Evaluation of industrial wastewater properties and microbial - - PowerPoint PPT Presentation

Evaluation of industrial wastewater properties and microbial diversity to improve power generation in Microbial Fuel Cells

Sharon Belinda Velasquez Orta

YES Conference, 2008

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Contents

Introduction Aim and objectives Methodology and experimental set-up Analysis of Results Conclusions Work being developed

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Introduction

Environmental Issues

Global Warming Wastewater discharges

Cost Pressures

UK energy costs will come

under great pressures due to increased import

Carbon emissions are going to

carry an increasing price tag

Customers are going to pick

suppliers that focus on sustainability

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Wastewater Treatment Systems

Primary Treatment Secondary Treatment (AD) Tertiary Treatment MFC Energy Wastewater Inlet Discharge High Chemical Oxygen Demand

I mages taken from www.rdn.bc.ca

Physical Biological Chemical I ntroduction

How do Microbial Fuel Cells (MFC) work?

Inside an MFC lives a colony of bacteria under anaerobic conditions. These bacteria are fed sewage which they oxidize to create a flow of current. MFCs consist of an anode and cathode similar to a conventional battery.

Sewage Treated water H+ Cathode (C+catalyst) Anode (C)

Air e-

Proton Exchange Membrane

Anaerobic Reactor

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Mechanism

Wastewater Microorganisms Electrons Electrode (Anode) Electrical Circuit Electrode (Cathode) Oxygen Protons Water CO2 C6 H12 O6 + 6 H2 O 6 CO2 + 24 H+ + 24e- 6 O2 + 24H+ + 24 e- 12 H2O Electrons Mediators or direct contact

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Methanogenesis

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Differences with Anaerobic WT

Conventional

– Hydrolisis – Fermentation – Methanogenesis

Methane and CO2

production

Biogas production to be

processed for electricity generation

T>20oC Microbial Fuel Cells

– Hydrolisis – Fermentation – Shuttle of electrons

Lower quantities of

Methane production

Electricity generation

directly from anaerobic processes

T < 20oC

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Designs

Logan, 2007 and Christensen, 2007

Substrate effect in MFC

Wastewaters: domestic, food processing, swine

wastewater and beer processing (Du et al, 2007).

Wastewater characteristics affect:

– rate of organic matter degradability – microbial ecosystem

rate of bacterial electron transfer

• verall MFC process efficiency

Why study wastewater characteristics?

– To increase the understanding of the mechanisms affecting

electron shuttling rates

– To explore for alternatives for MFC control and optimization

according to the type of wastewater used

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Aim and Objectives

“To study the substrate effect in MFC”

To compare the effect of using different

industrial wastewaters in bioelectricity generation :Bakery, brewery, paper and dairy

To determine the relationship between:

wastewater characteristics bacterial diversity Power Output

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Methodology

8 batch MFC+ controls

Inoculum: Anaerobic Sludge NO MEDIATOR COD, VFA, pH Current Polarization Subs 2: Brewery WW Subs 3: Beer WW Subs 1: Diary WW Subs 4: Paper WW Fix sample and store

• 20oC

DNA extraction, DGGE, Bionumerics

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Methodology: Wastewaters Characteristics

Wastewater Dilution (in tap water) CODs (mg/L) Anions (ppm) pH (NaCl

• r HCl)

Conductivity μS/cm

Diary WW 50/200 700

Fluoride: 0 Chloride: 138 Phosphate: 6 Sulphate: 31

7 832 Bakery WW 13/200 651

Fluoride: 12 Chloride: 11 Phosphate: 6 Sulphate: 8

7 79.6 Brewery WW 1.3/200 661

Fluoride: 1.3 Chloride: 5 Phosphate:3 Sulphate:10

7 180.6 Paper WW 200/200 600

Fluoride: Chloride: 189 Phosphate: Sulphate:241.3

7 1397

Results: current production

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50 100 150 200 250 300 50 100 150 200 250 300 Time (hr) Current x 10

• 3/ mA

MFC 1 - DAIRY 1 MFC 2 - DAIRY 2 MFC 3 - BREWERY 1 MFC 4 - BREWERY 2 MFC 5 - BAKERY 1 MFC 6 - BAKERY 2 MFC 7 - PAPER 1 MFC 8 - PAPER 2

2 1 3 4 5 6 7

Last Batch COD removal: Diary WW: 620 mg/L, 81 % Brewery WW: 515 mg/L 68% Bekary WW: 620 mg/L 85 % Paper WW: 460 mg/L 80 %

Results: polarization

Current Density / mAm-2 50 100 150 200 250 300 Voltage / mV 100 200 300 400 500 600 Power Density / mWm-2 10 20 30 40 50 60 Diary Wastewater Brewery wastewater Bakery Wastewater Paper Wastewater

Results: process parameters

Time / hr 260 270 280 290 300 310 320 % COD removal 20 40 60 80 100 Diary Wastewater Brewery Wastewater Bakery Wastewater Paper Wastewater Time / hrs 260 270 280 290 300 310 320 Total Volatile Fatty Acids / mgdm-3 20 40 60 80 100 120 140 160 180 Diary Wastewater Brewery Wastewater Bakery Wastewater Paper Wastewater

COD removal VFA concentrations

Why some WW are not producing electricity?

Electrochemical processes are being favoured in the reactor containing paper wastewater

1.

Effect of different conductivities

2.

Effect of different types and quantities of bacteria

3.

Effect of electron shuttle mediators

• 1. Results: conductivity

7100± 300 μS/cm 1390 μS/cm 832 μS/cm 180 μS/cm

• 2. Results: bacteria

• 3. Results: e- shuttle mediators

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Bacteria Mediator Anode e- e- e- e- Red - Ox e- e-

Are electron shuttle properties transferable?

Conditioning all reactors for one batch with paper wastewater and use again its corresponding wastewater.

Cyclic voltammetry

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green: paper ww, blue: brewery ww, red: dairy ww

Conclusions

All MFC systems achieved high COD removal rates

although only MFC fed with paper wastewaters developed a high current output.

MFC microbial biofilm communities differed

according to the wastewater type.

Current output differences were due to the presence

• f an electron shuttle compound.

Conductivity partially limited current output in all

cases.

The mediator was in some cases transferable to be

used in MFC reactors with different wastewaters.

Merci !