How to dredge a waste-water treatment plant pond?

A lagoon or pond at a wastewater treatment plant can be dredged to remove excess sludge.  First a dredge is placed in the water and connected to a pipeline.  An auger dredge is best for this application.  The dredge is propelled with a cable that is anchored along the shoreline.  The dredge auger agitates the material until it is sucked into the pump.  It is transported by the pipeline to a dewatering system.  The dewatering is usually either a belt press or geosynthetic dewatering tube.  The filtrate is returned to the pond, and the sludge disposed of properly.