Nitrogen removal and mass balance in newly-formed Myriophyllum aquaticum mesocosm during a single 28-day incubation with swine wastewater treatment

Abstract

The aim of this research was to assess the applicability of Myriophyllum (M.) aquaticum for swine wastewater treatment. Nitrogen (N) removal processes were investigated in M. aquaticum mesocosms with swine wastewater (SW), 50% diluted swine wastewater (50% SW), and two strengths of synthetic wastewater, 200 mg NH4+-N L−1 (200 NH4+-N) and 400 mg NH4+-N L−1 (400 NH4+-N). During a 28-day incubation period, the average NH4+-N and TN removal rates were 99.8% and 94.2% for 50% SW and 99.8% and 93.8% for SW, which were greater than 86.5% and 83.7% for 200 NH4+-N, and 73.7% and 74.1% for 400 NH4+-N, respectively. A maximum areal total nitrogen (TN) removal rate of 157.8 mg N m−2 d−1 was found in M. aquaticum mesocosms with SW. During the incubation period, the observed dynamics of NO3−-N concentrations in water and gene copy numbers of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), nirK and nirS in soil unraveled strong nitrification and denitrification processes occurring in M. aquaticum mesocosms with swine wastewater. The N mass balance analysis indicated that plant uptake and soil N accumulation accounted for 17.9–42.2% and 18.0–43.8% of the initial TN load, respectively. The coupled nitrification and denitrification process was calculated to account for, on average, 36.8% and 62.8% of TN removal for 50% SW and SW, respectively. These findings demonstrated that the N uptake by M. aquaticum contributed to a considerable proportion of N removal. In particular, the activities of ammonia-oxidizing and denitrification microbes responsible for nitrification and denitrification processes in M. aquaticum mesocosm accelerated NH4+-N and TN removal from swine wastewater.