Maximum Allowable Temperature for Nitrification in Industrial Wastewater Treatment Plant – Model Based Evaluation

The temperature dependency of kinetic parameters in Activated Sludge Models (ASMs) is modeled using the Arrhenius equation. The Arrhenius equation leads to a directly proportional relationship between bacterial activity and temperature which is contrary to the observed inverse relationship at higher temperature above 35°C. The wastewater temperatures at industrial wastewater treatment plants are often higher than 35°C and in many cases necessitate external cooling for optimum biological treatment. In these situations, it is often desirable to minimize the cooling costs by operating the plants at as high a temperature as permissible for desired treatment objectives. To assess the effect of operational temperature above 35°C, it is important to develop an alternative kinetic parameter-temperature model which is applicable for a wider range of temperature. In this study a double Arrhenius model was developed and applied to an industrial wastewater treatment plant to estimate the maximum allowable temperature under various operation conditions. The proposed growth rate – temperature model is compatible with the presently used Arrhenius equation and requires only two additional parameters of Topt (optimum temperature) and θ2 (temperature coefficient at high temperature). Based on the simulation results for a specific industrial wastewater treatment plant, it was established that the operational temperatures as high as 38°C - 42.5°C may be allowed (depending on the plant operational conditions) to achieve the desired nitrification performance at the plant