In Vietnam, practical applications of biological methods in air pollution control are highly limited. This study evaluated and compared the ammonia removal performance in air of a cow-manure biofilter, commercial compost biofilter, and biotrickling filter with K3 biomedium cultured with attached microorganisms from activated sludge. The results indicated that with an inlet NH 3 concentration of 65-80 mg/m 3 (95-117 ppm), the treatment efficiency was highly promising with an output concentration

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... in the range of 2-5 mg/m 3 (3.0-7.5 ppm) and elimination capacity of 3-9 gNH 3 /m 3 .h. With an inlet concentration below 200 mg/m 3 , all three experimental models could remove ammonia to meet the emission standard (QCVN 19:2009/BTNMT) of 50 mg/m 3 . The study results indicated that the investigated biological technologies have potential for use in removing ammonia and other odorous gases in polluted air. This study investigated the removal of gaseous ammonia using cow manure, compost, and K3 material as biomedium in biofilters and biotrickling filters.