A series of laboratory experiments were carried out to investigate particle separation efficiency and flotation characteristics using CO2 bubbles. The primary objective of this study was to discover the feasibility of CO2 bubbles as an applicable unit of flotation process in water and wastewater treatment plants. Fundamental measurements were conducted to characterize the CO2 bubble from the physical viewpoint in water, including bubble size distribution and zeta potential under various operational conditions. In addition, the removal efficiency of solids was experimented using laboratory scale plant applied CO2 bubbles, namely the dissolved carbon dioxide flotation (DCF) process. CO2 bubble diameter was a little larger than air bubble diameter and macro-bubble numbers increased considerably above 202.65 kPa saturator pressures. The CO2 bubble demonstrated a little higher electrical charge in a typical pH range. This study confirmed the feasibility of CO2 bubbles in the flotation process for water treatment, as a part of reducing greenhouse gas emission. Further study is positively necessary to reduce the CO2 bubble size (larger than the air bubble size) and to prevent the formation of macro bubbles causing the reduction of water treatment efficiency, especially.