Biofilm nitrification: The effects of soluble and particulate organic matter and hydraulic regime

Ammonia can be toxic to aquatic life, cause eutrophication of surface waters and oxygen depletion in streams, rivers, and lakes. Ammonia is a component in wastewater not usually removed by conventional secondary treatment processes and thus must be removed in an additional step prior to discharge to protect surface receiving waters. An inexpensive process that can be integrated into biological waste treatment plants is bacterial nitrification. Organic matter and hydraulic regime are two important factors that affect biological ammonia oxidation (nitrification), and the effects of these parameters on biofilm nitrification have not been quantified satisfactorily for application to wastewater treatment plant operation.; The effects of soluble and particulate organic matter and hydraulic regime on biofilm nitrification were investigated in laboratory experiments using a pilot-scale rotating biological contactor (RBC) and in field experiments using two pilot-scale trickling filters. This research was conducted from October 1987 through April 1989. On the basis of these experiments, mathematical models of RBC and Trickling filter biofilm nitrification were developed and calibrated.; While previous investigators only considered influent soluble organic matter important for the design of biofilm nitrification processes, particulate organic matter (recycled biofilm solids) was found to inhibit nitrification to the same degree as soluble organic matter. In fact, total (soluble plus particulate) influent organic matter was found to be a better predictor of nitrification than soluble organic matter concentration alone. As part of the modeling process macroscopic ammonia removal kinetic coefficients have been developed that included the inhibitory effect of organic matter for both the RBC and trickling filter processes. Also trickling filter length and hydraulic loading effects on nitrification performance have been quantified.