event 07 jun. 2021

Publication // Reusing wastewater for agricultural irrigation: a water-energy-food Nexus assessment in the North Western Sahara Aquifer System

By C Ramirez, Y Almulla and F Fuso Nerini. Wastewater reclaim, treatment and reuse, has a great potential to alleviate water stress in the North Western Sahara Aquifer System (NWSAS), while supporting sustainable food production and energy efficiency. In their study the authors, supported by a GIS-based quantitative analysis, use a Nexus approach to shed light on synergies and trade-offs among selected Sustainable Development targets of interest.

category Research Papers, Publications and Books tag Water tag Food and Agriculture tag Water tag Irrigation tag Desalination tag Water resource management tag Energy tag Governance tag SDGs tag Economy tag Waste treatment globe Africa
Publication Reusing wastewater for irrigation

© C Ramirez, Y Almulla and F Fuso Nerini.

Abstract

The North Western Sahara Aquifer System stands out as one of the water scarcest regions in the world. Moreover, in recent decades agriculture activity has grown exacerbating the pressure on groundwater resources and pumping energy requirements.

In this study, a water-energy-food Nexus approach was used to assess the effect of capturing, treating and reusing wastewater for irrigation. GIS-based tools were used to capture the systems spatial dimension, enabling to match wastewater supply and water demand points, identify demand hotspots and evaluate techno-economically viable wastewater treatment options. Moreover, the minimum energy requirements for brackish water desalination were estimated. Seven domestic wastewater treatment technologies and one irrigation tailwater treatment technology were evaluated, making use of a levelized cost of Water methodology to identify the least-cost system. Four scenarios were constructed based on water-consumption behaviour of farmers towards changes in irrigation water pricing. The identified least-cost wastewater treatment technologies showed clear trade-offs, as different technologies were more cost-effective depending on treatment capacity requirements of the spatially distributed agglomerations.

The reuse of treated wastewater/tailwater in agricultural irrigation, showed improvement of groundwater stress, reducing on about 49% water abstractions and groundwater stress levels in the best case scenario. However, groundwater stress still fell on the extremely high category, highlighting the critical condition of the aquifer. Furthermore, reuse of wastewater/tailwater decreased dependency on groundwater pumping and the overall energy-for-water requirements, reducing by about 15% the total energy requirements in the best case scenario. However, to effectively preserve water resources and act holistically towards the sustainable development agenda, measures as better water pricing mechanisms, management strategies to improve water productivity and adoption of more efficient irrigation schemes may be needed.

The title picture, Figure 1, shows NWSAS systems, energy and water resource flows. The blocks represent the different systems, the arrows the water flows, the voltage icons the systems that require energy, and the numbers the order of processes: (1) extracting water from groundwater resources, (2) desalinating brackish water when needed, (3) supplying water demand for domestic and agricultural irrigation purposes, (4) reclaiming domestic wastewater and agricultural drainage (i.e. tailwater), (5) treating reclaimed wastewater, and (6) reusing treated wastewater in agricultural irrigation.

Figure 2. Water usage for all scenarios. At left: reused water after reclaim, treatment and allocation classified by population and irrigation source. Percentage bars indicate the share of reused water against the total demand. At right: overall water extractions classified by population and irrigation use. Percentage bars indicate the percentage of water saved compared to Baseline withdrawals.
Figure 2. Water usage for all scenarios. At left: reused water after reclaim, treatment and allocation classified by population and irrigation source. Percentage bars indicate the share of reused water against the total demand. At right: overall water extractions classified by population and irrigation use. Percentage bars indicate the percentage of water saved compared to Baseline withdrawals.

Keywords

water, energy, agriculture, Nexus, wastewater reuse, NWSAS, GIS

Published

April 2021

By

Environmental Research Letters, Volume 16, Number 4

Citation

Ramirez, C., Almulla, Y., & Fuso Nerini, F. (2021). Reusing wastewater for agricultural irrigation: a water-energy-food Nexus assessment in the North Western Sahara Aquifer System. Environmental Research Letters, 16(4), 044052. https://doi.org/10.1088/1748-9326/abe780

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Reusing wastewater for agricultural irrigation: a water-energy-food Nexus assessment in the North Western Sahara Aquifer System

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