VALORIZATION OF MAIZE SILAGE AND MUNICIPAL WASTEWATER SLUDGES: ENERGY PRODUCTION ENHANCED BY ULTRASONIC AND MICROWAVE PRE-TREATMENTS

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1 VALORIZATION OF MAIZE SILAGE AND MUNICIPAL WASTEWATER SLUDGES: ENERGY PRODUCTION ENHANCED BY ULTRASONIC AND MICROWAVE PRE-TREATMENTS B. Aylin ALAGÖZ Prof. Dr. Orhan YENİGÜN Prof. Dr. Ayşen ERDİNÇLER Boğaziçi University Institute of Environmental Sciences Istanbul, Turkey

2 Problem Definition A rise in the global population and a consequent increase in demand for oil and gas have resulted in a search for alternative and cost-effective renewable energy sources like biomass. Biomass, especially the waste material having a considerably high organic content like agricultural wastes and wastewater sludges, have a large biogas energy potential through the anaerobic digestion. Using the wastewater sludges and agro wastes as renewable energy sources also provides an alternative solution for the disposal problem of these gradually increasing wastes.

3 Why the biomass renewable energy sources are quite important for Turkey? There are plenty of various agricultural wastes, energy crops and wastewater sludges in Turkey to be used as renewable energy source 65 Mtons of agricultural wastes generated annually from cultivation The prediction show that the annual sludge production will reach up to 911 ktons by year 2040.

4 Biomass Energy Potential Turkey possesses a variety of biomass resources like forests, agriculture and animals. Although traditionally animal dung has been used for heating and cooking purposes for many years, it is slowly being converted to modern uses of biomass energy. Annual Biomass Potential of Turkey Type of Biomass Annual biomass potential (million tons) Energy potential (Mtoe)* Annual crops Perennial crops Forest residues Residues from agro-industry Residues from wood industry Animal wastes Other Total *Million Tons of Oil Equivalent

5 to investigate thoroughly: Aim of the Study the biogas production potential of the maize silage co-digested with the pre-treated wastewater sludge through the mesophilic anaerobic digestion. the effect of sludge pre-treatment (ultrasonication and microwave) on the co-digestion efficiency and the biogas production. Pre-treatment of the sludge sample was realized with: ultrasonication microwave 5

6 Anaerobic Digestion Microbially mediated biochemical degradation of complex organic material into simple organics and dissolved nutrients Advantages: producing renewable energy production of an odorless, humus-like, biologically stable end product preventing transmission of disease while stabilizing waste organic matter lower capital cost 6

7 Anaerobic digestion Hydrolysis Acidogenesis Acetogenesis Methanogenesis H 2 CO 2 NH 3 Carbohydrates Proteins Lipids Sugars Amino acids Fatty acids Alcohols Carbonic acids Volatile fatty acids NH 4 H 2 S CH 4 CO 2 Acetic acid

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9 Sludge Disintegration Methods Mechanical Sludge Disintegration High Pressure Homogenizer Stirred Ball Mill Lysate Centrifuge Mechanical Jet Technique Ultrasound Pulsed Electrical Field Application (PEF) Chemical Sludge Disintegration Mineral Acids or Alkali Ozone Fenton Process Thermal Sludge Disintegration Microwave Biological Sludge Disintegration

10 Ultrasonication Ultrasonic treatment acts to mechanically disrupt the cell structure and floc matrix. Cavitation: the bubbles form, grow and undergo violent collapse. Chemical reactions: OH, HO2, H radicals and hydrogen peroxide can be formed.

11 Microwave The application of microwave irradiation for sludge pre-treatment : releases intracellular bound water and generally involves heating in the range of C. causes to a rotation of dipole molecules under an oscillating electromagnetic field provides rapid, energy-efficient heating of water to the boiling point where the cells of microorganisms are ruptured and the bound water is released.

12 MATERIALS AND METHODS Sludge Substrates: Seed Sludge (Inoculum) Sewage Sludge Seed Sludge (Inoculum): from the full-scale anaerobic digester of a big yeast factory in İzmit Wastewater Sludge: from the recycling line of one of the largest advanced biological wastewater treatment plant located in İstanbul

13 Analytical methods used in the study Parameter ph ORP Conductivity COD TOC TS/VS VSS TVS Alkalinity TKN Ammonia-N Method and Special Instruments 4500-H B Method Electrometric (APHA, AWWA-WPCF-2006) ORION SA 520 ph meter 2580 B Method (APHA, AWWA-WPCF-2006) ORION SA 520 ph meter 2510 B Method (APHA, AWWA-WPCF-2006) WTW LF 320 Conductivity meter 5220 D Method Closed Reflux, Colorimetric (APHA, AWWA-WPCF-2006) HACH COD Digester, HACH DR/3 Spectrophotometer 5310 A Method (APHA, AWWA-WPCF-2006) 2540 B (APHA, AWWA-WPCF-2006) 2540 D and E (APHA, AWWA-WPCF-2006) 2540 G (APHA, AWWA-WPCF-2006) 2320 B Method Titration (APHA, AWWA-WPCF-2006) 4500 E Method Titration (APHA, AWWA-WPCF-2006) Gerhardt Vapodest Digester Apparatus 4500 E Method Titration (APHA, AWWA-WPCF-2006) Gerhardt Vapodest 12 Distillation Apparatus

14 Analytical methods used in the study (cont.) Nitrite, nitrate 4500 Method (APHA, AWWA-WPCF-2006) Phosphate Chloride Sulfate 4500-P E Method Ascorbic Acid (APHA, AWWA-WPCF-2006) HACH DR/3 Spectrophotometer 4500-Cl B Method Argentometric (APHA, AWWA-WPCF-2006) 4500-SO 4-2 E Method Turbidimetric (APHA, AWWA-WPCF-2006) HACH DR/3 Spectrophotometer CST CST Instrument (Vesilind, 1988) VFA Gas Chromatograph HP 5890 CH 4, CO 2, O 2 Gas Chromatograph HP 6850

15 Sludge Characteristics Parameter Unit Inoculum Sewage Sludge TS mg/l VS mg/l MLSS mg/l MLVSS mg/l COD mg/l scod mg/l TKN mg/l NH 4+ mg/l TP mg/l PO -3 4 mg/l SO -2 4 mg/l Alkalinity (as CaCO 3 ) mg/l ph Conductivity ms/cm 20, Salinity Total Coliform kob/100ml 1* x10 7 Fecal Coliform kob/100ml 5* x10 6 Fecal Streptococ kob/100ml 1*10 5 1x10 6

16 MATERIALS AND METHODS (cont.) Batch fed anaerobic digestion 2.5 L with 1.6 L active volume 40 days of digestion A water bath at an average temperature of 37 C (kept constant by an automatic heat controller) Flushing with nitrogen gas for 5 minutes

17 The Experimental Setup The bottles equipped with a V shape gas collection ports at the top. One opening for MiliGascounter (MGC) to measure the amount of biogas produced. One opening to take samples for gas composition (CH 4 and CO 2 ) analysis by using a HP 6850 Gas Chromatograph. (Carboxen 1010 plot column 30 m x 0.53 mm) equipped with a thermal conductivity detector.

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19 RESULTS AND DISCUSSION

20 Reactor Contents Reactors Content R1 Inoculum + SS R2 Inoculum + SS (50%) + MS (50%) R3 Inoculum + SS (40%) + MS (60%) R4 Inoculum + ultrasonically disintegrated SS for 15 min (50%) + MS (50%) R5 Inoculum + ultrasonically disintegrated SS for 30 min (50%) + MS (50%) R6 Inoculum + disintegrated SS with microwave (50%) + MS (50%)

21 Applied Pre-treatments «Ultrasonication» This equipment was operated in the study at the frequency of 20 khz, %65 amplitude and a supplied power of 200W. For each sonication experiments, 400 ml of wastewater treatment sludge was filled in a glass beaker with the temperature adjustment. The sludge samples were sonicated at two different sonication durations of 15 and 30 minutes.

22 Applied Pre-treatments «Microwave» The Speedwave MWS-3+ Microwave Digestion System was used for the thermal disintegration. Vessel type/volume: DAP-60S (60ml) Working pressure: 40 bar / 580 psi Multiple arrangement:12 vessels A staged temperature profile was applied for pre-treatment. Holding time of samples was 30 minutes and average temperature was 175 C. For each experiments, 400 ml of wastewater treatment sludge was used.

23 Effect of Ultrasonic Disintegration on Particles Size Distribution

24 Reactor Conditions Initial ph values of the reactors were adjusted to about 7. Final ph values of the reactors ranged between The initial alkalinity concentrations in the reactors ranged between mg CaCO 3 /L. Final alkalinity concentrations ranged between mg CaCO 3 /L.

25 TS Contents and Removals

26 VS Contents and Removals

27 scod Contents and Removals

28 Microbiology Results of the Reactors Reactors Total Coliform Initial [kob/100ml] Total Coliform Final [kob/100ml] Fecal Coliform Initial [kob/100ml] Fecal Coliform Final [kob/100ml] Fecal Streptococ Initial [kob/100ml] Fecal Streptococ Final [kob/100ml] R1 2.7x10 6 1x x x R2 5.3x10 6 1,7x x x R3 3.2x10 6 6x x x R4 3.5x10 6 9x x x R5 2.7x10 6 3* x x R6 2.0x10 6 2* x x

29 Cumulative Biogas Productions (ml)

30 Methane Content of Biogas (%)

31 Biogas and Methane Yields (L/g VS removed)

32 CONCLUSIONS Anaerobic co-digestion of the wastewater sludge and maize silage was a viable alternative for the improvement of the biogas production. Also an alternative solution for the disposal problem of the wastewater sludges.

33 CONCLUSIONS (cont.) The anaerobic co-digestion of sewage sludge with the maize silage resulted in higher methane yields than those in reactor R1 containing wastewater sludge alone. In reactor R2 and R3, the cumulative biogas production was almost two times higher than in reactor R1 containing wastewater sludge alone.

34 CONCLUSIONS (cont.) The most efficient biodegradation and the highest biogas and methane yields were obtained in reactor R6 having the mixture of 30-minute microwaved wastewater sludge and maize silage. In reactor R6, biogas and methane yields were about 0.44 L/g VS removed and 0.31 L CH 4 /g VS removed respectively. In all the pre-treated reactors, higher methane yields were obtained than in reactor R1 containing just wastewater sludge. about 33-45% increase depending on the applied pre-treatment technique.

35 Thank you for your kind attention... Any Questions???