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Experience with Sewage Sludge Ash

Experience with Sewage Sludge Ash. Shane Donatello Institute of Prospective Technological Studies Joint Research Centre European Commission. Personal Background.

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Experience with Sewage Sludge Ash

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  1. Experience with Sewage Sludge Ash Shane Donatello Institute of Prospective Technological Studies Joint Research Centre European Commission Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  2. Personal Background • Thesis titled: “Characteristics of incinerated sewage sludge ashes: Potential for phosphate extraction and re-use as a pozzolanic material in construction products”. • 5 Q1 Journal publications related to ISSA, well cited (approx. 128 citations to date) • Invited reviewer for some 10-20 manuscripts related to ISSA in journals such as Chemosphere, Construction & Building Materials, Cement and Concrete Composites and Waste Management. • 2004 – 2006: Working in the water industry • 2006 – 2009: PhD at Imperial College • 2010 – 2013: Post-Doc at Eduardo Torroja Institute • 2013 – present: Policy officer with European Commission Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  3. Contents • ISSA chemical properties: • Major elements • Minor elements • ISSA disposal: • Waste codes, what to do with mirror wastes • EU Landfill classes • Waste Acceptance criteria (leaching tests) • ISSA in the context of EN 196 and EN 197. • Supplementary cementitious materials • Pozzolancity • Water demand Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  4. ISSA ChemicalProperties • Major elements (big variation possible but always top 5 are Si, Al, Fe, Ca and P) • Importance of: stormwater, soils, hardness, process control Strongly influenced by fine sands Strongly influenced by choice of dewatering aids etc. A sign of combustion efficiency, should be < 4% Strongly influenced by tertiary sludge and % municipal vs industrial wastewater influent Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  5. ISSA ChemicalProperties • Minor elements (big variation but invariably top 5 are Zn, Cu, Ni, Pb and Cr) • Clear link to plumbing joints and pipework (stainless steel) • Also linked to affinity to bind to sludge (i.e. organics) Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  6. ISSA disposal (i.e. landfill) • Important to know  disposal restrictions and economics are a driver for reuse • Basic considerations of Landfill Directive 99/31/EC: • Waste needs to be “pre-treated” prior to landfill • Reduce biodegradable waste to landfill • Splits landfills into three categories: • Inert landfill • Non-hazardous landfill • Hazardous landfill • Cost factors: transport, gate fees & taxes • National policies (e.g. UK Tax) Inert tax Non-haz tax Haz tax Cost Availability Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  7. ISSA disposal • Is ISSA inert, non-hazardous or hazardous? • Relevant legislation has changed several times since my PhD! • But still same basic steps: • 1 – Consult European Waste Catalogue: • Find relevant waste code • 2 – Leaching test: • Compare with Waste Acceptance Criteria Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  8. ISSA disposal • European Waste Catalogue (EWC) • Set out originally by Decision 2000/532/EC • Amended by Waste Framework Directive (2008/98/EC) • And more recently by Decision 2014/955/EU • Code for ISSA is 19 01 13* as follows: • 19 wastes from waste management facilities, off-site wastewater treatment plants and the preparation of water • 19 01 wastes from incineration or pyrolysis of waste • 19 01 13*fly ash containing dangerous substances (mirror waste*) • * i.e. if there are dangerous substances  haz. waste • if no dangerous substances  non-haz waste Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  9. Donatello et al., 2010. Waste Management, 30, p.63-71 Lapa et al., 2007. J. Hazard Mater., 147, p.175-183 ISSA disposal • Does ISSA contain dangerous substances then?? • But difficult to determine, can look at heavy metal content. • But what about speciation? What about bioavailability? • Look at H14 definition of “Ecotoxicity” in Directive 2008/98/EC: • H14: “Ecotoxic” waste which presents or may present immediate or delayed risks for one or more sectors of the environment • Two approaches: chemical analysis and biological assays Inconclusive Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  10. ISSA disposal • Waste Acceptance Criteria • Provision made in Annex II of Landfill Directive 99/31/EC • Details set out in Decision 2003/33/EC • Test is specified in EN 12457 (parts 1-4) • Basic (simplified) explanation is: 1750g H2O 175g ISSA  0.45µm filter 24h rotated at 30rpm  vacuum  Leachate (ICP-MS) Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  11. ISSA disposal • Waste Acceptance Criteria (added importance now) • Interpretation of leaching results: Surprising that most common metals (Zn, Cu, Pb, Ni and Cr and not a problem Main problems are Se, Mo and Sb Linked to ash separation technology • ISSA should NEVER go to inert waste landfill in the EU. • Technically, ISSA should go to hazardous waste landfill Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  12. ISSA IN THE CONTEXT OF EN 196 AND 197 • Why important? • Sets out the framework for CE marking for cement on EU market • 5 categories of Portland Cement (I to V) • 27 Sub-categories • Restrictions on: • Combination with supplementary cementitious materials (SCMs) • Physical / chemical properties of cement powder, cement pastes and cement mortars Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  13. ISSA IN THE CONTEXT OF EN 196 AND 197 • Main SCMs are: • Blast furnace slag • Silica fume • Natural pozzolana (volcanic ashes) • Calcined pozzolana (e.g. MK) • “Fly ash” (i.e. coal fly ash only ) • Burnt shale • Limestone • All except limestone are pozzolanic • All have well studied effects on PC hydration • ISSA  “others” (i.e. max 5%) • Cement composition (EN 197-1) • ISSA cannot be used >5% in CE cements  but no clear limit in concretes + pre-fab…. Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  14. ISSA IN THE CONTEXT OF EN 196 AND 197 • Let´s try to make a case for ISSA to be included • Should be able to meet same requirements as coal fly ash • Those requirements are: • LOI value < 9.0% (ideally < 5.0%) as per EN 196-2 (1 hour duration) • Reactive SiO2 content must be > 25.0%. • (Reactive SiO2 = Total SiO2 – insoluble SiO2 as per EN 196-2). • Will ISSA meet these requirements? • For LOI  no problem • For reactive SiO2  I never checked – quite complicated analysis! Interesting to know… • But what about other elements (especially P)…..? Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  15. ISSA IN THE CONTEXT OF EN 196 AND 197 • Minimum requirements for cements • ISSA >5% interesting for pre-fab and ready mix applications • Methods defined in EN 196. Especially interesting is pozzolanicity. Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  16. ISSA IN THE CONTEXT OF EN 196 AND 197 • Is ISSA a pozzolanic material? Several different tests possible….. • Test 3 - Frattini test (EN 196-5)  add test pozzolan with cement and water, seal container, store at 40 degrees C for 8d, filter, measure [CaO] and [OH]. Compare results to standard lime solubility curve. SF 20% = +ve MK 20% = +ve FA 20% = +ve ISSA 10% = -ve ISSA 20% = -ve ISSA 40% = +ve On or above the curve = not pozzolanic Below the curve = pozzolanic Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  17. ISSA IN THE CONTEXT OF EN 196 AND 197 • So then, is ISSA a pozzolanic material? • It depends on the method you use! • See my study: Donatello et al., 2010, Cem Conc Comp., Vol. 132, p.121-127. • More details also published in my thesis • ASTM C618 test  negative • Saturated lime test  positive • EN 196-5 test  negative with smaller amounts of ISSA, positive with higher amounts of ISSA. • AFTER MUCH THOUGHT…..CONCLUSION IS: • ISSA is not pozzolanic, but can remove limited quantities of Ca from solution via surface absorption mechanisms Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  18. ISSA IN THE CONTEXT OF EN 196 AND 197 • Minimum requirements for cement pastes and mortars • Difficult to meet strength requirements going >30% ISSA. • Increased water demand (EN 1015 test) a big problem • ISSA has similar problem to MK for water demand • Even a problem at 10% • Possible solutions: • milling ISSA? • admixtures? • work to be done…. Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  19. SomeMarketConsiderations • Quantities of ISSA produced • In the UK, where some 20% of SS was incinerated  100,000 t/yrISSA • Possible use in cement on market limited to 5% content • But cement market is very big (i.e. UK = 10,000,000 t/yr) • If all ISSA equally blended into UK cement  1% content • Sale of prefabricated concrete blocks in UK  no standard limit on % ISSA • Possible use of ISSA as a fine aggregate filler in concrete too • Not cost competitive with sand unless…. • it is delivered for free, • or better, you are paid to take it!!! • joint ventures and partnerships with water utilities best way forward Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  20. CONCLUSIONS • Major and minor elements in ISSA are always the same but can vary in individual importance. • Waste classification of ISSA is up for debate: but NOT inert • Look at it as an incentive for reuse rather than a problem. Market can easily take all ISSA. • But take care, leaching tests of ISSA from lab oven may not be equivalent to industrial ISSA • ISSA is just not pozzolanic! • Use up to 20% is possible without major rethinks needed. • Important problem to address is water demand. Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  21. THANK YOUfor your attention Any comments and questions welcome. Contact details: Shane Donatello shanedonatello@hotmail.com https://www.researchgate.net/profile/Shane_Donatello https://www.linkedin.com/pub/shane-donatello/4a/4a8/177 Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015

  22. ISSA ChemicalProperties • What is a pozzolan / pozzolanic material? • ASTM C125: ‘‘a siliceous and aluminous material which, in itself, possesses little or no cementitious value but which will, in finely divided form in the presence of moisture, react chemically with calcium hydroxide at ordinary temperature to form compounds possessing cementitious properties” • Pozzolanic activity: useful property in SCMs • e.g. lower heat of hydration, “filler effect”?, improved durability? • Reaction is: CH + S  C-S-Hor CH + AS  C-A-S-H • Well known examples include FA, BFS, SF and MK. • All have thermal history (exposed to >700 degrees C) • All have amorphous silica / aluminosilicates Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015 22

  23. ISSA IN THE CONTEXT OF EN 196 AND 197 • Is ISSA a pozzolanic material? Several different tests possible….. • Test 1 - ASTM C618  basically compare compressive strength of 2.75:1 mortars containing 20% of test pozzolan with control mortar after 7 and 28 days. At 10% sub: ISSA is the worst material At 20% sub: Sand is the worst material (ISSA very close) At 30% sub: ISSA is the worst material Sand ISSA FA SF MK *results from my thesis Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015 23

  24. ISSA IN THE CONTEXT OF EN 196 AND 197 • Is ISSA a pozzolanic material? Several different tests possible….. • Test 2 - Saturated lime test  add test pozzolan to a solution of saturated lime, seal container, store at 40 degrees C for 8d, filter, measure [CaO] and [OH]. After 1 day ISSA and SF by far most reactive After 3 days SF and ISSA reaction virtually complete After 7 days, MK and FA reactions almost complete After 28 days, only sand is still not reacting. ISSA FA Sand MK SF Control *results from my thesis Workshop on Reuse of Sewage Sludge Ash in the Concrete Industry - 16th September 2015 24

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