An anoxic/oxic submerged constructed wetlands process for wastewater treatment: Modeling, simulation and evaluation

• An anoxic/aerobic wetlands system was developed for purifying wastewater.
• The influences of many factors on the pollution removal rate were measured.
• A mathematical model was used to describe the purification process.
• The model parameters were calculated using experimental datum fitting.
• Sensitivity analysis was performed for the evaluation of operation conditions.

An innovative anoxic/oxic (A/O) constructed wetlands (CWs) system was applied to remove the nutrient substrate in wastewater, and mathematical modeling for organic degradation, nitrification and denitrification in this system was then developed. A sensitivity analysis was performed for the parameters and operating conditions, and found that the treatment efficiency is affected by the organic loading rate, temperature, and recycling rate. Furthermore, actual measurements were used for calibration of the model. Its parameters were determined by fitting experimental data under various conditions, and the predictions of the simulation correlate well with the experimental observations. These model and simulation techniques were applied to evaluate and design the A/O wetland system. The results indicate that the removal rates of COD and nitrogen are above 95% and 50%, respectively. The flow rate does not affect the removal rate of the substrates, and a higher influent COD or lower ammonia concentration results in a better efficiency in the purification rate. The nitrogen removal rate could be improved by optimizing the interaction between the recycle rate and the influent ammonia.

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