1. ANAEROBIC DIGESTION OF MUNICIPAL WASTE PRESENTED BY: Mr. Thomas McAndrew Ms. Ciara Coughlan Ms. Ann Phair

2. Anaerobic Digestion of Municipal Sludge Introduction Types of waste treated by A.D. A.D. of municipal Sludge

3. Municipal Sludge Composition of sludge W.W.T.P. produce two types of sludge: primary sludge Secondary sludge

4. Municipal Sludge Feedstock for A.D. Toxic substances Bioagents Disinfectants Long straw Quality and Quantity - why important Quality For good quality biogas need high organic matter Quantity How much will depend on which products are a priority Can leave dormant

5. Pre-treatment of Municipal waste Why? Aerobic v’s anaerobic Screening and grit removal Primary sedimentation Secondary treatment Sludge thickening using a picket fence thickener

6. Case Study of Tullamore Treatment Plant Secondary treatment Biofilm tanks

7. Case Study of Tullamore Treatment Plant Sludge thickener used Picket fence thickener

8. Case study of Tullamore Treatment Plant Post anaerobic digestion Belt Press machine

9. Definition of Anaerobic digestion Anaerobic digesters produce conditions that encourage the natural breakdown of organic matter by bacteria in the absence of air.

10. The Microbiology Of The Process This occurs in 4 stages: 1) Hydrolysis 2) Acidogenesis 3) Acetogenesis 4) Methanogenesis

11. Metabolic Stages of Production of Methane 1 st Stage Hydrolysis C 6 H 10 O 4 + 2H 2 O C 6 H 12 O 6 + 2H 2 2 nd Stage Acidogenesis Decomposition of products

12. Metabolic Stages of Production of Methane 3 rd Stage Acetogenesis C 6 H 12 O 6 2CH 3 CH 2 OH + 2CO 2 4 th Stage Methanogenesis CO 2 + 4H 2 CH 4 + 2H 2 O

13. Biological Process

14. Parameters for Optimum Digestion Temperature pH Carbon to Nitrogen Ratio

15. Basic Components Of Anaerobic Digesters 1) Feedstock Storage 2) Handling System 3) Digestion Tank 4) Gas and Residue Recovery Systems

16. Type of AD Systems Anaerobic Lagoons Contact Stirred Tank Reactor (CSTR) Upflow Anaerobic Sludge Blanket Reactor (USAB) Fixed Film Anaerobic Filters

17. Parameters for Optimum Digestion Temperature Carbon to Nitrogen Ratio pH

18. Products of A.D Biogas Fibre Liquor

20. Biogas methane carbon dioxide hydrogen sulphide ammonia

21. Using the biogas Heat the digester Generate heat Cooking Convert it to electricity Combined heat and power (CHP) plant

23. Digestate Remains after the gas has been removed –Fibre –Liquor

24. Fibre Contains Plant nutrients No odour Uses Low-grade fertiliser Alternative to peat

25. Liquor Low level but a large range of nutrients A high water content Used as a liquid fertiliser Lagoons or large tanks Produce small amounts of methane

26. The Advantages of A.D Wide range of organic Reduction approximately 80% of the odour potential Boost the local rural economy Reducing land and waste pollution A.D provides on site energy for the process

27. The Disadvantages of A.D Create traffic movement Generate noise The liquor and the fibre can contain animal by products Rigorous monitoring of wastes