1. Description and working principle InNitri® (Inexpensive Nitrification) is a new, side stream nitrification process offered by Mixing & Mass Transfer (M2T) Technologies, Inc. It allows nitrification at short SRT values, even at low winter temperatures and provides nitrification in a substantially smaller aeration tank than is required for conventional nitrification design. The InNitri® process was developed to provide an inexpensive alternative for plants in northern climates that need to upgrade their air or pure oxygen activated sludge process for year-round nitrification or nitrogen removal (MT 2002).