The new line of “fourth generation” sonar transducers is designed for improved sensing of interface levels in clarifiers and thickeners. The new sensors offer improvements in overall power, penetration and calibration density range. They provide better capability under high-suspended solids loading, ‘sliming’ and generally upset process conditions. In municipal water and wastewater plants, it is important to measure RAS and Floc (Fluff) level in secondary clarifiers, bed level for primary clarifiers as well as bed level in thickeners. Orca Sonar Interface products can now be used for control, not just used for monitoring purposes. Sonar sensors may be used to locate and track layers of differing density within a process tank. The Orca sonar can allow the user to control flocculent dosing, control settling time and control the density of a bed. Various sensors have been tried in this demanding environment, but none have proved accurate or reliable enough for use in control strategies. The new Hawk transducer designs include three to seven sonar crystals mounted in a single head. Each sonar array produces a concentrated sonar beam, providing more emitted power and collecting more returned signals. Array transducers yield better penetration, higher sensitivity, and better overall performance in the most difficult environments.