Located next to the River Yare, Trowse Terminal Pumping Station (PS) is one of the largest in Norfolk, dating back to Victorian times. Operated by Anglian Water, it handles most of the wastewater from Norwich, which is then pumped on to Whitlingham Sewage Treatment Works (STW).

As part of an ongoing energy programme, Anglian Water (AW) asked ITT Water & Wastewater (now Xylem), in conjunction with Panks Pumps, ITT’s energy partner for the East of England, to carry out an energy efficiency assessment of the Trowse Terminal PS, with a view to improving the energy performance of the aging station.

Trowse is a critical PS for AW and one of its top half hourly monitored pumping stations.

Serving a population of 265,000 people, Trowse accounts for 80% of the consented dry weather flow to Whitlingham STW, which equates to 53,000m3/d of wastewater.

At the site there are three storm pumps and six dry weather flow pumps installed in a dry well. The dry weather flow pumps, installed in 1989, were 450/450 170kW pumps, discharging via two 1200mm rising mains to Whitlingham STW. The first three pumps discharged via the old main and the latter three, discharged via a new main, added in 1989. The pumps had been refurbished several times but were regularly blocking, resulting in expensive downtime and increasing the risks of sewage entering the adjacent River Yare.

Following a full energy survey of the site by Panks Pumps, a potential £59,000 annual saving was projected if the three pumps discharging into the new main were replaced with energy saving ITT Flygt pumps. With the supply of energy efficient pump products, including installation and associated alterations to the dry well, the full investment would take less than five years to fund through energy savings.

One year on, following a validation exercise to confirm the projected energy capture, the results have been even better than predicted. The actual energy saving were higher than forecast equating to a saving of 727,648kWh of energy per year, reducing the payback time for initial investment to less than four years. And even with two pumps running simultaneously the volume is at an acceptable decibel level.

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