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

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 (similar to 60%) was observed with potassium chloride (KCl), whereas the lowest value (similar to 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 mu m. 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 longterm operations.

Automated summary

This study investigated the feasibility of a novel protocol for simultaneous wastewater treatment and sustainable fertigation in an osmotic membrane bioreactor. The results showed that different fertilizers had critical effects on system performance, with potassium chloride resulting in the highest water recovery and ammonium nitrate causing the lowest. The fouling layer on the membrane was mainly composed of irreversible and hydrophilic foulants, with protein and polysaccharides being the dominant compounds. Based on the performance matrix, a fertilizer index was constructed using multi-criteria decision analysis, with MAP identified as the most suitable fertilizer. Numerical simulation also revealed that MAP maintained high performance during long-term operations.