Research on the Optimization of Key Parameters for Heterotrophic Bacteria Assimilation Nitrogen Removal Technology in Aquaculture Tailwater

With the rapid development of the global aquaculture industry, the issue of effluent pollution from aquaculture has become increasingly severe. Effective management of aquaculture effluent is an urgent requirement for the sustainable development of the aquaculture industry, with a key focus on the efficient removal of nitrogen. Heterotrophic bacteria assimilation technology offers advantages such as high efficiency and resource recovery; however, its application in effluent treatment remains limited. Therefore, this study aimed to identify the optimal carbon source for the heterotrophic bacteria assimilation process and to optimize its operating parameters using response surface methodology (RSM). The results revealed that the sucrose group achieved the highest total ammonia nitrogen (TAN) removal rate of 85.1%, significantly outperforming molasses (77.0%) and glucose (62.9%), with microbial biomass also significantly higher than in the other groups. Metagenomic analysis indicated that sucrose promotes the formation of efficient denitrifying microbial communities by enriching the phylum Bacteroidota and the denitrifying functional bacteria Xanthomarina , thereby significantly enhancing denitrification efficiency. The optimal carbon source was determined to be sucrose. Using the optimal parameters of microbial biomass at 1.7 g/L, a hydraulic retention time of 36 h, and a chemical oxygen demand-to-total nitrogen (COD/TN) ratio of 26, the removal rates of total nitrogen (TN), TAN, and nitrite nitrogen (NO 2 − -N) exceeded 85%, while the removal rate of nitrate nitrogen (NO 3 − -N) surpassed 60%. A significant interaction was observed between microbial biomass and hydraulic retention time, which notably affected denitrification efficiency ( p < 0.05). This study provides theoretical support for the harmless and resourceful treatment of aquaculture effluent, contributing to the green and sustainable development of the aquaculture industry.