A nitrogen transformation model for multi-layer enhanced groundwater remediation technology.

Area of Science:

• Environmental Science
• Water Treatment Engineering
• Biogeochemistry

Background:

• Ammonia nitrogen contamination poses a significant threat to groundwater quality and ecosystem health.
• Conventional remediation methods often face limitations in efficiency and sustainability.
• The multi-layer enhanced groundwater remediation technology (MET) offers an integrated approach combining physical, biological, and plant-based treatments.

Purpose of the Study:

• To investigate the nitrogen transformation mechanisms within the MET for ammonia nitrogen removal.
• To develop and validate a nitrogen transformation model for predicting the performance of MET.
• To assess the long-term effectiveness of MET in remediating ammonia nitrogen-contaminated groundwater.

Main Methods:

• Development of a nitrogen transformation model incorporating key variables (organic, ammonia, nitrate nitrogen) and processes (ammonification, nitrification, denitrification, assimilation, plant absorption, adsorption-desorption, volatilization).
• Calibration of unknown model parameters using data from bench-scale experiments.
• Validation of the model by comparing simulated effluent concentrations with measured values under specific operating conditions (hydraulic load: 14.68 m³/m²/d, initial ammonia nitrogen: 25.0 mg/L).

Main Results:

• The validated nitrogen transformation model accurately predicted ammonia nitrogen and nitrate nitrogen concentrations in the effluent, with relative deviations of 4.17% and 2.05%, respectively.
• Continuous operation of the MET for 45 days achieved a total ammonia nitrogen removal rate of 92.07%.
• Simulated and measured average ammonia nitrogen concentrations in the effluent were 1.701 mg/L and 1.775 mg/L, respectively.
• Simulated and measured average nitrate nitrogen concentrations in the effluent were 11.474 mg/L and 11.244 mg/L, respectively.

Conclusions:

• The developed nitrogen transformation model provides a reliable tool for forecasting the long-term remediation effects of MET on groundwater nitrogen.
• MET demonstrates significant efficacy in removing ammonia nitrogen from contaminated groundwater.
• The integrated approach of MET offers a promising solution for sustainable groundwater remediation.