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

– 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)

Chigwell Row Plant

Langham Plant

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

• Reservoir: 25,000 ML

Essex and Hanningfield

Area

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

• Pre ozone• Flash Mix• Pulsator Clarifier• Pellet Reactor Softener• Rapid Gravity Filter• Intermediate Ozonation• GAC Adsorption• Chlorination

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)

• 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

Thermal Ozone Destruct

Rapid Mix

• Original tanks were too large– floc growth began before exiting tank– Coagulant addition to tank effluent

Coagulant Addition• Addition on effluent weirAddition on effluent weir• Ferric SulfateFerric Sulfate

– 6 mg-Fe/L6 mg-Fe/L• Polymer (LT20)Polymer (LT20)

– 0.1 mg/L0.1 mg/L

Coagulation

• Removes phosphate– otherwise it would interfere with softening

process

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

• Sludge draw off– four hoppers– valves opened separately on a cycle

On-line Iron Analyzer

• Measures total Iron– colorimetric method

• Purpose: to monitor floc carryover– usually mirrored by

turbidity

Pumping Station

• From pulsator to softener

Lime Hoppers

Lime Saturator

Pellet Reactor Softener

• controllers

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 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 Bottom

Pellet Draw-off

Pellet Reactor Softeners

• Entry of water at bottom

Top of Pellet Reactor

Pellet Reactor Softener

• overflow

Pellet Reactor Softener

• Overflow weir

Pellet Reactor Softener

• Treated water flume

Pellet Reactor Softener

• Waste sand with “chalk”

Pellet Reactor Softener

• Effluent sand

Pellet Reactor Softener

• Sand conditioning

Rapid Gravity Filters

• Anthracite/Sand• Air scour backwash

– washwater returned to reservoir

Intermediate Ozone

• Entrance security system

Intermediate Ozone

• Liquid residual monitors– all read zero!

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

• Top of contactors• Norit carbon• backwash every 12 days

– just for “good practice”

Chlorinators

• Vacuum system

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