Nitrification and denitrification potential associated with semi-permeable swine waste lagoon covers

Abstract

Ammonia emission from swine waste lagoons presents a serious environmental challenge to pork producers. One promising control is the use of semi-permeable lagoon covers which act to limit ammonia emissions by minimizing the effect of wind on the lagoon surface. These lagoon covers may also act as an attachment site for biofilm development, but microbial analysis of the cover technology is needed to validate their usefulness. Samples of mature cover and its associated biofilm and lagoon wastewater liquids were collected from three swine waste sites, and their potential nitrifying and denitrifying activities were compared to new cover material in laboratory aerobic and anaerobic incubations. Potential nitrification activity for the mature cover samples ranged from 0 to 1.6 mmoles NO2- m-2 d-1 during a 24-hour period, whereas new cover (no biofilm) and negative (no inoculum) control samples produced no nitrite in the three experiments. Lagoon wastewater samples had limited nitrification potential and produced from 0 to 0.5 mmoles NO2- m-2 d-1 (5 L volume for comparison). Potential denitrifying activity (measured over 8 days) for the mature cover samples consumed from 2.0 to 3.7 mmoles NOx- (NO3-+ NO2-) m-2 d-1. No nitrate or nitrite was consumed in the new cover or negative control samples, whereas microorganisms in the wastewater consumed from 0 to 2.9 mmoles NOx- m-2 d-1. We conclude that the semi-permeable cover served as a useful support for the production of a beneficial biofilm community with the capacity to transform NH3 to N2 via a coupled nitrifying and denitrifying process.