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