Digestor Cleaning and On-Site Sludge Processing at a Wastewater Treatment Works

10 July 2026

McBreen Environmental successfully delivered a major digestor cleaning and sludge processing project at a wastewater treatment works.

The works involved the removal, screening and dewatering of digestate from redundant primary digestors, helping the client safely manage significant volumes of material while maintaining operational efficiency across the site.

Using a combination of specialist pumping, screening, storage and dewatering equipment, the project maximised material recovery, reduced off-site transport requirements and kept the programme on schedule.

Challenges

The redundant primary digestors contained an unknown volume and consistency of digestate, making production rates difficult to predict.
The client required an average processing rate of approximately 30m³ per hour to meet programme deadlines.
Multiple contractors worked simultaneously on site, requiring close coordination to ensure operations remained safe and efficient.
A demanding programme required extended working hours, multiple crews and continuous monitoring to maintain productivity.

The McBreen Solution

Digestate removed from the primary digestors was transferred into temporary open storage tanks before being pumped through a D:MAX mobile screening unit using a Molex pump.

The screening process removed rags, grit and other debris from the sludge, with the separated solids collected into skips for disposal. The screened liquid was then transferred into a KOKS mobile storage container before undergoing further treatment.

To improve sludge quality for dewatering, polymer dosing was introduced ahead of processing through a mobile decanter centrifuge. This produced a dewatered sludge cake suitable for transportation and beneficial agricultural reuse, while the separated centrate was returned directly to the treatment works for further treatment within the existing process.

During the project, increasing volumes of processed material created a need for additional storage capacity. Following a client request late on a Friday afternoon, McBreen Environmental mobilised an 86,000-litre KOKS storage trailer, which was delivered, installed and fully operational by Monday morning. The rapid mobilisation ensured processing continued without impacting programme delivery.

Results

By carrying out screening, storage and dewatering directly on site, McBreen Environmental delivered an efficient solution that:

Maintained high processing rates throughout the project.
Reduced the volume of material requiring transport.
Minimised disruption to the operational treatment works.
Responded rapidly to changing site requirements through the mobilisation of additional storage capacity.
Delivered the works safely and in full compliance with environmental regulations.