Removal of carbon, nitrogen, and phosphorus in pig manure by continuous and intermittent aeration at low redox potentials

A laboratory experiment was conducted to study the effect of intermittent and continuous aeration at an airflow rate of 0.0667 l min(-1) l(-1) of manure on redox potential, pH, organic carbon, total Kjeldahl nitrogen (TKN), ammonium nitrogen (NH4+-N) and soluble orthophosphate. Results showed that aeration at this rate could not bring redox potential up to truly aerobic level. A reduction of 24 and 26.4% in TKN and organic carbon, respectively, was observed during the continuous aeration process. The continuous aeration at this airflow rate also reduced the initial NH4+-N by 32.3%. Intermittent aeration was approximately as half as efficient in 4 removal of organic carbon, TKN and NH4+-N as the continuous aeration. However, within a 24 h aeration period, 75% of soluble orthophosphate was removed from solution for both treatments, suggesting that the phosphorus removal efficiency was independent of aeration schemes, so energy could be saved while still maintaining the removal efficiency. (C) 2002 Silsoe Research Institute. Published by Elsevier Science Ltd. All rights reserved.