Orica introducing system to extend sewer life and avoid corrosion to the UK

1. Extending Sewer Asset Life and
Deferring Major Capital Expenditure
with the use of
SulfaLock HiGel™
Stuart Jessop
Orica Watercare
Orica Watercare

2. Introduction & Background
• HiGel™ is a sacrificial alkaline surface coating
which protects against aggressive acid attack
• HiGel™ is suited to applications where:
– assets are deteriorating
– asset retains structural integrity
– Capital not available for asset rehabilitation
• Trial work on SWC sewers
– Sans Souci 250 m x 1m box section
– NGRS 4.2 km (2006-08)
– SWSOOS 10.4 km (2009-10)
• HiGel™ coating lasts between 2 & 3 years
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™ 2

3. Sulphide Generation &
Acid Production
Reactions in a sewer system
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™ 3

4. Sulphide Generation &
Acid Production
Two-part process:
i. Reduction of sulphates to sulphides
• Occurs in the slime layer
• Anaerobic conditions
• Sulphate Reducing Bacteria
• Sulphide is released to form gaseous H2S at sewer
surface (equilibrium)
ii. Oxidation of sulphides to sulphuric acid
• Moisture enables the gaseous H2S to absorb into the
sewer wall
• H2S is oxidised to sulphuric acid by Sulphur Oxidising
Bacteria, thiobacillus concretivorious
• Thiobacillus bacteria will proliferate in the range of pH 1
to pH 6.
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™ 4

5. Concrete Corrosion
• Sulphuric acid reacts with concrete to form calcium
sulphate as a by-product (gypsum)
– Soft, expansive compound with no binding or structural
properties
• Corrosion rate dependent on:
– wastewater pH
– aqueous sulphide concentrations
– the flux of H2S(g) to the pipe wall
– rate of sulphuric acid production
– the alkalinity of the pipe material
• Surface pH - measure of concentration of acid present
• Indicator of corrosion potential
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™ 5

6. Sewer Wall pH - Corrosion Rate
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™ 6

7. Corrosion Protection Mechanism
• Sacrificial alkaline surface coating
– Neutralises remaining acid
• Residual alkalinity
– Neutralises acid as it is formed
• High wall pH
– Retard the proliferation of sulphide oxidising bacteria,
thereby reducing the amount of acid production
• Natural ‘buffer’ pH 9.8
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™ 7

8. SulfaLock HiGel™
HiGel™ Properties
• 60% aqueous suspension of Mg(OH)2
• Thixotropic non-Newtonian liquid
– Gelling characteristic
– Pumpable
– Adheres to structures allowing a 2 mm coating to be
built up
– No excessive run-off
• Non hazardous
• Non dangerous-good
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™ 8

9. Process - CCTV
CCTV
• Before cleaning
• After HiGel™ application
• Provides baseline & quality control
• Ensure adequate removal of corroded concrete
• Ensure complete HiGel™ coverage
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™ 9

10. Process - CCTV
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™ 10
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™

11. Remote Application Equipment
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™ 11
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™

12. Remote Application Equipment
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™ 12
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™

13. Process - Cleaning
Surface Preparation
• Water cleaning
• Removal of slime layer and loosely bonded
corrosion by-products
• Medium pressure (4.3 bar)
• Ensure a firm base for HiGel™application
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™ 13
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™

14. Process - Cleaning
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™ 14
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™

15. Process - Application
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™ 15
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™

16. Process - Application
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™ 16
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™

17. Process - Application
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™ 17
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™

18. Process - Application
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™ 18
Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™

19. Process - Application
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Extending Sewer Asset Life and Deferring Major Capital Expenditure with the use of SulfaLock HiGel™

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