Abstract
Waste streams with high ammonia nitrogen (NH3-N) concentrations are very commonly produced due to human intervention and often end up in waterbodies with effluent discharge. The removal of NH3-N from wastewater is therefore of utmost importance to alleviate water quality issues including eutrophication and fouling. In the present study, vacuum thermal stripping of NH3-N from high strength synthetic wastewater was conducted using a rotary evaporator and the process was optimized and modeled using response surface methodology (RSM) and RSM–artificial neural network (ANN) approaches. RSM was first employed to evaluate the process performance using three independent variables, namely pH, temperature (°C) and stripping time (min), and the optimal conditions for NH3-N removal (response) were determined. Later, the obtained data from the designed experiments of RSM were used to train the ANN for predicting the responses. NH3-N removal was found to be 97.84 ± 1.86% under the optimal conditions (pH: 9.6, temperature: 65.5 °C, and stripping time: 59.6 min) and was in good agreement with the values predicted by RSM and RSM–ANN models. A statistical comparison between the models revealed the better predictability of RSM–ANN than that of the RSM. To the best of our knowledge, this is the first attempt comparing the RSM and RSM–ANN in vacuum thermal stripping of NH3-N from wastewater. The findings of this study can therefore be useful in designing and carrying out the vacuum thermal stripping process for efficient removal of NH3-N from wastewater under different operating conditions.
Highlights
Nitrogen (N) is an indispensable element for all living organisms and a fundamental component of animal and plant proteins
No additional organic carbon source was added to the synthetic wastewater as the primary focus of the study was to check the feasibility of employed process in efficient ammonia removal and recovery from wastewater without any losses
This study showed less significant effect of pH and stripping time compared to temperature on NH3 -N removal, which are in line with earlier findings [30,67]
Summary
Nitrogen (N) is an indispensable element for all living organisms and a fundamental component of animal and plant proteins. Vacuum decreases the normal boiling point temperature, fortifies liquid–gas phase NH3 mass transfer and results in an enhanced NH3 stripping This process has a few issues, such as that water vapor from the evaporating flask can either be condensed in the acid solution or leave the system through vacuum exhaust [30]. In comparison to other NH3 -N removal processes from wastewater, the vacuum thermal stripping is relatively new, and an optimization of the process parameters is needed to ensure effective and efficient NH3 -N removal and recovery. The present study was focused on the vacuum thermal stripping process for NH3 -N removal from synthetic wastewater using a rotary evaporator. To the best of our knowledge, this is the first attempt comparing the RSM and RSM–ANN approaches in the vacuum thermal stripping process for NH3 -N removal from wastewater
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