Characteristics of Ammonia in Alkaline Stabilization Facility of Sludge from Sewage Treatment Plant

Abstract

The characteristics of ammonia generated from alkaline stabilization facilities was investigated which are for organic sewage sludge from wastewater treatment plants.The highest concentration of ammonia was found in mixing and curing process in alkaline stabilization facility and ammonia mainly showed a range of 87.78 ppm(66.62 mg/㎥) to 1,933 ppm(1,467.01 mg/㎥) by detection tube. This is presumed to occur because nitrogen oxides are converted into ammonia as the sewage sludge is mixed with lime. In some facilities, hydrogen sulfide and methyl mercaptan were detected in relatively high concentrations, but odor materials except ammonia were not detected in most of the facilities.The concentration of ammonia caused by process was generally high in the order of "mixing > curing > output > storage > drying > input."It was found that odor compounds are removed by wet absorption using sulfuric acid and sodium hypochlorite in the 5 alkaline stabilization facilities currently in operation. Each facility was designed to meet the concentration of after-treatment emission in 1 ppm(0.76 mg/㎥), 50 ppm(37.95 mg/㎥) or 100 ppm(75.89 mg/㎥), but no facility satisfied the design standard for their emssion limit.In case of ammonia, some workplaces in alkaline stabilization facilities exceeded the exposure limits established by the Ministry of Labor. It appears that proper ventilation should be provided for the safety of workers in future. No odor compound including ammonia was found by detection tubes in the border of the facilities, but trace amounts of odor compounds are expected to exist, given the current operational status of facilities.