ISO/PRF TR 20736

TECHNICAL ISO/TR
REPORT 20736
First edition
Sludge recovery, recycling, treatment
and disposal — Guidance on thermal
treatment of sludge
Valorisation, recyclage, traitement et élimination des boues — Lignes
directrices pour le traitement thermique des boues
PROOF/ÉPREUVE
Reference number
ISO/TR 20736:2021(E)
ISO 2021
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ISO/TR 20736:2021(E)
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Foreword ........................................................................................................................................................................................................................................vi

Introduction ..............................................................................................................................................................................................................................vii

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Abbreviated terms .............................................................................................................................................................................................. 3

5 Sludge properties................................................................................................................................................................................................. 4

5.1 General ........................................................................................................................................................................................................... 4

5.2 Physico-chemical characteristics ............................................................................................................................................ 4

5.2.1 General...................................................................................................................................................................................... 4

5.2.2 Dry matter ............................................................................................................................................................................. 4

5.2.3 Loss on ignition ................................................................................................................................................................. 4

5.2.4 Calorific value ..................................................................................................................................................................... 5

5.2.5 Grease, scum and screening ................................................................................................................................... 5

5.2.6 Physical consistency and others ......................................................................................................................... 6

5.3 Chemical and microbiological characteristics ............................................................................................................. 6

5.3.1 General...................................................................................................................................................................................... 6

5.3.2 Sulfur .......................................................................................................................................................................................... 6

5.3.3 Phosphorus ........................................................................................................................................................................... 7

5.3.4 Nitrogen ................................................................................................................................................................................... 7

5.3.5 Chlorine and other halogens ................................................................................................................................. 7

5.3.6 Organic micro pollutants .......................................................................................................................................... 7

5.3.7 Trace elements................................................................................................................................................................... 8

5.3.8 Pathogens ............................................................................................................................................................................... 8

6 Thermal processes fundamentals ...................................................................................................................................................... 8

6.1 General ........................................................................................................................................................................................................... 8

6.2 Drying ............................................................................................................................................................................................................. 9

6.3 Hydrolysis .................................................................................................................................................................................................10

6.4 Incineration ............................................................................................................................................................................................11

6.5 Pyrolysis.....................................................................................................................................................................................................12

6.6 Gasification ..............................................................................................................................................................................................13

6.7 Thermolysis ............................................................................................................................................................................................14

6.8 Carbonization ........................................................................................................................................................................................14

6.9 Wet oxidation ........................................................................................................................................................................................14

6.10 Melting ........................................................................................................................................................................................................15

6.11 Pasteurization .......................................................................................................................................................................................15

7 Technologies ..........................................................................................................................................................................................................16

7.1 General ........................................................................................................................................................................................................16

7.2 Drying ..........................................................................................................................................................................................................16

7.2.1 Direct dryers .....................................................................................................................................................................16

7.2.2 Indirect dryers ................................................................................................................................................................20

7.2.3 Solar dryers .......................................................................................................................................................................22

7.3 Hydrolysis .................................................................................................................................................................................................23

7.4 Incineration ............................................................................................................................................................................................24

7.4.1 Fluidized bed furnace ...............................................................................................................................................24

7.4.2 Multiple hearth furnace (MHF) ........................................................................................................................28

7.4.3 Hybrid furnace ................................................................................................................................................................31

7.4.4 Others .....................................................................................................................................................................................32

7.5 Pyrolysis.....................................................................................................................................................................................................33

7.6 Gasification ..............................................................................................................................................................................................33

7.7 Thermolysis ............................................................................................................................................................................................35

7.8 Carbonization ........................................................................................................................................................................................36

7.9 Wet oxidation ........................................................................................................................................................................................36

7.10 Melting ........................................................................................................................................................................................................37

7.11 Pasteurization .......................................................................................................................................................................................39

7.12 Emerging technologies ..................................................................................................................................................................40

7.12.1 General...................................................................................................................................................................................40

7.12.2 Oxidation technologies ............................................................................................................................................40

7.12.3 Enzymatic sludge hydrolysis ..............................................................................................................................41

7.12.4 Plasma gasification .....................................................................................................................................................41

7.12.5 Ultrasound pretreatment ......................................................................................................................................41

7.12.6 Microwave irradiation ..............................................................................................................................................41

7.12.7 Infrared radiation .......................................................................................................................................................42

7.13 Design aspects ......................................................................................................................................................................................42

7.14 Auxiliary equipment ........................................................................................................................................................................42

7.14.1 General...................................................................................................................................................................................42

7.14.2 Transport, receiving area, storage and feeding systems ............................................................43

7.14.3 Heat supply and recovery .................. ....................................................................................................................43

7.14.4 Gas cleaning ......................................................................................................................................................................44

7.14.5 Ash and other residues handling ....................................................................................................................44

7.14.6 Wastewater treatment .............................................................................................................................................44

7.14.7 Process monitoring .....................................................................................................................................................44

7.14.8 Safety systems .................................................................................................................................................................45

8 Operational aspects ........................................................................................................................................................................................45

8.1 General ........................................................................................................................................................................................................45

8.2 Drying ..........................................................................................................................................................................................................46

8.3 Hydrolysis .................................................................................................................................................................................................46

8.4 Incineration ............................................................................................................................................................................................46

8.4.1 General...................................................................................................................................................................................46

8.4.2 Fluidized bed furnace ...............................................................................................................................................47

8.4.3 Multiple hearth furnace ..........................................................................................................................................48

8.5 Pyrolysis.....................................................................................................................................................................................................49

8.6 Gasification ..............................................................................................................................................................................................49

8.7 Thermolysis ............................................................................................................................................................................................49

8.8 Carbonization ........................................................................................................................................................................................49

8.9 Wet oxidation ........................................................................................................................................................................................49

8.10 Melting ........................................................................................................................................................................................................50

8.11 Pasteurization .......................................................................................................................................................................................50

8.12 Hazards .......................................................................................................................................................................................................50

9 Management of energy and secondary resources ..........................................................................................................50

9.1 General ........................................................................................................................................................................................................50

9.2 Drying ..........................................................................................................................................................................................................51

9.3 Hydrolysis .................................................................................................................................................................................................51

9.4 Incineration ............................................................................................................................................................................................51

9.5 Pyrolysis.....................................................................................................................................................................................................52

9.6 Gasification ..............................................................................................................................................................................................53

9.7 Thermolysis ............................................................................................................................................................................................54

9.8 Carbonization ........................................................................................................................................................................................54

9.9 Wet oxidation ........................................................................................................................................................................................54

9.10 Melting ........................................................................................................................................................................................................54

9.11 Pasteurization .......................................................................................................................................................................................54

9.12 Thermal treatments and circular economy .................................................................................................................55

10 Management of residues ...........................................................................................................................................................................55

10.1 General ........................................................................................................................................................................................................55

10.2 Flue gas .......................................................................................................................................................................................................55

10.2.1 Characteristics and parameters .......................................................................................................................55

10.2.2 Equipment ..........................................................................................................................................................................57

10.3 Ashes .............................................................................................................................................................................................................59

10.3.1 Composition/parameters ......................................................................................................................................59

10.3.2 Processes and equipment .....................................................................................................................................60

10.4 Wastewater .............................................................................................................................................................................................61

11 Decommissioning of installations ...................................................................................................................................................61

11.1 General ........................................................................................................................................................................................................61

11.2 Specific considerations .................................................................................................................................................................61

12 Co-management with other organic wastes ..........................................................................................................................62

12.1 General ........................................................................................................................................................................................................62

12.2 Specific considerations .................................................................................................................................................................63

12.3 Additional storage and transport aspects ....................................................................................................................65

12.3.1 General...................................................................................................................................................................................65

12.3.2 Storage ...................................................................................................................................................................................65

12.3.3 Transport .............................................................................................................................................................................66

13 Assessment of sustainability ................................................................................................................................................................66

13.1 General ........................................................................................................................................................................................................66

13.2 Environmental aspects ..................................................................................................................................................................67

13.3 Economical aspects ..........................................................................................................................................................................67

13.4 Social aspects.........................................................................................................................................................................................67

Annex A (informative) Calorific values calculations .........................................................................................................................69

Annex B (informative) Various systems to input sludge into a household waste incineration

plant ................................................................................................................................................................................................................................70

Annex C (informative) Case studies ....................................................................................................................................................................72

Annex D (informative) Regulatory aspects .................................................................................................................................................86

Bibliography .............................................................................................................................................................................................................................89

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This document was prepared by Technical Committee ISO/TC 275, Sludge recovery, recycling, treatment

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Sludge treatment and management is globally a growing challenge for most countries: