Nitrification of Potable Water Using Trickling Filters

Abstract Due to the nitrogenous oxygen demand and the carcinogenic chloramines that are formed, ammonia needs to be removed from potable water before it can be consumed. Ammonia may be removed chemically or biologically. Biological ammonia removal (nitrification) is carried out by two different nitrifying bacteria, Nitrosomonas and Nitrobacter . Due to the low specific growth rates of these bacteria, high nitrification rates can be secured only in attached growth systems such as trickling filters. This allows retaining the slow‐growing nitrifiers even at high hydraulic loadings. The choice of filter medium is of great importance because it provides the surface for bacterial growth and determines the air and water flow characteristics of the filter. Recirculation may enhance nitrification in trickling filters for high hydraulic and ammonia loads, whereas iron and manganese inhibit nitrification. Modeling of nitrification in trickling filters allows proper design of the filters and prediction of their performance. Such mathematical models have been used to develop operating diagrams that may be used to ensure safe and complete nitrification of potable water for a wide range of flow rates and ammonia feed concentrations.