Transcript Document

Innovations in Oxidation Technologies
to treat difficult wastewaters
Dr Peter Barratt
Business Manager
Environmental & Clean Technology
Air Products (Europe)
Oxidation:
The range of technologies
Ozone
Thermal
Wet
Oxidation
Ozone
Non- or poorly&
biodegradable Biological
Incineration
Organic
Component
Aerobic Biological
Stabilization
or
Thermal Wet Oxidation
Aerobic
Biological
Biodegradable
1
2
3
4
5
Organics Concentration (%)
Requiring Destruction
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High Purity Oxygen in Water
for Aerobic Biology… why?
 Increased Saturation Concentration (Cs)
– Oxygen in Air
– Oxygen
=
=
9.1mg/l @ 20oC
43 mg/l @ 20oC
 Rate of Oxygen Mass Transfer
– dC/dt = KLa (Cs - C)
– Pure oxygen maximises the oxygen
deficit, so oxygen dissolves faster
 Process benefits
– Microbes enjoy well oxygenated
conditions
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The Activated Sludge Process
Clarifier
Feed
Mixed Liquor
or
“Sludge”
Treated water
Settled Sludge
Returned Activated Sludge
(RAS)
Excess Sludge
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The Activated Sludge Process
Clarifier
Feed
Treated water
Mixed Liquor
or
“Sludge”
OXYGEN
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Settled Sludge
Returned Activated Sludge
(RAS)
Excess Sludge
OXYGEN
Classical Oxygenation by
sidestream oxygen injection
Pure Oxygen
Typically from
Liquid Oxygen
The OXY-DEP® process
Venturi-type
device
Secondary Ejector
Water
Intake
Recirculation Pump
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April 2005
Activated Sludge Basin
Paper Industry lagoon
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New development
OXY-DEP® VSA
On-site generated oxygen
 Technology
– Oxygen generator (Vacuum Swing
Absorption) linked to a low energy mixer
– Standard sizes:
• 150 lpm
(262kg/d)
• 500 lpm
(875kg/d)
• 2800 lpm
(5000kg/d)
– Simplicity and cost in line with aeration
– Process benefits of oxygen
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OXY-DEP® VSA
OXYGEN GENERATOR
MIXER-OXYGENATOR
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Aerobic Biological Treatment
 Aeration
• Typically 1 - 2kgCOD/m3/day
– MLSS 1.5 – 5g/l
• Up to 0.5kgNH3-N/m3/day
 Oxygenation
• High Rate Biological Treatment
processes
– Typically 2 – 5kgCOD/m3/day
• MLSS 3 – 20g/l
– Up to 5kgNH3-N/m3/day
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OXY-DEP® MB Process
Membrane
OXY-DEP
reactor
Effluent
O2 Inlet
Feed
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Wash
tank
OXY-DEP® MB benefits
 Refractory COD is treatable
 High rate system
– Above 30kgCOD/m3/day
 Low waste sludge production rate
– zero in 3 months (rendering)
 Provides potentially re-usable
water
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Oxygen - common uses in aerobic
biological treatment
 Increase treatment capacity of an
existing aerated plant
 Reduce odours, foams and aerosols
 Cater for peak organic and ammonia
loads as required
 Improve sludge quality
 Reduce regulatory risk and improve
environmental image
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Direct Ambient Oxidation
 Oxidation Processes
• Rising Main Injection (sewers)
– avoids H2S and corrosion
• Sulphide (S-) Oxidation
– e.g. lagoons
• Ozone
– Hard COD and colour removal
O2 & O3
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Ozone
 Unstable oxidant
 Generated on site
 Precursor to .OH
 Water treatment
 In conjunction with biological
treatment
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CHEMOX Reactor for O3
Gas
Outflow
Impinging
Zone
Liquid
Outflow
Guide Tube
Main Tube
Nozzle
Liquid Feed
Gas Inflow
Pump
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CHEMOX - landfill leachate
Existing Plant
 CHEMOX
 1.8
O3 :COD ratio*
 > 2.2
 4 hours
HRT
 10.3 hours
 500 mg/l
CODin
 500 mg/l
 <150 mg/l
CODout
 <150 mg/l
 4 kWh/kgO3
Powerdiss
 8 kWh/kgO3
*:
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April 2005
ozone applied/COD removed
CHEMOX - landfill leachate
Existing Plant
 CHEMOX
 1.8
O3 :COD ratio*
 4 hours
 > 2.2
 10.3 hours
COST ADVANTAGE
 500 mg/l
COD
 500 mg/l
HRT
in
 <150 mg/l
CODout
 <150 mg/l
 4 kWh/kgO3
Powerdiss
 8 kWh/kgO3
17% lower in capital
29% lower
in
operation
*
: ozone applied/COD removed
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Other Ozone
Applications
 Sludge solids oxidation
– Activated sludge in-process
 Pathogen removal in reused water
 Alternative clean oxidant in
chemical synthesis
 Selective destruction of problem
bacteria e.g. bulking
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Oxygen reuse technology
after ozone production
 Normally, conversion of O2 to O3 is
6% to 12% by weight. Therefore:
– Oxygen off-gas use in other
processes
– Long Loop Recycle (LLR)
– Short Loop Recycle (SLR)
• O2 and O3 separated after the
ozoniser, and O2 recycled to
produce O3
• 98% conversion of O2
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SLR Benefits - example
Straight
Through
Total
$2.50
40% Savings
Cost
$2.00
15% Savings
SLR Total
$1.00
$0.50
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Capital
Power
Oxygen
8
12
16
Ozone Concentration [wt%]
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