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

Roadmap towards Energy Neutral Sewage Treatment Works in Hong Kong

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Po-Heng (Henry) LEE

• Dept. of Civil and Environmental Engineering

The Hong Kong Polytechnic University

Butcher Ding's Dismembering Bulls: Taoism

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Beef Cuts vs STW Cuts

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ENERGY à C & N

My Taoism in Science & Engineering: Thermodynamics

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13.7 8 Today 13 10 12 11 9 6 1 2 3 4 5 7 Unit: Unit: Billions years

Big Bang Earth Formed People Appear

Quraks 10-18 Nucleon

Molecule

Atom Smallest Cell Solar System Mountain Human Sun Galaxy 10-15 10-10 10-9 10-5 DNA Length 10-3 106 1 109 1015 1021 Unit: Mit Unit: Miter er

Mass, Energy & Time

Sample Collection

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A"er degri)ng Primary effluent Secondary effluent Primary Sludge A"er Thickening (secondary sludge) A"er Anaerobic Diges>on

1 2 4 5 3 6

Sample Collecting: Shatin & Shek Wu Hui STWs

Oxygen Bomb Calorimetry Experiment

Mix sample with combus>on aid Make a pellet Weigh the pellet Place the pellet into capsule Connect nichrome wire Assemble the oxygen bomb Charge bomb with

• xygen

Weigh deionized water Put bomb into jacket, connect the electrode, fill water Set up, ignite, record

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• Samples dried for ~48 h at 104 ̊C

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

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Strategies: Energy Neutral/Positive Saline STWs

Energy Conserva>on

• Smart

aera>on

• Shortcut

denitrifica>on

• Mainstream

Anammox

Energy Produc>on

• Pretreatment

with mono- or co-diges>on

• Solid Oxide

Fuel Cells

• Energy

recovery from ammonium

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Sewage 1st clarifier

C ─ N ─

C + N +

Mainstream Energy Efficient Anammox

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Packed-Bed O2-Controled System with 50 mg/L NH4

+-N

Reactor Aerator

Influent Effluent Air Aerated Recycle

Effect of DO/NH3 Ratio

20 40 60 80 100

0.55 0.65 0.75 0.85 0.95 1.05 % Removal DO/NH3 Ra9o

N Removal NH3 Removal

• TA: total species of anammox bacteria; KS: Candidatus Kuenenia stuttgartiensis;

BA: Candidatus Brocadia anammoxidans, BF: Candidatus Brocadia fulgida

Sample KS/TA % BA/TA % BF/TA % Seeding 20.48 0.03 0.17 Site 1 2.73 14.27 0.02 Site 2 1.60 19.38 0.89 Site 3 2.46 28.25 1.75 Site 4 1.02 33.67 1.98

Shifted from KS to BA with concentrated to dilute

Anammox Dominant species

Saline Mainstream Anammox

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

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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

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C and N fuels from Sludge

CH4(g)+2O2(g) à CO2(g)+2H2O(l) ΔHR

0=-890 kJ/mol

(1) CH4(g)+ 4N2O(g) à CO2(g) +2H2O(l)+ 4N2(g) ΔHR

0=-1219 kJ/mol

(2) CH4(g)+4NH3(g)+5O2(g)CO2(g)+2N2(g)+8H2O(l) ΔHR

0=-2125 kJ/mol

(3)

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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

• xygen

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Scherson et al., 2013

NH3, CH4, and CO2 Reformation using Solid Oxide Fuel Cell

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NH3 CH4 N2 CO2 N2 Cathode Electrolyte Anode O2- O2

(U.S. Serial No. 62/353,137)

• Prof. Ni Meng

Performance of NH3, CH4, and CO2 Reformation

> 50 to 60% Energy conversion efficiency (30% in combustion)

> Using additional fuel (NH3-N)

• C decomposition can be avoid due to CO2 and NH3 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

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High Gravity (HIGEE) in Rotating Packed Bed Reactor

Effective Gas liquid separation induced by 100 G

• Prof. Yi-Hung Chen

Ammonium Removal from Concentrated Wastewaters

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1 1 2 5 4 3

On-site Treatment Condi9on: QL of wastewater = 7 L/min

• Conc. of NH4-N = 5630 mg/L

pH = 11.5-12 Removal efficiency = 90–98% Power Specifica9on (Full-rated) Rotor: 3 hp Liquid Pump: 1.5 hp Air Pump: 1.5 hp Energy consump9on: Below half of full rated power = 2.2 kW

300 600 900 1200

ω (rpm)

85 90 95 100

η (%)

• 1. Influent tank
• 2. RPB
• 3. Effluent tank
• 4. Air pump
• 5. Scubber

T D

Con9nuous Supply of Fresh Air or Steam Rota9ng Packed Bed (RPB) Clear Effluent Clear Air Con9nuous Inflow of Ammonia-rich Wastewater

• 1. Converted to ammonium sulfate
• 2. Recovery of ammonia solu9on
• 3. Burning as fuel

Neutralizer/ Recovery

H2S Issue

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H2S Removal from Biogas

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T D

Con9nuous inflow of Biogas with 1-3 vol.% H2S

On-site treatment condi9on: QG of biogas = 20 L/min Ini9al conc. of H2S = 1–3 vol.% Alkaline: 30 wt.% NaOH Removal efficiency = 90–99%

Rota9ng Packed Bed (RPB)

Purified Biogas

Circulated Alkaline Solu9on

Power Specifica9on (Full-rated) Rotor: 0.5 hp Liquid Pump: 0.5 hp Biogas Pump: 0.5 hp

Energy consump:on: Below half of full rated power = 0.56 kW

• Prof. Yi-Hung CHEN

H2S 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

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Mexa-584L M pH M ATI-C16 M

Alkaline solvents (QL = 0.12-0.6 L/min, G/L = 100-500) 10-30 wt.% NaOH or MDEA (N-methyldiethanolamine) H2S CO2 Air dilu9on

Exceed purified biogas

Biogas with 1-3 vol.% H2S QG: 10-60 L/min Requirements: 100 ppm to atmosphere 650 ppm to combus9on (100 ppm for SOx) 1 ppm to fuel cell

Removal efficiency = 90–98%

Sewage Enhanced 1st clarifier AFMBR: Anammox Effluent (Permeate)

Summary

• Enhanced 1st treatment to remain C and N in sludge
• Ammonia and methane into energy with higher

conversion efficiency

• Mainstream Saline Anammox

Sludge Anaerobic Digestion Digestate CH4 NH3

ENERGY

Thank you very much

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