THE EFFECT OF PARTICULATE ORGANIC-MATTER ON BIOFILM NITRIFICATION

The effects of particulate and soluble organic matter (BOD) on nitrification were investigated in laboratory experiments using a bench-scale rotating biological contactor (RBC). This work was initiated by lower than expected nitrification rates in the second stage biofilm processes at the Longmont Waste Water Treatment Plant (LWWTP). It was hypothesized that this was due to particulate matter since soluble BOD in the influent was low. For a range of 12 and 82 mg/ L total BOD to the pilot RBC; particulate BOD was found to inhibit nitrification to the same degree as soluble BOD. In fact, total (soluble plus particulate) influent organic matter was found to be a better predictor of nitrification than soluble organic matter concentration. The inhibition of nitrification by particulate BOD suggests that clarified influent should be used for nitrifying biofilm processes, total BOD < 20 mg/L. Trough dissolved oxygen profiles were not correlated to nitrification.