Integrated industrial effluent (IIE) released from SIIDCUL causes serious environmental problems in the vicinity of Haridwar, India. Therefore, this study investigated the potential of water fern (Azolla pinnata R.Br.) for phyto-treatment of IIE. Laboratory experiments with six IIE concentrations (0 as control with bore well water, 20, 40, 60, 80 and 100%) were performed for bio-removal of selected physicochemical, microbiological and heavy metal parameters of IIE in pot type experiments. The overall results described maximum removal of physico-chemical (pH, EC, TDS, BOD, COD, TKN, Ca, Mg, Na, K), microbiological (MPN and SPC) and heavy metals (Cd, Cu, Cr, Fe, Pb, Mn, and Zn) parameters in 60% concentration of IIE, respectively. The stimulus effect of IIE concentration on pollutant removal process was confirmed using Kruskal–Wallis post hoc test, one way ANOVA (p < 0.05), and linear regression (R² < 0.85) tools. Besides this, A. pinnata relative plant growth rate was also maximum in 60% IIE treatment. This is the first report on phytoremediation of IIE while findings of this study showed that A. pinnata was useful for the eco-friendly treatment of SIIDCUL IIE and could minimize potential wastewater management issues.

Salinity-induced soil degradation poses a significant challenge to agricultural productivity and requires innovative crop-management strategies. In this study, the synergistic effect of biochar and TiO₂ nanoparticles (NPs) obtained from moss (Leucobryum glaucum (Hedw.) Ångstr.) biomass on the growth, yield, biochemical, and enzymatic response of Chinese spinach (Amaranthus dubius L.) grown under salinity stress was investigated. Purposely, A. dubius was grown under different combinations of arable soil, biochar, TiO₂ NPs, and saline soils. The produced biochar and TiO₂ NPs were characterized using microscopy image analysis, X-ray diffraction patterns (XRD), energy-dispersive X-ray spectroscopy (EDX), zeta potential, particle size distribution, and Fourier-transform infrared spectroscopy (FTIR). The results showed that saline stress caused a significant (p < 0.05) decline in growth, yield, and biochemical constituents of A. dubius compared to control treatments. However, the combined application of biochar and TiO₂ NPs significantly (p < 0.05) alleviated the saline stress and resulted in optimum fresh weight (30.81 g/plant), dry weight (4.90 g/plant), shoot and root length (28.64 and 12.54 cm), lead number (17.50), leaf area (12.50 cm²/plant), chlorophyll (2.36 mg/g), carotenoids (2.85 mg/g), and relative water content (82.10%). Biochar and TiO₂-NP application helped to reduce the levels of stress enzymes such as catalase (2.93 µmol/min/mg P), superoxide dismutase (SOD: 2.47 EU/g P), peroxidase (POD: 40.03 EU/min/g P), and ascorbate peroxidase (3.10 mM/mg P) in saline soil. The findings of this study suggest that the combination of nanotechnology and biochar derived from unconventional biomass can be a viable option to mitigate salinity-related challenges and enhance crop yield.