Inverness, Scotland


2001, extension 2006


Surface water


Earth Tech Engineering Ltd


Potable water production


Scottish Water (previously “The North of Scotland Water Authority”)


40 MLD (10.6 MGD)


In 2001, Scottish Water has installed a new 34 MLD (9 MGD) water treatment plant for potable water supply to the town of Inverness and surrounding area. The raw water source is a blend from Loch Ashie (7 MLD) and Loch Duntelchaig (27 MLD). Major goals of the plant upgrade included:
  • Micro-organism barrier
  • Color removal
  • Minimize the waste flow
Prior to the construction of the full scale plant, tests have been carried out to confirm coagulation combined with ultrafiltration (UF) is capable of achieving these goals.
Objective bench scale tests (0,08m2) and pilot trails (70m2) have successfully been carried out. These trials showed that membrane technology is an appropriate and cost-effective solution to reach the goals. Because of the limited sewer capacity, the waste volume had to be minimized. By introducing a secondary ultrafiltration most of the waste stream of the primary is reused with the result that the total waste stream is minimal. In 2006, the plant was expanded to 40 MLD (10.6 MGD).

 system design

The backwash waste from the secondary UF system is discharged to sewer whilst the secondary permeate is blended with the primary permeate. Waste from CEB is neutralised prior to discharge.

water quality

unit  feed  permeate 
 1 -25
0.2 – 4.0  < 0.1 
°Hazen  2 - 25  < 5 
 10 – 20,000
 0 - 10,000
0 – 100

scope of supply

7+2 UF skids including 768 Xiga 40 membrane modules

Plant automation

Engineering & commissioning