Integrated process for biogas production from algal biomass 1 th May 2012 Francesco Ometto

Transcription

1 Integrated process for biogas production from algal biomass 1 th May 2012 Francesco Ometto

2 Project summary Integrated process for biogas production from algal biomass Verify the viability of an integrated process for producing algae for nutrient removal in a wastewater treatment system and, subsequently, using their biomass in digester to produce biogas. Start date: 2 nd August 2010 End date: 2 nd August 2013

3 Background Wastewater algal treatment Wastewater Waste sludge Residual N and P HARVESTING 1 2 PRODUCTS Ultra Clarified Water DIGESTION 3 A D WWTP Algal tertiary treatmnet Energy recovery

4 1. Harvesting The harvesting process is expensive >20% of overall algal culture process Economic Harvesting process

5 Harvesting energy demand Technology -3 Energy kwh m Centrifuge 1 Pressure filter 0.88 Hydrocyclone 0.3 Vacuum filter 5.9 Dissolved Air Flotation

6 Low energy harvesting technologies DAF - Dissolved Air Flotation (0.3 kwh m ) -3 BDAF Ballasted Dissolved Air Flotation (0.04 kwh m ) -3 Increasing coagulant dose

7 Ballasted Dissolved Air Flotation Sludge scraper Floc & bead aggregate Hydrocyclone to separate floc and bead Micro beads Separated beads leave from top & are recycled New bead added to make up for any loss during recycle Clarified water Recycled bead are introduced at base of flocculation zone Bead pump Bead recycle line Flocculated material sinks to be removed from the base 60-80% less energy compare with DAF

8 Biomass (cells/ml) Protein & carboydrate (mg/l) Flotation drivers Algogenic Organic Matter (AOM) characteristics change over time and effect the harvesting performance: DOC, scc, spc. ZP, ph, Charge density 2.0E E+07 C.vulgaris E E+07 S.obliquus E E E E E E E Time (days) 0.0E Time(days) Protein (mg/l) Carbohydrate (mg/l) Cells/mL Protein (mg/l) Carbohydrate (mg/l) Cells/mL

9 DAF vs BDAF Scenedesmus flocs (Light microscope x40) Scenedesmus beads flocs (Light microscope x40)

10 Open questions How stongh are the algal flocs? How much coagulat is left on the water/biomass? Does the coagulant contamination effect the AD treatmnets? How recover effectively the beads? Possible CRA/UDE Secondement project 2.3

11 2. Algal products Many traditional algal products on the market Identify all the possible alternative for the downstream algal biomass treatment

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13 Alternative products Bio-plastic Bio-fuels Currently, the algal market suffers a high lack of available biomass. There are many companies able to process the feedstock but only a few facilities able to produce enough quantity of algae paste.

14 3. Algal digestion Algal membrane are very difficult to break; C/N ratio might have a detrimental effect; Anaerobic digestion improvement

15 m3 CH4/kg VSadd Biochemical Methane Potential (BMP) Actual digestion ww sludge S. obliquus C. Sorikiniana S. maxima

16 Pre-treatments Treatments conditions time Thermal treatment 105 C -120 C 30 8h Chemical-thermal treatment 105 C -120 C (NaOH, H2SO4) 30 8h CAMBI 170 C 8bar 30 Enzymes 37 C, ph, U/g 1 8h Ultrasound Adapted bacteria population The treatment efficiency will be evaluated considering: FVS/VS scod spc (soluble proteins content) scc (soluble carbohydrate content) Cells counting

17 Pre-treatment experiment Initial results TREAMENT PARAMETERS Sc. Obliquus Ch. Sorokiniana Sp. Maxima pre post pre post pre post scod mg/l spc mg/l TERMAL 100 C 3h scc mg/l ph Cells distroyed 20% 0% 0% Cells effected 100% 100% 90% scod mg/l spc mg/l TERMAL 100 C 3h H2SO4 scc mg/l ph Cells distroyed 80% 80% 100% Cells effected 100% 100% 100% The pre-treatment efficiency will be validate for Biogas production improvement

18 Methane [m3*kg-1 VSadd] CAMBI pre treatment effects 0.9 BMP DIGESTED CELL time [d] Untreated Treated Seed RESIDUAL CELL

19 Open questions Characteristics of the digestate (C, N, P, H content) WWSludge/algae co-digestion performs AD of real wastewater alage

20 ENERGY Summary How the algal treatment effects the energetoic balance of a WWTP? WWTP Algal treatmnet Energy recovery ENERGY A D

21 To be continued...

22 Thank you In life, there is nothing to fear and everything to understand. Marie Curie ( )