Roadmap towards Energy Neutral Sewage Treatment Works in Hong Kong - PowerPoint PPT Presentation

Roadmap towards Energy Neutral Sewage Treatment Works in Hong Kong Po-Heng (Henry) LEE Dept. of Civil and Environmental Engineering The Hong Kong Polytechnic University 1

Butcher Ding's Dismembering Bulls: Taoism 2

Beef Cuts vs STW Cuts ENERGY à C & N 3

My Taoism in Science & Engineering: Thermodynamics Solar Unit: Miter Unit: Mit er S mallest DNA Mountain Sun Galaxy Quraks Nucleon Atom Human Molecule System C ell Length 10 -18 10 -15 10 -10 10 -9 10 -5 10 -3 1 10 6 10 9 10 15 10 21 Mass, Energy & Time Unit: Billions years Unit: 6 2 1 13.7 13 12 11 10 9 8 7 5 4 3 Today Big Bang 4 People Appear Earth Formed

Sample Collecting: Shatin & Shek Wu Hui STWs Sample Collection A"er A"er A"er Primary Secondary Primary Thickening Anaerobic degri)ng effluent effluent Sludge (secondary Diges>on 4 1 5 2 3 6 sludge) 5

Oxygen Bomb Calorimetry Experiment • Samples dried for ~48 h at 104 ̊C Mix sample with Place the pellet into Make a pellet Weigh the pellet Connect nichrome combus>on aid capsule wire Put bomb into jacket, Weigh deionized Assemble the oxygen Charge bomb with connect the water Set up, ignite, record bomb oxygen electrode, fill water 6

What we learn from this survey? > Sludge contains more energy than sewage > Sewage energy is much more dilute so that is difficult to capture > Energy content from Ammonium nitrogen is around 10-35% of organics carbon 7

Strategies: Energy Neutral/Positive Saline STWs Energy Energy 1 st clarifier Sewage Conserva>on Produc>on C ─ N ─ • Smart • Pretreatment aera>on with mono- or • Shortcut co-diges>on denitrifica>on • Solid Oxide • Mainstream Fuel Cells Anammox • Energy C + recovery from ammonium N + 8

Mainstream Energy Efficient Anammox 9

Packed-Bed O 2 -Controled System with 50 mg/L NH 4 + -N Reactor Aerator Effluent Air Influent Aerated Recycle

Effect of DO/NH 3 Ratio 100 80 % Removal 60 40 N Removal 20 NH3 Removal 0 0.55 0.65 0.75 0.85 0.95 1.05 DO/NH 3 Ra9o

� Anammox Dominant species Shifted from KS to BA with concentrated to dilute Sample KS/TA % BA/TA % BF/TA % Seeding 20.48 0.03 0.17 Site 1 2.73 14.27 0.02 1.60 19.38 0.89 Site 2 Site 3 2.46 28.25 1.75 Site 4 1.02 33.67 1.98 TA: total species of anammox bacteria; KS: Candidatus Kuenenia stuttgartiensis; � BA: Candidatus Brocadia anammoxidans, BF: Candidatus Brocadia fulgida

Saline Mainstream Anammox § C/N ratio <2 via Anammox-based processes for C and N removal § Saline effect? 13

HK Waste Wate Treatment Plants Shek Wu Hui Yuen Long Tai Po Sha Tin seawater? hbp://"s.com.hk/epd

Maximal Energy Production with Sludge 15

C and N fuels from Sludge CH 4(g) +2O 2(g) à CO 2(g) +2H 2 O (l) Δ H R 0 =-890 kJ/mol (1) CH 4(g) + 4N 2 O (g) à CO 2(g) +2H 2 O (l) + 4N 2(g) Δ H R 0 =-1219 kJ/mol (2) CH 4(g) +4NH 3(g) +5O 2(g) � CO 2(g) +2N 2(g) +8H 2 O (l) Δ H R 0 =-2125 kJ/mol (3) 16

Coupled Aerobic–Anoxic Nitrous Decomposition Operation (CANDO) > Ammonium partial oxidization into nitrous oxide via chemical or biological approaches > Methane combustion with Nitrous oxide > Approximately 20 to 30% more energy yield than combustion with oxygen 17 Scherson et al., 2013

NH 3 , CH 4 , and CO 2 Reformation using Solid Oxide Fuel Cell Prof. Ni Meng O 2 Cathode Electrolyte Anode O 2- NH 3 CH 4 N 2 CO 2 N 2 (U.S. Serial No. 62/353,137) 18

Performance of NH 3 , CH 4 , and CO 2 Reformation > 50 to 60% Energy conversion efficiency (30% in combustion) > Using additional fuel (NH 3 -N) • C decomposition can be avoid due to CO 2 and NH 3 in SOFC • No NOx emission • 60% of a net energy output greater than conventional combustion • A techno-economic analysis shows that the net energy ratio improves from 1.11 to 1.75 in Hong Kong West New Territories (WENT) Landfill Facility 19

High Gravity (HIGEE) in Rotating Packed Bed Reactor Prof. Yi-Hung Chen Effective Gas liquid separation induced by 100 G

Ammonium Removal from Concentrated Wastewaters Neutralizer/ Con9nuous Recovery On-site Treatment Condi9on: Inflow of Clear Air Q L of wastewater = 7 L/min Ammonia-rich 1. Converted to ammonium sulfate Conc. of NH 4 -N = 5630 mg/L Wastewater 2. Recovery of ammonia solu9on pH = 11.5-12 T 3. Burning as fuel Removal efficiency = 90–98% Power Specifica9on (Full-rated) Rota9ng Rotor: 3 hp Packed Bed (RPB) Liquid Pump: 1.5 hp D Con9nuous Supply of Air Pump: 1.5 hp Clear Effluent Fresh Air or Steam Energy consump9on: Below half of full rated power = 2.2 kW 100 5 95 2 η (%) 90 1. Influent tank 3 1 1 2. RPB 4 3. Effluent tank 21 85 4. Air pump 300 600 900 1200 21 5. Scubber ω (rpm)

H 2 S Issue 22

H 2 S Removal from Biogas Prof. Yi-Hung CHEN Purified Biogas Rota9ng T Packed Bed (RPB) Circulated D Con9nuous inflow of Alkaline Biogas with 1-3 vol.% H 2 S Solu9on Power Specifica9on (Full-rated) On-site treatment condi9on: Rotor: 0.5 hp Q G of biogas = 20 L/min Liquid Pump: 0.5 hp Ini9al conc. of H 2 S = 1–3 vol.% Biogas Pump: 0.5 hp Alkaline: 30 wt.% NaOH Removal efficiency = 90–99% Energy consump:on: Below half of full rated power = 0.56 kW 23

H 2 S S Remo mova val fro rom m Bi Biogas s by y Rotating Pa Packe cked Be Bed: Field Exp Experi rime ments s at Ba Bali WWTP Biogas with Removal efficiency = 90–98% 1-3 vol.% H 2 S Q G : 10-60 L/min M ATI-C16 M H 2 S M CO 2 Mexa-584L Air dilu9on Requirements: Exceed pH 100 ppm to atmosphere purified biogas 650 ppm to combus9on Alkaline solvents (100 ppm for SOx) (Q L = 0.12-0.6 L/min, G/L = 100-500) 1 ppm to fuel cell 10-30 wt.% NaOH or MDEA (N-methyldiethanolamine) 24

Summary Enhanced 1 st clarifier Effluent Sewage ( Permeate) AFMBR: Anammox CH 4 ENERGY NH 3 Anaerobic Sludge Digestate Digestion • Enhanced 1 st treatment to remain C and N in sludge • Ammonia and methane into energy with higher conversion efficiency • Mainstream Saline Anammox

Thank you very much 26