Optimizing Effluent and Sludge Treatment for Kraft Pulp Mills with regards to Energy Production, Consumption and Carbon Footprint.

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1 Optimizing Effluent and Sludge Treatment for Kraft Pulp Mills with regards to Energy Production, Consumption and Carbon Footprint. Hans Peter Zwiefelhofer, Paul Woodhead, Mauro Coutinho and David C. Meissner

2 Selectar Aerobic Selector Low Load Activated Sludge Stage Final clarifier < 2% BOD out ~ 0,2 kg excess sludge per kg COD removed f/m ratio: 0,1 kg BOD / kg MLSS - day BOD vol. loading: 0,5 kg BOD / m³ - day Sludge age: days Total HRT: 35 hours 2

3 FIBRIA Três Lagoas and VERACEL 3

4 Attisholz - 2 Stage Process 100% BOD in 1 st Aeration Stage Intermediate clarifier 2 nd Aeration Stage Final clarifier < 2% BOD out ~ 0,7 kg excess sludge per kg BOD removed 1 st stage f/m ratio: 0,2 kg BOD/kg MLSS -day BOD vol. loading: 3,4 kg BOD/ m³ - day Sludge age: 3 5 days BOD removal: 80% 2 nd stage Total HRT: 18 hours f/m ratio: 0,2 BOD/kg MLSS - day BOD vol. loading: 0,8 kg BOD/ m³ - day Sludge age: 8-15 days BOD removal: > 80% 4

5 IP Luiz Antonio Effluent Treatment plant 5

6 % Process Operation BOD -reduction in the biological stages 100% 95% 90% 85% 80% 75% 70% 65% 60% 55% 50% jan/09 fev/09 mar/09 abr/09 mai/09 jun/09 jul/09 ago/09 set/09 out/09 nov/09 dez/09 ZPR IP-LA Monthly verage 6

7 Selectar Aerobic Selector Low Load Activated Sludge Stage Final clarifier < 2% BOD out ~ 0,2 kg excess sludge per kg COD removed f/m ratio: 0,1 kg BOD / kg MLSS - day BOD vol. loading: 0,5 kg BOD / m³ - day Sludge age: days Total HRT: 35 hours 7

8 Attisholz - 2 Stage Process 100% BOD in 1 st Aeration Stage Intermediate clarifier 2 nd Aeration Stage Final clarifier < 2% BOD out ~ 0,7 kg excess sludge per kg BOD removed 1 st stage f/m ratio: 0,2 kg BOD/kg MLSS -day BOD vol. loading: 3,4 kg BOD/ m³ - day Sludge age: 3 5 days BOD removal: 80% 2 nd stage Total HRT: 18 hours f/m ratio: 0,2 BOD/kg MLSS - day BOD vol. loading: 0,8 kg BOD/ m³ - day Sludge age: 8-15 days BOD removal: > 80% 8

9 Flow and Load Comparison SCENARIOS Greenfield Greenfield Treatment process - 2 Stage Attischolz Process Selectar Sludge handling - anaerobic digestion, dewatering I Daily load or Unitary rate Flowrate m³/d simultaneous aerobic stabilization and dewatering Daily load or II unitary rate BOD inlet mg/l Air flow 9m depth Blower s consumed power kw Reactor volume (1st STAGE + 2nd STAGE) Total "Biological" Volume = Reactors and Settlers Total "Biological" Volume = Reactors and Settlers including Anaerobic Digester Total HRT (including biological settlers) Excess sludge production m³ m³ m³ h 17,7 28,5 kgtss/d kgvss/d

10 Statements 1. Biomass contains energy! 2. From biomass we can produce primary energy! 3. Why biodegrade biomass using a lot of energy if we can use it for better purposes? 10

11 Typical uses of the Excess sludge 1. Do simultaneous stabilization = oxidation; 2. Landfill the dewatered sludge; 3. Direct use in foresting; 4. Compost the sludge with other waste material to produce a sellable fertilizing humus replacement / soil improver; 5. Burn it i.e. in the biomass boiler; 6. Produce primary energy from the biomass in anaerobic digestion; 11

12 Sludge is valuable 1. Biomass is valuable. 2. Organic fraction in the sludge and the N and P content. 3. The value of sludge can be different. 12

13 Excess sludge production Oxygen required Attisholz Process Selectar Process 13

14 Value of the sludge 14

15 Anaerobic digestion and the four steps 15

16 Anaerobic Digestion Plant

17 Cell disintegration techniques 1. Working with thermophilic temperatures (> 50º C); 2. By mechanical disintegration with centrifuges; 3. Biological, using enzymes; 4. Thermal disintegration using high temperature (> 150º C) and pressure; 5. Ultrasonic pretreatment. 6. Others 17

18 Ultrasound process 18

19 Test results Hamburg 19

20 ETE ZPR/Rosenthal and first stage Attisholz process 20

21 Ultrasound pilot plant container 21

22 Ultrasound pretreatment 22

23 The 5 reactors 23

24 The reactor top with gas counter 24

25 Final values considering biogas and sludge reduction after anaerobic digestion SCENARIOS Greenfield Greenfield Treatment process - 2 Stage Attischolz Process Selectar Sludge handling - anaerobic digestion, dewatering I Sludge before digestion kgtss/d kgvss/d Sludge after digestion kgtss/d kgvss/d Digester volume 12 days m Biogas production Nm³/d CH 4 production Nm³CH4/d Chemical energy kcal/day Electrical energy production kwh/d Energy consumption for sonication kwh/d simultaneous aerobic stabilization and dewatering II Energy for mixing and pumps kwh/d Net energy gain kwh/d Net Blower s consumption (-) electric energy gain from biogas kwh/d Sludge concentration - dewatering % 25% 15% Sludge production after dewatering unit ton/d 100,5 122,0 25

26 Conclusions Combining the ATTISHOLZ process with Anaerobic Digestion gets us: Less energy for the biological treatment Less sludge to dispose of Additional energy from biogas Lower carbon footprint Better P-removal Smaller plant footprint Have another look at your sludge concepts 26