What Is a Decanter Centrifuge (Sedimentation Centrifuge)? Working Principle and Applications

A decanter centrifuge is a horizontal sedimentation centrifuge — a machine that separates solid-liquid mixtures continuously. The name “decanter” derives from the verb “to decant” — the process of separating the clarified liquid from the settled solids. The defining difference from other separation devices is that a decanter operates continuously: the feed slurry is pumped in without interruption, the solid phase is conveyed out at one end by the scroll, and the liquid phase overflows at the other end — no machine shutdown is needed to discharge solids.

The machine is well suited when the feed stream contains a high solids content and large-throughput solid-liquid separation is required. This is why the decanter centrifuge has become the central piece of equipment in wastewater treatment plants, food processing facilities, and many industrial phase-separation processes.

The decanter operates on a fundamental principle: when rotating at high speed, the centrifugal force (G-force) acting on the mixture is many times greater than gravity, causing phases of different densities to separate rapidly. Inside the conical-cylindrical rotating bowl, the denser solid phase is forced outward against the bowl wall, while the lighter liquid phase migrates toward the axis. A co-axial scroll conveyor, rotating at a differential speed relative to the bowl, continuously scrapes the solid cake along the bowl wall toward the conical discharge end, while the clarified liquid flows back toward the cylindrical end and overflows through adjustable weir plates.

The three key operating parameters are G-force (governs separation efficiency), differential speed between bowl and scroll (determines solids retention time and cake dryness), and flocculant polymer dosage for sludge applications. A larger bowl diameter provides higher processing capacity; on HAUS machines, bowl diameters range from 200 to 800 mm depending on model, with flow rates from 1 to 180 m³/h.

Many users confuse the decanter with the disk-stack separator because both are centrifuges. However, they address different problems. The decanter excels with streams that have a high solids content and require continuous solids discharge via the scroll. A disk-stack separator uses a stack of conical discs to divide the flow into thin layers, achieving very high G-force to separate fine phases — such as cream from milk or water from oil — when the solids content is very low.

When advising on equipment selection, correctly identifying the right family of machines from the outset prevents misguided investment: thick sludge streams call for a decanter, while streams requiring two clear liquid phases to be separated call for a separator.

The most frequently cited application is sludge dewatering in wastewater treatment: the decanter reduces sludge moisture content to lower transport volume and processing costs, typically combined with flocculant polymer dosing to improve sludge cake dryness. In the food industry, decanters separate vegetable oils, isolate proteins, and clarify or classify raw materials. In other industrial processes, the machine handles solid removal, liquid clarification, and recovery of valuable solid fractions.

• Environmental (HAUS DDE): sludge dewatering at municipal and industrial wastewater treatment plants.
• Food (HAUS DDF): oil separation, protein isolation, and raw-material clarification using sanitary-grade stainless steel construction.
• Industrial (HAUS DDI): solid-liquid separation across diverse production lines.

Because the machine operates with corrosive media or under hygienic requirements, wetted parts are typically manufactured from AISI 304 or 316 stainless steel depending on the severity of the application.