Primary treatment


Raw wastewater has a high content of large materials, such as toilet paper, textiles, napkins, as well as plastic bags, pieces of wood. Such materials must be removed as the first part of the treatment process, not least to prevent clogging and possible malfunction of mechanical equipment at the wastewater treatment plant. The screening station is therefore the first step in the mechanical treatment of wastewater.

Effective washing of the detained material will reduce the amount of disposal significantly and prevent odour problems. Grundfos offers pump and control solutions for the effective backwash of the screens, ensuring reliable operation of your screening station.

The Grundfos Hydro MPC range of multistage pressure boosting systems means you can manage your pressure zones with ease, and together with our range of level sensor accessories will ensure effective washing of the entire screening station.

Sand, grit and grease removal

Once wastewater has been screened for the removal of large materials, mechanical treatment’s next step is the removal of grit and grease. Removing these prior to commencing biological treatment of wastewater is essential for ensuring the smooth operation of the wastewater treatment plant.

The usual solution is an aerated grit and grease chamber, where aeration operates continuously to keep organic matter in suspension while grit and grease is removed through sedimentation and floatation. If sand and grit are not removed and continue to the primary clarifier or even further in the plant, a significant increase of clogging and wear on equipment could result.

Removal of grit requires robust and durable pumps. The Grundfos ranges of SE/SL and S pumps with vortex impellers are specifically designed for durable use with heavy sewage flows and can be installed dry or submerged. They offer the reliability you need to ensure safe operation. Diffuser systems from Grundfos offer fine or coarse bubble diffusers for large air flows for the separation processes of the grit and grease removal.

Equalisation tank

The equalisation tank is where excess wastewater can be stored during heavy rain. Equalisation tanks can be an effective way of cost-optimising the wastewater treatment plant as this allows for the construction of smaller tanks for treatment and ensures a steady hydraulic load through the plant.

Grundfos offers a range of pumping and control solutions as well as mixers and cleaning equipment that together ensure reliable and automatic operation of the stormwater tank. Once the hydraulic load is reduced and capacity is available, you can get wastewater moving again with perfect efficiency.

Stormwater tanks can be built to almost any size and shape. The inlet and outlet can be managed by gravity, by a pump system or a combination of both, depending on hydraulic conditions in the system. Grundfos has the pumps to cope with these heavy demands. The Grundfos ranges of SE/SL, S and KPL/KWM pumps are specifically designed for durable use with heavy flows and can be installed dry or submerged. The Grundfos range of level sensor accessories ensures that your pumps system can control possible fluctuations in demand for performance. This ensures the optimum delivery of wastewater to and from the equalisation tank.

Efficient mixing and cleaning of equalisation tanks is essential to minimise operation costs avoid odour problems. The Grundfos range of RainJets is especially designed for this purpose, offering a robust construction and easy service and maintenance. The RainJets can work either alone or together with the robust and durable AMD mixer.

Control and monitoring systems increase the potential for improving both efficiency and reliability. In addition to variable speed drives (Grundfos CUE), Grundfos supplies motor protection (MP204) to monitor motor conditions, ensuring optimal operation.

Primary clarification

Following mechanical treatment, the purpose of primary clarification is to reduce the organic load prior to biological treatment. Simply by letting particles settle by gravity, a significant part of organic impurities in wastewater can be removed, and this is a cost-effective way to reduce the size and cost of biological treatment.

It is important to create optimal conditions for settling under primary clarification, and therefore the flow conditions and water velocities are designed to favour sedimentation. The settled matter resulting from primary clarification is referred to as primary sludge, which is then pumped from the primary clarifiers to sludge treatment. The Grundfos ranges of SE/SL and S pumps with vortex impellers are specifically designed for durable use with heavy sewage flows and can be installed dry or submerged.

Chemicals and poly-electrolytes can be added to increase efficiency and improve sludge settling, helping remove up to 80% of the suspended matter. Grundfos can supply complete dosing pumps systems for large or small volumes and based on different technologies for precipitation and flocculation and pH adjustment, and PLC-controlled, fully automatic systems to handle preparation and the reliable dosing of organic coagulants or poly-electrolytes.

Grundfos can supply the specialist expertise to help meet your performance objectives, from the initial identification of needs, to the selection, installation, operation, and maintenance of the pumping and dosing solution. Grundfos commissioning agreements ensure correct installation and service agreements cover all eventualities, from routine maintenance to spare parts.


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