Graduation Year

2023

Document Type

Thesis

Degree

M.S.E.V.

Degree Name

MS in Environmental Engr. (M.S.E.V.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Mauricio E. Arias, Ph.D.

Committee Member

Sarina J. Ergas, Ph.D.

Committee Member

Mahmood Nachabe, Ph.D.

Keywords

adsorption media, ammonia nitrogen, landfill leachate treatment, process-based numerical model, sub-surface flow wetland

Abstract

Due to their efficiency in removing ammonia nitrogen, Constructed Wetlands (CW) are currently considered a very useful method for on-site leachate treatment. In recent years, the use of adsorbent media in CWs, such as zeolite and biochar, to improve pollutant removal efficiency has been explored and these studies indicate that incorporating zeolite can improve the nitrification process, while the addition of biochar can enhance the denitrification process and the removal of organic compounds. However, studies on mechanistic/process models simulating performance of adsorbent-amended CWs for treating landfill leachate are limited. This study presents simulation results for both unamended and adsorbent-amended hybrid subsurface flow CW systems using a continuously-stirred-tank-reactor-in-series model for ammonia nitrogen and COD removal. The numerical process model is developed in Python 3.7 and is calibrated and validated with data collected from a pilot-scale system operated in Hillsborough County Landfill, Florida. The model considers changes in water storage, nitrogen transformations, COD removal, DO cycling, effects of temperature and enhancement effects for zeolite and biochar. Model parameters that could not be found in the literature were obtained by model optimization. A parameter sensitivity analysis was done before model calibration and normalized root mean square error (NRMSE) was used for calibration metric. The low NRMSE values (below 0.3) achieved for effluent’s Ammonia Nitrogen and COD demonstrated the model’s sufficient capacity to simulate the effluent concentrations under varying conditions. The error in predicting pollutant removal efficiency was less than 13.3% and 3% for unamended system and adsorbent-amended system respectively. In addition, the model was scaled up to evaluate the removal efficiency for a large-scale system using the Southeast Hillsborough County Landfill in Lithia, Florida as a case study. The landfill produces 118680 tons of landfill leachate per year (86,0000 gallons per day) containing high total ammonia nitrogen (average 366 mg/L) and COD concentration (average 473 mg/L). Using total VF-CW area of 98,000 m2 and HF-CW area of 294,000 m2, the removal efficiency for the adsorbent-amended full-scale system was predicted to be 99.2% for ammonia nitrogen and 35.9% for COD.

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