Forward osmosis dewatering of seawater and pesticide contaminated effluents using the commercial fertilizers and zinc-nitrate blend draw solutions

Abstract

Fertilizer driven forward osmosis (FDFO) process would be feasible due to the possible prevention of the drainage of dewatered and concentrated pesticide effluent from agricultural pesticide industries to the environment. Instead, it would be possible to return the concentrated pesticide solution to the processing cycle, and on the other hand, employ directly the obtained diluted fertilizer draw solution for irrigation. This study investigated the performance of zinc-nitrate/amino-acids blends as fertilizer type draw solution, and distilled water, saline water (seawater), and synthetic wastewater containing pesticides as feed. The results indicated that the synergetic effect of blended type fertilizer presented significantly higher osmotic pressure and water flux than the sum of their individual ones, especially when the amount of amino acid increased. Conversely, an ignorable reverse flux of blended fertilizer draw solute was observed. The fertilizer blend with a molar ratio of 1:6 zinc-nitrate/amino-acid achieved the higher average fluxes of 34.7 and 23.92 L/m2h from distilled and saline waters compared to common draw solutions such as metal salts. Furthermore, the FDFO exhibited a high rejection (over 99%) of bentazon and imidacloprid in feed solutions compared to other agricultural pesticides due to their larger molecular weight and molecular size. The applied FDFO represented a significant reduction in specific energy consumption (from 0.17 to 0.049 kWh/m3) in a bench-scale setup as compared to the RO process almost at the same water permeation flux and the rejection of bentazon.