icwes15 - reducing corrosion in wwt inlet tanks by returning mixed liquor. presented by anna b...
TRANSCRIPT
Corrosion Problems
Concrete & metal corrosion
Costly repairs, maintenance
and upgrades
Methods to
Reduce Corrosion:
Open-to-air tanks
Extraction of gases
Chemical dosing
What causes the Problem?
What is Hydrogen Sulphide?
Chemical Formula H2S
“rotten egg gas”
colourless, very poisonous, flammable gas
Where does H2S come from?
Organic matter in sewage decaying without the
presence of an oxygen source.
What does H2S do?
H2S forms which corrodes
concrete and metallic structures in enclosed tanks
The Mixed Liquor Idea
What is Mixed Liquor?
Biological mass (activated sludge, “bugs”)
and sewage combined
Why and How does it work?
Contains Nitrate (oxygen source)
Contains certain bacteria that reverse the H2S production
Dilution effect – dilution is the solution!
Why is it a ?
Readily available – cheap and simple
Nothing new is introduced to the process – no additional operational
hazards
Plant Modifications simple – redirecting the ML to the inlet works
Basic Process Layout
Biological Activated
Sludge Tank
(treatment)
Raw Sewage
WA
S
Effluent
Inlet Works
H2S off gas
H2S in liquid
Mixed Liquor
Trial Methodology
Third Stage
Full Scale Trials What, How and When do we do it?
Second Stage
Bench Scale testing What and How do we prove it?
First Stage
Literature Review Would it Work and Why?
Undertaking Full Scale Trial
Install ML pipes
Onsite Testing &Monitoring Reviewing data and dealing
with problems Wet Weather
Diurnal Flow Pattern
Sewage Quality
Stability of H2S in liquid
Implications….
Increased life of assets
Reduced maintenance/replacement
Reduced odour emissions (happy neighbours)
Reduction in chemical usage
Increased understanding for design purposes
Thanks To…
My colleagues at Hunter Water Australia for
providing guidance and support
Hunter Water Australia for dedicating time
and resources
Hunter Water Corporation for funding a large
part of this project
Special Thanks to all of YOU!