Hanningfield WTP

1. Hanningfield WTP Essex & Suffolk Water

2. UK Water Supply Only Companies

8. 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)

9. Chigwell Row Plant

10. Langham Plant

12. 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

20. Hanningfield Dam • Reservoir: 25,000 ML

21. Essex and Hanningfield Area

22. 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

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

24. 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

25. 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

26. Thermal Ozone Destruct

27. Rapid Mix • Original tanks were too large • floc growth began before exiting tank • Coagulant addition to tank effluent

28. Coagulant Addition • Addition on effluent weir • Ferric Sulfate • 6 mg-Fe/L • Polymer (LT20) • 0.1 mg/L

29. Coagulation • Removes phosphate • otherwise it would interfere with softening process

30. Pulsator • Degremont design • 3 m/hr overflow • upflow sludge blanket • draw and release on 40 s & 10 s cycle • 0.5 meter draw up

34. Pulsator Sludge Removal • Sludge draw off • four hoppers • valves opened separately on a cycle

35. On-line Iron Analyzer • Measures total Iron • colorimetric method • Purpose: to monitor floc carryover • usually mirrored by turbidity

37. Pumping Station • From pulsator to softener

38. Lime Hoppers

39. Lime Saturator

40. Pellet Reactor Softener • controllers

41. 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

42. 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”

43. Pellet Reactor Bottom

45. Pellet Draw-off

46. Pellet Reactor Softeners • Entry of water at bottom

47. Top of Pellet Reactor

48. Pellet Reactor Softener • overflow

49. Pellet Reactor Softener • Overflow weir

50. Pellet Reactor Softener • Treated water flume