Bekkelaget Wastewater Treatment PlantRashid Abdi Elmi

rashid.elmi@vav.oslo.kommune.no

From Pollution to Solution

Rock caverns

Gas holder

Admin building

Holmenkollen ski jump arena

4

5

Sewage as a resource

Sewage

Treated wastewater

Improving water quality and biodiversity in the Oslo fjord – due oxygen rich effluent

Biogas

Upgraded fuel - Fuel for public transportation

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

City of Oslo – main sewer system

Prepared enabling change 6

VEAS WWTP

Bekkelaget WWTP

212 m

Cavern dimensionsWater treatment1. Inlet tunnel2. Screens, sand and grit

removal3. Primary settling/ direct

precipitation4. Bio step, activated

sludge5. Clarifiers6. Extra space(not in use)7. Sand filters

Sludge treatment8. Digesters9. Sludge treatment10. Sludge treatment11. Ventilated air

treatment – odor control

12. Biogas, upgrading (out)

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)– Nitrogen, phosphorus and organic matters are removed

• Flow rates between 1900-4000 l/s is treated chemically and partly filtration (< 3000l/s)– 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

Primary sludgeBuffertank

Buffer Silo

Silo

Bio sludge

Dewatering

Thickener

Digester Digester

Biogas

OverflowMagasin~35.000m3

4000 l/s < Q < 6000 l/s

Sand, grit and screenings FeSO4

PAX-18

Activated sludge ClarifierPrimary Filter

PrecipitationPrimary

1900 l/s<Q< 4000 l/s

Q=1900 l/s

PAX-18

Q<1900 l/s

Biogas Upgrading Plant

Oslo fjord

Mixed liquor recycle

Sludge recycle

Belt Thickener

Nitrogen removal – Biological treatment processes

O2

Organic carbon (carbon source)

InfluentSewage

Nitr

ifica

tion

Denitrification

O2

Ammonia nitrogen

NH4

Nitrate

N0-2

Nitrate

N0-3

Nitrogen gas

N2

Organic nitrogen - Urea

1st Step

2nd Step

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

Gas tank

Activated coal - filter

Gas drier

CO2 absorption

CO2 removal/ COOAB recovery

Odorizing the bio-methane

High pressure compressor

CO20,5 bar

2 bar

200 bar

17

Produced upgraded biogas (biomethane)

2010 2011 2012 20130

500,000

1,000,000

1,500,000

2,000,000

2,500,000

1,04 mill. Nm3

1,44 mill.Nm3

1,99 mill.Nm3

2,05 mill.Nm3

Nm3

18

Biomethane value chain

Producer End

Biomethane

Money flow

Exhaust emission and noise

S/N Units Diesel Bio-methane Reduction %

NOx g/km 8.1 1.9 78Particulate

matter g/km 0.3 0.005 98

CO2 kg/km 2.6 0 100Noise dBA 111 100 92

Oslo kommuneVann- og avløpsetaten

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

The potential of Biomethane in Oslo

2000

1100

240

66

64

62

Source: AGA-Linde

Electricity Pellets Oil Upgradert biogas (biomethane)

-25

-20

-15

-10

-5

0

5

10

15

20

14

5

0.2

-21

Net energy production: 21-14-5-0,2 =1,8 GWh/yr

GWh

Net Energy production

PAX18 Polymer Lime Iron sulphate Ethanol0

100

200

300

400

500

600

700

800

900

300

50 45 25

775Greenhouse emission from chemical consumption = 1195 ton CO2/yr

Gree

nhou

se e

miss

ion

ton

CO2/

yrGreen Emission for chemical consumption

Elec

tric

ity

Pelle

ts Oil

Chem

ical

con

sum

ption

Biom

etha

ne

-7000

-6000

-5000

-4000

-3000

-2000

-1000

0

1000

2000

3000

1800

85 90

1195

-6400

Totale Green Emission 3200 - 6400 = -3200 ton CO2/yr

CO2

emis

sion

ton

CO2/

yrTotal Greenhouse Emission

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!