Field-scale assessment of soil, water, plant, and soil microbiome in and around Rania-Khan Chandpur Chromium contaminated site, India.

Rania-Khan Chandpur site, (Kanpur Dehat, Uttar Pradesh, India), one of the highly Chromium (Cr) contaminated sites in India due to Chromite Ore Processing Residue (COPR), has been investigated at the field-scale. We found that the area around the COPR dumps was hazardously contaminated with the Cr where its concentrations in the surface water and groundwater were > 40 mgL-1, its maximum contents in the COPRs and in the soils of the adjoining lands were 9.6 wt% and 3.83 wt%, respectively. By exploring the vegetation and microbial distribution across the site, we advocate the appropriateness of Cynodon dactylon, Chrysopogon zizanioides, Cyperus sp., and Typha angustifolia as the most suitable phytoremediation agent because their association with Cr remediating bacterial species (Pseudomonas sp., Clostridium sp. and Bacillus sp.) was strong. Using this remarkable information for the bioremediation projects, this site can be re-vegetated and bioaugmented to remediate Cr in soils, waterlogged ditches, surface water, and in groundwater systems.

Cultivation of Navicula sp. on rice straw hydrolysate for the production of biogenic silica.

Rice straw hydrolysate (RSH) prepared at room temperature was found to be rich in silica (140 ± 4.1 mg L-1) and other nutrients (nitrate-N: 160 ± 4.3 mg L-1, total dissolve phosphate: 164 ± 6.7 mg L-1, ammoniacal-N: 439.8 ± 17 mg L-1). The aim of this work was to study four RSH dilutions (10, 30, 50, 70% v/v) to cultivate Navicula sp. with modified ASN-III as a control. The best result was achieved in 30% RSH in terms ofdoubling time (d = 1.49 days) and growth rate (µmax = 0.46 day-1). Compared to control, specific growth rate and biomass productivity were increased by 2.93 folds and 1.85 folds, respectively. Cultivation in 5 L reactor with optimized 30% RSH yielded frustule (54.2 ± 1.9%), carbohydrate (12.4 ± 1.2%), lipid (18.9 ± 1.4%), and protein (8.2 ± 0.6%). The residual solid fraction showed 18.99% increased theoretical methane yield than raw rice straw. Overall, the present process offers a sustainable solution to manage rice straw residue and recover nanoporous silica.