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Hanningfield WTP. Essex & Suffolk Water. UK Water Supply Only Companies. Essex Plants. Chigwell Row: 90 ML/d ozone: atmospheric pressure static mixer 18 slow sand filters (6 with GAC sandwich) 10 cm GAC on bottom Hanningfield: 220 ML/d Lever le Haye: 120 ML/d

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hanningfield wtp

Hanningfield WTP

Essex & Suffolk Water

essex plants
Essex Plants
  • Chigwell Row: 90 ML/d
    • ozone: atmospheric pressure static mixer
    • 18 slow sand filters (6 with GAC sandwich)
      • 10 cm GAC on bottom
  • Hanningfield: 220 ML/d
  • Lever le Haye: 120 ML/d
    • slow sand (all sandwich) (no ozone)
  • Langford: 60 ML/d
    • 2 stage ozone (diffusers)
  • Langham: 55 ML/d
    • ozone: pressurized static mixer
    • 12 slow sand filters (10 sandwich)
suffolk plants
Suffolk Plants
  • Barsham
    • River Waverly
    • post GAC, no ozone
  • Lound
    • lake source, no pesticides (no ozone)
  • Ormesby
    • River Buer, pesticide problems
    • considered ozone, but ruled out in final design
    • 8 GAC contactors
hanningfield dam
Hanningfield Dam
  • Reservoir: 25,000 ML
raw water
Raw Water
  • DOC = 5-6 mg/L
  • algae
    • blue greens are particularly troublesome
  • formerly produced high levels of THMs
    • pre-chlorination
  • phosphate = 2-4 mg-PO4/L
treatment train
Treatment Train
  • Pre ozone
  • Flash Mix
  • Pulsator Clarifier
  • Pellet Reactor Softener
  • Rapid Gravity Filter
  • Intermediate Ozonation
  • GAC Adsorption
  • Chlorination
ozonation
Ozonation
  • Liquid Oxygen Feed
    • owned and operated by BAA (?)
  • Three Degremont Generators
    • 18 kg/hr each
  • Dose: designed for 5 mg/L total, current application is much less
    • 0.75 mg/L as pre
    • 0.35 mg/L intermediate
    • no residual out of either tank
    • ceramic diffusers
ozone continued
Ozone (continued)
  • Purpose
    • algae control
    • pesticide removal
      • isoproturon: most importantly - works well
        • mecoprop, diuron, chlortoluone, 2,4-D also
      • doesn’t work so well alone for atrazine or simizine
        • but concentrations of these are dropping anyway
    • THM control
rapid mix
Rapid Mix
  • Original tanks were too large
    • floc growth began before exiting tank
    • Coagulant addition to tank effluent
coagulant addition
Coagulant Addition
  • Addition on effluent weir
  • Ferric Sulfate
    • 6 mg-Fe/L
  • Polymer (LT20)
    • 0.1 mg/L
coagulation
Coagulation
  • Removes phosphate
    • otherwise it would interfere with softening process
pulsator
Pulsator
  • Degremont design
    • 3 m/hr overflow
    • upflow sludge blanket
    • draw and release on 40 s & 10 s cycle
    • 0.5 meter draw up
pulsator sludge removal
Pulsator Sludge Removal
  • Sludge draw off
    • four hoppers
    • valves opened separately on a cycle
on line iron analyzer
On-line Iron Analyzer
  • Measures total Iron
    • colorimetric method
  • Purpose: to monitor floc carryover
    • usually mirrored by turbidity
pumping station
Pumping Station
  • From pulsator to softener
pellet reactor softeners
Pellet Reactor Softeners
  • “Fast” alternative to precipitative softening
    • applicable to waters at 8 C or higher
      • as temp drops below 6 C, Lime carryover occurs
    • most used for groundwater
      • where there are now extreme low temperaturs
    • only a few others for surface water
      • Leiden, Netherlands
  • Use of sand accumulators
    • fine sand rises to to and stays there until it grows larger
pellet reactor softeners1
Pellet Reactor Softeners
  • Degremont Design
    • 8 units x 30 ML/d each
    • 5 minute contact (fast)
    • 80 m/hr overflow at center of tank
      • where sludge blanket is located
  • Lime addition (48 mg/L dose ?)
  • Introduction of Silver Sand
    • 0.2 mm as clean sand
    • 2-3 mm after accumulation of “chalk”
pellet reactor softeners2
Pellet Reactor Softeners
  • Entry of water at bottom
pellet reactor softener3
Pellet Reactor Softener
  • Treated water flume
pellet reactor softener4
Pellet Reactor Softener
  • Waste sand with “chalk”
pellet reactor softener6
Pellet Reactor Softener
  • Sand conditioning
rapid gravity filters
Rapid Gravity Filters
  • Anthracite/Sand
  • Air scour backwash
    • washwater returned to reservoir
intermediate ozone
Intermediate Ozone
  • Entrance security system
intermediate ozone1
Intermediate Ozone
  • Liquid residual monitors
    • all read zero!
intermediate ozone2
Intermediate Ozone
  • A view through the observation window
  • 3-chamber contactor
  • ability to add peroxide at 4 points for atrazine control
    • not used
gac adsorption
GAC Adsorption
  • Top of contactors
  • Norit carbon
  • backwash every 12 days
    • just for “good practice”
chlorinators
Chlorinators
  • Vacuum system
final disinfection
Final Disinfection
  • Chlorination mostly
    • residuals
      • 0.8 mg/L at plant effluent
      • 0.1-0.5 at end of system
    • about 50 ug/L THMs
    • CT standard is about 20-30 for surface water (10 for groundwater)
      • company standard, none imposed by DWI
  • Post contactor ammoniation (summer only)
    • some nitrite problems
      • need occasional chlorine pulse
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