Improving irrigation water quality using a pilot algal treatment system: A case study from northern Chile

This study evaluates a three-stage integrated water treatment system for the removal of boron and arsenic from irrigation water in the arid commune of Camiña, northern Chile. The system combines ion exchange for boron removal, a 500 L reactor with non-living Chlorella vulgaris biomass for arsenic removal, and automated storage and drip irrigation. Operated continuously at 2.96 m 3 /day for one year, it achieved average removal efficiencies of 44 % for boron and 20 % for arsenic, with maximum removals of 78 % and 66 %, respectively. Garlic crops irrigated with treated water showed improved agronomic outcomes. Large bulb frequency increased from 35 % to 49 %, and extra-large bulbs from 13 % to 23 %. A techno-economic analysis indicated operating costs of 2.61 USD/m 3 . A preliminary life cycle assessment estimated greenhouse gas emissions at 2.22 kg CO 2 -equivalent per m 3 treated, with low chemical and biosorbent inputs. This represents one of the first pilot-scale applications of an algal-based arsenic removal system directly integrated with crop irrigation. The system offers a modular, resource-efficient, and environmentally sustainable solution suitable for rural agricultural communities dependent on marginal water sources. • Algal system removed boron and arsenic from irrigation water. • Achieved up to 78 % boron and 66 % arsenic removal in the field. • Treated water improved garlic and carrot yield and quality. • Reactor used non-living Chlorella vulgaris as biosorbent. • LCA and cost analysis confirm low emissions and OPEX.