Settled sludge, as well as clearwater, must be continuously removed from the clarifier tank. For sludge removal, different systems are available — sludge agitators in combination with an inclined tank bottom, flushing mechanisms, and rotary or chain scraper systems.
Generally, effluent launders are designed as perforated pipes or rectangular channels with an overflow weir. The design must go hand in hand with the design of the lamella plate settlers. An incorrect design can result in a hydraulic overload of the effluent launders or in short circuit flows through the lamellas. Moreover, both of these issues can significantly affect the clarifier system’s performance. One important factor for avoiding these risks is correct alignment of the effluent launders to the inclined water level of the clarifier tank. This can be solved by using adjustable weirs.