Assessing the influence of pronounced diurnal temperature variations in nontemperate zones on the denitrification/nitrification rate using the COST Benchmark activated sludge model no. 1 simulation

Activated sludge plants are usually designed using formulae based on fixed wastewater temperatures. In some nontemperate zones, these procedures may need altering, particularly for areas that experience large diurnal and seasonal temperature variation such as in desert or high-altitude environments. This study investigates these temperature effects on the denitrification/nitrification rate by utilising the COST Benchmark activated sludge model no. 1 (ASM1) simulation model. The COST Benchmark was developed under the European Cooperation in Science and Technology programme Action 624 which specifically focused on the Optimal Management of Wastewater Systems. Various simulations and associated control strategies were carried out using gPROMS software package (Process Systems Enterprise Limited, London, UK) to ascertain the following: any likely nutrient removal implications; use of a nitrate and/or ammonia sensor coupled to a strategy to change the solids loading inventory to minimise falls in nitrification rate during night time hours; and changes to controller set point levels during the day and night to reflect diurnal load, flow and temperature variations using a temperature-dependent control algorithm. It was found that inclusion of temperature dependency in simulation models may prove beneficial when designing plants located in these regions.