Activated Carbon Filters
Activated carbon filters are used for different purposes as pre-treatment to various process needs.
The high adsorptive capacity of activated carbon enables it to remove the test, odour causing compounds & other traces of organics from the water. However, not all organic compounds are removed with the same degree of efficiency.
Granular Activated Carbon filters are very effective as a de-chlorination agent. Hence, it is adopted as a pre-treatment filter before the resin based / RO based treatment plants. GAC filters employed for organic removal are similar to pressure sand filters with generally similar design, filtration rates & backwashing arrangements, with the flow rate adjusted to suit the lower density of GAC. The GAC is placed in the filter over the support gravel. Media depth is a function of the empty bed contact time (EBCT). GAC characteristics will very according to the material from which it is made whether wood, coconut shell or peat.
The carbon has to be replaced when the break through occurs. Activated carbon filters are of steel construction with the system operating on the feed water pumping pressure.The water flow from the top to the bottom across the filter bed with the filtered water discharged from the bottom. The filter pump is sized to have adequate head to discharge filtered water to the filtered water tank or further process units.
The filter bed is periodically back washed to loosen the bed to expose the compacted area. Back wash water is sourced from the filtered water tank and pumped counter current to the filtration mode operation. Dirty Backwash water from the filter is routed for further treatment before recycling back to the system. Hot water backwash is adopted in some cases where the volatile are removed for extending the life of the carbon. Air scouring blowers are provided to improve the cleaning of the filter bed during the filter back wash sequence. Special care is taken for sizing of the filter internals and frontal piping to facilitate filtration and back washing.