SBRs (sequencing batch reactors) are used as a treatment method in some communities, often because they can accommodate large variations in hourly flow rates. One frustration that operators have shared with us is that SBR plants often produce too much sludge for useful land application.

Sludge volumes can be reduced effectively by a number of methods, including:

• Sludge drying tubes
• Sludge drying beds
• Gravity belt thickeners
• Belt filter presses
• Centrifuges

Each of these methods reduces the total sludge volume by removing excess water. Water can often be 80% to 95% of the volume of the sludge, and even very simple methods of removing that water can dramatically reduce the total volume.

Gravity belt thickeners can achieve very high levels of volume reduction, and belt filter presses can reduce volumes even more.

Digestion methods (both aerobic and anaerobic) can also be used to reduce sludge volumes.