Wastewater Centrifuge

**Alfa Laval NX-418 Decanter for Wastewater Sludge 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.

Separation Technologies

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. Again, these technologies have drawbacks, including labor and equipment reliability issues that limit their widespread use in wastewater treatment plants.

Mechanical separation using a wastewater centrifuge has many advantages for continuously processing large quantities of wastewater. As with all technologies, centrifuges also have some drawbacks highlighted below.

Sharples P3000 Wastewater Decanter — **Sharples P3000 – 40 GPM – Wastewater Decanter**

Operation

A wastewater centrifuge is a separation machine that utilizes a centrifugal force of 3,100 Gs to separate the wastewater from sludge. The sludge accumulates on the bowl periphery, and the internal auger scrapes towards the sludge discharge ports. The water flows out through the bowl’s liquid outlet at the opposite end.

Types

Three types of centrifuges apply to wastewater depending on the type and amount of sludge. The following section describes these broad categories.

Sludge Thickening or Dewatering Type

**Alfa Laval NX-314 Decanter Centrifuge**

A sludge dewatering or sludge thickening centrifuge is a decanter-type horizontal de-sludger that can remove water from slurries to thicken the sludge. In other words, a heavy-duty industrial centrifuge dewaters and concentrates (thickens) the sludge, also known as a sludge thickening machine. These machines are available in different sizes to continuously process large quantities of sludge-laden water.

Livestock farm manure, municipal sewage, car washes, and oilfield drilling mud produces wastewater with high sludge content of up to 50%. The primary objective of such applications is to reduce the sludge volume to minimize handling and disposal costs. The recovered water is often clean enough to be reused or discharged with minimal environmental impact.

Clarifying Centrifuge for Mining Effluent

A wastewater clarifier centrifuge is a disc-stack type, a high-speed, self-cleaning separator that produces very high centrifugal forces that can separate micron-level suspended particles. The particles are pushed toward the bowl wall and automatically purged during the cleaning cycle. The cleared centrate discharges the bowl continuously through a centrally located outlet port.

Alfa Laval WSPX-303 Concentrator Centrifuge — **Alfa Laval WSPX-303 Wastewater Concentrator Centrifuge**

Wastewater from mining applications is one such example. This stream contains minute silt and clay particles that are difficult to separate with a wastewater decanter. A high-speed disc centrifuge has sufficient g-force to pull out these particles and clarify the water.

Separator for Industrial Oily Wastewater

Industrial wastewater often carries oil in addition to sludge. This oily water is challenging because it cannot be disposed of in standard drains. A three-phase industrial centrifuge separates the oil from the water, making it disposable.

Industrial cleaning fluid containing shop-floor sludge and oil from the manufacturing run-off is ideal for separation with a liquid-liquid-solid separator.

Alfa Laval Decanter Centrifuge for Vegetable Processing Wastewater — **Alfa Laval Decanter – Onion Processing Wastewater**

Benefits

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, which significantly reduces 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 the need for replacement or even significant rebuilds.

Low Operating Expense

Unlike belt and filter presses, centrifuges do not use filter media, which significantly benefits 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.

Specifications and Sizing

Centrifuge specifications and sizing depend highly on the manufacturer and the customer’s capacity throughput requirements. Listed below are some specific technical details and sizes of the commonly used dewatering separators from Alfa Laval.

Dewatering Centrifuge

Manufacturer	Alfa Laval Decanter
Model	NX-418-B31-G	NX-314-B31-G
Rated Capacity	170 GPM	80 GPM
Capacity on Wastewater with 5% Sludge	100 GPM	40 GPM
Capacity on Wastewater with 10% Sludge	60 GPM	25 GPM
Motor Power	20 ~ 25 HP	10 ~ 15 HP
Weight	4,000 Lbs	2,500 Lbs
Size / Dimensions	3′ x 10′ x 4′ (H)	3′ x 8′ x 4′ (H)
Material of Construction (MOC)	316L Stainless Steel	316L Stainless Steel
Wear Protection – Auger	Tungsten Carbide Hard Surfaced Auger	Tungsten Carbide Hard Surfaced Auger
Wear Protection – Sludge Ports	Stellite Bushings	Stellite Bushings
Wear Protection – Inlet Feed Zone	Hard Surface or Stellite Insert	Hard Surface or Stellite Insert

**Alfa Laval WHPX-513 Centrifuge for Waste Water Clarification**

**DMPX-028 Self-Cleaning Disc Stack Centrifuge for WasteWater**

Manufacturer	Alfa Laval Separator
Model	WHPX-513	DMPX-028
Type	Hi-Speed; Disc-Stack; Self-Cleaning
Efficiency	Solids Particles down to 0.5 µ
Rated Capacity	100 GPM	30 GPM
Capacity with 5% Sludge (Max.)	80 GPM	12 GPM
Motor Power	15 HP	10 HP
Skid Weight	4,000 Lbs	3,500 Lbs
Size / Dimensions	6′ x 7′ x 7′ (H)	4′ x 5′ x 6′ (H)
Bowl Material of Construction (MOC)	316L SS w/ Some Red Metal Parts
Disc Stack Configurations	2-Phase or 3-Phase
Control System	Fully Automatic PLC & Touchscreen

Applications

Dolphin Centrifuge has supplied industrial decanters and disc-stack clarifiers for a wide range of wastewater applications. Some of these applications are listed below.

Bakery Bread Mold – Wash-water
A bakery in Texas produced over 20,000 gallons of wash water from bread mold washing daily. The water was contaminated with flour, bread crust, and other organic residues. The Dolphin-Centrifuge pilot tested the water, recommended, and supplied an Alfa Laval NX-414 Decanter rated at 40 GPM on the water with light solids.
University Composting Leachate
A university in California was having trouble handling abnormally high solids in the composting leachate. The leachate also carried a small amount of oil. Dolphin Centrifuge supplied a Sharples P-3000 Decanter (pictured above) accompanied by an Alfa Laval WHPX-510 (3-phase) oily water separator centrifuge.
Tortilla Factory Wash-Water
Dolphin Centrifuge supplied an Alfa Laval NX-314B-31 Decanter to thicken the flour sludge in a tortilla factory wastewater stream. The compacted sludge reduced waste hauling and disposal costs by over 60%. Separated water was clean enough for sewer discharge.
Small Municipal Water Treatment Plant
A small municipality in the mid-west needed a sludge-thickener for their sewage treatment operation. Dolphin Centrifuge supplied an Alfa Laval NX-418B-31 Decanter centrifuge with a Chemical Dosing attachment. Municipal sewage dewatering is a common application, and the decanter works as expected to produce dry cake minimizing disposal costs.
Large Onion Factory – Process Water
One of the largest onion producers in California was having issues with its organic sludge-carrying wastewater disposal. Dolphin Centrifuge supplied an Alfa Laval NX-416 2-Phase Decanter centrifuge to dewater the organic sludge from the wash water. The process throughput was approximately 40 GPM with a sludge load of about 20% by volume.
Automotive Supplier Industrial – Wash-Water
A Detroit-based auto supplier generated over 10,000 gallons of wash water from the floor and pit washing every week. The wash water carried oil in addition to the sludge. Dolphin Centrifuge supplied a 2-step water recovery system with an Alfa Laval NX-314 Decanter, followed by an Alfa Laval MOPX-207 ‘Self-Cleaning’; 3-Phase Disc-Stack Centrifuge as a polisher to remove the oil.