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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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