Can we reduce energy intensity of wastewater treatment? Can we develop technologies to utilise carbon, phosphorus and nitrogen in wastewater?

Transcription

1 Can we reduce energy intensity of wastewater treatment? Can we develop technologies to utilise carbon, phosphorus and nitrogen in wastewater? Dr Tim Muster AiGroup Water Member Reference Group, 20 th March 2014 Water for a Healthy Country Flagship

2 Aims of presentation 1. Can we reduce energy intensity of wastewater treatment? YES WE CAN We can shift from energy using to energy producing. What are the barrier to this? 2. Can we develop technologies to utilise carbon, phosphorus and nitrogen in wastewater? We can develop new technologies it s about implementation at present There are key technologies that Australia should be investing in Phosphorus is a special case that possibly requires political intervention

3 Drivers: Human Sustainability Key requirements to 2050 mainly related to population growth (OECD) Greater environmental issues (Biodiversity, nutrient handling) Decrease energy consumption (CO 2 control and associated environmental issues) Increased need for treated water (Potable) Increased fertilizer production (N,P,K required) Source: J. Foley, Scientific American, April 2010, pp Slide 3

4 What is in wastewater Resource Mass (kg/ml) Value ($/kg) Mass per capita (kg) Value per capita ($/yr) Total tonnes (City of 4 million) Total value for 4 million ($m) Water $ $480 Nitrogen (NH 3 ) 75 $ $ ,000 $12.2 P (struvite) 15 $ $4.28 5,400 $17.1 Carbon (CH 4 ) $7.43 a $29.7 a Electricity priced at $50/MWh Source: Based upon the work of Tony Priestley, CSIRO, Presented at OzWater Slide 4

5 Wastewater Industry Changes Producing Recycled Water Producing Energy? 1. Push for energy neutral or positive 1. Energy in wastewater approx. 5.9 GJ/ML 2. Current treatment 2 7 GJ/ML to treat CH 4 recovery with anaerobic digestion Source: Australian Water Recycling Centre of Excellence, Strategic Research Plan Carbon Trading 1. Large WWTPs in top 500 CO 2 e emitters. Significant direct emissions of CH 4 and N 2 O Energy-efficient Biological Nitrogen Removal Producing nutrients? NO - 2 NH 3 NO 3 - Anammox N 2 Granular sludge

6 Energy production (anaerobic digestion) Proven technology and already utilised Characteristics of carbon in raw wastewater 64% biodegradable 51% suspended 36% refractory 49% soluble Improved pretreatment More efficient lysis ultrasonic treatment Enzymic (i.e. proteases, amylases, lipases) Hydrolysis (i.e. temperature phased digestion, temperature + pressure) Additional feedstocks Algae: improved dewatering and cell lysis Co digestion of solid municipal waste Slide 6

7 Nitrogen & Ammonia Global ammonia production ~177m tonnes (2008) Energy intensive to make; 40 GJ/tonne or 10.2 MWh/t Nitrogen is initially present as NH 3 in wastewater (urea + protein breakdown) At ~40 45 mg/l, accounts for >55% of total N of treatment plant influent Builds up to high concentration during anaerobic digestion Limits methane production Encourages struvite precipitation Special properties Ammonia is highly water soluble Present as ammonium ion below ph 9 (pka = 9.25). Slide 7

8 Cost to Remove/Recover Nitrogen Process Cost (US$/ kg N Captured Ammonia removed or recovered) Mainstream N/dN $1.80* No N/dN Sharon $0.90* No Anammox $0.15* No Air stripping $2.40* Yes Steam stripping >$ Yes Clinoptilolite (adsorption) $2.80* Yes CASTion $6.72* Yes Electrochemical (theoretical) $3.25 Yes Bulk ammonia price $0.50 Based on electrical costs of US$0.178/kWh *Philips et al IWA/WEF Nutrient Removal and Recovery, Miami + Jeremiasse, A., BlueTech Weminar, Feb. 20 th Recovery of ammonia does not appear viable need step change in technology

9 The opportunity in separating C and N Current Primary Sedimentation Aerobic O 2 supply (60% of total energy) Anoxic N removal using 50% of dissolved carbon Possible Sludge treatment energy generation (14% efficiency) Improved coagulation Dynamic Filtration Energy efficient deammonification O 2 supply reduced by 60% No Carbon required Sludge treatment energy generation (40 50 % efficiency) This Challenge $ m for Australia Resource Recovery CSIRO Slide 9

10 Phosphorus: a special case P is essential to all lifeforms, there is No replacement Declining resources, declining quality of ore Increased processing costs Increased contamination Few countries have significant resources Move to decrease dependence on imports Unstable prices There is a need to decrease contamination Phosphate rock has high uranium, cadmium, other Human waste recycling Could supply approx. 5% of Australian P requirements Source: Data from OECD, US Geological Survey

11 Australia Australian Agriculture: $32b industry & looking to expand P deficient soils Australia is a large user of P Limited P reserves (2.5% of global reserves) High dependence on Imports 5 th largest user Increasing at a rate of 14% (FIFA,2008) Urbanisation Population gathers the P resource Australia should be a global leader despite modest population Population living in Urban Areas (%) Australia China India United States World Year Cornell and White (2008)

12 Methods for P removal Biological Accumulation into biomass Activated sludge, granular sludge EBPR, POAs, NPOAs Algae, plants..i.e. duckweed Coagulation (alum, ferric, lime) Methods for P Recovery Biosolids to land (low value/impurities/limited P bioavailability/poor quality control/storage an issue) Chemical extraction (expensive) Adsorption (expensive compared to coagulation looking to lower cost) Precipitation/crystallisation as inorganic Mg and Ca phosphates (now possible) Slide 12

13 Nanotechnology for P Recovery P uptake from wastewater that will enable it to have improved bioavailability in soils. Manufacture at scale Adsorbents with added agronomic value Cheap starting materials Clean up wastewater Take up P to 3.5 wt% Easily separable from water

14 Precipitation from Digester Liquor Many processes: Ostara, NuReSys, Multiform Harvest, DHV Crystalactor, Phospaq etc Wastewater Primary Treatment Return Sludge P / (N) Fertilizer Mg 2+, Ca 2+ caustic delivery, or addition of adsorbent Centrate Containing soluble P and NH3 Fermentation Sludge Anaerobic Digestion Centrifuge Key to early adoption: - High levels of soluble P problematic in existing process - Independent commercial company managing product - Direct manufacture of high-value product Slide 14

15 Crystallisation of Phosphorus Hydroxylapatite Struvite % - Direct manufacture of highly pure P fertilizer Merrilite/ Whitlockite Brushite CHPH Newberyite Purity data for phosphorus products Element Cd Ni As Cr Estimated level in sewage sludge (mg/kg P) Struvite directly from wastewater (mg/kg P) Purity of commercial fertilizers (mg/kg P) Monetite Total P Removal Data: Various sources. See Burn et al. WERF, Muster et al. Chemosphere (2013)

16 Agronomic Value There are good indications Data: Iowa State University, Northeast Research and Demonstration Farm; ISRF

17 Is Struvite Manufacture Economically Feasible? Not just yet based on current value of P but DO NOT compare to rock phosphate value Business cases are much better if environmental and/or operational benefits exist 30 Return on investment encouraged by: Improvements in Technology Increased fertilizer price Demonstration of fertilizer value Victorian Dept. Primary Industries study 15 out of18 P fertilizers exceeded Cd levels $1 struvite fertilizer results in $10 increase in yield Enables local productivity. Cost US$/ kg P Projected Value (P only) Estimated Production Cost (Ostara 2011) Estimated Real Value of Struvite Technology Improvements? Year *Data on Ostara from Philips et al IWA/WEF Nutrient Removal & Recovery, Miami. * Estimated value builds in value of increased purity and Mg/ammonia contributions to price. Slide 17

18 Productivity Crop yield cannot exceed the most limiting resource (water, light, nutrients) In the 19 th Century crops were limited by P Access to P Doubling of yield What could Melbourne add to Vic productivity? Total amount of P from 4m population Over 4000 tonnes Amount struvite manufacturable (40% recovery) 1600 tonnes (P) Total value of struvite P alone ($ 4.8m) $350/t Actual value ($8m) $600/t P application to support agricultural production 1 10 kg P/ ha Total ha that would benefit from struvite (4m population) ha ( to 1.6 m) Typical yield (grain) 2 t/ha (range ) Typical grain price $330 / t Net Production Value (grain) $211 m Productivity of fertilizer Essentially doubles yield Increase in productivity $105 m Other key factors: -Future P price -Cannot manage nutrients in Urban Water Cycles alone (> 4 times excess and would not support productivity)

19 Further Detail on Technologies How do we make the right technology choices to meet future demands and pressures?

20 Local Pressures/Drivers There are many local pressures that will influence technology choices: Water security (volume & cost) Energy cost & reliability of supply GHG emissions (cost) Zero discharge meeting regulations (nutrients, solids, contaminants) Urbanisation Productivity (water, energy, nutrients) Phosphorus security Energy security Slide 20

21 Benchmarks Processes seen as efficient and/or productive: Water: coagulation/flotation, membrane filtration, source control Energy: autotrophic bacteria, anaerobic digestion (production) Heat: recovery for heating, improving process efficiency Phosphorus: biological accumulation (PAOs, anaerobic digestion), incorporated into struvite, source control Nitrogen: removal by autotrophic bacteria, incorporation into struvite, source control Are there synergies between these technologies? YES Slide 21

22 Synergies 1 1. Greater removal of C during primary wastewater treatment 2. Implementation of N removal requiring lower C to treat high proportion of NH 3 3. Increased yield of methane from anaerobic digestion N Removal with minimal need for carbon -Anammox -Granulated sludge Treated Water Waste Water Sedimentation & Coagulation / A Process Anaerobic Digestion Slide 22

23 Synergies 2 Use of membranes in conjunction with anaerobic digestion enables: - Water recycling - Increased solids retention time (increased methane yield) - Reduces digester size (capital investment) Methane Yield Waste Water Anaerobic MBR Treated Water Slide 23

24 Synergies 3 Use of waste heat to improve anaerobic digestion enables: - Reduced digester size (capital investment) - Increased methane yield - Decreased biosolids production Methane Yield Waste Water Anaerobic Treated Water Waste Heat Slide 24

25 Synergies 4 1. Anaerobic digestion 2. Struvite precipitation followed by Anammox to remove ammonia Methane Yield Waste Water Anaerobic Digestion Treated Water -High in soluble P -High in ammonia Struvite Precipitation - Easy separation of high quality P product Anammox to remove remaining ammonia Treated Water Slide 25

26 Towards production facilities : an example 60% decrease in energy consumption Anammox Mainstream treatment to remove N P adsorption Treated Water Membrane Processes Recycled water NH 3 return Waste heat Waste Water Control of C Sedimentation & Coagulation, Coarse Filtration/ Rapid mixing) Methane Methane Stripping Electricity Generation P Recovery Crystallisation Additional Carbon source Pretreatment -hydro(lysis) Anaerobic Digestion N Recovery >40% P as pure fertilizer >100% increase in methane production Biosolids: -Improved Value -Biochar -Bioleaching Slide 26

27 Final messages 1. Wastewater treatment should produce: Water, Energy, high value P fertilizer, biosolids 2. Australia should invest in: Anaerobic digestion Deammonification technologies (ability to implement) Struvite manufacture 3. Phosphorus is a special case that possibly requires political intervention P issue is possibly a greater challenge to mankind than climate change P cannot be managed productively within Urban Water Cycles

28 Future progression Water has the highest value will continue to control investment Push to decrease energy; GHG accounting adds to pressure Advances in the low carbon removal of N from wastewater Enables more C to be captured as energy if anaerobic digestion utilised Additional anaerobic digestion will make more soluble P available Greater ability to produce higher value P product (struvite) Need to understand and/or develop market for struvite Decreased biosolids production Integration of technologies creates synergies: working towards clarifying industry benefits Better define transition starting from existing processes and infrastructure. Slide 28

29 Thank You Co-authors: Stewart Burn, Anna Kaksonen, Grace Tjandraatmadja, Maneesha Ginige, Ka Yu Cheng, Nigel Goodman, Grant Douglas, Simon Hardin, Tim Harvey, David Beale, Geoff Dumsday, Karen Rouse. Contact Details: CSIRO Urban Water Karen.Rouse@csiro.au