Introduction. Anaerobic Treatment. High Rate Renewable Energy Production with the Static Granular Bed Reactor (SGBR) 4/4/2014

Transcription

1 High Rate Renewable Energy Production with the Static Granular Bed Reactor (SGBR) Tim Ellis, Ph.D., P.E., Associate Professor Dept. of Civil, Constr. & Environ. Eng. Iowa State University Ames, IA Introduction Short overview of anaerobic digestion Definition of high rate systems Developments at Iowa State University Case studies Anaerobic Treatment Historically, anaerobic organisms Slow growers unstable (failed systems led to stuck digesters ) Anaerobic treatment is a net energy producer Potential to produce equiv. 5, bpd Save 2, bpd in aeration costs Anaerobic yield is ~2% of aerobic yield 1

2 Anaerobic Digestion in Developing Countries Biogas Cookstove Community Biogas Plant, China Renewable Energy at Treatment Plants Low vs. High Rate Waste Treatment Modern wastewater treatment plants have been using high rate (low F:M) systems for over 1 years for aerobic treatment For anaerobic treatment which produces energy, we ve been using low rate (high F:M) systems Few alternatives to conventional AD Conventional AD requires long detention times, heating, mixing 2

3 High Rate Anaerobic Systems Separate solids retention time (SRT) from hydraulic retention time (HRT). SRT = mass of solids in system (g) / daily rate of solids wasted (g/day) HRT = Volume of Reactor / Flow rate Can achieve much high organic loads due to retention of biomass. Higher organic loads makes more economical design due to smaller reactor. High Rate (low F:M) Digestion In 198 s Lettinga - UASB reactor Upflow process washed out flocs Led to anaerobic granule development Detention times of 1 day or less. Requires a low solids wastewater Requires recirculation pumping, and gas solids liquid separator Typically requires heating to 35ºC to operate satisfactorily three phase separator biogas effluent weir effluent gas bubbles baffles granular sludge distribution baffle influent flocculent sludge recirculation pump UASB granule gas bubble floc particle 3

4 Anaerobic granules Current Research and Development at Iowa State University New high rate system Maximize biomass density (low F:M) Minimize effluent solids Meet NPDES permit requirements for surface water discharge in some instances Maximize potential to generate renewable energy in the form of biogas SGBR Defined High-rate, downflow anaerobic reactor Biomass=Anaerobic granules (seeded from existing reactors containing granules) Submerged Biomass Gas filled headspace Gravel underdrain biogas influent water level effluent granule bed gravel underdrain 4

5 COD Removal COD Removal, Efficiency, % % Removal effiency (%) COD Removal, % 4/4/214 SGBR vs UASB 1 9 SGBR UASB UASB (Jeison & Chamy) EGSB (Jeison & Chamy) UASB (Yan & Tay) UASB (Fang and Chui) UASB (Zoutberg & Eker) UASB (Ramasamy et. al.) UASB (Jhung & Choi) AFF (Jhung & Choi) UASB (This study) SGBR (This study) Organic Loading Rate, g/(l d) Organic Loading Rate, kg/m 3 d Comparison with other systems (slaughterhouse wastewater) 1 SGBR achieved greater COD removal than other systems This Study EGSB (Núñez & Martínez) 25 C ASBR (Massé & Masse) UASB (Ruiz et al.) AF (Ruiz et al.) OLR, kg COD m -3 d -1 Short Start-up Time (Pork Slaughterhouse in Iowa) TSS COD Time (Days) REACTOR STARTUP 5

6 SGBR Results Pork Slaughterhouse COD Rem., % COD concentration (mg/l). TSS concentration (mg/l). Removal effiency (%). Removal effiency (%) 4/4/ Influent Effluent Removal Influent Effluent Removal Time (Days) SGBR Results Landfill leachate SGBR This Study Berrueta et al. Lin et al OLR, kg/m 3.d Tulare, CA 6

7 Existing Lagoon 7-d detention time, poor performance periodically 7

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9 Tulare, CA Operating Results Backwashing Efficiency 9

10 Summary Simple, effective and economical method to treat a wide variety of municipal, industrial, and agricultural waste streams and produce a renewable source of energy Recirculation pumping, mixing, baffling, heating not required with SGBR Stability of system ensured by its ability to retain active biomass (measured SRTs from 8 to 2 years!) Hydraulic detention times typically hours Questions? 1