The Road to Zero - Treating Sewage without Using Energy

1. The Road to Zero - Treating Sewage without Using Energy John Tattersall Global Director of Water Technology

2. The Road to Zero Sewage contains Energy Sewage is largely composed of partially degraded food waste The remaining organic waste contains energy ~20 W/PE (based on 120g/h/d COD) 2

3. The Road to Zero So what have we done historically? • Added more energy • We used to be fairly good • Higher standards driving higher energy usage • New technology – more energy ~2-4 W/PE 3

4. The Road to Zero Digestion - Redresses the balance This is not new – over 100 years old Recent years change in emphasis from stabilisation to energy resource Use of regional sludge centres 4

5. The Road to Zero Example Energy Balance (300 mg/l BOD)

6. The Road to Zero How do we get to Zero = Energy Generated Energy Consumed 6

7. The Road to Zero WERF ENER1C12 research project • Objective: • Provide research to develop new approaches that will allow wastewater treatment plants to be energy neutral, and thus able to operate solely on the energy embedded in the water and wastes they treat. (from WERF Energy Management Challenge Exploratory Team Report, January 2011) 7

8. The Road to Zero Typical BOD removal Understanding the energy balance • 26% of influent chemical energy remains in dewatered biosolids • 36% of influent chemical energy converted to digester gas 8

9. The Road to Zero Optimised operation including CEPT • Reduced blower electricity usage • Increased digester gas production 9

10. Strass WWTP Austria (Prof B Wett) Improved Energy sufficiency A/B Process On line ammonia control of intermittent aeration High efficiency CHP (38% yield electricity from Biogas) Deammonification of liquors The Road to Zero An early example of Success 1996 49%energy generated/energy used 2005108% energy generated/energy used 10

11. Many processes to improve digestion Thermal hydrolysis Enzymic hydrolysis Sonic disintegration Mechanical disintegration Electrical discharge In this context look at the overall energy balance The Road to Zero Improve the digestion 11

12. The Road to Zero Davyhulme • New Regional Sludge Treatment • Thermal Hydrolysis followed by digestion • Processes up to 121,000 TDS/year • Generates enough electricity to power itself, the associated liquid treatment plant and provide excess power to the grid (Up to 11.5 MW) Courtesy United Utilities 12

13. The Road to Zero New technologies - Deammonification Autotrophic Anaerobic Environment Anammox bacteria • 63% reduction in Oxygen demand • Almost 100% reduction in Carbon demand • Much reduced in Biomass production • Reduced CO2 emissions (4.7 - 0.7 ton CO2/ton N)

14. The Road to Zero AnamMOX • Bacteria discovered in 1999 • Plants now working/in design for liquor treatment • The big question – Will it work for main stream treatment ?

15. The Road to Zero Paradigm shift: sewage is a valuable resource! RENEWABLE ENERGY TREATMENT PLANT Net zero energy treatment is just part of the picture REUSE INFLUENT ORGANIC = ENERGY BENEFICIAL BYPRODUCTS 15

16. The Road to Zero Thank You John Tattersall tattersallj@bv.com 01737 856552 16