How Powdered Activated Carbon (PAC) works.
Activated carbon is an effective adsorbent with wide environmental applications such as in the treatment of drinking water, wastewater, contaminated soil and groundwater. Powdered activated carbon (PAC) was used for the first time in drinking water to remove undesirable odor and taste. Recently, the use of PAC has been considered for wastewater treatment application in both pilot and full-scale for the elimination of micropollutants. The use of powdered form of activated carbon is more preferable since combination of small particle size and longer contact time leads to high surface loading and adsorption sites.
PAC has a high adsorption capacity of organic matter and can thus adsorb pharmaceutical residue and other micropollutants. Just one gram of activated carbon has a surface area between 500 and 1200 m2, depending on the quality of the carbon and has the best effect on larger molecules and less polar substances. Several factors affect the removal of micropollutants by PAC adsorption. This includes hydrophobicity of the compound and the nature and concentration of the dissolved organics in the wastewater matrix. The high amount of dissolved organics decrease the efficiency of PAC adsorption. Hydrophilic or polar compounds, due to their low octanol-water partition coefficient, are adsorbed to activated carbon at very low level.
PAC is activated through incineration. The used activated carbon, that has adsorbed the micropollutants, needs to be separated, collected and then sent for destruction or re-activation. This is a process that require a lot of energy and has a substantial environmental footprint.