CASE26 · Water & wastewater · Pumps
Verifying inlet-pump efficiency after replacement
Five-minute and monthly operating data were used to compare wastewater throughput and electricity before and after inlet-pump replacement. Flow-normalized performance improved while the reported treatment capacity remained broadly comparable.
01 · CASE ANALYSIS
Verification challenge
Wastewater inflow changes with time, rainfall and tank level. A simple comparison of electricity totals could therefore confuse changes in pumping demand with the effect of replacement.
The PLC’s level-based unit count and pump combinations were checked before comparing flow and power at corresponding level/head conditions.
02 · CASE ANALYSIS
Data & method
The comparison used tank-level control rules, pump combinations, flow in m³/h, power in kW, one month of total inflow and electricity on each side of replacement, and five-minute data for representative maximum-inflow days.
UPI = pump electricity (kWh) ÷ treated wastewater volume (m³). Monthly and representative-day UPI were cross-checked against flow–power scatter patterns.
| Indicator | Before | After | Interpretation |
|---|---|---|---|
| Monthly UPI | 0.076 kWh/m³ | 0.071 kWh/m³ | 6.8% improvement (reported) |
| Maximum-flow-day UPI | 0.078 kWh/m³ | 0.071 kWh/m³ | 8.9% improvement (reported) |
| Monthly average power | 211 kW | 167 kW | Demand differed; not the savings-rate basis |
| Maximum throughput | Approximately 5,277 m³/h | Approximately 5,149 m³/h | Capacity broadly maintained |
03 · CASE ANALYSIS
Observed results
Monthly UPI changed from 0.076 to 0.071 kWh/m³, with a reported improvement of 6.8%. On maximum-flow representative days, UPI changed from 0.078 to 0.071 kWh/m³, with a reported improvement of 8.9%.
Average monthly power fell from 211 to 167 kW. Because average inflow differed, this power reduction was used as an operating-pattern indicator rather than the primary savings rate.
Maximum throughput was approximately 5,277 m³/h before and 5,149 m³/h after replacement under three-pump operation. The source interpreted the capacity as broadly maintained.
04 · CASE ANALYSIS
Measurement & verification
The principal finding is improved electricity per unit of treated volume within the reported comparison periods. It is not a claim of a universally applicable pump savings rate.
For longer-term M&V, account for flow, tank level/head, active units, rainfall-related inflow changes and operating time. Compare equivalent service conditions and keep PLC logic changes distinct from equipment replacement effects.
05 · CASE ANALYSIS
Engineering lesson
Pump optimization must satisfy required flow and head while reducing energy input. Parallel operation, variable speed and the actual operating point need to be evaluated as a system.
This framework also applies to water supply, process water and cooling-water systems. A future forecasting or anomaly-detection layer would be an extension rather than an observed result of this project.
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