When considering an influent lift station design for a new facility or replacement, there are three basic design concepts. The advantages and disadvantages of each option depend on site specific features and operational preferences. The options are:
- Self-priming centrifugal pumps – In this option, the centrifugal pumps pull a lift out of the wet all and are kept out of the confined space. The benefits are that the pumps are much easier to access and maintain, and kept out of the process which reduces wear and corrosion. The pumps can also handle pretty much any solids that come through, which is helpful with influent lift stations. Disadvantages are that the pumps are less efficient than other options. The ability to pull a lift is also limited, and depending on depth of the influent pipes the pumps might need to be located below grade. Due to the ease of maintenance and trash handling capabilities, this option is the Probst preferred if conditions allow.
- Submersible pumps in a wet pit – The most traditional and simple concept, with a single wet well and the submersible pumps located in the wet well. The primary benefits are that it can work at any depth of wet well at high efficiency levels, requires the smallest footprint and has limited above grade infrastructure. The drawbacks are that the pumps can be difficult to maintain and generally don’t last as long because of corrosion issues, and the ability to handle solids is more limited. Submersible “chopper” style pumps exist, but have limited flow ranges. Stainless steel options on submersible pumps to improve longevity exist, but are expensive.
- Submersible pumps in a dry pit – Considered a hybrid option between the first two. Dry-pit submersible or pedestal pumps can be in a separate dry vault adjacent to the wet well. This offers the advantage of higher efficiency pumps and keeping them out of the process fluid. It still has the disadvantage of requiring confined space entry and reduced solids handling capacity.
In all options the pumps can be controlled on/off, or dynamically using a level sensor and VFDs.
Understanding each unique situation and selecting the correct pump to meet your facility needs can be challenging. The expert team at That Probst Group can help identify the best solution for you.
The Probst Group