PURPOSE: To remove ammonia without the necessity for post treatment by using as an adsorbent for ammonia-containing gas a material obtained by heating peat or humus soil containing humic substances in the presence of moisture and an oxidant.

CONSTITUTION: Prior to the operation of the degassing tower 2, the adsorbent 8A is heated to approx. 70°C by the heating pipe 9A, and air is passed through the blower 4 and the pipe 12, mixed with hydrogen peroxide from the pipe 13, and i- troduced into the adsorption tower 7A to oxidize the surface of humus. Waste water generated in washing gas from the thermal decomposition of urban wastes is charged into the inlet pipe 1 and also air is supplied from the pipe 5 of the blower 4 into the lower part of the degassing tower 2. While the air goes up in bubbles in the waste water, it deprives the waste water of its ammonia to become waste gas containing ammonia which is, in turn, is sent to the adsorption tower 7A or 7B where ammonia is adsorbed and removed.