Continuous Deflective Separation Unit. Essentially a large perforated stainless Steel Drum mounted in a 20m deep pit, installed off the side of a storm drain tunnel. The water and debris flows into the Unit via a diversion wall that also doubles as a pit of sorts. The water, when traveling at speed, say, in a flood, spins around the drum, separating trash and litter from the water. The water is then sent back out into the tunnel via a syphon system, while the litter debris is sent to the bottom of the Units pit, or remains floating on the top.
These devices work well. But unfortunately they can ruin a drain for exploration, as very often the diversion wall can create a deep muddy blockage. If the wall has been built with an overflow pipe, you can usually unblock it, then wait an hour for the waist deep pit to empty. If there isn't an overflow pipe, as has occurred with some setups in Sydney Drains, that section of the system becomes inaccessible.