Conveyed Product

Sludges of differing densities and temperatures

Key Specifications

Tailored pump solutions for the UK's second-largest sewage treatment plant

Built N300-36 transfer pumps in record time, measuring 11 m in length, weighing 7 tons

High-precision design:
Machined from a 1.7 ton piece
of tool steel with precision
down to 0.2 mm, the rotor
is 6 m in length and
weighs 0.7 tons

Full-service package

Cost Savings

Minimal need for replacement parts

Short downtimes
Reduced labor costs

Pump Type


Thames Water operates one of the UK's largest sewage treatment plants. Located in West London, it treats sewage for around 2.1 million residents. A plant of this size requires both pumps and service levels that are extraordinary. SEEPEX delivered both.

Originally built in the 1930s, the Mogden sewage treatment plant has undergone major expansions over the decades to keep up with exploding population growth.

SEEPEX has a longstanding relationship with Thames Water, having worked with them in framework agreements for over 20 years to reduce the cost of ownership of progressive cavity pumps and improve the efficiency of processes where progressive cavity pumps are used.


Task and Target

SEEPEX were approached by an EPC contractor with a pump duty to transfer 180 m³/h of 6-8% dry solids thickened sludge to a sludge dewatering facility 18.5 km away.

This was no small challenge given the distance, capacity and the %ds content of the sludge to be transported. Various pump technologies were reviewed. Some were not able to handle the high dry solids concentration, while others required either multi-stage pumping or had the potential of generating high pulsation spikes.



  • Pump type N, pump range NS
  • Conveying 6-8%ds thickened sludge
  • Transfer distance: 5 km
  • Capacity: 180 m³/h
  • 11m in length, 7 tons in weight, 250 kW drives


Solution and Results

The selected pumps could easily handle the 6-8%ds thickened sludge and had the ability to pump the 18.5km without any need for intermediate pump stations. In addition, inverter drives were fitted so that the large volume of sludge in the discharge pipework was accelerated slowly on start-up, thereby preventing pressure spikes.

“The extraordinary SEEPEX N300-36 long distance transfer pumps were a milestone in technological development and the biggest progressive cavity pumps in existence at that time in terms of both weight and length at 7 tonnes and over 11 metres long respectively, and fitted with 250 kW drives.”
Jörg Brune
Head of Mechanical Development & Innovation Strategies

A SEEPEX inter-departmental project team of 30 people worked together to design, manufacture and deliver these giant pumps in record time.

Almost 20 years after their installation in 2003, these gigantic pumps are still in operation, which is a testimony to SEEPEX’s workmanship, product quality and service excellence.



  •  On start-up, inverter drives slowly accelerate the large volume of sludge in the discharge pipework preventing pressure spikes
  • Extraordinary pumps transfer 6-8%ds sludge a distance of 18.5 km without investing in intermediate pump stations



  • Reduced investment cost due to elimination of multi-stage pumping
  • Substantially lower lifecycle costs due to the pumps’ efficiency and reliability compared to other pump technologies