1. Waste Water Treatment Works Waste to Energy
Andrew Dixon, Renewable Energy Specialist

2. DCWW energy schemes
Renewable Energy Programme : By 2015
Anaerobic Digestion 11 sites, 11 MW
Hydro 20 sites, 2 MW
Solar Photovoltaic 15 sites, 2 MW
Wind 1 site, 2.5 MW
On track for carbon reduction: 25% from 2007 to 2015
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3. Hydro – in delivery
Hydro - Live
kW capacity
500 +
101 - 500
0 - 50
51 - 100
Wind – in planning
Solar PV - Live
Digestion CHP or AD - live
Status
Renewable Energy Generation Sites
Biomass heating – in delivery
Hydro – in feasibility / design
Strata Florida
Llys y Fran Res
Maerdy
Tyn y Waun
Crai
Preselli WTW
Llwyn-on
Sluvad
Nash
Swansea
Cefn Dryscoed
Eign
Cardiff
Afan
Llanfoist
Lliedi’s
Penycefn
Eithinfynydd
Portmadog
Ffynon Lugwi
Cowlyd
Alwen
Brenig
Ruthin
5 Fords
Queensferry
Kinmel Bay
Glascoed
Usk
Cilfynydd
Ponthir
Cog
Dol-y-Mynach
Glaslyn
Dolbenmaen
Ponsticill
Bolton Hill
Builth Wells
Penthir

4. Waste to Energy at WwTW
Variety of opportunities
Driers
Incinerators
Liming
Anaerobic Digestion
־Sewage Gas - CHP
־Gas to Grid – Biomethane injection
־Vehicle Fuel
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5. Cardiff WwTW – The Process
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6. Thermal Hydrolysis vs Conventional Digestion
More biogas - more electricity!
Stabilises sludge – regulatory requirements
Greater sludge destruction – less to dispose to land
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Sewage Gas – Advanced Anaerobic Digestion

7. Plant capacity
30,000 TDS capacity – sewage sludge
12 – 18 day Hydraulic Retention Time
Three 1.5 MW engines
־20 GWh electricity per year (equiv. To over 3,000 homes!!)
־~10,000 tonnes CO2 saved per year
־Heat from engines used in the process
“Enhanced” treated sludge to land
99.9999% pathogen kill (99% for conventional digestion)
Nutrient enrichment of soils
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Cardiff WwTW – Vital Statistics

8. Benefits of Advanced Digestion
Economic
Energy Security
Cost saving & Revenue generating
Registration under CHP Quality Assurance
Environmental
Carbon reductions
‘Enhanced’ Sludge Status – disposal to land bank
Efficient use of resources – Heat and Power
Environmental Permits govern operation
־Forthcoming Industrial Emissions Directive
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9. Safe Sludge Matrix
Sludge use and agriculture governance
No conventional sludge to grassland
Interval periods – between disposal and harvest
־Varies from 10 months to 30 months
Sewage company must test soil
־Dependant on crop/grazing
־pH of soil
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10. Other Waste to Energy Initiatives
Dwr Cymru:
Cardiff East WwTW - AAD
Afan WwTW - AAD
Cog Moors WwTW (Dinas Powys) - AD
Other Schemes:
Avonmouth (Wessex Water)
Tremorfa Energy from Waste plant (Viridor)
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11. Thank You
Andrew Dixon
Renewable Energy Specialist
Dwr Cymru Welsh Water
Andrew.Dixon@dwrcymru.com
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