Do you know what GAC or granular activated carbon is? GAC or granular activated carbon is a hybrid mixture of diverse graphite platelets interconnected by non-graphitic carbon bonding. GAC has good adsorptive capacity which enables it to remove various contaminants from gases, liquids, air and water. Moreover, GAC is an eco-friendly product that is reactivated by thermal oxidation and is used for the same application for multiple times.
EPA or Environmental Protection Agency of the U.S. and other health departments regard that adsorption through GAC is the most effective technology for removing organic materials from surface water.
Production of Activated Carbon
Activated carbon is produced from varieties ofcarbon-rich materials like peat, coconut shells, woods, lignite, subbituminous coal, anthracite and bituminous coal. By chemical or thermal activation these materials get converted to activated carbon. In thermal treatment, steam gasificationis used and in chemical activation, inorganic reactive additives are used at a low temperature.
Adsorption by Granular Activated Carbon or GAC
How does the process of adsorption take place? When electronic structure of activated carbon which is the adsorbent interacts with some odor or taste causingsubstance like geosmin, then adsorption takes place. Porous surface of activated carbon kinetically attracts molecular compounds. GAC, when paired with UV disinfection system or by its own, is effective in removing the following –
- DBPs or Disinfection byproducts related to chlorine and other alternativedisinfectants.
- Organic materials produced from decaying plants or other natural matters that act as precursors for DBPs.
- Odor and taste causing compounds.
- Algal toxins like anatoxin-A, cylindrospermopsinand microcystin-LR.
- Personal care items and pharmaceuticals.
- Endocrinedisrupting compounds.
Filtration by Granular Activated Carbon or GAC
GAC has proved to be an efficient physical filtration mode in water treatment plants. Further, it also protects the quality of the water by adsorption of chemical contaminants or odor and taste causing compounds. Want to have a new GAC filter? Well, before designing any new Granular Activated Carbon filter or attaching a filter with GAC, it is necessary to take into account certain practical considerations. They are –
- Filter on-stream timing
- Hydraulic requirements
- Availability of backwash water
- Properties of GAC like its density, abrasion resistance and adsorption ability
- Evaluation of the cost required to convert a filter into GAC
Make sure that the filter design allows optimal expansion offering a few inches of clearance between bottom and top of backwash trough. Thus, GAC not only filters water but also its residual substance.