Arsenic removal from geothermal influenced groundwater with low pressure NF pilot plant for drinking water production in Nicaraguan rural communities

Bayardo Gonzalez; S G J Heijman; L C Rietveld; D van Halem

doi:10.1016/j.scitotenv.2019.02.222

Arsenic removal from geothermal influenced groundwater with low pressure NF pilot plant for drinking water production in Nicaraguan rural communities

Sci Total Environ. 2019 Jun 1:667:297-305. doi: 10.1016/j.scitotenv.2019.02.222. Epub 2019 Feb 27.

Authors

Bayardo Gonzalez¹, S G J Heijman², L C Rietveld², D van Halem²

Affiliations

¹ Delft University of Technology, Faculty of Civil Engineering and Geosciences, Stevinweg 1, 2628, CN, Delft, the Netherlands. Electronic address: B.J.GonzalezRodriguez@tudelft.nl.
² Delft University of Technology, Faculty of Civil Engineering and Geosciences, Stevinweg 1, 2628, CN, Delft, the Netherlands.

PMID: 30833235
DOI: 10.1016/j.scitotenv.2019.02.222

Abstract

This research evaluated the effect of different fluxes (16, 23 & 30 L/m² h) and temperatures (31,35 & 43 °C) on the rejection of As(V) during nanofiltration (NF) of natural geothermal influenced groundwater in Nicaragua. A NF pilot plant powered by solar panels was built and operated in rural community Telica, exposed to As-rich drinking water sources due to geothermal influences. The results showed that even at high temperatures it is possible to obtain high rejection of As(V) (0.87-0.9) during NF filtration (recovery 10%; flux 16 L/m² h) of geothermal influenced groundwater, with the additional advantage of requiring low operating pressures (1.2 bar ~ 12mwc). The permeate concentration (~5 μg/L) complied with the WHO guideline for drinking water and the concentrate (~55 μg/L) could be used by local villagers for daily activities (e.g., laundry and bathing). For all investigated fluxes and temperatures the order of rejection of As(V) (as HAsO₄^2-), compared with the other anions, could be interpreted on the basis of its charge, hydrated radius and hydration free energy. At lower temperatures (31 and 35 °C) permeate quality improved slightly (~3 μg/L), but although an increased temperature had a negative effect on the As rejection, As concentrations in the permeate never exceeded 5 μg/L, while the required TMP dropped - depending on the flux - with 0.5 to 1 bar. This decrease in required pressure might be of huge benefit in deserted, rural locations where electricity is scarce, as with an overhead tank of 10-15 m a gravity-fed NF system would be feasible.

Keywords: Arsenic; Drinking water; Geothermal sources; Nanofiltration; Nicaragua.