A Roadmap for Smarter Nutrient Management in a Carbon and Energy Constrained World. Samuel Jeyanayagam, PhD, PE, BCEE

Transcription

1 A Roadmap for Smarter Nutrient Management in a Carbon and Energy Constrained World Samuel Jeyanayagam, PhD, PE, BCEE 91 st Annual Conference 21 June 2016

2 The Importance of Carbon Without carbon, life as we know it would not exist It has high propensity to combine with other elements to form stable, very large & complex compounds. Living forms have 10 Million C-based compounds that may be categorized as follows: Carbohydrates: starches & sugar (1g = 4cal) Lipids: fats & oils (1g = 9cal) Proteins: enzymes & antibodies (1g = 4cal) Nucleic acids: RNA & DNA Carbon is energy 2

3 Carbon is a Valuable Resource Traditional view: C is a pollutant (cbod) that must be removed by oxidizing it energy input Evolving view: It is a valuable resource that can be diverted to:»drive nutrient removal»produce energy (anaerobic digestion)»recover carbon-based commodities 3

4 Presentation Outline Carbon for: Nutrient control Energy production Resource recovery 4

5 Phosphorous Removal Two methods available for P removal: Chemical Biological Basic concept: Particulate P Sol. Reactive P (srp) Phosphorus removal occurs when sludge is wasted. This presentation will focus on biological P removal because it is directly linked to the availability of carbon. 5

6 Biological P Removal Removal exceeding metabolic requirements Enhanced Biological P removal (EBPR) Luxury P removal Excess P removal Bio-P Mediated by specialized heterotrophs, Phosphorous Accumulating Organisms (PAOs) 6

7 What Drives the EBPR Process? PAO PHB Glycogen Poly- Phosphate EBPR is driven by the cyclical storage & consumption of 3 storage components within PAOs: PHB (Poly-β-hydroxybutyrate): Stored food (Carbon) Poly-Phosphate: Stored P Glycogen: Another Carbon product. Converted to and derived from PHB 7

8 Enhanced Biological P Removal (EBPR) Mechanism Carbon source (VFAs) P Release O2 CO2 + H2O Excess P Uptake Energy (E i ) Energy (E d ) PHB PHB Polyphosphate Anaerobic Zone DO, NO 3 Cell Synthesis Why does EBPR work? Polyphosphate Aerobic (DO) Energy Investment = E i PHB: Poly-β-hydroxybutyrate Energy Dividend (E d )= x E i 8

9 Six Prerequisites for Reliable EBPR 1. Feed the PAOs 2. Protect the anaerobic zone 3. Maximize P uptake in the aerobic zone 4. Maximize solids capture 5. Minimize recycle loads 6. Minimize competition The primary focus of the above factors (except #4) is to maximize PAO growth. Of the active biomass, PAOs represent: 10% in a secondary process 40% in a healthy EBPR process 9

10 Feed the PAOs EBPR is fueled by adequate & consistent supply of biodegradable carbon (Volatile fatty acids, VFA) Sources of VFAs: Sewer fermentation On-site fermentation (primary sludge or MLSS) Purchased acetic/propionic acid Industrial discharges Soft drink bottlers Breweries 10

11 Fermentation Mechanism 100 lb Hydrolysis lb Primary Solids Solubilized Substrate SRT Sensitive Solids must be retained long enough to degrade Acid Formers lb Methanogens Short Chain Volatile Fatty Acids X Methane HRT Sensitive Relatively short HRT to avoid methane formation. Happens in sewers; but not consistent. Use engineered fermenters to provide a consistent supply of VFAs on-site. 11

12 Types of Fermenters In-line Activated primary (primary solids) RAS fermentation (RAS solids) Off-line (primary sludge) Complete-mix fermenter Single stage static fermenter Two-stage mixed fermenter thickener Unified fermenter & thickener (UFA) 12

13 How Much Carbon is Needed for Healthy EBPR? Carbon requirement: 7 to 10 mg VFA/mg P removed Measure of adequate VFAs cbod:tp 25:1 COD:TP 45:1 VFA:TP 10:1 rbcod:tp 15:1 Influent to biological system Must consider recycle loads rbcod = VFA + Organics that can be fermented to VFA 13

14 Conventional Nitrogen Removal Autotrophs Aerobic Nitrate NO 3 Heterotrophs Anoxic Nitrite NO 2 O 2 Carbon 25% 40% Nitrite NO 2 Ammonium NH 4 O 2 75% Carbon 60% Nitrogen N 2 High carbon & high energy demand 14

15 Short-cut Nitrogen Removal Nitrate NO 3 Nitrite NO 2 O 2 MeOH 25% 40% Nitrite NO 2 Ammonium NH 4 O 2 75% MeOH 60% Nitrogen N 2 15

16 Low-Carbon, Low-Energy TN Removal Anammox (Anaerobic Ammonium Oxidation) Nitrite NO 2 Ammonium NH 4 O 2 37% Nitrogen N

17 Presentation Outline Carbon for: Nutrient control Energy production Resource recovery 17

18 Wastewater contains 5-10 times the energy needed to treat it. WE&RF 18

19 Anaerobic Digestion is a Major Route for Recovering Energy from Influent Carbon Mainstream Treatment Process Plant Influent Plant Effluent A D Primary Sludge (Influent Carbon) B WAS B C Anaerobic digestion To Dewatering & Disposal A Carbon Diversion B WAS Biodegradability C Advanced AD D External Carbon Source Chemically Enhanced Homogenization Acid Hydrolysis FOG Wastes A-B Process Pressure Release Thermophilic Digestion Food Wastes Sonication Phased Digestion Industrial Wastes Thermal Hydrolysis OFMSW Pulsed Electric Field 19

20 What is Carbon Diversion or Redirection? The diversion of influent biodegradable material away from secondary treatment to energy recovery. The Good:» Lower aeration demand» More biogas for beneficial use» Lower Biosolids Production» Smaller Bioreactors/More Bioreactor capacity» Sets plant up for future technologies like Mainstream Anammox The Bad:» Less carbon available for EBPR & denitrification 20

21 Carbon Redirection Strategies Available approaches for redirecting influent carbon for energy production Conventional Primary Treatment Chemically Enhanced Primary Treatment (CEPT) High Rate Biological Contact» A-B Process» Captivator Anaerobic treatment (UASBs, AnMBR) 21

22 Conventional Primary Treatment vs. CEPT Conventional Primary Treatment BOD 5 BOD 5 55% to 75% of Infl. BOD 5 to Secondary Treatment Chemically Enhanced Primary Treatment Ferric or Alum Polymer 25% to 45% of Infl. BOD 5 to Anaerobic Digestion BOD 5 BOD 5 20% to 60% of Infl. BOD 5 to Secondary Treatment 40% to 80% of Infl. BOD 5 to Anaerobic Digestion 22

23 What is the A-B Process? BOD oxidation minimized Adsorption promoted Carbon (BOD) directed to AD Headworks High Rate Activated Sludge A-Stage Low Rate Activated Sludge B-Stage Effluent RAS RAS WAS with adsorbed BOD Biogas Dewatering Thickening Anaerobic Digestion Biosolids Disposal 23

24 Captivator System By Evoqua Vertical Loop Reactor (VLR) DAF Contact Tank Aeration Basins Final Clarifier Anaerobic Digestion Credit: Evoqua Water Technologies,

25 Kilowatts Carbon Diversion Achieves Energy Use Optimization & Energy Recovery used Energy Comparison 30 MGD Plant Aeration energy used Energy created from biogas created 600 used 700 created Conventional Plant Credit: Evoqua Water Technologies; Captivator Systems, Plant with Carbon Diversion (Captivator ) 25

26 Anaerobic Treatment of Liquid Stream Upflow Anaerobic Sludge Blanket (UASB) reactor Developed by Lettinga >30 years ago in the Netherlands Methane production Elimination of aeration Reduced sludge production Nutrient rich effluent amenable to nutrient recovery 26 26

27 Presentation Outline Carbon for: Nutrient control Energy production Resource recovery 27

28 Recovery of Carbon-based Products WE&RF 28

29 Closing Thoughts The plant of the future will face a competition for carbon» Nutrient removal» Energy production» Resource recovery No one size fits all solution How will your plant evolve as the WRRF od the future? Include a roadmap fro carbon management in the master plan 29

30 Intensive Stakeholder Engagement is Key to Planning the Plant of the Future Guest et al. 30

31 Knowing is not enough, we must apply! Willing is not enough, we must do! Goethe German Playwright 31

32 Thank You! So near, yet so far! 32 32

33 A Roadmap for Smarter Nutrient Management in a Carbon and Energy Constrained World Samuel Jeyanayagam, PhD, PE, BCEE Samuel.Jeyanayagam@Ch2m.com 91 st Annual Conference 21 June 2016