Vann- og avløpsetaten

From Pollution to Solution
Bekkelaget Wastewater Treatment Plant
Rashid Abdi Elmi
rashid.elmi@vav.oslo.kommune.no
Holmenkollen ski jump arena
Rock caverns
Gas holder
Admin building
4
Sewage as a resource
Treated
wastewater
Improving water quality and biodiversity in
the Oslo fjord – due oxygen rich effluent
Upgraded fuel - Fuel for public
transportation
Biogas
Zero CO2 emission/carbon neutral
Sludge for
agriculture
farmland
Fertilizer 140 tons phosphorus per year
(110 000 bags of mineral fertilizer , 30
kg/bag)
Energy
extracted from
wastewater
250 GWh for District heating:
21 000 apartments, 12,000 kWh/yr pr apartment .
Reduction CO2 73 000 ton, corresponds to the
emission from 25 000 private vehicles
5
City of Oslo – main sewer system
Bekkelaget
WWTP
VEAS WWTP
Prepared enabling change
6
Cavern dimensions
Water treatment
1. Inlet tunnel
2. Screens, sand and grit
removal
3. Primary settling/ direct
precipitation
4. Bio step, activated
sludge
5. Clarifiers
6. Extra space(not in use)
7. Sand filters
Sludge treatment
8. Digesters
9. Sludge treatment
10. Sludge treatment
11. Ventilated air
treatment – odor
control
12. Biogas, upgrading (out)
212 m
12
Discharge consent – Compliance limit
 New discharge consent from 01.01.2009:
•
Nitrogen:
70% of all nitrogen must be
removed
•
Phosphorus:
90% of all phosphorus must be
removed
•
Organic matters:
70% of organic matters as
BOD5,must be removed
•
And the total amount of overflow must be less than 2% of the total loads of
nitrogen, phosphorus and organic matters
 NB: The population growth coupled with climate changes resulting to increased to both
hydraulic and pollutant loads poses as daunting challenge in meeting present and future
stringent discharge compliance limits.
Treatment capacities – operational modes
•
Dry weather flow 1450 l/s or approx. 125.000 m3/d – it is subjected
to biological and chemical treatment with filtration as final step
(max capacity 1900 l/s)
–
•
Flow rates between 1900-4000 l/s is treated chemically and partly
filtration (< 3000l/s)
–
•
Nitrogen, phosphorus and organic matters are removed
Phosphorus is removed and organic matters is partly removed
Flow rates between 4000 - 6000 l/s is treated through 3 mm
screens: Objects such
–
Objects such as rags, paper, plastics, and metals are removed
Wastewater treatment process- Flowchart
PAX-18
Primary
Precipitation
Magasin~35.000m3
Oslo
fjord
Q<1900 l/s
Primary
Sand, grit and
screenings
Q=1900 l/s
Clarifier
Activated sludge
Filter
FeSO4
Sludge recycle
4000 l/s < Q < 6000 l/s
Biogas
Bio sludge
Thickener
Primary sludge
Buffertank
Belt Thickener
Digester
Silo
Digester
Biogas Upgrading Plant
Dewatering
Silo
Overflow
PAX-18
Mixed liquor recycle
1900 l/s<Q< 4000 l/s
Buffer
Nitrogen removal – Biological treatment processes
Influent
Sewage
Organic nitrogen - Urea
Ammonia nitrogen
NH4
O2
Nitrification
1st Step
Nitrate
N0-2
2nd Step
O2
Nitrate
N0-3
Denitrification
Organic carbon
(carbon source)
Nitrogen gas
N2
Sludge treatment process

Thickening
Reduces the content of water in sludge to reduce hydraulic
load on the digesters.
 Primary sludge thickened in belt thickener with polymer
 Bio sludge thickened in centrifugal thickening with polymer

Digesters
Thermophilic anaerobic digestion process, whereby the
incoming sludge is pre-heated before entering the digesters
 Digestion in the digesters , at 55 °C in 15 days

Dewatering
Reduces the content of water in sludge to reduce transport
costs
 Centrifugal dewatering with polymer (30-35% DS)

Sludge storage tanks
Acts as buffer in order to obtain uniform loading of the
system and stores sludge during unexpected failure system.

Sludge Production
Generated at the plant is approximately 5500 -6000 tons DS/yr
Facts and Goals for the City of Oslo.
 CO2 emissions from private and public transport is
approximately 50- 80% of the total emissions in
the city of Oslo.
The City of Oslo’s main goal is:
 To cut 50% of greenhouse emissions by the
year 2030.
LP COOAB ® process – Low Pressure CO2 Absorption
CO2 absorption
Gas drier
Gas tank
High pressure
compressor
Activated coal - filter
200 bar
CO2
0,5 bar
2 bar
CO2 removal/ COOAB
recovery
Odorizing
the biomethane
Produced upgraded biogas (biomethane)
2,500,000
2,000,000
1,99 mill.
2,05 mill.
Nm3
Nm3
2012
2013
1,44 mill.
Nm3
1,500,000
1,04 mill.
Nm3
Nm3
1,000,000
500,000
0
2010
2011
17
Biomethane value chain
Producer
End
Biomethane
Money flow
18
Exhaust emission and noise
S/N
Units
Diesel
Bio-methane
Reduction %
NOx
g/km
8.1
1.9
78
Particulate
matter
g/km
0.3
0.005
98
CO2
kg/km
dBA
2.6
111
0
100
100
92
Noise
Oslo kommune
Vann- og avløpsetaten
The potential of Biomethane in Oslo
Oslo: 600 000 p.e. 10 – 12 million Nm3 biomethane
Buses
Personal vehicles
Sewage sludge
150 – 200
6 000
Household organic
waste
200-250
8 000
Total
350 - 450
14 000
62
64
66
240
1100
2000
Source: AGA-Linde
Net Energy production
Net energy production: 21-14-5-0,2 =1,8 GWh/yr
20
15
14
10
5
5
0.2
0
Electricity
GWh
-5
Pellets
Oil
Upgradert biogas
(biomethane)
-10
-15
-20
-21
-25
Green Emission for chemical consumption
Greenhouse emission ton CO2/yr
900
Greenhouse emission from chemical consumption
= 1195 ton CO2/yr
800
775
700
600
500
400
300
300
200
100
50
45
25
Polymer
Lime
Iron sulphate
0
PAX18
Ethanol
Total Greenhouse Emission
Totale Green Emission 3200 - 6400 = -3200 ton CO2/yr
3000
2000
1800
1195
85
90
Pellets
Oil
-2000
-3000
-4000
Biomethane
-1000
Chemical consumption
0
Electricity
CO2 emission ton CO2/yr
1000
-5000
-6000
-7000
-6400
Challenges facing Bekkelaget WWTP

This include among others;

Population growth in Oslo is taxing Bekkelaget
wastewater treatment Plant and creating a need for
new plants. Oslo will have in the range of 1.1 million
inhabitants (including Nittedal municipality) in 2020.
This represents a population increase of 18-25%
since 2009 (Figure). Bekkelaget WWTP was
dimensioned for 270 000 p.e. in 2000, in 2013,
Bekkelaget serves 331 000 p.e.

Climate change – Many of the earliest sewer
systems were combined sewers, designed to collect
both sanitary wastewater and storm water runoff in
a single system. Increased Hydraulic Loads hence
increased pollutant loads (NTot and PTot ).

Stringent discharge consent for 70 % Nitrogen
and 90 % phosphorus removal including overflow
and the total amount of overflow must be less than
2% of the total loads of nitrogen, phosphorus and
organic matters
Expansion of Bekkelaget WWTP
THANK YOU FOR YOUR ATTENTION!