Today, multi-disc screw presses have become a common choice for sludge dewatering in municipal wastewater treatment plants and industrial wastewater projects around the world. Compared with traditional belt filter presses and centrifuges, they generally require less installation space, offer a higher level of automation, and are well suited to continuous operation.

What many people may not realise, however, is that the multi-disc screw press was not an entirely new invention. Its development reflects the wastewater industry’s ongoing effort to adapt sludge dewatering technologies to changing operational needs.

Screw Press Technology Did Not Begin with Sludge

The concept of the screw press predates modern sludge treatment by many decades.

As early as the beginning of the twentieth century, screw presses were already widely used in industries such as food processing, papermaking, brewing and vegetable oil production for continuous solid-liquid separation. Their operating principle is straightforward: a rotating screw gradually increases compression, squeezing free water from the material as it moves through the press.

This concept was later introduced into sludge treatment. However, early screw presses designed for sludge dewatering faced a significant challenge—screen clogging.

Fine sludge particles and fibres easily accumulated on the filter surface, requiring frequent cleaning and maintenance. This limited the wider application of conventional screw presses in wastewater treatment.

Why Did the Multi-Disc Screw Press Emerge in Japan?

The development of the modern multi-disc screw press was driven less by a new dewatering principle than by changing engineering requirements.

During the 1970s and 1980s, Japan experienced rapid urbanisation while facing limited land availability, rising labour costs and an increasing number of small and medium-sized wastewater treatment plants. These facilities did not necessarily require the highest treatment capacity. Instead, they needed compact equipment that could operate continuously with minimal maintenance and operator intervention.

Japanese environmental equipment manufacturers therefore began asking a different question:

Could a screw press retain the advantages of continuous operation while eliminating the screen-clogging problems associated with conventional designs?

The answer eventually led to the development of the now familiar combination of fixed rings, moving rings and a screw shaft—the foundation of today’s multi-disc screw press.

A Small Innovation That Changed the Industry

In 1990, the Japanese company AMCON obtained key patents related to this technology and officially launched the VOLUTE™ Sludge Dewatering Press in 1991. The moving-ring self-cleaning mechanism significantly reduced screen clogging and flushing water consumption, establishing the technological foundation for the modern multi-disc screw press.

The significance of this innovation was not that it produced dramatically drier sludge.

Instead, it made sludge dewatering systems:

• capable of continuous operation;
• less dependent on manual supervision;
• more water-efficient during cleaning; and
• easier to maintain over the long term.

In other words, it changed not only how sludge was dewatered, but also how sludge dewatering systems could be operated.

In 1998, Japan also completed one of the first engineering demonstrations using oxidation ditch sludge directly with a multi-disc screw press. The project simplified the treatment process for small and medium-sized wastewater plants and further accelerated adoption of the technology throughout Japan.

From Japan to the Global Market

Since the early 2000s, tightening environmental regulations and rising operating costs have reshaped priorities across the wastewater industry.

Rather than focusing solely on sludge cake moisture content, plant operators have increasingly begun evaluating dewatering systems based on factors such as:

• lifecycle cost;
• automation;
• operational stability;
• energy and water consumption; and
• maintenance requirements.

These priorities closely matched the strengths of the multi-disc screw press.

As a result, a technology originally developed in Japan gradually expanded into Europe, North America and Southeast Asia. One notable example is the Nigg Wastewater Treatment Works in Scotland, where traditional belt filter presses were replaced by VOLUTE Disc Press systems to improve operational efficiency while reducing energy use and maintenance requirements.

Today, multi-disc screw presses are used in dozens of countries and have become an established sludge dewatering solution for municipal wastewater treatment as well as industries including food processing, brewing, chemicals and manufacturing.

The Evolution of a Machine Reflects the Evolution of the Industry

Looking back, the history of the multi-disc screw press is about more than the development of a single piece of equipment.

In the past, sludge dewatering technology was largely judged by one question: How dry can the sludge cake become?

Today, the industry is placing greater emphasis on long-term operational stability, ease of maintenance and continuous, reliable performance. The priorities have shifted, and equipment has evolved accordingly.

From this perspective, the multi-disc screw press was never intended to replace every type of sludge dewatering equipment. Rather, it was developed to meet a different set of operational needs.

Different sludge characteristics, treatment capacities and process requirements still call for different dewatering technologies. Selecting the right solution ultimately depends on the specific application and the overall design of the treatment system.