Abstract: A method for accelerating the startup of biological nitrification systems for wastewater treatment and preventing or reducing the effects of toxic or inhibitory materials or excursions of pH, temperature or dissolved oxygen upon nitrifying organisms. A rapidly metabolized soluble or miscible organic material containing little or no nitrogen is added to the carbon-consuming step of the process. Heterotrophic organisms consume the added material together with soluble ammonia to generate additional organisms. The soluble ammonia concentration in the wastewater is reduced to a non-toxic, less toxic, or less inhibitory level.