The utilization of agro-biomass/byproducts for effective bio-removal of dyes from dyeing wastewater: A comprehensive review

The dyeing wastewaters are composed of complex chemical compositions, which are toxic and cause biotic risks. For eco-friendly remediation of such toxicants, agro-based materials are used as biosorbent/adsorbent and co substrate in both physiochemical and biological treatment processes. The present study comprehensively reviews the efficacy of agro-biomass/byproducts (belonging to plants, microbes and animals) either as biosorbents (raw biomass) or adsorbents (modified biomass) for direct removal of dyes and their role as co-substrate to stimulate the biodegradation/decolourization of dyes by bacteria and fungi. In physiochemical process, agrobased biosorbents/adsorbents with porous structures and cellulosic content (>= 40%) could exhibit excellent potential for removal of both ionic and non-ionic dyes from aqueous medium. Advancement of chemically modified agro-wastes in the form of bio-composites, or doped with nano-materials are used to enhance the sorption of dyes from wastewater in column-flow mode. In biological processes, co-substrate such as jack-fruit seed-powder, sago-waste, and molasses can act as e over bar -donor, nutritional supplement, and solid-phase substratum for bacteria in dye decolourization medium, which reduces the color and organic loading in bio-treated water. Such low-cost agro-based co-substrates could be used in bioreactors for biodegradation of dyes and coupled bioenergy production at industrial scale. However, it is required to investigate the potential of biosorbent for real dyeing-wastewater treatment, comprehensive economic analysis of the agro-based bio-treatment process, a suitable solid-phase co-substrate for immobilization of microorganism to reduce sludge, and reusability of agrowastes for effective treatment of wastewater.