Abstract:
Abstract: In order to study the characteristics of ammonia (NH3) emission and the variation of its chemical properties under different wind speeds, an equipment for storing biogas slurry and monitoring the NH3 volatilization was designed. Sampling and monitoring of ammonia gas by using forced aeration method, this equipment was used to investigate the NH3 volatilization and degradation of total nitrogen (TN), chemical oxygen demand (COD) of biogas slurry under the wind speeds of 0 (confined storage, WS0), 1 m/s (gas flow 32.33 m3/h, WS1), and 2 m/s (gas flow 65.72 m3/h, WS2). Results showed that the NH3 volatilization of chicken manure biogas slurry showed similar patterns in three wind speed conditions, which increased during the early period followed by decreasing, and all reached their peaks on the 12th day, being of 2.28, 4.42 and 7.21 g/(m2·d), respectively. The total amount of ammonia volatilization during storage is 1.80, 3.90 and 7.12 g, respectively. The temperature of the biogas slurry fluctuated within the range of 13-24 ℃ during the storage, and this temperature fluctuation trend is similar to the changing trend of room temperature for all three conditions. The initial pH value of the chicken manure biogas slurry was 8.38, showing a weak alkalinity. During the storage process, the pH values of WS0, WS1, and WS2 increased continuously, and reached 9.17, 8.82, and 8.92 at the end of storage. The nitrogen element in the chicken manure biogas slurry was mainly kept in the form of ammonium nitrogen, which accounted for 84.99% of the total nitrogen content at the beginning of the test. The concentrations of ammonium nitrogen showed an increasing pattern firstly, and reached their peaks in the seventh day, being of 3 451.27, 3 562.60, and 3 582.67 mg/L, then followed by decreasing, being of 3 030.20, 2 762.67, and 2 794.87 mg/L at the end of the storage. The decline percentages of the ammonium nitrogen were 7.64%, 15.79%, and 14.81% in three conditions, respectively. The declines of TN and COD were positively correlated with the wind speed. The TN content of the biogas slurry decreased by 10.97%, 18.95%, and 25.83%, and the COD concentration decreased by 10.38%, 18.61%, and 20.35%, for WS0, WS1and WS2, correspondingly. Together, these results provide evidence for designing reasonable storage environment of biogas slurry and NH3 mitigation measure.