Nitrogen removal performance and bacterial communities in zeolite trickling filter under different influent C/N ratios.

In this study, the degradation performance of nutrients in zeolite trickling filter (ZTF) with different influent C/N ratios and aeration conditions was investigated. Microaeration was beneficial for enhancing NH-N removal performance. Due to the sufficient carbon source supply under a C/N ratio of 8, a high removal efficiency of NH-N and TN was simultaneously observed in ZTF. In addition, TN removal mainly occurred at the bottom, which might be explained by the sufficient nutrients available for bacteria to multiply in this zone. The abundant genera were Acinetobacter, Gemmobacter, Flavobacterium, and Pseudomonas, all of which are heterotrophic nitrification-aerobic denitrification (HNAD) bacteria. In addition, biofilm only slowed down the adsorption rate but did not significantly reduce the adsorption capacity of zeolite. Bio-zeolite had NH-N well adsorption capacity and bio-desorption capacity. Biological nitrogen removal performance was superior to physicochemical absorption of zeolite. The results suggested that the physicochemical of zeolite and biochemical reactions of microorganism coupling actions may be the main nitrogen transformation pathway in ZTF. Our research provides a reference for further understanding the nitrogen removal mechanism of zeolite bioreactors.