Porous lignocellulosic biomass enhances ammonia biotransformation in aquaponics water

Abstract

The aquaculture industry faces significant challenges in maintaining fish production due to the high concentrations of ammonia, which needs to be addressed in an environmentally sound and economically viable approach. The present study explores the use of cheap, readily available, and environmentally friendly sugarcane bagasse and luffa sponge fiber as porous lignocellulosic biomass for biotransforming ammonia in experimental aquaponics water. A 45-day experiment was set up, with Pangasianodon hypophthalmus as the experimental fish in tanks containing aquaponics water. The study consists of a control (CON) and three treatments, viz. BAF (Bagasse), LuF (Luffa fiber), and MixF (Bagasse + Luffa fiber). Weekly spiking of ammonia at different doses was carried out (2, 2.5, 3, 5, and 10 mg L⁻¹). Porous lignocellulose reduced ammonia, resulting in lower stress and better growth through two mechanisms, viz., substrate for the autotrophic nitrifiers to perform nitrification shown by the increase in nitrite with the decrease in ammonia and the assimilation of ammonia by the aerobic heterotrophs using the lignocellulose as a carbon source, which is indicated by the increase in the colony-forming units in terms of biofloc in the water. The result showed the ammonia removal efficiency to be highest in MixF with 67.75% ± 3.26 after 96 h of spiking 10 mg L⁻¹ TAN, followed by BAF and LuF, while the control group was ineffective at 10 mg L⁻¹ TAN. The treatment groups also showed higher fish yield performance and better hematological and serum biochemical parameters as compared to the control group, as plant-assisted bioremediation protects fish against ammonical stress. The study addresses the critical issue of ammonia management in aquaculture by developing an economically sound and sustainable bioremediation model based on the combined effect of biofilm and biofloc. The research enhances the understanding of ammonia’s impact on cultured species and offers a novel, cost-effective solution using lignocellulosic biomass.