Silica Sequestration from Hypersaline Nanopermeate Using a Native Nitzschia Consortium and Simultaneous NaCl Recovery Favoring ZLD Conditions

In pursuit of zero liquid discharge (ZLD), industries rely on advanced effluent treatment systems such as reverse osmosis (RO) and nanofiltration (NF). However, silica present in textile effluents causes RO membrane fouling, flux reduction, and reduced membrane life. The present study demonstrates a sustainable approach for simultaneous silica removal and NaCl recovery using diatoms. The diatom consortium (D consortium: Nitzschia inconspicua and Nitzschia anatoliensis ) isolated and enriched from an industrial site exhibited high salt tolerance and efficient silica uptake without requiring external nutrients. A lab-scale bioreactor (5 L) inoculated with this consortium achieved ∼80% (from 142.19 to 29.62 mg L –1 ) silica removal at 96 h HRT with high biomass yield (1.67 ± 0.40 mg L –1 ). Despite effective silica removal, residual color persisted in the treated effluent (53.32 ± 10 Hazen), which hinders the reuse of reclaimed NaCl for dyeing. Thus, silica-less hypersaline nanopermeate was post-treated with an optimized dosage of sodium hypochlorite, which helped to achieve complete color removal, enabling the recovered salt to be reused in the dyeing unit. The diatom biomass was thermally processed to generate biosilica, adding further value to the process. The finding highlights a transformative “waste-to-wealth” pathway for sustainable management of textile effluent within the ZLD framework.