Prelim elimin inary ary ev eval aluati uation on of of Scenedesmus obliquus gr growth th on on or organic nic solid olid waste diges estate, wi with di differ eren ent mechani echanical pretr trea eatm tmen ent P. Scarponi, A. Costa Devoti, A. Volpi Ghirardini, C. Cavinato Department of Environmental Science, Informatics and Statistic, Unversity Ca’ Foscari of Venice, Italy
STATE OF ART Anaerobic digestion (AD) is a widespread biotechnology for organic fraction of municipal solid waste ( OFMSW ) or industrial food waste treatment to produce energy (biogas). AD system is an efficient methodology to treat this type of waste PROBLEM but at the same time AD effluent had substantial nitrogen, phosphorus and other pollutants load, that avoid its environmental release . RESEARCH CARRIED We tested S. obliquus growth on OFMSW ‐ AD effluent in order OUT to evaluate microalgae strain growth capacity and effect on AD digestate.
OFMSW+waste activated Lipid sludge Protein AD Biogas Microalgae Biomass AD effluent treatment Effluent cleaned PHA Cha, b and carotenoid
OFM OFMSW di digestate char characteriz rizatio tion The anaerobic digestate was collected in a wastewater Value treatment plant (WWTP) in north ‐ east of Italy pH 7,6 Total alkalinity (g CaCO 3 /l) 1,69 Partial alkalinity (g CaCO 3 /l) 2,84 + (mg N/l) N ‐ NH 4 573 It was tested on S. obliquus with VFA (mg/l) 80 three pretreatment conditions: • Without pretreatment ( no PT ); sCOD (mg/l) 300 • Centrifugation ( AC ) • Filtration ( AUF )
Experimental set up S. obliquus growth was tested in: • mixotrophic and heterotrophic conditions; • Inoculum and digestate dilution was 1:10; • Bubbling and mixed in continuous; • Light irradiation (2010 LUX).
Cellular count 160 140 120 Max value in control condition 100 Cell milion * ml 80 60 40 20 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 Day Day MIxotrophic Digestate no PT Heterotrophic Digestate no PT Mixotrophic Digestate AC Heterotrophic Digestate AC Autotrophic Mixotrophic 1 g/l Glu Heterotrophic 1g/l Glu Mixotrophic Digestate AUF Heterotrophic Digestate AUF S. obliquus could growth on OFMSW digestate with or without pretretment, using ammonia and organic compounds. Illumination is a fundamental factor for microalgae growth on this substrate.
Dry weight (g/l) St. dev. Phototrophic 0,12 ± 0,01 Mixotrophic (1 gl ‐ 1 glu) 0,15 ± 0,002 Mixotrophic no PT 0,3 ± 0,1 Mixotrophic AC 0,42 ± 0,08 Mixotrophic AUF 0,5 ± 0,04 Productivity (g/l*d) St. dev. Mixotrophic (1 gl ‐ 1 glu) 0,018 ± 0,0003 Mixotrophic no PT 0,033 ± 0,02 Mixotrophic AC 0,053 ± 0,01 Mixotrophic AUF 0,063 ± 0,005 Digestate pretreatment gave best results for microalgae growth, the difference on dry weight and productivty between AC and AUF was small, so we deduced aswell that just one AC cycle will be enough like pretreatment.
Ammonia reduction % Ammonia removal In all test condition, initial 100 ammonia concentration was 50 90 Nl ‐ 1 . At the end of test an 80 ammonia reduction of 95,3 % (± 70 3,5) was observed. % NH 3 removal 60 Mixotrophic Digestate no PT 50 Probably this result was not Mixotrophic Digestate AC 40 correlated only to microalgae Mixotrophic Digestate AUF 30 growth but it was also caused by ammonia stripping by bubbling 20 and pH increased by 10 photosynthetic activity. 0 0 1 2 3 4 5 6 7 8 9 Day
Mixotrophic Digestate no PT Mixotrophic Digestate AC Mixotrophic Digestate AUF Chloroph Chlor phyll yll a, a, b 0,08 and tot and total 0,07 caroten ca tenoid Chlorophyll a, b anc Carotenoid tot accum accumula latio tion 0,06 0,05 µg/ml *cell 0,04 Mixotrophic control 0,03 (µg ml ‐ 1 *cell) Media St. dev. 0,02 Ch a 6,11 ± 1,8 Ch b 7,4 ± 2,4 0,01 Carotenoid tot ‐ ‐ 0 Cha Chb Carotenoid tot
AC and AUF pretreatment on OFMSW gave best growth Scale up in countinuous results in mixotrophic mixotrophic condition conditions. only with AC Next pretreatment . Evaluate studies: Pretreatment and nutrient removal and by ‐ illumination permit S. products production and obliquus growth on this accumulation . wastewater with ammonia reduction of about 95%. Conclusion
Thank Thank yo you fo for the the atte attent ntion
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