Portable dredges equipped with auger excavators are used to maintain the Werribee and Carrum water treatment facilities serving the City of Melbourne, Australia. The dredges at both facilities remove sludges from built-in waste settling basins.
At Werribee, a model MC915 Mud Cat dredge pumps sludge over a distance of 1200 meters. It pumps 12 hours a day, 6 days a week. The dredge at the Carrum facility pumps sludge a distance of 1400 meters and moves 28 m3 of dry solids per hour. The MC915 at Carrum pumps 12-18 hours a day, 7 days a week.
The dredges are designed for removing sedimentation and sludge, and recovering minerals from tailing ponds, lakes and canals. The dredge is equipped with a diesel-driven pump capable of sucking up sediment deposits that are 46 centimeters deep in one pass, and 2.74 meters wide to depths of 4.57 meters. Its underwater auger directs the sediment to the vacuum suction, which carries it off. The auger excavator, mounted on the end of a hydraulically operated boom, is equipped with knives which dislodge and cut up material with a scissors-like action. The spiral auger in the cutter head drives the material to the pump suction intake. The rotating cutting action removes sediment, yet maintains extremely low turbidity.
The portable dredge leaves waterway floors even and ridge-free without breaking through the natural seals or bottom liners of lakes or ponds. A patented mud shield shrouds the excavator, entrapping suspended material and minimizing turbidity. Teeth along the forward edge provide additional cutting capability when material protrudes above the water. A high-powered centrifugal pump feeds the material through a discharge pipe to a spoil area up to a half mile away. The dredge comes equipped with a 20-centimeter diameter pipe in 6-meter sections which can be hand assembled over land or water.
Reprinted from Pollution Equipment News