A Separation and Desalination Process for Farmland Saline-Alkaline Water

Abstract

Salination poses serious hazards to farmland soil. For the purpose of solving soil salination, desalination of water sources, and other problems faced by arid areas, a separation and desalination process for farmland saline-alkaline water is proposed; a separation and desalination device based on this process is also presented and tested. Results indicate that water associated with the pretreatment device satisfied the working conditions of the composite nanofiltration (NF)-reverse osmosis (RO) membrane system. The composite NF-RO membrane system produced a better filtering effect than either the NF membrane or the RO membrane. When used for filtering saline-alkaline water, the composite NF-RO membrane system achieved a desalination rate of 96.06%, a total hardness removal rate of 98.93%, and a Cl- removal rate of 99.32%, adhering to the standard for irrigation water quality. The flashing-condensation process realized a fresh water recovery rate greater than 70%. During brine evaporation using solar salt making processes, the primary compound of crystals precipitated was NaCl (with a relative content of 93%), suggesting that the precipitates have the potential values of industrial salts. These findings offer new technical references for solving the problem of farmland irrigation water faced by saline-alkaline areas worldwide.

Design and Testing of a Separation and Desalination Device for Farmland Saline–Alkaline Water in Arid Areas

“…The saline-alkaline water col lected from the sampling site was protected from direct sunshine under a sunshade on the test site. The test site was located at the Soil Tank Laboratory of Tarim University, Alar City, Xinjiang, China, as shown in Figure 2 [31]. The test time was from 9:00 to 20:00 every day, working continuously for 8 days (from 9 June 2021to 16 June 2021), collecting 1000 L of water samples every day.…”