Backwashing Activated Carbon | James Cumming & Sons

Granular Activated Carbon (GAC) contactors can operate as either combined filters/contactors or Biological Activated Carbon contactors or as Adsorber/contactors. All require backwashing when either triggered by head loss limits or excessive biomass growth. The process involves briefly taking the contactor offline, air scouring and backwashing, then returning the contactor to service. The deeper the bed of GAC, the longer the contact time which results in more efficient removal of contaminants and longevity of the GAC. Activated Carbon contactors are usually installed downstream of Dual Media filters which means the time between backwashes for Activated Carbon is usually much longer than that for Filter Media

A general guide to backwashing James Cumming & Sons’ Granular Activated Carbon is:

Wastewater treatment plant. Reservoir for purification of sewage.

Drain Down

After the contactor is taken off line, initiate the Drain Down of until the water level in the contactor reaches approximately 100mm above the surface level of the Granular Activated Carbon.

Initial Air Scour

Next, perform an Initial Air Scour by introducing air at a minimum rate of 45m/h to break up any crust formed on the surface of the Granular Activated Carbon. This step typically lasts a minimum of five minutes.

Combined Air/Water Wash

After loosening the bed with the Initial Air Scour, continue the process by maintaining the air scour while simultaneously introducing the water wash at a maximum rate of 13m/h.

Sustain this combined air/water wash for a duration of 30 to 60 seconds before stopping the air scouring to ensure that the system expels all air bubbles well before the water level reaches the top of the washout troughs.

This precautionary measure helps prevent air bubbles from carrying the Activated Carbon granules over and into the washout troughs, thus maintaining the depth of carbon and the resulting contact time.

Water Wash

Once the water level reaches the top of the washout troughs, increase the water wash to the optimal rate, which is the rate to achieve a 30% bed expansion of the Granular Activated Carbon.

For our Australian Activated Carbon, the backwash rate achieve to achieve a 30% expansion at various water temperatures can be obtained by contacting the helpful staff at James Cumming & Sons.

The water wash will typically take around five to 10 minutes.

It is important to note that the previous air scour step may result in a slight amount of dust, which can affect the clarity of the backwash water.

Resuming filtration

Once the backwash water clears and reaches an acceptable level of clarity, the backwashing process has effectively removed accumulated particles and debris from the Granular Activated Carbon.

At this point, the contactor can be brought back on line to resume its regular production operations, ensuring clean, efficient and high-quality water output.

Talk to the experts in Filter Media & Activated Carbon Manufacturing

Backwashing helps maintain optimal carbon performance and extends the lifespan of the bed. This process not only ensures the delivery of clean and high-quality water but also reduces the risk of clogging and system malfunctions.

At James Cumming & Sons, we have over 115 years of expertise in pioneering the use of Australian coal for industry. We work with countless industries, including potable water, wastewater, desalination pretreatment, wastewater, and industrial process water , to deliver safe, customised water treatment solutions.

We can assist with the selection of the optimal product for your project requirements. For more information on C&S Brand Australian Filter Coal, C&S Brand Australian Activated Carbon or more specific details about backwashing, contact a member of our expert team today.