Abstract
An aerobic nitrite-denitrifying bacterium Pseudomonas putida Y-12 was used to remove sole and mixed nitrogen sources at 15 °C. When strain Y-12 was incubated for 4 days with a sole nitrogen source and initial NH4+-N, NO3−-N, and NO2−-N concentrations of 208.1, 204.7, and 199.0 mg/L, respectively, the removal ratios of NH4+-N, NO3−-N, and NO2−-N were 98.8, 73.6, and 77.1%, respectively. The average removal rates of NH4+-N, NO3−-N, and NO2−-N reached 2.14, 1.57, and 1.60 mg/L/h, respectively. Intermediate products (NO3−-N and NO2−-N) were detected at a low level. Total nitrogen removal was mainly achieved during the stationary phase in the denitrification process. All the results indicated that strain Y-12 could perform heterotrophic nitrification and aerobic denitrification at 15 °C, which was beneficial for future applications in wastewater treatment at low temperatures.
Highlights
Human activities, such as excessive use of artificial fertilizer, excessive throwing of fish feed, and improper discharge of livestock waste or industrial effluents, lead to nitrogen accumulation in water environments [1,2]
Alcaligenes faecalis NR [15] was only able to oxidize NO2 − -N to NO3 − -N instead of denitrifying it to nitrogenous gas. These results might be ascribed to the denitrifying enzyme activity, which was not activated or lacking, and a similar result was reported in Acinetobacter calcoaceticus HNR [12]; neither periplasmic NR nor cd1-type NiR activity was detected under aerobic conditions by strain HNR
NH4 + -N was removed in the presence of other nitrogen sources at low temperatures
Summary
Human activities, such as excessive use of artificial fertilizer, excessive throwing of fish feed, and improper discharge of livestock waste or industrial effluents, lead to nitrogen accumulation in water environments [1,2]. Excessive nitrogen in water bodies may do harm to both aquatic life and human beings. More and more bacteria with abilities of heterotrophic nitrification and aerobic denitrification (HN-AD) have been reported since Roberson firstly separated the aerobic denitrifier [9,10,11,12]. These bacteria could realize nitrification and denitrification occurring in one aerobic system, and balance the alkalinity produced via
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