Fertilizer draw solution index in osmotic membrane bioreactor for simultaneous wastewater treatment and sustainable agriculture

Abstract

This study investigated the feasibility of applying a novel protocol for constructing a fertilizer draw solution (DS) index used in osmotic membrane bioreactor (OMBR) for simultaneous wastewater treatment and sustainable fertigation. The results indicated that system performance (i.e., water flux, reverse salt flux, contaminant removal) varied critically under different fertilizers. In which, the highest water recovery (∼60%) was observed with potassium chloride (KCl), whereas the lowest value (∼20%) was observed with ammonium nitrate (NH₄NO₃), which corresponded to the highest reverse salt flux. With all fertilizers, the membrane fouling layer thickness was in the range of 15.7-45.7 μm. The foulant were mostly irreversible and hydrophilic, with protein and polysaccharides were the dominant compounds. NH₄NO₃ and NH₄H₂PO₄ (MAP) fertilizers caused the highest and lowest fouling resistances, respectively. Based on the matrix of performance aspects, the very first DSI was constructed for the assessment of fertilizer suitability. Principal component analysis (PCA) showed that fouling resistance played a pivotal role in the total variation of the system. The multi-criteria decision analysis (MCDA) suggested MAP as the most appropriate fertilizer with the highest fertilizer DS index (0.90), followed by KH₂PO₄ (0.67), KCl (0.65), NaNO₃ (0.58), and NH₄NO₃ (0.16). A numerical simulation using an artificial intelligence-based technique revealed that MAP is also capable of maintaining high performance during long-term operations.

Keywords: Draw solution index; Fertilizer suitability; Fouling properties; Multi-criteria decision analysis; Principal component analysis.