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-PO 4 /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/L Polymer (LT20)Polymer (LT20) –0.1 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 at end of system –about 50 ug/L THMs –CT standard is about for surface water (10 for groundwater) company standard, none imposed by DWI Post contactor ammoniation (summer only) –some nitrite problems need occasional chlorine pulse