Overview
Activated carbon is a highly porous carbon material with an enormous internal surface area (800 to 1,200 sqm/gr) created by thermal or chemical activation of carbonaceous raw materials such as coconut shell, coal, or wood. This internal surface adsorbs dissolved organic molecules and certain inorganic species from water through physical attraction forces, removing them from the water phase without introducing additional chemicals.
Activated carbon is used in water treatment as an adsorptive polishing step. It targets dissolved species that coagulation, sedimentation, and filtration cannot remove. Its applications range from taste and odour control in potable water to dechlorination of cooling tower makeup, removal of dissolved hydrocarbons from process water, and odour control in wastewater treatment effluent. The correct form (granular vs. powdered) and grade (raw material, activation level, mesh size) are selected based on the specific contaminants present and the treatment system design.
GAC vs. PAC: Granular Activated Carbon (GAC) is used in fixed-bed filter columns where water flows through a bed of carbon granules continuously; the bed is regenerated or replaced when adsorption capacity is exhausted. Powdered Activated Carbon (PAC) is dosed as a slurry into the water stream for contact, then removed by coagulation-sedimentation-filtration. GAC suits continuous, long-term treatment; PAC is used for seasonal or intermittent needs (e.g., taste/odour episodes) without the capital cost of a GAC filter.
Product Forms
Applications
| Application | Form | Notes |
|---|---|---|
| Taste & odour removal | PAC (emergency/seasonal) or GAC (continuous) | Geosmin and 2-MIB compounds (earthy/musty algal metabolites) are efficiently adsorbed by activated carbon; PAC dose 5–20 mg/L effective for most events |
| Dechlorination of process water makeup | GAC bed (in-line) | Residual free chlorine in supply water degrades RO membranes and ruins ion exchange resins. GAC contactors are the standard protection upstream of these systems |
| Removal of dissolved organics from industrial water | GAC bed or PAC dosing | Petroleum hydrocarbons, BTEX, phenols, and solvent traces in process water streams; coal-based GAC preferred for high-MW organics |
| Colour and organics polishing — effluent | GAC bed (tertiary treatment) | Polishing step after biological treatment to remove residual colour, COD, and trace organics before discharge; relevant where effluent quality must meet PROPER Biru/Hijau level |
| Cooling tower makeup dechlorination | GAC bed | Removes chlorine before water enters the cooling loop; protects corrosion inhibitors from chlorine oxidation degradation and prevents accelerated pitting of copper and stainless steel heat exchanger surfaces |
| Condensate polishing | GAC + mixed bed ion exchange | Removes organic carbon and trace hydrocarbons from steam condensate before return to boiler, protects boiler from organic decomposition fouling |
Petrochemical & LNG Applications
Activated carbon is a standard component of industrial water treatment systems in refineries, petrochemical plants, and LNG terminals, where process water quality requirements are stringent and multiple sources of organic contamination must be addressed simultaneously.
In refineries and petrochemical complexes, GAC filters are installed upstream of reverse osmosis (RO) demineralisation units to remove chlorine and dissolved organics that would otherwise foul or damage RO membranes. Membrane manufacturers' warranties typically specify maximum free chlorine and total organic carbon (TOC) levels in the feed water. In addition, refinery wastewater effluent treatment plants may include a GAC polishing stage to remove residual dissolved hydrocarbons, phenols, and colour from biologically treated effluent before discharge to meet PROPER Biru or AMDAL permit limits.
In LNG terminals, activated carbon is used in the desalination pre-treatment train to remove organic fouling precursors from seawater before it enters RO units. Seawater, particularly in tropical coastal areas adjacent to industrial zones, can contain significant concentrations of natural organic matter, algal metabolites, and petroleum-derived organics that would foul the RO membranes rapidly without carbon pre-treatment. GAC beds, sometimes preceded by ultrafiltration, protect RO membranes and significantly extend their operational lifetime between replacement cycles.