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Swedish University of Agricultural Sciences (2020)

Farm-based technologies for management of risks from irrigation with wastewater-polluted sources in Cochabamba, Bolivia

Perez Mercado, Luis Fernando

Titre : Farm-based technologies for management of risks from irrigation with wastewater-polluted sources in Cochabamba, Bolivia

Auteur : Perez Mercado, Luis Fernando

Université de soutenance : Swedish University of Agricultural Sciences

Grade : Doctoral thesis 2020

Résumé
Wastewater irrigation is a global practice that allows reusing water and nutrients in agriculture, but also poses risks of introducing pathogens/pollutants into agricultural systems and food. In order to manage these risks, on-farm measures can be implemented as barriers along the pathway that pathogens/pollutants must follow to reach the population/place at risk, in cases where treatment plants are not a viable option. The aim of this thesis was to evaluate several on-farm measures in terms of i) reduction in health/environmental risks, and ii) feasibility of implementation in the context of an agricultural system producing lettuce with wastewater-polluted irrigation source (river water) in a semi-arid area of Bolivia. The microorganisms assessed for health risks from consumption of lettuce from the studied system were Ascaris lumbricoides, enterotoxigenic Escherichia coli (ETEC) and rotavirus, while the environmental risks assessed were nitrogen excess in soil under high and low irrigation efficiencies. The risks were assessed in four scenarios : 1) direct use of river water (baseline scenario), 2) baseline scenario with biochar filtration, 3) baseline scenario with riverbank filtration, and 4) baseline scenario with water-source substitution (the river water) two weeks before harvest. Water quality and performance data of tested on-farm measures were collected in field studies and laboratory experiments and used as input for risk assessments. Health risks were above WHO recommended health targets in the baseline scenario, while the nitrogen input to soil was at least two-fold the lettuce requirement. The health target was achieved by riverbank filtration for A. lumbricoides and ETEC, and by onfarm filtration for A. lumbricoides. Only on-farm biochar filters reduced the estimates of nitrogen accumulation near the equilibrium point (0 kg ha-1) for high efficiency irrigation. No reduction in risk was found for wastewater substitution in this study. The implementation of riverbank filtration was found to be highly dependent on local context (soil properties), while implementation of biochar filters were constrained by the high surface area required. This research contributed to the body of knowledge by testing on-farm measures not previously investigated and by identifying bottlenecks that affect the feasibility/reliability of the studied on-farm measures for risk management.

Mots Clés  : Pathogens, nutrient recycling, farm-based measures, health, ecotechnology, irrigation scheduling, biochar filtration, riverbank filtration, risk assessment

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Page publiée le 27 mai 2020