Transcript 08 N removal by PND - Murdoch University

PND –A Novel WasteWater Treatment
Process Designed Around Biology
Dr. Ralf Cord Ruwisch
PND - Wastewater Treatment
Technology Adopted from Nature
Dr. Ralf Cord Ruwisch
Background of Invention:
•
15 Years of R&D on Advanced Wastewater Treatment
•
4 PhD candidates (now working as engineers/scientists)
•
Numerous publications
•
Most promising outcome (PND) now a patent application in
international phase
•
Inventor team: Dr. Ralf Cord-Ruwisch, Dr. Leonie Hughes
•
IP holder: Murdoch University
Objective of Waste Water Treatment
Avoid:
1. Outbreaks of disease
2. Pollution by solids
(Prim. Treatment)
3. Pollution by soluble organics
(Sec. Treatment)
4. Pollution by nutrients, e.g. N
(Tert. Treatment)
The last two steps are biological and essential to
minimise pollution and enable water reclamation
Pollution by Nitrogen
N-pollution leads to algal
blooms
Key pollutants are:
• Ammonia
• Nitrate
Pollution by Nitrogen
Algal blooms can be spectacular
Pollution by Nitrogen
Also at “normal levels around cities” N
pollution can turn toxic
Pollution by Nitrogen
Evan at “low levels” N pollution can kill reefs
and other ecosysmtems
Pollution by Nitrogen
Legislation asks for lowest N-levels with best
proven technology
N-Removal inWastewater Treatment
In Wastewater
Nitrogen is present
as ammonia.
Extremely high
numbers of
biodegrading
bacteria are needed
to remove it.
Arial view of Biological Wastewater Treatment in Perth
“Challenge to keep up with expanding population”
Why is N removal difficult ?
N removal requires 2 processes:
Aerobic:
Ammonia + O2  nitrate
(nitrification)
Anoxic:
Nitrate + Organics  N2 (denitrification)
Traditional plants can’t make both processes work
 Residual N pollution in urban areas
Reason: Traditional Design based on maximum O2 supply
Problem of Traditional Approach
CO2
Organics
Ammonia
Aerobic
O2
• Organics are
converted to CO2.
Nitrate
• Nitrogen is merely
converted into
another form.
• Additional nitrate
removal is needed.
Problem of Traditional Approach
Organics
Ammonia
CO2
N2
Aerobic
Anoxic
Nitrate
O2
Nitrate con only be removed by anoxic denitrification.
However…
Problem of Traditional Approach
Organics
Ammonia
CO2
N2
Aerobic
Anoxic
Nitrate
O2
To carry out Nitrate removal, organics are needed !
Problem of Traditional Approach
Organics
Ammonia
CO2
N2
Aerobic
Anoxic
Nitrate
O2
The organics needed for pollutant release as N2 have
been destroyed in the aerobic step.
Problem of Traditional Approach
Organics
Ammonia
CO2
N2
Aerobic
Anoxic
Nitrate
O2
Current practice is to take a portion of the untreated
organics from raw wastewater. Problem: Ammonia
addition.
Problem of Traditional Approach
Organics
Ammonia
CO2
N2
Aerobic
Anoxic
Nitrate
O2
Various add-on technologies have been developed:
• Multiple aerobic/anoxic steps
• Sophisticated O2 control (SND)
Problem of Traditional Approach
Organics
Ammonia
CO2
N2
Aerobic
Anoxic
Nitrate
O2
Problems of existing plants:
Expensive, Incomplete N removal, High maintenance,
Learning from Biology (Nature)
Organics
Ammonia
CO2
N2
Aerobic
Anoxic
Nitrate
O2
What happens in nature when highly polluted waste comes
in contact with bio-degrading bacteria ?
A
Continued over-supply
with organics
trains wastewater bacteria
to store lipids (fat)
C
PHB
Learning from Biology (Nature)
Organics
Ammonia
Lipid
Anoxic
Ammonia
In nature:
• No energy for excessive O2 supply.
• Organics removal by anoxic storage as lipid
Learning from Biology (Nature)
Organics
Ammonia
Lipid
Anoxic
Ammonia
Aerobic
Nitrate
O2
Subsequent O2 supply can initiate Nitrification
Learning from Biology (Nature)
Organics
Ammonia
Lipid
Anoxic
Ammonia
Aerobic
Nitrate
O2
Needed:
• Organics for Nitrate removal.
• Oxidation of Lipids (either needs O2 or Nitrate).
Learning from Biology (Nature)
N2
Nitrate
Lipid
Anoxic
Aerobic
Ammonia
O2
By recycling Nitrate containing water back:
• N removal is completed
• Nitrification and Denitrification operate in parallel…
Learning from Biology (Nature)
N2
Nitrate
Lipid
Anoxic
Aerobic
Ammonia
O2
… resulting in unrestricted N removal.
Parallel Nitrification and Denitrification (PND)
N2
Nitrate
Lipid
Anoxic
Aerobic
Ammonia
O2
Trad. Design:
Heavy handed O2 supply +
Fixing up the consequences.
PND:
Building around the biology
Performance of PND
N2
Nitrate
Lipid
Anoxic
N (mM)
3
Aerobic
Ammonia
O2
PND
2
SBR
1
0
0
100
Compared to state of art SBR technology:
PND removed N more completely, faster,
Time (min)
400
with less O2
(direct competition between PhD students: “Beaten hands-down without even trying”)
Performance of PND
N2
Nitrate
Lipid
Anoxic
N (mM)
3
Aerobic
Ammonia
O2
PND
2
SBR
1
0
0
100
Theory (modelling) supports results:
Nitrifying bacteria percentage:
>80% in PND
< 10% in SBR
Hence 8 times faster rates expected
Time (min)
400
Performance of PND
N2
Nitrate
Lipid
Anoxic
N (mM)
3
Aerobic
Ammonia
O2
PND
2
SBR
1
0
0
100
Time (min)
Key disadvantage of PND:
Separation of biomass from liquid required repeatedly:
PND: (3-5)
Trad. Systems (2)
However, other advantages to users:
400
Advantages for Users of the Technology
• Can meet lowest demands (>98%) for N removal
Barrier Reef Water Re-use
• Less (about 20%) aeration energy
• Smaller footprint (upgrading)
• Less process control !
• No risk of the greenhouse gas N2O emission
• Enables P removal (insufficient time to explain)
Implementation Options
•
New plants (however industry is very conservative)
•
Retrofitting existing plants
•
Step by Step implementation (pizza)
•
Set to become The New Standard ?
Arial view of Biological Wastewater Treatment in Perth
“Challenge to keep up with expanding population”
Development Stage
We are Here!
Synthetic lab
scale trials R&D
Lab trials on
real
Wastewater
Pilot Plant
Design & Cost
Feasibility
Engineering & market
input required
Pilot Plant
Construction
and Trials
Pilot or Demonstration
Site required +$$$’s
Licensing
Licensee
required
We are looking for…
• A potential demonstration site
• Engineering and Market expertise
• A potential licensee
Please Contact
Samantha Dymond
Email: [email protected]
Phone: 08.9360.7481
Ralf Cord-Ruwisch
Email: [email protected]
Spare
Current State of the Art: Simultaneous
Nitrification and Denitrification
Reaction Rate
Precise O2 control needed
De-nitrif.
SND
Dissolved O2 (mg/L)
Nitrif.
 Skilled operators
 Not always reliable
 Slowing down  incr. footprint
 Wasteful: COD and O2
 Emerging evidence of N2O
emission