This study was conducted to assess the pollutant uptake capability of water lettuce (Pistia stratiotes L.) in terms of bioaccumulation, enrichment, and translocation of heavy metals grown in sugar mill effluent. Results showed that the maximum fresh weight (328.48 ± 2.04 gm kg⁻¹), total chlorophyll content (2.13 ± 2.03 mg g⁻¹ fwt), and relative growth rate, RGR (11.89 gg⁻¹ d⁻¹) of P. stratiotes were observed at 75% concentration of the sugar mill effluent after 60 days of phytoremediation experiment. The bioaccumulation factor (B_F) of different heavy metals was greater than 1 with 50% and 75% concentrations of sugar mill effluent and this indicated that P. stratiotes was hyperaccumulator or phytoremediator of these metals. The enrichment factor (E_F < 2 for Cu, Fe, Cr, Pb, Zn, and Mn) and (E_F > 2 for Cd) indicated that P. stratiotes mineral enrichment deficient and it moderately enriched the different heavy metals. Moreover, translocation factor (T_F) was less than 1 which indicated the low mobility of metals in different parts (root and leaves) of P. stratiotes after phytoremediation. Therefore, P. stratiotes can be used for phytotreatment of sugar mill effluent up to 50% to 75% concentrations and considered as hyperaccumulator aquatic plant for different heavy metals and other pollutants from the contaminated effluents.

Heavy metal pollution from industrial wastewaters has become an issue of global concern. These wastewaters are frequently used for inland irrigation which possess a serious risk of heavy metal contamination of both soil and cultivated crops. The problem is more common in developing countries like India where industrial wastewaters are often discharged without appropriate treatments. Therefore, this study aimed at assessing the impact of paper mill effluent for irrigation on the growth, productivity, and heavy metal accumulation potential of two rice (Oryza sativa L.) varieties (PB-1121 and PR-121). Water, soil, and rice crop samples were obtained from the vicinity of Saharanpur city, Uttar Pradesh, India, and subsequently analyzed for selected physicochemical and heavy metal parameters. Results showed that paper mill effluent and nearby Kali River water had significant (p < 0.05) loads of pollutants that impacted the soil properties. Moreover, the maximum plant height (123.48 ± 4.86 and 98.83 ± 2.02 cm); total chlorophyll (6.70 ± 0.25 and 6.64 ± 0.17 mg/g); leaf carotenoids (0.67 ± 0.08 and 0.63 ± 0.05 mg/g); starch content (71.08 ± 2.05 and 72.60 ± 1.63%); amylose content (25.10 ± 1.32 and 20.28 ± 1.24%); crop yield (4270.20 ± 75.12 and 5830.58 ± 63.10 kg/ha); and straw yield (5472.05 ± 93.90 and 6683.76 ± 61.26 kg/ha) of PB-1121 and PR-121, respectively, were observed using Kali River water irrigation source as compared to paper mill effluent and borewell water. The order of heavy metal accumulation in rice straw and grain followed: Fe > Mn > Zn > Cu > Cr > Cd. Similarly, the bioaccumulation factors for heavy metals in rice straw and grain were observed as >1 and 1). As a result, the findings of this study provide useful information about the current state of heavy metal pollution and the health risks associated with rice crops irrigated with contaminated water sources.

This study investigated the potential of water lettuce (Pistia stratiotes L.) for removal of copper, iron and mercury (Cu²⁺, Fe³⁺ and Hg²⁺) from their aqueous solution amended at different concentration (5, 10 and 15 mg L⁻¹). The different plant growth attributes viz., fresh plant biomass, total chlorophyll content, kinetic plant growth rate and plant root size were estimated. The results showed that the highest removal of selected metals (Cu²⁺: 53.20%, Fe³⁺: 83.20% and Hg²⁺: 62.14%) was observed in 5 mg L⁻¹ treatment. The fresh plant biomass (Cu²⁺: 45.57; Fe³⁺ 90.82 and Hg²⁺ 47.27 g), chlorophyll content (Cu²⁺: 2.99 ± 0.03; Fe³⁺ 4.26 ± 0.06 and Hg²⁺ 3.02 ± 0.03 mg g⁻¹ fwt), kinetic growth rate (Cu²⁺: 0.0004; Fe³⁺ 0.0011 and Hg²⁺ 0.0006 gg⁻¹day⁻¹) and plant root size (Cu²⁺: 12.28; Fe³⁺ 16.54 and Hg²⁺ 12.86 cm) were maximum in 5 mg L⁻¹ treatment. The translocation factor of Cu²⁺, Fe³⁺ and Hg²⁺) was also < 1 in 5 mg L⁻¹ treatment. The Kruskal–Wallis test showed that the contents of Cu²⁺ and Hg²⁺ were statistically significant (P < 0.05) while Fe³⁺ was not significant (P > 0.05) in the plant tissues. This study suggested that the most efficient remediation of Cu²⁺, Fe³⁺ and Hg²⁺ and the maximum growth of P. stratiotes can be achieved at 5 mg L⁻¹.

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.