Egham Water Treatment Works

Flow: 2920 m3/h

Source

• Thames River

Screening

• With surface boom

Rotating Mesh Screen

Debris from Screens

Pre-ozone in-line injector

• Purpose: to help with coagulation

• They also add pre chlorine to breakpoint any ammonia– needed ~80% of time?

Pre-O3 injector and static mixer

• 4 elements• 700 mm diameter

• 196 mbar headloss• 97% transfer efficiency

Gravity Settling Tanks

• Sludge blanket

• submerged conical sludge collectors– can be barely

seen here– suspended

from above

• Nigel describing sludge cones to class

Dual Media rapid filters

• Anthracite & Sand

• siphons (good practice)

Intermediate Ozone Building

Liquid Oxygen Tank

Liquid oxygen equipment

LOX handling

• Heat transfer

Ozone Generator

• Trailigaz

• One of 3 units– only one in use that day

Ozone Generator

• No blue glow, because of pure O2

Intermediate O3 Monitor

• Purpose of inter ozone: disinfection

• criteria: 0.4 mg/L residual after 4 minutes in contact tank

GAC contactors

• Modular design

• Avoided need for expensive in place concrete– problems with

leaks

Final Disinfection

• Free chlorine– shoot for a residual of about 0.5 mg/L– requires a dose of ~ 2-3 mg/L

• Addition of sulfur dioxide– to achieve target FRC

• THMs are low (~30 ug/L)– except when prechlorinating– final pH is about 7

Sludge Centrifuge