Effects of Different Nitrogen Sources and Environmental Factors on the Nitrogen Removal Performance of Bacillus hwajinpoensis SLWX2

Abstract:

Bacillus hwajinpoensis SLWX2 is a bacterium strain isolated from maricultural environments that can effectively remove NH4+-N, NO2–-N, and NO3–-N from water. In this study, the effects of different nitrogen sources (NH4+-N, NO2–-N, and NO3–-N) and environmental factors (temperature, pH, C/N, and salinity) on growth and nitrogen removal were studied. The results showed that the growth of Bacillus hwajinpoensis SLWX2 was consistent with the removal of the three forms of inorganic nitrogen, which occurred mainly in the logarithmic growth phase. There was no delay in growth of the bacterial cells and NH4+-N removal, and no NO2–-N nor NO3–-N was produced when NH4+-N was used as the sole nitrogen source. Further, there was no accumulation of NH4+-N and NO3–-N when NO2–-N was used as the sole nitrogen source, but there was a long delay in growth and NO2–-N removal. NH4+-N was not detected, but NO2–-N first accumulated and then decreased when NO3–-N was used as the sole nitrogen source. The experimental results showed that the effects of the environmental factors on the growth of SLWX2 correlated with its ammonium removal function. The strain showed good growth and ammonium removal performance under the conditions of weak acids, neutral, and weak bases (pH 6~8.5), temperature 28~40℃, C/N 5~25, and NaCl 0~30 g/L. The optimal conditions for SLWX2 were temperature of 30℃, C/N 25, pH 8.0, and salinity 25. The strain SLWX2 showed high efficiency in removing NH4+-N, NO2–-N, and NO3–-N in water, and it has a wide adaptation range to environmental conditions, which suggests its huge potential in bio-removal of nitrogen in waste water from industries and aquaculture.