Belt presses are a continuous sludge dewatering technology that removes water from sludge through a sequence of gravity drainage and mechanical compression stages. Unlike filter presses that work in batches, or centrifuges that use high-speed rotation, belt presses operate at low speed and rely on the progressive application of pressure between two moving filter belts to achieve dewatering.

The process begins with the conditioned sludge being spread evenly across a moving belt in the gravity drainage zone. In this zone, free water drains away through the belt under gravity, reducing the sludge to a consistency that can be handled by the pressure zone that follows. This initial gravity drainage step is important to the overall performance of the press, as it reduces the load on the pressure zone and improves the consistency of the cake produced.

From the gravity zone, the sludge passes into the wedge zone where the two belts converge and initial pressure is applied. The sludge then moves through a series of rollers of decreasing diameter, each applying increasing pressure to squeeze more water from the sludge. The resulting cake is discharged at the outlet end and collected for disposal.

Belt presses offer high throughput and relatively low energy consumption compared to centrifuges. Their open design makes them accessible for inspection and maintenance, and belt replacement, while requiring downtime, is a manageable maintenance task. Wash water is used continuously to clean the belts between passes, and managing wash water consumption and the filtrate return stream is part of operating the system effectively.

Used across municipal and industrial wastewater treatment operations, belt presses are a proven dewatering technology suited to facilities where continuous operation and reasonable cake dryness are the primary requirements.