Sludge Workshop 3rd April 2017 Zagreb. Isabelle LEBLANC -

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1 Sludge Workshop 3rd April 2017 Zagreb Isabelle LEBLANC - isabelle.leblanc@veolia.com

2 Waste water treatment produce Typical city of 100,000 PE (France) Conventional wastewater treatment plant Treated water 55 m 3 /PE.year 55 m 3 /PE.year 20 kgds/pe.year 2 m 3 /PE.year (1%DS) m 3 /year Dewatered (20%DS) 100 kg/pe.year = t/year Ten 20 ton trucks leaving the WWTP every week Sludge Worshop Zagreb 03/04/2017 2

3 What is? Raw H 2 O Sludge is essentially water (99%) This water could be separated in : Free Water (60%) extractible by mechanical devices Linked Water (30%) extractible by thermal means Internal water (10%) not easily extractible Dry Solids could be separated in : Volatile Solids (65-80%) Mineral Matter (20-35%) % VS DS 1% DS 35-20% MM 3

4 Sludge characteristics o Main parameters o Sludge DS content o Volatil solid content VS = +/- Organic content o µpollutants (heavy metals, PAH, PCB) and pathogens o Thermodynamics : LCV (low calorific value) LCV - Fuel-oil Dry wood City gas 6.7 kwh/ kgvs (= 4.7kWh/kgDS for 70%VS) 12.4 kwh/kg (10.3 kwh/l) kwh/kg 9.88 kwh/nm 3 4

5 Sludge challenge o Volume increasing o Public reluctance o More stringent regulations 5

6 Requirement for land application o Lowering of the regulated limits (ex : French Regulation, dec 1997 & 1998) o Heavy metals, PAHs, PCB and pathogens also considered

7 Requirement for land application o Lowering of the regulated limits (ex : French Regulation, dec 1997 & 1998) o Heavy metals, PAHs, PCB and pathogens also considered o Sludge shall not only be harmless but must also present an agricultural interest (e.g. nutrients : nitrogen, phosphorus) o Traceability : blending forbidden, screenings, fats and grits not allowed o Storage manditory : 6 to 10 months (often out of the waste water plant) o What if? : alternative routes demanded

8 Landfilling for harmless wastes (, MSW) French order 09-sept 1997 relative to household wastes and related wastes storage centers o Construction & operation o Biogas and leachates have to be collected and treated o Waste checking prior to enter o «Traceability»: no waste mixing, identification o Visual Control, no radioactivity o Sampling o DS > 30%

9 Sludge disposal routes in France Sludge production in France : TDS/y Land spreading : 45% Composting : 25% Agriculture Incineration : 20% (specific or co-incineration) Landfilling : 10% Municipal - 12 M TDS/y estimated for 520 M Inhab. Land spreading Composting Incineration Landfilling 9

10 Disposal routes : costs and DS content Disposal costs range in France DISPOSAL routes Landspreading Composting Incineration Landfilling DS content in 20-25% 20-30% 25% 30% Liquid also accepted Disposal Cost* ( /wet T) (*) Range of values depending on regional context. Prices without transport. Transport cost 0,2 /wet T/kilometer 10

11 What can we do with this? o Reduce : o Volume o Elimination cost o Disturbance o Recover value from : o Energy o Products 11

12 Different ways to answer client demand Drying Dry Oxidation Thickening Dry Oxidation Drying END USER A Digestion Wet Oxidation 12

13 Physical approach Drying Dry Oxidation Thickening Dry Oxidation Drying END USER A Digestion Wet Oxidation 13

14 Dewatered for land spreading (Mass balance for PE) m 3 Raw 250 m 3 Thickened 100 tons Dewatered Classical solution for all size WWTP near rural area When land spreading is allowed Thickening 65 % VS DS 35 % MM 1% DS 8% DS 20% DS 14

15 Dried for use off site (Mass balance for PE) m 3 Raw 250 m 3 Thickened 100 tons Dewatered A solution for all size WWTP Reduce transportation cost or increase energy content 22 tons Dried Thickening 65 % VS Drying 65 % VS DS 35 % MM 35 % MM 1% DS 8% DS 20% DS 90% DS 15

16 Oxidation for elimination on site (Mass balance for PE) m 3 Raw 250 m 3 Thickened 80 tons Dewatered A solution for medium and large size WWTP When land spreading is not allowed or possible Thickening Oxidation 65 % VS 8 tons Ashes DS 35 % MM 100% MM 1% DS 8% DS 25% DS 100% DS 16

17 Biological approach Drying Dry Oxidation Thickening Dry Oxidation Drying END USER A Digestion Wet Oxidation 17

18 AD allows to recover value from Volatile Solids Anaerobic Digestion Centrâtes Sludge Hot water Digestate Water file Land Spreading Gas holder Flare Biogas Heat Bio methane injection or biofuel Electricity and heat Strong points The weight of residual (digestate) is reduced Biogas could produce heat and electricity or heat and biomethane 18

19 AD to produce biogas & digestate (Mass balance for PE) m 3 Raw 330 tons Thickened 300 tons Raw Digestate A solution for all size WWTP near rural area BIOGAS kwh biogas To recover energy & agricultural use of digestate 70 tons Dewatered Digestate Thickening Digestion 50% VS 50% VS DS 50% DS MM 50% MM 1% DS 6% DS 5% DS 22% DS 19

20 AD for biogas and dried digestate (Mass balance for PE) m 3 Raw 330 tons Thickened 300 tons Raw Digestate BIOGAS kwh biogas A solution for medium and large size WWTP 70 tons Dewatered Digestate 17 tons Dried Digestate Thickening DS Digestion 50% VS 50% VS Drying 1% DS 6% DS 5% DS 22% DS 90% DS 50% VS 50% MM 50% MM 50% MM 20

21 Thermal Hydrolysis, AD and Drying (Mass balance for PE) m 3 Raw 100 tons Dewatered Digestion 160 tons Raw Digestate BIOGAS kwh biogas 45 tons Dewatered Digestate A solution for medium and large size WWTP Biogas max & Dried digestate DS Thermal Hydrolysis 40% VS 60% MM 1% DS 20% DS 7% DS 25% DS DS Drying 12,5 tons Dried Digestate 40% VS 60% MM 90% DS 21

22 Thermal Hydrolysis, AD and Oxidation (Mass balance for PE) m 3 Raw 100 tons Dewatered Digestion 160 tons Raw Digestate BIOGAS kwh biogas 45 tons Dewatered Digestate A solution for medium and large size WWTP Biogas max & No digestate DS Thermal Hydrolysis DS 40% VS 60% MM 1% DS 20% DS 7% DS 25% DS Oxidation 8 tons Ashes 100% MM 100% DS 22

23 Biological approach Drying Dry Oxidation Thickening Dry Oxidation Drying END USER A Digestion Wet Oxidation 23

24 Wet oxidation Oxidation of VS T C 250 =, Pressure = 50 bars, O 2 Sludge is unsuitable for agricultural use Low fertilizer demand High concentrations of pollutants Long spreading distances Landfill disposal or Incineration are not acceptable Restrictive regulations Limited acceptability to customers and local population Energy content of is too low to allow auto thermal incineration A local demand for mineral substrate exists 24

25 Devolving options depending on the type of residues Agriculture Mineral reuse Use as fuel Waste storage installation Thickened No No No Dewatered No Compost No No Dried No Dried digestate No Technical sand No No Ash No No Optimized cost Medium cost High cost 25

26 Sludge treatment : to answer the new challenges faced by cities Implementing solutions for components recovery Biogas, bio methane or carbon dioxide Dried or digestate as a solid fuel Components in the and centrates (nitrogen, phosphorus) Benefiting from regulations offering incentives Subsidized energy purchase prices Electricity or bio methane purchase requirements (in some countries) Finding alternative solutions instead of direct incineration or landfilling Less costly More acceptable to populations Able to minimize the environmental impact Managing their overall costs Investments and operating costs related to benefits 26

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