Reducing the costs of pumping waste water using power logging and real-time efficiency displays
Snoxell, J., Southern Water, UK
(free)
Abstract
Pumping waste water is an expensive business. The raw flow pumped through the sewer network is aggressive and waste water pumps deteriorate rapidly over time. Industry data suggests that pump efficiency can reduce by over 20% in 10 years, or more rapidly in extreme conditions (WRc 2009).
The energy cost of raw waste water pumping in Southern Water is around £10m/year and we are looking at new ways of improving performance in this area.
We are using on-line power logging to monitor our largest waste water pumps in detail with the objective of reducing costs by monitoring individual pump efficiency, selecting the most efficient pumps at all times and identifying blockages quickly.
In order to monitor a large number of pumps simply and intervene quickly we have adopted a RAG system displayed in real time via telemetry, with pump efficiency calculated at the outstation.
This paper describes the conclusions from a 6-month study at Southern’s Elizabeth St pumping station in Dover and the developments that have arisen from this work.
Introduction
Pumping waste water is an expensive business. The energy costs for pumping raw water to treatment plants in Southern Water in 16/17 was around £10m (excluding treatment plant inlet pumps).
This flow generally contains road grit and other debris and consequently waste water pumps often deteriorate quickly; industry data shows that the efficiency of typical waste water pumps can decline by around 20% or more in 10 years (WRc 2009).
Most waste water pumping stations are arranged as Duty/Assist, or Duty/Assist/Standby and pump duty is rotated on hours run or time. As a result we don’t know whether the most efficient pump in a pump set is running or even what the efficiency of any individual pump is, since most pumps are not logged individually for power.
All we have is the energy consumption of the site (on which we are charged) and this may include a variety of pumps (eg storm pumps) and other equipment, making it difficult or impossible to identify inefficiencies in individual pumps.
The situation is complicated further by variations in rainfall which will bring storm pumps into operation at intervals, all of which are included under the single site meter.
Where we do monitor individual pumps in detail the results can be quite surprising.
This paper sets out the results of detailed pump efficiency monitoring over a 6-month period at two large Southern Water waste water pumping stations and the developments that this has led to in improving pump operation.
