Juncus rigidus high biomass and cellulose productivity under wastewater salinity stress - A paradigm shift to the valorization of RO reject water

Krupali Dipakbhai Vyas; Aneesha Singh

doi:10.1016/j.scitotenv.2024.173076

Juncus rigidus high biomass and cellulose productivity under wastewater salinity stress - A paradigm shift to the valorization of RO reject water

Sci Total Environ. 2024 May 9:933:173076. doi: 10.1016/j.scitotenv.2024.173076. Online ahead of print.

Authors

Krupali Dipakbhai Vyas¹, Aneesha Singh²

Affiliations

¹ Applied Phycology and Biotechnology Division, CSIR-Central Salt and Marine Chemicals Research Institute, Bhavnagar, India; Academy of Scientific & Innovative Research (AcSIR), Ghaziabad 201002, India.
² Applied Phycology and Biotechnology Division, CSIR-Central Salt and Marine Chemicals Research Institute, Bhavnagar, India; Academy of Scientific & Innovative Research (AcSIR), Ghaziabad 201002, India. Electronic address: aneeshas@csmcri.res.in.

PMID: 38734100
DOI: 10.1016/j.scitotenv.2024.173076

Abstract

The use of water purifiers is intensively catching up and disposing of reverse osmosis reject water is of great concern. Reject water management using conventional methods is costly and harmful to the environment. To address this issue, the present study aims to utilize reverse osmosis reject wastewater using an eco-friendly approach. Juncus rigidus was treated with reject wastewater containing different salinity levels. Wastewater-treated plant dry biomass increased with increasing reject water salinity, and 625.3 g dry biomass recovered in treatment-B (~18,520 ppm). However, ~23,220 ppm wastewater salinity was lethal to the plants. The cellulose was extracted by alkali hydrolysis. The cellulose content in the wastewater-treated biomass was significantly higher in Treatment-B compared to both the control and Treatment-A (~12,744 ppm). The water salinity enhanced the cellulose (26.49 %) production in J. rigidus. Cellulose purity was confirmed using spectroscopic and thermogravimetric means. XRD shows highest crystallinity Index (77.29) with a d-spacing of 4.7 Å and 5.7 nm crystallite size in treatment-B. FTIR results reveal well-defined relevant peaks for OH, CH, CO, CH₂, C-O-C, CO groups in treatment-B cellulose. Salinity impacts carboxyl groups in treatment B cellulose with a sharper and intense peak at 1644 cm^-1 responsible for water absorption. Treatment-B exhibits higher thermal stability due to increased crystallinity. DSC shows endothermic depolymerization of cellulose with distinct peaks for different treatments. Morphological traits got better with increasing salinity with no adverse effect on cellulose. Salinity moderately affected the water absorption capacity of cellulose. All cellulose samples were devoid of gram-negative bacteria known by microbial test. This pioneering work underscores the plant's remarkable capacity not only to accomplish the circular economy by the valorization of wastewater obtained from various water purifiers for Juncus cultivation for cellulose production for diverse applications but also to generate income from wastewater.

Keywords: Cellulose; Halophyte; Juncus rigidus; Reverse osmosis reject water; Salinity.