Sludge and slurry are some of the hardest fluids to pump. They are thick, abrasive, full of solids and often corrosive, and the wrong pump will clog, wear out fast or fail to prime. Power Energy Gulf supplies sludge and slurry pumps in Saudi Arabia and the GCC from two Italian manufacturers, Nova Rotors and Fluimac. This guide explains the difference between sludge and slurry, the pump types that handle them, and how to choose.
Sludge and slurry: what is the difference?
Sludge is a thick, semi-solid mass left over from a process, for example sewage and wastewater sludge, tank bottoms, or residues from industrial treatment. It is often viscous and may not flow on its own. Slurry is a mixture of solid particles in a liquid, such as mineral concentrates, mining residues, drilling mud or cement slurry. Slurries are often abrasive. Both need a pump that can pass solids without clogging and without wearing out quickly.
Which pump for which duty?
- Progressive cavity pumps for thick sludge and high pressure. A helical rotor turns inside a rubber stator and moves the fluid forward in sealed chambers, with steady flow and no pulsation.
- Hopper progressive cavity pumps for very thick sludge that barely flows, using a hopper and an auger to feed the pump.
- Air-operated double diaphragm (AODD) pumps for dirty, abrasive or corrosive fluids with solids, where compressed air is available. They run dry and need no mechanical seal.
- Peristaltic (hose) pumps for abrasive slurries and fluids with a high solids content, because the fluid touches only the hose.
- Grinders placed upstream of a pump to cut down solids before they reach it.
Nova Rotors progressive cavity pumps for sludge
Nova Rotors, an Italian manufacturer founded in 1990, makes the Diamond range of progressive cavity pumps for sludge disposal, wastewater treatment and sludge processing. The main series are:
- N series: the standard industrial pump, designed to API 676. It handles viscous and non-viscous fluids with or without solids, up to 520 m3/h and 48 bar. Nova Rotors lists it for waste sludge, mining residues, mine water and drilling muds.
- H series: hopper pump with an auger feed screw, for poorly flowing substances up to 18% dry matter that do not form bridges. It handles up to 520 m3/h and 24 bar.
- HS series: a heavier hopper pump for substances up to 35% dry matter, up to 520 m3/h and 48 bar.
- HSB series: the HS design with a bridge breaker wheel, for non-flowing products up to 40% dry matter that tend to form bridges or blockages.
All of these can work at temperatures from -40 to 150 degrees C. See our Nova Rotors pumps page for the full range.
Wobble pumps and grinders
For smaller sludge duties, Nova Rotors Wobble floating stator pumps are compact and cheap to maintain because they have few parts. The R series reaches 6 m3/h and the RL series 14.4 m3/h, both up to 4 bar. They are listed for sludge disposal and wastewater treatment.
The Terminator TG grinder cuts down solids upstream of the pump, protecting pumps from damaging solids and cutting unplanned downtime. It handles flow up to 100 m3/h.
Fluimac diaphragm pumps for sludge and slurry
Fluimac Phoenix AODD pumps handle viscous, corrosive and abrasive fluids and fluids with suspended solids, with viscosities up to 50,000 cP. Fluimac lists them for sludge extraction, wastewater and filter-press feeding, and builds them in stainless steel, polypropylene and PVDF. ATEX versions are available for explosive atmospheres. See our diaphragm pumps page. For abrasive slurries and high solids content, Fluimac Helios peristaltic pumps are self-priming and can run dry.
How to choose a sludge or slurry pump
- Solids content: percentage of dry matter, and the size and hardness of the particles.
- Abrasiveness and chemistry: this sets the materials of the rotor, stator, diaphragm or hose.
- Flow and pressure: how much, how far and how high you need to pump.
- Feeding: if the sludge does not flow to the pump, a hopper pump or a screw feed is needed.
- Utilities and area: compressed air for AODD, and ATEX rating if the area is hazardous.
For a closer comparison of the two most common choices, read progressive cavity vs AODD pumps for viscous fluids and sludge.
Frequently asked questions
What is the best pump for sludge?
For thick sludge at higher pressure, a progressive cavity pump is usually the best choice. For very thick sludge that does not flow to the pump, a hopper progressive cavity pump is used. For smaller or intermittent duties, an air-operated diaphragm pump is a good option.
What is the best pump for abrasive slurry?
Peristaltic pumps and diaphragm pumps handle abrasive slurries well, because the abrasive fluid does not touch seals or close-clearance parts. Progressive cavity pumps are also used, with a stator and rotor material chosen for abrasion.
Can a diaphragm pump handle sludge?
Yes. Air-operated diaphragm pumps pass solids, run dry and need no mechanical seal, so they are widely used for sludge and wastewater transfer and filter-press feeding.
How much dry matter can a hopper pump handle?
Nova Rotors rates its H series up to 18% dry matter, the HS series up to 35% and the HSB series, with a bridge breaker, up to 40%.
Power Energy Gulf supplies sludge and slurry pumps across Saudi Arabia and the GCC. Contact us with your fluid, solids content, flow and pressure, and we will recommend a suitable pump.