Positive Displacement Pumps for Water and Wastewater Treatment: Buying Guide

Executive buying summary

Positive displacement pumps are essential for water and wastewater treatment, moving liquids with a consistent volume per cycle, making them ideal for precise dosing and high-pressure applications. Selecting the right pump involves balancing performance requirements with factors like space constraints, operator skill levels, and long-term maintenance needs. Total cost of ownership is influenced by energy consumption, repair frequency, and the availability of skilled technicians. A significant risk is selecting a pump unsuitable for the specific fluid characteristics, leading to premature failure and operational disruption.

• Careful consideration of the fluid's properties, such as viscosity and solids content, is paramount for selecting the appropriate pump type.
• Compliance with relevant standards, including those related to safety, energy efficiency, and hygiene, is a mandatory requirement.
• The required flow rate and pressure head must be accurately determined to ensure optimal pump sizing and performance.
• Operator training and readily available service support are crucial for maximising pump lifespan and minimising downtime.
• Lifecycle costs, including energy consumption and maintenance, should be factored into the overall purchasing decision.

Equipment types compared

Key features to look for

• Materials of Construction: The pump's materials must be compatible with the fluid being handled to prevent corrosion or degradation; ask for material certifications and chemical compatibility data.
• Sealing System: Consider the type of seal (mechanical, packed) and its suitability for the application to minimise leakage and environmental impact; enquire about seal material options and maintenance requirements.
• Drive Mechanism: Evaluate the motor type (electric, pneumatic, hydraulic) and its efficiency, considering energy consumption and operating costs; request motor specifications and efficiency ratings.
• Variable Speed Drive (VSD) Capability: A VSD allows for flow rate adjustment, optimising energy use and process control; confirm VSD compatibility and control options.
• Instrumentation and Control: Assess the pump’s ability to integrate with existing control systems and provide feedback on performance; check for communication protocols and remote monitoring capabilities.
• Noise Levels: Excessive noise can be disruptive and require additional mitigation measures; request noise emission data and consider vibration dampening options.
• Ease of Maintenance: Simple access to wear parts and straightforward maintenance procedures reduce downtime and repair costs; inquire about maintenance schedules and spare part availability.
• Footprint and Mounting Options: The pump's size and mounting requirements must align with available space and structural capacity; request detailed dimensions and mounting instructions.

Pros and cons of each equipment type

Reciprocating Pumps

Pros:

• Capable of generating high pressures.
• Suitable for viscous fluids.

Cons:

• Can be noisy in operation.
• Higher maintenance requirements due to moving parts.

Rotary Lobe Pumps

Pros:

• Handle fluids with solids effectively.
• Gentle pumping action, minimising shear.

Cons:

• Lower efficiency compared to other types.
• Can be susceptible to clogging.

Peristaltic Pumps

Pros:

• Excellent for precise metering.
• Fluid only contacts the tubing, ensuring purity.

Cons:

• Limited flow rates and pressures.
• Tubing requires periodic replacement.

Screw Pumps

Pros:

• Efficient for high-volume applications.
• Handle fluids with high solids content.

Cons:

• More complex design.
• Higher upfront cost.

Gear Pumps

Pros:

• Versatile for a wide range of applications.
• Relatively compact.

Cons:

• Can be noisy.
• Limited ability to handle solids.

Which facilities each type suits

• Reciprocating Pumps: High-pressure dosing applications in advanced wastewater treatment plants, sludge dewatering.
• Rotary Lobe Pumps: Handling sludges and viscous materials in sewage treatment, food processing.
• Peristaltic Pumps: Chemical dosing in disinfection processes, precise reagent addition.
• Screw Pumps: Large-scale water transfer and boosting in municipal water treatment.
• Gear Pumps: General purpose pumping tasks in various water and wastewater processes.

Buyer's checklist

1. Confirm the fluid's viscosity, solids content, and temperature to ensure pump compatibility.
2. Verify the required flow rate and pressure head, accounting for pipework losses.
3. Check for compliance with relevant standards, including BS EN 809 and UKCA or CE marking.
4. Assess the site's power supply and ensure compatibility with the pump's motor.
5. Evaluate operator skill levels and arrange for adequate training.
6. Establish a maintenance schedule and secure access to spare parts.
7. Consider the pump's noise emissions and implement mitigation measures if necessary.
8. Review the pump's energy efficiency and calculate lifecycle costs.
9. Obtain detailed performance curves and warranty information from the supplier.
10. Validate the pump's performance after installation and commission it properly.