Sludge treatment plays an important role in the treatment of wastewater. The production of sludge from wastewater treatment by the activated sludge method is relatively high, which causes problems in the treatment and disposal processes. The main purpose of sludge treatment is to reduce its water content, in addition to the prevention of pollution of the environment; one method of the activated sludge treatment methods is "Thickening by Floatation", which could reduce the water content of the sludge, facilitating the disposal process. In the present study, the floatation method is used to increase the sludge solid content by bubbles of carbon dioxide, which is directly prepared from sodium bicarbonate and hydrochloric acid, without the use of pressurized CO2, which results in the floatation of activated sludge solid particles. A floatation cell, composed of a glass column with a square base (13.5 x 13.5 cm) and height (50 cm), is used. The quantity of sodium bicarbonate ranged from 5 to 6.5 g/L; and that of the hydrochloric acid (10% concentration) ranged from 10 to 13 mL/L. The efficiency of this system was discussed with varying parameters, such as chemicals addition and initial solid content of sludge. The floatation cell showed a good result, regarding the increasing of the thickened sludge by floatation, from (0.6-1.1) % of solid content to (3.25-4.75) %; in addition, the current study has also shown better results, compared to the conventional pressurized CO2 cell.