Abstract
Fundamental characteristics of the bark as an adsorbent for ammonia removal were experimentally explored. Packing media in the bark bed at a sewage sludge composting plant, which consists of 80% of bark and 20% of compost, was used in this study. Saturated adsorption amount of ammonia under static condition was 2900 mg/100g-dry for moist bark and 420mg/100g-dry for dry bark. Required contact time of ammonia with the bark for adsorption is short since 90 to 96% of ammonia is adsorbed immediately after exposure to the bark. A large part of ammonia adsorbed on the bark was detected as ammonia nitrogen in the extracted liquid of the bark and it decreased gradually since chemical reaction with organic component of the bark in the first stage and subsequently nitrification might have occurred. Nitrite and nitrate nitrogen in the extracted liquid might have been denitrified under anaerobic condition partially formed in the bark and resulted in the gradual decrease. Removal rate of ammonia nitrogen and nitrite and nitrate nitrogen reached the maximum of 0.087mg NH3-N/h·g-dry and 0.38 mg NO2,3-N/h·g-dry, respectively.
