Water treatment specialists from the Netherlands and Argentina are uniting to help find a sustainable solution to remove arsenic from groundwater. 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 (AySA) and partners Royal HaskoningDHV, TRAIDE, and KWR Water Research Institute (KWR) with support of the Embassy of the Netherlands in Buenos Aires, according to Gerard van den Berg, project manager of KWR.
As part of the two-and-a-half-year Low Energy Arsenic Free (LEAF) 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 50mg/l. Countries such as the Netherlands have gone further, mandating 10mg/l 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 10mg/l 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.
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 said 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.”