The Environmental Services & Solutions Expo (ESS Expo), held recently in Birmingham, UK, brought together companies and technologies from across the environmental sector, including water treatment, resource and waste management, energy and the circular economy. Meanwhile, the Water Environment Federation’s Technical Exhibition and Conference (WEFTEC 2026) is set to take place in New Orleans, USA, from 28-30 September, bringing together water industry professionals and companies from around the world to showcase new equipment, processes and solutions.

These major industry events reflect how the focus of sludge treatment is gradually expanding. In the past, sludge treatment was largely centred on thickening, dewatering and final disposal. Today, technologies such as drying, anaerobic digestion, thermal treatment and resource recovery are receiving increasing attention. This shift reflects a broader change in the way sludge is being viewed: treatment is no longer simply about how to dispose of sludge, but also about what can be done with it after dewatering and how its energy and material value can be recovered.

For a long time, the main objective of sludge treatment seemed straightforward: remove as much water from the sludge as possible, then find a suitable way to deal with the remaining solids. In wastewater treatment plants, sludge dewatering was therefore often regarded as a key endpoint in the treatment process. Sludge would be thickened, conditioned and dewatered into a sludge cake, which could then be landfilled, incinerated, used in agriculture or otherwise disposed of, depending on local conditions.

In recent years, however, more projects have started looking beyond dewatering. Can the sludge be dried further? Can its organic matter be converted into energy? Can materials be recovered after thermal treatment? Can anaerobic digestion be used to produce biogas? As a result, sludge is gradually being viewed not simply as waste that needs to be treated, but as a material whose water content, organic matter, nutrients and energy value may need to be reassessed.

1. Dewatering Still Matters, but It Is No Longer the End Point

This does not mean that conventional sludge dewatering technologies are being phased out. On the contrary, as downstream treatment options become more diverse, the importance of dewatering is becoming even more apparent.

Sludge contains a large amount of water. Transporting insufficiently dewatered sludge means paying to move large quantities of water with little practical value. If the sludge is subsequently dried, a higher moisture content means greater energy demand. If it is sent for thermal treatment such as incineration or pyrolysis, the water content can also have a direct impact on treatment efficiency and the overall energy balance.

Dewatering may therefore no longer be the final step in sludge treatment, but it can have a significant influence on the cost of what comes next. In the past, the question was often: “How dry can this equipment make the sludge?” Increasingly, the more relevant question is: “What degree of dewatering will allow the sludge to move most effectively to the next stage?”

Although this may appear to be simply a change in how the question is phrased, it reflects a broader change in sludge treatment philosophy. Dewatering equipment is no longer considered solely as a standalone unit for removing water. It needs to fit into the wider sludge treatment process.

2. Sludge Treatment Is Moving from “Reduction” Towards “Recovery”

If sludge is viewed simply as waste, the objective is generally to reduce its weight and volume and then complete final disposal in a compliant and economical way. But sludge contains more than water and residual solids. Its organic matter can serve as a feedstock for biogas production through anaerobic digestion, while nutrients such as nitrogen and phosphorus may also have resource recovery potential. In some thermal treatment processes, sludge can be further converted into usable solid products.

As a result, more wastewater treatment projects are beginning to reconsider sludge from the perspective of resource recovery. Anaerobic digestion, for example, is already used for sludge stabilisation and energy recovery. Under anaerobic conditions, microorganisms break down organic matter in the sludge and produce biogas containing methane. After treatment, the biogas can be used for power generation or heating, or further upgraded for other applications.

Another area receiving attention is the combination of dewatering, drying and thermal treatment. Further reducing sludge moisture can lower the energy required for subsequent thermal processes and create more suitable conditions for incineration, pyrolysis and other treatment routes. In some projects, the products generated through thermal treatment may also be used for material or energy recovery.

These approaches do not mean that every wastewater treatment plant needs to build a complete resource recovery system. Rather, they point to a broader trend: the value of sludge treatment is gradually being assessed not only in terms of “how to dispose of it”, but also in terms of “what can be recovered from it”.

3. Why Does Dewatering Equipment Remain an Important Part of the System?

Resource recovery may sound more complex than conventional dewatering, but the more complex the downstream process becomes, the more important stable upstream treatment is.

The same type of sludge can behave very differently depending on its moisture content. Transport costs, storage requirements and the energy required for subsequent drying can all be affected. Where sludge needs to be transported to a regional treatment centre, reducing the proportion of water being transported becomes even more important. For projects involving drying or thermal treatment, however, dewatering is not simply a matter of achieving the lowest possible moisture content. Excessive dewatering may require additional capital investment or operating costs, while insufficient dewatering can increase the burden on downstream processes.

The practical objective is therefore not simply “the drier, the better”, but to determine an appropriate level of dewatering based on the intended downstream treatment. This is also why modern sludge treatment equipment increasingly needs to be selected from a whole-system perspective, rather than by comparing individual machines solely on processing capacity, cake moisture content or price.

4. Equipment Selection Is Increasingly Influenced by Downstream Processes

When sludge is ultimately sent through a conventional disposal route, equipment selection may focus mainly on processing capacity, sludge cake moisture content, operating costs and ease of maintenance. However, if the sludge will subsequently undergo drying, anaerobic digestion, incineration, pyrolysis or another resource recovery process, more factors need to be considered when selecting the upstream equipment.

For example, sludge being transported to a regional treatment centre needs to be considered in terms of transport distance and cake volume. Sludge entering a drying system requires consideration of the moisture content after dewatering and the resulting energy demand. Where thermal treatment is involved, the design also needs to take into account the requirements of the final process, including the characteristics and moisture content of the sludge.

This means that sludge dewatering equipment is gradually becoming less of an isolated unit and more of an integrated part of the overall sludge treatment chain. The equipment is not simply responsible for removing water; it also needs to be matched to where the sludge goes next.

5. Resource Recovery Will Not Be the Only Answer for Every Sludge Project

It is important to note that the growing interest in resource recovery does not mean that every sludge project should adopt drying, pyrolysis or energy recovery.

Sludge treatment is highly dependent on local conditions. Sludge characteristics, production volume, energy prices, transport distances, available land, regulatory requirements and final disposal options can all vary from one project to another. For some smaller wastewater treatment plants, investing in complex resource recovery facilities may not be economically viable. Stable thickening, dewatering and compliant disposal may still be the more appropriate solution.

For projects with large sludge volumes, high energy demand or suitable conditions for regional centralised treatment, however, resource recovery may offer additional economic value.

The real change taking place in the industry is therefore not that “all sludge should be recovered as a resource”, but that sludge treatment is moving beyond a sole focus on reduction and disposal towards a more comprehensive consideration of volume reduction, transport, energy, materials and the value of the final use.

6. Dewatering May Be Only the Beginning of the Sludge Treatment Chain

From this perspective, the role of sludge dewatering is also changing. It still performs the fundamental functions of reducing water content, lowering volume and facilitating transport, but it can also serve as an important link between upstream sludge treatment and downstream resource recovery.

Future sludge treatment systems may no longer simply follow:

Thickening → Dewatering → Disposal

Instead, different treatment routes may be developed according to the conditions of each project, for example:

Thickening → Dewatering → Digestion → Biogas Recovery

or:

Thickening → Dewatering → Drying → Thermal Treatment → Resource Recovery

More complex combinations are also possible.

The key consideration is not whether one technology will replace another, but how different equipment and processes can be combined to make the overall sludge treatment system more economical and reliable.

Haibar has long specialised in solid-liquid separation and sludge treatment equipment. Based on different sludge characteristics, treatment capacities and downstream disposal or treatment requirements, we provide sludge thickening, sludge dewatering and related auxiliary equipment and systems, including screw sludge dewatering presses, belt filter presses, belt thickeners, rotary drum thickeners and sludge conveying equipment.

As the end point of sludge treatment continues to evolve, equipment selection also needs to be considered from the perspective of the entire treatment process. If you are planning a new sludge treatment system or reassessing the treatment and disposal of existing sludge, feel free to share your operating conditions and requirements with us. We would be glad to discuss a suitable treatment route with you. > Contact us.