Wastewater Centrifuge | Sludge Dewatering & Thickening

Types of Wastewater

Wastewater is a generic term for water with solid or liquid contaminants. For example, municipal wastewater has organic sludge, and industrial wastewater carries industrial or inorganic sludge, etc.

Generation in large volumes is the other aspect of wastewater; therefore, the separation equipment must process large amounts of contaminated fluid.

Wastewater from the sources, as mentioned earlier, contains bulk sludge, which is easier to separate. On the other hand, wastewater from mines and oilfield drilling operations contains fine, suspended solids requiring smaller mesh filtration or higher g-force centrifuges.

We also have industrial effluent water, which contains oil in addition to the solids or sludge. This application may need two different centrifuges to separate the sludge and the oil from the de-sludged water.

Wastewater Centrifuges — Types and Capacities (Full Article)

Separation Technologies for Wastewater

Filtration is not an option for this application, given the type and volume of wastewater that needs to be purified. Other separation technologies, such as belts and filter presses, have limited uses in wastewater separation duties. These technologies often suffer from labor intensity and equipment reliability issues that limit their widespread use in modern wastewater treatment plants.

Mechanical separation using a wastewater centrifuge has significant advantages for continuously processing large quantities of wastewater. Unlike static filters, centrifugal separation is dynamic, self-cleaning, and requires minimal operator intervention.

Wastewater Centrifuge Operation

A wastewater centrifuge utilizes a centrifugal force of 3,100 Gs or higher to separate wastewater from sludge. The denser sludge accumulates on the bowl periphery, where an internal auger (scroll) scrapes it towards the discharge ports.

Simultaneously, the clarified water flows out through the liquid outlet at the opposite end of the bowl. This process happens continuously, allowing for high-volume throughput without the downtime required for filter cleaning or media replacement.

Types of Wastewater Centrifuges

Three types of centrifuges apply to wastewater depending on the type and amount of sludge. The following sections describe these broad categories for industrial and municipal use. For a detailed technical comparison, see our decanter vs disc stack centrifuge comparison.

Sludge Thickening or Sludge Dewatering Centrifuge

A sludge dewatering or thickening centrifuge is a decanter-type horizontal de-sludger engineered to remove water from slurries and consolidate sludge into a dry cake. These heavy-duty machines are built to process high-solids streams continuously without clogging.

Livestock farm manure, municipal sewage, car washes, and oilfield drilling mud often produce wastewater with sludge content as high as 50%. The primary goal is to reduce disposal volume and recover clean water suitable for reuse or safe environmental discharge.

Clarifying Centrifuge for Mining Effluent

A wastewater clarifier is a high-speed, self-cleaning disc-stack centrifuge that generates over 7,000 Gs. This extreme force is required to separate micron-level suspended particles that would simply pass through traditional filters or decanters.

Mining effluent and wash-water streams often contain minute silt and clay particles. A high-speed disc centrifuge pulls these particles out in a single pass, discharging clear centrate and automatically purging collected solids in a concentrated "sludge shot."

Separator for Industrial Oily Wastewater

Industrial effluent often carries oil in addition to sludge. This oily wastewater is a regulatory challenge because it cannot be disposed of in municipal drains without expensive treatment.

A 3-phase industrial centrifuge separates the oil from the water while simultaneously removing solids. Industrial wash-water containing shop-floor sludge and tramp oil is ideal for this type of liquid-liquid-solid separation.

Benefits of Centrifuges for Wastewater

Centrifuge offers many benefits compared to other dewatering and separation technologies. A brief description of some of the advantages follows.

Reduced Transportation and Disposal Expenses

Centrifuges produce dry sludge cake, significantly reducing transportation costs (up to 50%). Dry sludge also reduces disposal costs because the disposal volume is a fraction of the wet sludge.

Equipment Durability and Longevity

Industrial decanters are heavy-duty machines that have long service lives. Their material of construction (Stainless Steel) provides corrosion resistance in corrosive processing applications.

These centrifuges have superior erosion protection in critical areas for enhanced wear protection. It is not uncommon for these dewatering machines to operate for decades without needing replacement or even significant rebuilds.

Low Operating Expense

Unlike belt and filter presses, centrifuges do not use filter media, significantly benefiting these machines' users. Also, this eliminates the labor cost related to media replacement.

The only operational expense associated with centrifuges is maintenance. The only parts that need occasional replacement are the bearings because a decanter has fewer moving parts than filter presses.

Minimized Operator Requirements

Most sludge-thickening and dewatering centrifuges are fully automatic. The control systems have built-in sensors with self-correcting features to allow operator-free processing.

Other methods mentioned above need manual service to replace media or perform other periodic functions.

Compact Size for Processing Capacity

Centrifuges are compact when compared to other dewatering equipment. For equivalent capacity, a decanter footprint is often a fraction of other comparable machines. This small size makes them a viable option for wastewater de-sludging in confined areas in treatment plants.

The centrifuge equipment's compact size means that its location can be changed or moved to the worksite for ease of use and flexibility. A typical NX-314 decanter measures just 3 feet by 8 feet by 4 feet high while processing up to 80 GPM.

Wastewater Centrifuge Specifications and Sizing

Centrifuge specifications and sizing depend highly on your specific process and throughput requirements. Below are the technical details for the most common Alfa Laval dewatering and clarification systems.

Dewatering Decanter Specifications

Wastewater Clarifier (Disc Stack)

Case Studies: Wastewater Sludge Dewatering

Wastewater Centrifuge Models for Sale

Dolphin Centrifuge maintains a diverse inventory of Alfa Laval wastewater centrifuges in Warren, MI. All systems are fully reconditioned to OEM standards and shipped as turnkey, plug-and-play modules.

Dewatering Decanter Centrifuges (High Sludge)

Model	Capacity	Standard Options
Alfa Laval NX-418B-31G	20 to 100 GPM	Feed Pump w/ VFD; Sludge Auger w/ Gear Reducer; Bearing Temp Monitoring; Automatic Back-Drive Control.
Alfa Laval NX-314 B-31G	3 to 40 GPM	Feed Pump w/ VFD; Fluid Tank w/ Level Sensor; Sludge Auger; Torque Lock safety system.
Sharples P-3400 / P-3000	3 to 100 GPM	Contact Dolphin Centrifuge for custom configurations and available accessory skids.