Rethinking Pumping Station Design in the Era of Water Efficiency
Water is a precious commodity, and with water-saving utilities forming a key part of modern-day construction, we ask how this affects a pumping station design.
The rules of both Sewers for Adoption and DCG are based upon calculated flow rates taken from historic data, yet arguably, this may not reflect the needs and effective handling of today's sewage.
Sewage contains less water, more solid content, and with the addition of rags and fats, sewage is more difficult to handle than ever.
The Septicity Challenge
Septicity, and the production of a dangerous byproduct, H2S (hydrogen sulphide), occurs when sewage has limited direct access to oxygen (traditionally a 4–6-hour period of retained time). The primary trigger point for such an event is within the pumping station rising main, resulting in the requirement of additional plant, such as chemical dosing systems, to counter such hazards, which can be costly. Learn more about Septicity in Pumping Stations.
Efficiency vs. Practicality: Are We Designing for Reality?
Today’s pump manufacturers focus on efficiency; more output for less power input. Yet, pump efficiency combined with the handling of today’s sewage, we again ask if the two align and truly reflect our needs in the UK.
The combination of a pump with suitable solids passage in direct coordination with the correct sizing of the rising main is key, ensuring reliable operation whilst limiting the associated risk of septicity occurring.
The Trade-Off: Bore Size vs. Operational Risk
There is a common recommendation to use larger bore rising mains to facilitate solids passage and ease installation. However, this approach can be counterproductive. Larger diameter mains inherently increase retention time, thereby heightening the risk of septicity and associated consequences.
Conversely, smaller bore mains—while potentially increasing frictional losses and requiring higher kW motors—can reduce retention times and lower the septicity risk. Although operational costs may rise due to higher energy usage, this must be weighed against the much higher costs of:
- Pump blockages
- Emergency maintenance
- Environmental compliance issues
- Chemical dosing plant installation and operation
Looking for expert guidance on pumping station design?
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