Simple model for the prediction of ammonia volatilization from water basin: effect of water temperature and pH

Ammonia is a primary chemical used for preserving rubber latex. Consequently, the wastewater from concentrated rubber latex processing contains high ammonia concentration. The volatilization of ammonia from such wastewater may cause an air pollution problem such as the formation of an acid rain or an aerosol of ammonium nitrate and ammonium sulfate, which can seriously affect environment and human being. To assess the air pollution problem regarding atmospheric ammonia volatized from wastewater, the model for the prediction of ammonia volatilization rate and flux is therefore desirable. The purposes of this study were to investigate the effects of water temperature and pH on ammonia volatilization process and to develop a model to describe ammonia volatilization rate and flux including such effects.Ammonia volatilization from water was studied by using a volatilization tank (surface area = 780 cm2, volume = 7 L) placed in a water bath in order to control the water temperature. The temperature and pH in the range of 25 to 50ºC and 5 to 11 were respectively investigated. The overall mass transfer coefficients of ammonia were measured as a function of temperature and pH. The quadratic multiple regression technique was used to obtain the model for mass transfer coefficient from experimental data. The model suggests that the overall mass transfer coefficient of ammonia increases with increasing water temperature and pH while the temperature-pH interaction retards the increasing characteristic of mass transfer coefficient. Thus the increasing in mass transfer coefficient at higher temperature and pH was slower than that at the lower one. The simple model for the prediction of ammonia volatilization rate and flux was developed based on mass transfer theory and mass transfer coefficient model obtained from this study. This simple ammonia emission model can be used to predict ammonia volatilization rate and flux at any pH, water temperature and ammoniaconcentration in water