond knowledge exchange to include new ways of working. It has received support from company president, Malena Galmarini.

Christian Taylor, planning manager at AySA, said: “The technology is suitable for removing arsenic and is aligned with our energy efficiency strategy. It is necessary to continue studying this process at different scales, as it can be very useful for rural populations in Argentina.”