Automatic Sludge Blanket Level Detector

The Automatic Sludge Blanket Level Detector from Markland Specialty Engineering (Canada) monitors and controls interface levels in sedimentation basins and clarifiers (including lamellas) and automates sludge removal when treating wastewater biosolids. It allows users to program de-sludge pumps to operate only when necessary, preventing carryover, optimising feed density for improved filter press/centrifuge/digester performance, bettering outflow for reuse. In addition, in dissolved air flotation units, it adjusts the speed of the surface skimmer to match variations in the thickness of the floating sludge layer; in sequential batch reactors, it controls the decant valve, enabling cycle time to be kept to a minimum. By eliminating unnecessary pumping, wastewater treatment plants can reduce wear-and-tear on pumps, downtime for maintenance, and energy usage.

The detector uses a vertical probe, submerged only to a depth required to encompass the desired sludge level range (often offset from the bottom of the tank).  LED-phototransistor sensors, running the length of the probe, are sequentially scanned to locate both settled bed and overlying cloud layer, automatically adjusting intensity for different concentrations.  When sludge levels reach the preferred maximum or minimum, the controller signals a computer/control system to turn the sludge removal pumps on or off.  This instrument’s slim profile makes it well suited for obstructed/constricted areas; for example, the curved walls of lamellas do not affect readings.  The all-PVC probe is corrosion-free. Analogue and relay outputs are available. No calibration is required. A wireless data link is available.