Evaluation of ammonia emission from dairy manure leachate after solid-liquid separation during mesophilic aeration

This study was conducted to investigate the digestion characteristics and to evaluate ammonia emission on the dairy manure leachate after solid-liquid separation during mesophilic aerobic digestion. Aerobic digestion was carried out following the recommended criteria for livestock manure resource management. Dairy manure leachate after solid-liquid separation was uniformly mixed and diluted to approximately 10,000 ppm based on the biological oxygen demand (BOD) criterion, and no mixing was performed at 39°C. Aeration was set at 0.03 m3 air/m3 /min, and the daily water loss due to evaporation was replenished at a similar temperature to the liquid. Temperature, pH, ammonia gas production, COD, suspended solids (SS), total nitrogen (TN), total phosphorus (TP), and total potassium (TK) contents were measured and analyzed during the experimental periods. The statistical analysis of the research results was conducted using in SAS MIXED PROC, and significance was tested at p < 0.05. During the 30-day aerobic digestion of dairy manure leachate, the pH increased from 7.6 to 8.2, ammonia levels increased until the 7th day and then gradually decreased until the 30th day, and COD decreased by approximately 88%, SS by approximately 79%, TN by approximately 71%, TP by approximately 22%, and TK by approximately 25%. In this study, it is predicted that aerobic digestion of dairy manure leachate, following the recommended BOD criteria (10,000 ppm) for livestock manure resource management, would excrete approximately 136.44 mg/m2 of ammonia and produce liquid compost with an organic matter content of around 20%.