Screening and characterization of an Alcaligenes sp. HHVWA23 and the efficiency of nitrogen removal by biochar immobilization.

Nitrogen pollution in water environments is increasingly severe, and green microbial nitrogen removal has gained significant attention because of its high efficiency, safety, low cost, and eco-friendliness. A strain HHVWA23 with heterotrophic nitrification aerobic denitrification (HNAD) capabilities was isolated from an aquaculture environment and identified as Alcaligenes sp. The removal efficiencies for total-nitrogen (TN), ammonia-nitrogen (NH-N) and nitrite-nitrogen (NO-N) were 99 %, 98 % and 89 %, respectively. The bacterium was encapsulated using bamboo powder, chitosan, and carboxymethyl cellulose through immobilization technology. Two different concentrations of bamboo powder were tested to optimize the carbon source requirements, enhancing the strain's environmental adaptability. The efficiency of nitrogen removal under temperature from 18 to 34 °C, C/N ratio from 2.5 to 20, and salinity from 10 to 50 over 85 %. After 30 days of storage or 3 cycles of reuse of bamboo-powder-microbial-microcapsule (BP-MM) the nitrogen removal rate reached 93 %. Furthermore, the nitrogen removal efficiency in both aquaculture and domestic wastewater was higher than the free HHVWA23, and 2 % BP-MM could completely remove nitrogen from the wastewater. This study successfully developed BP-MM with outstanding performance in colonization, stability, nitrogen removal, and environmental adaptability, thus providing valuable technical support for mitigating nitrogen pollution in aquatic environments.