1. No category

Ozone technology for the
tertiary wastewater treatment
of pulp and paper plants
Florian Milz
Sales and Application Engineer
WEDECO Ozone Products
Content
Ozone and Biology
• treatment needs
• principle effects
• compare with alternatives
• Case Study A
• Case Study B
• Case Study C
• Summary
P&P process and waste water
•
•
•
•
•
5 – 20 m3/water is used per 1 t of product
0.5 – 5 kg COD per 1 t of product
20 – 30 kg COD per Adt pulp (modern Kraft Mill)
non biodegradable COD is 4 – 8 kg per Adt pulp
200 – 500 mg/L COD after biological treatment
(Adt = air dry ton of pulp)
P&P process and waste water
Carbohydrates have a BOD/COD ratio of 0.6 to 0.65 and are
easily degradable. They represent the most of the
biodegradable matter in P&P effluents.
But a small amount of the effluent content is nonbiodegradable (i.e. BOD/COD < 0.1). The remaining COD is
called hard COD.
P&P process and waste water
Treatment Needs for COD reduction – The
Problem
•
•
•
•
•
Most Industrial Waste Waters treatment concepts
include biological steps
Overall COD is only reduced to a certain limit with
biology treatment
Effluents from biology may contain higher COD levels
than allowed by regulations
Further COD reduction of hardly biodegradable COD is
requested
Ozone-Bio combination is a possible treatment
solution
Solutions to reduce hardly biodegradable
COD
Concept
Comments
Chemical,
flocculation, filtration
More generally used. To consider: Chemical consumption, chemicals in
final treated water, chemical sludge to be disposed.
Membrane
Nanofiltration is needed to achieve the required COD reduction. To
consider: High energy consumption for operation, cost of membranes,
membrane cleaning and treatment of concentrate.
Adsorption
COD adsorption on Carbon is effective. To consider: High cost of PAC,
management demands to regenerate exhausted GAC, not flexible in
achieving a certain COD reduction.
Oxidation
Ozone and/or advanced oxidation is an effective solution. To consider:
Higher cost with an increased amount of oxidant for higher reduction
rates.
Oxidation combined
with biology
Extends the benefits and range of cost effectiveness, by limiting the
oxidation effect to the amount necessary to produce biodegradable by
products.
Process Combination „Ozone – Biology“
1
Bio
2
Bio
3
Bio
4
Ozon
Ozon
Ozon
Bio
Bio
Bio
Ozon
Ozon
Bio
Case Study A
Full Scale Installation Ozone/Bio for « Hard COD » elimination
Today Customer produces 460,000 adt/y of newsprint and super
calendered paper.
The mill increased its capacity whereas the COD discharge limit
remained... Further purification by biological processes was not
possible
Case Study A
Full Scale Installation Ozone/Bio for « Hard COD » elimination
A tertiary treatment combining ozonation and biological fixed-bed
filtration was implemented.
The tertiary treatment stage was designed on the basis that 130
mg/l COD have to be degraded by the combined process and
considering a specific ozone consumption level of
1 gO3/gCODelim..
Case Study A
Full Scale Installation Ozone/Bio for « Hard COD » elimination
Type of Mill
Production Capacity
Products
Expansion projects
Wastewater flowrate
= Paper mill with 3 paper machines
= 600.000 ton/a
= Newsprint, Magazine, etc.
= 2000 start-up of PM 4 and PM 5
≈ 10 liter/kg of paper
Case Study A
A.S.2
ZKB
biofilm
reactor
Sed.
A.S.1
active
sludge 1
sed. 1+2
cooling
towers
Old WWTP
COD
400 mg/l
active
sludge 2
O2
Discharge limits:
COD < 270 mg/l
BOD5 < 20 mg/l
Sed.1
biofilters
Holding
Tank 1
biofilters
Holding
Tank 2
New bio plant
Sed.2
O3reactor
O3reactor
New ozone plant
Case Study A
Full Scale Installation Ozone/Bio for « Hard COD » elimination
. .. .. . ..
.
.
. . .
.. .. ... ..
. . .
.. . . . .
Ozone Generator
50 kg/h
V 40
= 40m³
m³
4 bar(g)
ReactionDegassing
tank
Ozone
destructor
river
Injector
Pump
holding tank
V = 600 m³
LOX
tank
84 m³ 84 m³ 84 m³
O3
buffer tank
(outlet biology)
330 m³/h
COD = 400 mg/l
Fixed-bed
Biofilter
Case Study A
Full Scale Installation Ozone/Bio for « Hard COD » elimination
Key aspects:
Amount of COD to be reduced 457 -> 305 -> 213 (mg/l)
Applied ozone dose to achieve COD reduction rate
1.5 (gO3/g CODred)
Amount of BOD increased after oxidation
Case Study A
Full Scale Installation Ozone/Bio for « Hard COD » elimination
Introduction
PumpInjection
Reaction –
degassing
tanks
Gas
distributi
on
Ozone
generato
r
Case Study A
Full Scale Installation Ozone/Bio for « Hard COD » elimination
Oxygen reuse
Case Study A
Full Scale Installation Ozone/Bio for « Hard COD » elimination
Case Study B
Full Scale Installation Ozone/Bio for « Hard COD » elimination
Today the customer produces 485,000 adt/y of super
calendered and offset papers.
An ozonation step with a capacity of 75 kg O3/h was added in
2004 to keep the outflow COD limits during the production of
brighter products.
The wastewater treatment plant (WWTP) has a capacity of
7,240,000 m3/y.
Case Study B
Full Scale Installation Ozone/Bio for « Hard COD » elimination
Case Study B
Full Scale Installation Ozone/Bio for « Hard COD » elimination
Case Study B
Full Scale Installation Ozone/Bio for « Hard COD » elimination
Case Study C
Pilot Tests for Eucalyptus based P&P effluents, Brazil
Installation of pilot plant in August 2012
Testing the O3 potential under real conditions on site
Ozone plant:
Generator Capacity 100gO3/h
Subsequent Bio filtration
Case Study C
Pilot Tests for Eucalyptus based P&P effluents
Case Study C
Pilot Tests for Eucalyptus based P&P effluents
Case Study C
Pilot Tests for Eucalyptus based P&P effluents
Case C
2,00
COD (mg/l)
1,90
1,80
1,70
200
1,60
1,50
100
1,40
1,30
1,20
0
1,10
1
2
3
4
5
6
7
8
9
10
11
Days
COD Inlet
COD Outlet
COD outlet Biofilter
Spec. O3 Dosage (gO3/gCODreduced
12
Spec. O3 Dosage
(gO3/gCODreduced)
300
Summary
The winning concept “Bio + O3 + Bio”:
•
Increasing costs and environmental limitations in the use of chemicals like
Aluminum salts, the disposal of large quantities of chemical sludge and
stricter COD limits increases the potentials of ozone
•
More flexibility in achieving a given COD reduction by varying the ozone
dosing
•
Oxidation with ozone gives additional benefits to water quality e.g. color
reduction, odor reduction, reduction of unwanted compounds AOX, EDTA
•
No handling of large amounts of sludge through > 90 % less sludge
production!
•
No handling of chemicals
•
No problems with leaving residual chemicals in the effluent.
•
Additional benefits by reusing the O2 containing offgas!
•
Ozone plants are easy to operate– automatic operation!
• Ozone can be produced on demand
Low operating costs compared to alternative technologies such as
Aluminum salts
Thank you!
Sustainable development is your ambition…
Ozone is our solution!
Thank you for your attention!
Fibria Jacarei, Brazil