Evaluation of surface water quality in basins of the Chilean Altiplano-Puna and implications for water treatment and monitoring.

Water quality characterization and assessment are key to protecting human health and ecosystems, especially in arid areas such as northern Chile, where water resources are scarce and rich in pollutants. The objective of this study was to review and assess available official water quality data in the Chilean Altiplano-Puna basins for a 10-year period (2008-2018), including water treatment systems. Within the 43,600 km2 of Chilean Altiplano-Puna territory, only 16 official water quality monitoring stations had up-to-date data, and the sampling frequency was less than 3 per year. Most of the water samples collected at the evaluated stations exceeded the drinking and irrigation water Chilean standards for arsenic, boron, and electrical conductivity. Moreover, the characteristics of the Altiplano-Puna affect water quality inside and beyond the area, limiting water usage throughout the Altiplano-Puna basins. Drinking water treatment plants exist in urban and rural settlements; however, the drinking water supply in rural locations is limited due to the lack of adequate treatment and continuity of service. Wastewater treatment plants operate in some urban locations but rarely exist in rural locations. Limited data impede the proper assessment of water quality and thus the evaluation of the need for treatment systems. As such, the implementation of public policies that prioritize water with appropriate quantity and quality for local communities and ecosystems is imperative.

The removal of arsenic and metals from highly acidic water in horizontal subsurface flow constructed wetlands with alternative supporting media.

A laboratory-scale horizontal subsurface flow constructed wetland system was used to quantify the arsenic removal capacity in the treatment of highly acidic, arsenic and metal-rich water: pH ≈ 2, Fe ≈ 57 mg/L, Pb ≈ 0.9 mg/L, Zn ≈ 12 mg/L. The system was operated in two stages, being As ≈ 2.1 mg/L in stage one, and ≈ 3.7 mg/L in stage 2. Limestone and zeolite were employed as main supporting media to build non-vegetated and vegetated cells with Phragmites australis. The system was very effective in the removal of arsenic and iron (> 96%), and lead (> 94%) throughout the whole experimental period, having the four treatment types a similar performance. The main effect of the media type was on the pH adjustment capacity: limestone cells were able to raise the pH to ≈ 7.1, whereas zeolite cells raised it to ≈ 3.8. The contribution of plant uptake to the overall removal of As, Fe and Zn was minor; accounting for less than 0.02%, 0.07% and 0.7% respectively. As such, pollutants were mainly retained in the wetland beds. Our results suggest that limestone is recommended over zeolite as wetland medium mainly due to its neutralization capacity.