Effect of alginate oligosaccharide on the efficiency of wastewater purification in ecological floating bed aquaculture

Abstract

Abstract In order to investigate the effect of alginate oligosaccharide (AOS) on the water purification efficiency of an ecological floating bed system used in aquaculture, water spinach was cultivated in aquaculture wastewater treated with varying concentrations of AOS (0.025, 0.05, 0.1, and 0.2 mg/L), with an ecological floating bed without AOS serving as the control group. Experimental results reveal that the addition of an appropriate amount of AOS to the wastewater in the ecological floating bed system promotes the growth of water spinach. This is evident in the increased plant height, stem diameter, main root length, number of roots, leaf area, aboveground fresh weight, belowground fresh weight, aboveground dry weight, belowground dry weight, seedling index, chlorophyll a, chlorophyll b, and chlorophyll content. The combination of 0.05 mg/L AOS with the ecological floating bed exhibits the most favorable results, with percentage increases in various indicators were 44.0%, 52.9%, 29.9%, 62.0%, 28.0%, 141.6%, 84.0%, 97.7%, 220.0%, 24.6%, 34.2%, 26.9% compared to the control group. The addition of AOS to the water spinach ecological floating bed system significantly enhances the removal efficiency of water turbidity, chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3−-N), total nitrogen (TN), and total phosphorus (TP) water quality indicators. The combination of 0.05 mg/L AOS with the ecological floating bed demonstrates the optimal removal efficiency. This experiment also investigated the differences in microbial community structure between the control group and the group with the optimal concentration of AOS to study the mechanism of action of AOS. This study offers crucial technical insights for further optimizing ecological floating bed technology and improving water purification efficiency.