Egham Water Treatment Works Flow 2920 m 3h

Egham Water Treatment Works Flow: 2920 m 3/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-O 3 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 O 2

Intermediate O 3 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 p. H is about 7

Sludge Centrifuge