Technical Evolutions in Sludge Treatment. André Visser

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1 Technical Evolutions in Sludge Treatment André Visser

2 What is sludge? Sludge of a WWTP DS percentage of % Embedded energy 1,6 MJ/kg sludge (13,3 MJ/kg ds) Composition 62 % organics 38 % inorganics 50 g Nitrogen/kg ds 18 g Phosphate/kg ds Copper 430 mg/kg ds Zinc mg/kg ds Mercury 1,1 mg/kg ds Fresh sludge also contains pathogens Page 2

3 Quality depends on? Type of municipality Type of industry Type of collecting system Type of treatment Type of sludge treatment Type of chemicals added to the system Page 3

Principles Sludge is an agglomerate of: Inorganic material Organic (dead) material Organic (living) material Water - intercellular water - extracellular bound

4 Principles Sludge is an agglomerate of: Inorganic material Organic (dead) material Organic (living) material Water - intercellular water - extracellular bound water - capillary water - free water Unique per location Composition difficult to change INTERCELLULAR WATER EXTRACELLULAR WATER CAPILLARY WATER FREE WATER Page 4

bound water - capillary water - free water Unique per location Composition

5 Sludge production Treatment Specific Gravity of sludge Dry Solids (range) Production (range) kg/l % DS g/(p.e.d) Primary sedimentation Activated sludge Extended aeration Operation and maintenance of wastewater treatment plants Page 5

020 4-10 20-40 Activated sludge 1.005 0.6 1.2 25-50 Extended aeration 1.

6 Why sludge treatment? Reduction of transportation costs Reduction of final treatment costs Recovery of valuable components Wastewater treatment Wastewater transport Sludge treatment Page 6

7 Process scheme (very low loaded extended aeration) Screens Aeration tank Final clarifier Sand Filtration Influent Effluent return sludge Sludge transport for further treatment Secondary sludge thickening Mechanical Sludge Thickening or Dewatering Sludge storage Page 7

return sludge Sludge transport for further treatment Secondary

8 Process scheme (very low loaded extended aeration) Page 8

9 Process scheme (low loaded) Screens Grit & grease Primary Clarifier Aeration tank Final clarifier Influent Effluent return sludge Mechanical Sludge thickening Biogas Co-generation Energy Primary sludge thickening Anaerobic digestion Mechanical sludge dewatering Sludge storage Page 9

Mechanical Sludge thickening Biogas Co-generation Energy Primary

10 Process scheme (low loaded) Page 10

11 Situation in The Netherlands 17 million inhabitants 350,000 ton DS/year This means 56 g/inhabitant.day 360 WWTP, 90 with digester 50 % of sludge is digested Disposal costs /year This means 340/t DS Energy content of sludge is 4.9 PJ P-content in sludge is ton/y Page 11

day 360 WWTP, 90 with digester 50 % of sludge is digested Disposal

12 DS scale for municipal sludge Page 12

13 DS scale for municipal sludge Page 13

14 Sludge thickening Gravity thickener Belt filter Drum thickener Decanter Flotation Page 14

15 Sludge thickening (gravitational) Sludge type DS-load (kg/(m 2.d)) DS % Primary sludge Activated sludge Extended aeration Digested (P + S) Page 15

d)) DS % Primary sludge 50-80 5-7 Activated

16 Sludge thickening (gravitational)! Page 16

17 Sludge thickening (gravity belt) Page 17

18 Anaerobic Sludge digestion To reduce and stabilize solids Three main phases Hydrolysis Acidification Methanogenic phase Biogas production CH 4 (50 75 %), CO 2 and other gasses l/kg ODS removed Parameters Temperature, loading, ph COD removal, fatty acids, micro-elements Page 18

4 (50 75 %), CO 2 and other gasses 400-900 l/kg ODS removed Parameters

19 Sludge digestion mesophilic thermophilic Page 19

20 Sludge digestion Page 20

21 Mixing systems a) Unconfined gasinjection b) Confined gasinjection c) Mechanical steering d) Mechanical pumping Page 21

22 Sludge dewatering Decanter Belt filter press Chamber press Membrane press Dewatering screw Operation and maintenance of wastewater treatment plants Page 22

23 Sludge dewatering Difference in specific weight Separation by floc size Page 23

24 Sludge dewatering Separation by floc size Difference in specific weight Page 24

25 Sludge conditioning Mineral reagents for FP (FeCl 3 & Ca(OH) 2 ) Synthetic polyelectrolytes (emulsions or powder) Combination Others like heat or freezing treatment, elektro-osmosis Page 25

26 Sludge conditioning Page 26

27 Sludge transport Page 27

28 Final sludge treatment Sludge inciniration Sludge drying (pellets) Sludge composting Fertilizer for agriculture Landfilling Page 28

29 Legislation NL < 1995 Sludge used as fertilizer on land 1995 Forbidden to use sludge as fertilizer 1998 Landfill ODS < 10 % of TS EU-legislation for use of biogas for fuel EU-Water Framework Directive (WFD) Kyoto agreement 20 % less CO 2 in 2020 National agreements on energy efficiency National agreements on P-recovery Page 29

30 M kg ds/a Final sludge treatment through the years 400 Afzet zuiveringsslib drying landfilling composting inciniration overig verbranden composteren stort Landbouw agriculture Page 30

31 Final treatment (NL in 2012) Sludge incineration (60 %) at 2 locations. Ash is used as filler in asphalt and mines. Cooling agent and energy source in brown coal energy plants (13 %). Drying (13 %) and used as energy source and filler in the cement industry. Sludge composting (14 %), addition of dry organic matter and finally as energy source for a power plant.!!! Realize that at the end 100% of the sludge is incinerated Page 31

32 Some developments in sludge treatment ORGANIC WASTE SEWAGE SLUDGE PLANT A SEWAGE SLUDGE PLANT B MECHANICAL THICKENING MECHANICAL THICKENING SLUDGE REDUCTION ANAEROBIC DIGESTION BIOGAS EXTRA BIOGAS N, P RICH WATER CENTRAL DEWATERING CHP INSTALLATION WWTP THIRD PARTY FUEL CELL UPGRADING TO CNG RECOVERY OF NUTRIENTS FINAL TREATMENT ELECTRICITY HEAT GAS STATION FOR TRANSPORT; GAS NETWORK Page 32

33 Co-digestion Digestion of sewage sludge with other wastes, like: external sewage sludge; food waste; industrial organic wastes; livestock manure. Addition of extra biomass more biogas energy output increases; emission reduction; well stabilization of organic wastes. A few aspects should be paid attention to: infrastructure for co-digestion has to be available; monitor the materials that enter the digester; proper mixing of the different sources. Page 33 Mixer in sludge fermentation tank

34 COD-balance in a convential WWTP * Page 34 * by Dr Sara Isabel Pérez Elvira

35 Principle of sludge reduction technologies Sludge floc Energy Energy Energy Energy Bacterial cel Inert particle Extracellular polymers Improving the hydrolysis rate Increase the biodegradability of biomass Decrease the required retention time for digestion And in that case also an increase of the sludge loading rate Page 35 * by Dr Sara Isabel Pérez Elvira

36 Just some reduction technologies Ultrasound Thermal Hydrolysis Plug Flow Digestion Page 36

37 Thermal Hydrolysis (Cambi) Page 37

38 Thermal Hydrolysis (Cambi) Claims compared with conventional digestion: 40 to 60% increase in biogas reduction in total solids of 15 to 20% increase in dewatering with 8 to10% DS 100% increase in digester capacity pathogen free biosolids Page 38 Up to 30 world-wide references.

39 Developments in final treatment Sludge drying Low Temperature Drying Solar drying Gasification and pyrolysis Super critical wet oxidation Page 39

40 Warning!!! Just a few possible scenario s eerste trap voorbezinking preprecipitatie microzeven droging + vergassing lage temperatuur BABE Sharon 1-AX Demon bio P superkritische vergassing indirect thermisch meestoken MBR Nereda korrel 1 e trap + 1-AX actief slib Cannibal droging direct thermisch meestoken cementoven HTU biologisch storten gravitaire indikking mechanische indikking natte oxidatie ultrasone voorbeh. thermische voorbeh. thermische voorbeh. stoomlevering enzymvoorbeh. co-verbranding W K K groen gas mesofiele gisting rwzi thermofiele gisting ontwatering wormenreactor verbranding tegendrukturbine condensatieturbine damprecompressie eindverwerking Page 40 Manage this from the beginning.

12:10 Lysotherm : 5 jaar ervaring met innovatieve slibhydrolyse. Bert Geraats (Eliquo)

12:10 Lysotherm : 5 jaar ervaring met innovatieve slibhydrolyse. Bert Geraats (Eliquo) LYSOTHERM A novel approach to thermal sludge hydrolysis 01.07.2015 ELIQUO WATER GROUP FACTS AND FIGURES STAFF HISTORY FIGURES >200 employees Engineers Technicians Sales, commercial staff 1986 ELIQUO WATER