Rotary Drum Screens

Rotary drum screens are energy efficient screening devices that are very effective in treatment applications that are high in grit and sand loads with variable flows and solid concentrations. These screens are also good at removing hairs, and fibrous materials that can wreck havoc on important downstream treatment processes such as membrane bioreactors.

Removing these materials during preliminary treatment minimizes the chances of the plants performance being compromised and increases the chances that subsequent treatment processes are trouble and maintenance free.

Drum screens offer some provisions that are typically not available on other micro and/or fine screens. This device combines screening, washing, compacting, and dewatering all in one unit. By combining these four operations, equipment and operation costs are greatly reduced.

For this type of fine screen, the screening medium is attached to a cylinder that rotates the flow regime. The construction of a the drum screen will depend on the direction of flow through the screen media. Either flow will enter through one end of the drum and out through the screen with debris being captured on the interior surface, or flow will enter the top of the unit and pass through with solids capture on the exterior.

Rotary drum screens that are fed internally have flow capacities that range from 0.03 to 0.8 m³/s or (0.7 to 19 mgd [metric system conversion]) per screen.

While drum screens that are fed externally have a capacity of less than 0.13 m³/s or (3 mgd). Sizes of drum screen varies from 0.9 to 2m or (3 to 6.6 ft) diameter and lengths from 1.2 to 4 m or (4 to 13.3 ft)

As the flow makes its way through the unit, screened water continuous on to the next process. While collected screenings are transported by the gyration of the drum screen toward the discharge chute where additional dewatering occurs. After dewatering, screenings are dumped into a container where they are stored for future disposal. As the drum screen rotates, the screen is scoured clean by a water jet stream.