Towards agro-environmentally sustainable irrigation with treated produced water in hyper-arid environments

Produced water (PW) is the main waste stream generated from oil and gas extraction. Nowadays, half of the global PW volume is managed through environmentally controversial and expensive disposal practices, such as re-injection through deep wells. In dry areas such as in the Arabian Peninsula, PW could be reused to irrigate crops, creating environmental, economic and social value. However, the quality of most PWs remains challenging as their high salinity, sodicity and alkalinity can degrade soil fertility and crop yield. Mitigating these negative impacts is costly as it requires specific PW treatment and irrigation management. Thus, the environmental sustainability and the cost of irrigation with PW are uncertain. The aims of this paper was to assess the agro-environmental sustainability of irrigating crops with PW in hot and hyper-arid climate and to estimate the operating cost of reusing PW for irrigation in order to compare this PW management approach to PW disposal in terms of environmental impacts and financial cost. To this end, a soil-water model was used to simulate irrigation of jojoba (Simmondsia chinensis) with oilfield-PW. Different irrigation strategies combining over-irrigation, PW blending and desalination were tested to preserve the soil structural stability and the crop yield. The operational costs of identified sustainable scenarios were estimated using a cost analysis. In this case study, the simulations showed that using an irrigation volume up to ∼390 % of the crop water needs with a blend composed of raw and desalinated PW in a 2:1 ratio could preserve the soil structural stability and the crop yield. However, for irrigation, the least-cost option was to mix raw and desalinated PW in a 1:4 ratio and to reduce the irrigation amount to just meet the crop water needs. Although the cost of managing PW in irrigation remains up to 2.5 times higher than PW disposal, this practice might be competitive considering the crop value generated and the increasing need for sustainable alternatives to PW disposal.