Prewashed GAC Installation
PLACEMENT OF GAC
Fill the vessel with pre-treated water to about 2/3 the final level of GAC. Gradually add GAC into the water, from around the perimeter, until reaching the desired finish level, ensuring that the water level remains above the level of GAC at all times. The GAC should spread and self-level when the bags are discharged into the water. Alternatively the vessel can be loaded dry but dust emission is a problem.
Agitate the carbon/water mix gently with low rate air scour, to assist in wetting the carbon. Allow the GAC to soak for a minimum of 2 hours.
WASHING OF GAC
After soaking in water for a minimum of 2 hours, backwash at a low rate for 5 minutes and slowly increase to the maximum design backwash rate for the vessels. Wash at the normal rate for about 15 minutes. This allows for any air to be removed from the bed. Any very fine material will be removed through the backwash troughs during the low rate wash when the water may look reasonably dirty.
Continue backwashing until the water looks reasonably clear. Once the backwash water is clear, all fines will have been removed, and the vessel is ready for service.
PERSONAL PROTECTION EQUIPMENT
Installation operators should wear full overalls, goggles, dust masks and safety boots. Those untying the bags should wear a safety harness, to prevent a fall into the water and GAC-filled vessel. Once the GAC has been installed, there should be no need for personnel to enter the filter to scrape the surface, as the product contains minimal fines, and these can be removed during the above backwash operations.