Arezoo Zangeneh - Department of Environmental Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran
Sima Sabzalipour - Department of Environmental Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran
Afshin Takdastan - Department of Environmental Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran
reza jalilzadeh yengejeh - Department of Environmental Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran
Morteza Abdullatif Khafaie - Department of Environmental Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran

This study evaluated the effects of different operating conditions and the air-to-water ratio (G/L) on the kinetics and the mass transfer coefficient of ammonia (KL) in the air stripping method for removing ammonium ions (NH۴+) from wastewater with low concentrations in municipal wastewater treatment plants (WWTPs). The impact of operating conditions including the temperature, initial ammonium ion concentration, pH, and air-to-water ratio (G/L) of <۲۰۰۰:۱ (۶۰:۱, ۷۰:۱, and ۸۰:۱) on KL in the air stripping method was investigated using artificial wastewater at laboratory scale. The NH۴+ concentrations in the wastewater samples were determined with the Nesslerization method (the standard method for the examination of water and wastewater). According to the results, the minimum (۰.۰۵۲۸ h-۱) and maximum (۰.۶۴۸۲۵ h-۱) of KL were obtained within ۱ to ۴ h in the operating status that included an initial ammonium ion concentration of ۳۳.۶۳-۵۲.۸۱ mg/l, a temperature of ۳۴-۴۵.۷ °C, a pH of ۹.۴۸-۱۲.۲, and an air-to-water ratio of ۶۰:۱-۸۰:۱. A comparison of the results of three regression models showed that the air-to-water ratio was the most effective factor on KL. Furthermore, in Model ۳ (multivariate linear regression model/comparing four parameters), the effects of the air-to-water ratio, pH, and temperature increased, leading to the acceleration and conversion of ammonium ions (NH۴+) to a gaseous form (NH۳). Also, the initial NH۴+ concentration and pH in Model ۴ (multivariate linear regression model by subgroup) at a low (۶۰:۱) and high (۸۰:۱) G/L ratio were the most influential factors on KL, respectively. The results of this study revealed that the air-to-water ratio (۶۰:۱, ۷۰:۱, and ۸۰:۱) could be used successfully for the elimination of ammonium ions from municipal WWTPs, leading to lower energy costs for the required aeration in the air stripping method.

Air stripping, Mass transfer coefficient, Ammonia, Air to water ratio, Municipal wastewater treatment plants