Dynamic temperature changes in wastewater treatment plants

Biological treatment processes, especially nitrification and denitrification, are very sensitive to temperature changes lower than 10°C. Short-term temperature changes occur frequently in many areas of the world, such as Northern Europe. To aid in the design and optimization of treatment plants, a dynamic model has been developed. The model predicts the hourly temperature in biological treatment tanks within 0.5 °C over a 1-month period when the hydraulic residence times range between 12 and 36 hours. Use of the model requires only the initial temperature in the treatment tank, 6- hour values for the meteorological parameters, and the hourly influent temperature. The major finding is that the temperature variation is very dependent on local wind conditions, which can be modified by windbreaks or (more expensively) by tank covers. The model can be used for quantitative calculations in the design process to minimize temperature drops during cold weather periods and, thus, reduce the required tank volumes.