Characterizing the transformation and transfer of nitrogen during the aerobic treatment of organic wastes and digestates

The transformation and transfer of nitrogen during the aerobic treatment of seven wastes were studied in ventilated air-tight 10-L reactors at 35 °C. Studied wastes included distinct types of organic wastes and their digestates. Ammonia emissions varied depending on the kind of waste and treatment conditions. These emissions accounted for 2–43% of the initial nitrogen. Total nitrogen losses, which resulted mainly from ammonia emissions and nitrification–denitrification, accounted for 1–76% of the initial nitrogen. Ammonification was the main process responsible for nitrogen losses. An equation which allows estimating the ammonification flow of each type of waste according to its biodegradable carbon and carbon/nitrogen ratio was proposed. As a consequence of the lower contribution of storage and leachate rates, stripping and nitrification rates of ammonia nitrogen were negatively correlated. This observation suggests the possibility of promotingnitrification in order to reduce ammonia emissions.

► Ammonia emissions varied depending on the nature of wastes and the treatment conditions.
► Nitrogen losses resulted from ammonia emissions and nitrification–denitrification.
► Ammonification can be estimated from biodegradable carbon and carbon/nitrogen ratio.
► Ammonification was the main process contributing to N losses.
► Nitrification rate was negatively correlated to stripping rate of ammonia nitrogen.