Strategies to improve the efficiency of tertiary nitrifying trickling filters

The long term effects of the conditions for a biofilm reactor are governed by slow microbial processes, such as the growth and decay of the bacteria. Simulations of a trickling filter model based on a multi species dynamic bi ofilm model and data from an experiment, where an NTF had been alternatingl y fed unnitrified and completely nitrified wastewater, agree fairly well. T wo different operating strategies of NTFs are studied by simulation: period ically inversing the order of two NTFs in series and varying the flow th ro ugh NTFs operating in parallel. The simulations indicate that both strategi es have a potential of increasing the nitrifying capacity of filters operat ing at low ammonium load, provided the influent concentrations of organic m atter are low. However, to what extent the capacity is increased depends on the specific death rate of the nitrifiers, which needs to be further studi ed.