Potential beneficial reuse of oilfield produced water for agricultural irrigation: effects on crop health, uptake, metabolism, and bioaccumulation

Abstract

With increasing water scarcity, the potential reclamation of oilfield produced water (PW) for food crop irrigation provides a means to augment dwindling water resources in the agricultural sector. However, concerns related to crop health and chemical residues in food crops as a result of irrigation with unconventional water supplies have grown. Rather than consider PW as a waste product requiring disposal by deep-well injection, the overarching objective of this dissertation was to evaluate the possible beneficial reuse of PW for use in agriculture, specifically by investigating the effects on crop health and metabolism as well as the uptake of inorganic constituents in crops irrigated with PW from O&G operations. In Colorado, much of the O&G operation coincides with arid areas of agricultural operation, providing a unique opportunity to study the potential for beneficial reuse. The approach combined greenhouse experiments, using actual PW of varying water qualities, with mass spectrometry (MS)-based metabolomics and ionomics analysis using gas chromatography (GC-MS) and inductively coupled plasma (ICP-MS), respectively, to assess how different water qualities influence plant uptake and metabolism.First, the physiological and morphological response of wheat irrigated with dilutions of Denver-Julesburg (DJ)-Basin PW was assessed, providing a framework for PW use guidelines to minimize effects on crop health. Second, water treatment technologies targeted at removal of salinity and organic chemical content from PW were compared to identify the impacts of inorganic contaminants and nutrient uptake in both wheat and sunflower and their associated soils. Third, multivariate statistical tools coupled with non-targeted metabolomics were used to establish a molecular phenotype for PW-irrigated wheat and demonstrated that physiological changes observed were the result of biochemical changes reflective of adaptation and tolerance mechanisms to the unique stressor imposed by PW. The results of this dissertation are novel and important as this investigation is the first of its kind to examine uptake and metabolism in food crops and the impacts upon irrigated soils using authentic oilfield PW and experimental treatment technologies of that water. Any expansion of the limited practice of PW reuse in agriculture will also require careful consideration of the many data gaps surrounding PW variability, composition, characterization, toxicity, treatability, and feasibility. The results of this dissertation are intended to motivate further efforts to address these data gaps, potentially leading to the beneficial reuse of these wastewaters.