Woven-fiber microfiltration coupled with anaerobic forward osmosis membrane bioreactor treating textile wastewater: Use of fertilizer draw solutes for direct fertigation

Abstract

A lab-scale Anaerobic Forward Osmosis Membrane Bioreactor (An-FOMBR) system was established for treating synthetic textile wastewater having Chemical Oxygen Demand (COD) of 3000 ± 150 mg/L using Fertilizer Draw Solutes (FDSs). The study was conducted by using Ammonium Sulphate (SOA), Mono-ammonium Phosphate (MAP), and Mono-potassium Phosphate (MKP) each having 1 Molar (M) concentration which can be used for sustainable water reuse in terms of fertigation without regeneration of FDSs. For treatment of textile wastewater, color and COD removal was found to be in the range of 92.3–96.4 and 97.8–99.2%, respectively. Among the three FDS, MAP showed the best performance for 71 days with stable biogas production. Flux recovery using MAP as DS was less than 75.2% as compared to SOA 78.8 and MKP 82.8% after osmotic backwashing. Fertilizer nutrient concentrations (NH4+1-N, K+1, and total phosphorus) in product water were observed low at the initial cycles, requiring minimum dilution for direct fertigation. Furthermore, for reverse solute reduction, low-cost Woven Fiber Microfiltration (WFMF) was coupled with An-FOMBR and the flux of WFMF was optimized at 2 LMH which exhibited the salinity level within the range of 4.5–7.5 mS/cm and assisted the An-FOMBR in exhibiting a continuous long-term operation in comparison with conventional osmotic membrane process and hence can serve as a sustainable solution for treating high strength textile wastewater.