Identification and denitrification characteristics of heterotrophic nitrification and aerobic denitrification strain U1 resistant to high concentrations of ammonia nitrogen

Abstract:

[Background] Municipal waste leachate is a kind of complex organic wastewater with high nitrogen content, which can causes serious environmental pollution if discharged directly into the environment. [Objective] To select heterotrophic nitrifying and aerobic denitrifying (HN-AD) strains that can tolerate high concentration of ammonia nitrogen in waste leachate and efficiently remove nitrogen from wastewater, and thereby provide functional strains to address nitrogen pollution in urban wastewater. [Methods] The strains that could tolerate high concentration of ammonia nitrogen were isolated from the waste leachate, and a strain with the strongest denitrification capacity was screened out and named U1. Based on 16S rRNA gene sequencing and physiological and biochemical characteristics, U1 was identified as Pseudomonas aeruginosa. Then we further investigated nitrogen removal ability of U1 in the presence of ammonia nitrogen of different initial concentration and different carbon sources, and at different rotation speeds, initial pH, and carbon-to-nitrogen ratios, and explored the optimal nitrogen removal conditions of U1 in combination with L₉(3⁴) orthogonal test. [Results] U1 with strong denitrification ability was isolated and the optimum denitrification conditions for this strain are as follows: ammonia nitrogen at initial concentration of 1 000 mg/L, mixed carbon source of brown sugar+ trisodium citrate, pH of 6.0, carbon-to-nitrogen ratio of 10, and rotation speed of 130 r/min. Under the optimum conditions, the maximum total nitrogen removal rate of U1 was 64.37% and the maximum ammonia nitrogen removal rate was 76.73%. For the waste leachate with total nitrogen and ammonia nitrogen amount of 2 345 mg/L and 1 473.8 mg/L, respectively, the maximum removal rate of total nitrogen by U1 was 27.86% and the maximum removal rate of ammonia nitrogen was 21.32%. [Conclusion] U1 can be used to treat wastewater with high-concentration ammonia nitrogen.