Treating Brackish Groundwater for Irrigation with Selective Electrodialysis & Nanofiltration

The Campo de Cartagena aquifer in southeastern Spain contains brackish groundwater that is considered low quality since it requires treatment prior to economic use. For example, the groundwater contains high concentrations of monovalent ions (Na⁺ and Cl⁻), which are detrimental to crop growth and must be removed before irrigation. Currently, the most widely used technology to remove the monovalent ions from water is reverse osmosis (RO) desalination, but this technology also removes divalent ions that are beneficial to crop growth (Mg²⁺, Ca²⁺, and SO₄²⁻). In this study, two technologies, selective electrodialysis (SED) and nanofiltration (NF), are evaluated to treat the brackish groundwater as an alternative to RO. Unlike RO, both SED and NF can remove monovalent ions from the brackish groundwater feed stream while retaining the divalent ions, producing an irrigation product rich in nutrients. Using a bench-scale experimental setup for each water treatment method, the monovalent-divalent selective performance of commercial SED and NF membranes are quantified and compared, using a feed stream representative of the water present in the Campo de Cartagena aquifer. Specifically, the pH and total dissolved solids (TDS) of the feed stream are varied to experimentally optimize the monovalent-divalent selectivity for each process. In addition to comparing the membrane performance, this thesis also evaluates practical considerations in the implementation of both technologies. The primary results of this work show that both SED and NF have potential as technically feasible alternatives to RO, but further analysis is needed to determine the economic feasibility of these two processes for this application. NF and SED have the potential to produce a nutrient rich irrigation product, ultimately creating less waste and saving farmers money on fertilizer.

Name thesis:degree_name

Master

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Mechanical Engineering

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2023

Author dc:creator

• Heath, Samuel M.

Advisor dc:contributor.advisor

• Lienhard, John H.

Statement dc:rights

• Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)
• Copyright retained by author(s)

Licence dc:rights.uri

• https://creativecommons.org/licenses/by-nc-nd/4.0/

Handle dc:identifier.uri

https://hdl.handle.net/1721.1/152963

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/152963