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Blended Fertilizers as Draw Solutions for Fertilizer-Drawn Forward Osmosis Desalination
journal contribution
posted on 2012-04-17, 00:00 authored by Sherub Phuntsho, Ho Kyong Shon, Tahir Majeed, Ibrahim El Saliby, Saravanamuthu Vigneswaran, Jaya Kandasamy, Seungkwan Hong, Sangyoup LeeIn fertilizer-drawn forward osmosis (FDFO) desalination,
the final
nutrient concentration (nitrogen, phosphorus, potassium (NPK)) in
the product water is essential for direct fertigation and to avoid
over fertilization. Our study with 11 selected fertilizers indicate
that blending of two or more single fertilizers as draw solution (DS)
can achieve significantly lower nutrient concentration in the FDFO
product water rather than using single fertilizer alone. For example,
blending KCl and NH4H2PO4 as DS can
result in 0.61/1.35/1.70 g/L of N/P/K, which is comparatively lower
than using them individually as DS. The nutrient composition and concentration
in the final FDFO product water can also be adjusted by selecting
low nutrient fertilizers containing complementary nutrients and in
different ratios to produce prescription mixtures. However, blending
fertilizers generally resulted in slightly reduced bulk osmotic pressure
and water flux in comparison to the sum of the osmotic pressures and
water fluxes of the two individual DSs as used alone. The performance
ratio or PR (ratio of actual water flux to theoretical water flux)
of blended fertilizer DS was observed to be between the PR of the
two fertilizer solutions tested individually. In some cases, such
as urea, blending also resulted in significant reduction in N nutrient
loss by reverse diffusion in presence of other fertilizer species.