A Separation and Desalination Process for Farmland Saline-Alkaline Water

Qiaonan Yang,Jie Li,Can Hu,Yichuan He,Jie Zhang,Zhilin Sun,Xiaokang Yi

doi:10.3390/agriculture11101001

Qiaonan Yang, Jie Li + Show 5 more

Open Access

https://doi.org/10.3390/agriculture11101001

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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.

Highlights

Accepted: 9 October 2021Salination poses serious hazards to farmland soil, it has a significant effect on crop growth environments and groundwater resources [1,2]
3 Cl− content: Cl− contents of the original saline-alkaline water, water yielded by the primary and secondary reverse osmosis (RO) membranes, and water yielded by the tertiary NF membrane were measured using an ion chromatograph
Salinity of the saline-alkaline water fluctuated within the range of 15,993–17,108 mg/L; and salinity error (S) of the water sample was ±0.34 mg/L

Summary

Introduction

Accepted: 9 October 2021Salination poses serious hazards to farmland soil, it has a significant effect on crop growth environments and groundwater resources [1,2]. Saline-alkaline lands are irrigated to dissolve soil salts, discharging soluble salts from topsoil into deep soil (or leaching them out) through infiltration [11]. In this manner, harmful salt contents in the soil are reduced through lateral seepage into drainage canals, making the soil arable [12]. Harmful salt contents in the soil are reduced through lateral seepage into drainage canals, making the soil arable [12] This measure may make it difficult to desalinate saline-alkaline water discharged after salt leaching

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