The Suspended Solids Density Meter from Markland Specialty Engineering measures and monitors the concentration of primary, secondary, return-activated and backwash sludge/silt and slurries in pipes, tanks and clarifiers. Its ultrasonic sensor allows users to program underflow pumps to turn off before sludge becomes too thin and helps optimize dosing and feed density. The nonintrusive in- line pipe spool-piece is simple to install, calibrate and clean. A throw-in-style version can be used as an automatic single-point interface detector, turning pumps on when the rising sludge blanket contacts it. 855/873-7791; www.sludgecontrols.com.