×
Saving water at Stanger Mill
2,000 m3
of water recovered
per day
Stanger Mill abstracts water under licence from the Mvoti River, but cannot sustain processes when there is low flow, forcing some plants to shut. Through process modelling and mass balances it was established that approximately 2,000 m3 of water per day – a significant amount – was used for backwashing filters at the process water plant. The backwash water was then discharged into the nearby Mbozambo lake.
The mill implemented a backwash recovery project which involved sampling and testing the backwash stream for turbidity, suspended solids, as well as cations and anions. An ion balance was conducted, from which the mill concluded that the backwash
stream could be utilised in the process if the suspended solids were removed. The recommendation was made that the backwashed water be pumped upstream to the nearby water clarifier, allowing settling of the suspended solids, and the clean supernatant to overflow back to the process water plant for reuse.
This was achieved by connecting the backwash and forward wash outlet pipes from each of the six filters to a newly installed common header that discharges the water into the newly constructed sump. Construction began in June 2022 and the
project was successfully commissioned in September 2022. The system is currently recovering 2,000 m3/day on average, an amount that represents 11.5% of the mill’s
total water usage.
Performance against our Thrive25 target aligned with SDG6:
Clean Water and Sanitation
| Reduce specific water use in water-stressed locations by 23% (m3/adt)1 |
44.5 m3/adt |
43.0 m3/adt |
 |
1ADT = dry solids content of 90% and moisture content of 10%.