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Wastewater treatment and energy production: The Werribee high rate algal
pond pilot plant study.
Howard Fallowfield1, Neil Buchanan1, Nancy Cromar1, Gwyneth Elsum2, Wade Mosse2 Ken Baxter2 & Ashraf
Abdelmoteleb3. 1School of the Environment, Flinders University,
Adelaide; 2Melbourne Water Corporation, Victoria.and 3Smart Water Fund, Victoria
(email: howard.fallowfield@flinders.edu.au)
Bioenergy Australia Conference “Biomass for a low carbon future” The Sebel, Albert Park, Victoria, Australia 26th -28th
November 2012.
Microalgae & Wastewater Treatment :
Systems and Processes
Waste stabilisation ponds - unmixed
Portugal Bolivar, SA (150ML/d)Western Treatment Plant,
Melbourne (400ML/d)
Gainsville, Florida(1982)
Montpellier, France(1992)
Holister, California (1982)
High Rate Algal Ponds (HRAPs) - mixed
Algae-bacteria wastewater treatment: Biological processes
High rate algal ponds (HRAP): Characteristics
• Shallow (30 – 60 cm) meandering channel design
• Mixed by simple paddlewheel• Mean surface velocity 0.2 m s-1
• Maintains solids – algal cells in suspension - maximising O2production for treatment
• Homogenous chemical environment
• Shorter retention times for treatment (5 – 12d)
– Reduced evaporative loss– Less land area required
Kingston on Murray HRAP
Rationale for integrating wastewater treatment and biomass energy production
Issues associated with ‘clean’ microalgal culture(1) Availability of phosphorus
Cordell, D (2009) The story of phosphorus: 8 reasons why we need to rethink the management of phophorus resources in the global food system available at http://phosphorusfutures.net/http://phosphorusfutures.net/
Issues associated with ‘clean’ microalgal culture(2) Availability of nitrogen
Impact of Rising Natural Gas Prices on U.S. Ammonia Supply, United States Departmentof Agriculture, WRS0702 (2007)
Sustainable Development of Algal Biofuels in the United States (2012), National Research Council of the National
Academies
Concerns of high importance
Supply of the key nutrients for algal growth—nitrogen, phosphorus, and CO2.
– 39GL algal biofuel ( 5% of U.S. demand for transportation fuels) requires 6 -15 X 106 TN and 1-2 x 106 TP
– Equivalent to 44 -107% of the TN and 20 - 51 % of TP current use in the United States.
The quantity of water (whether freshwater or saline water) required for algae cultivation
– 1 L of gasoline equivalent of algal biofuel estimates suggest require 3.15 - 3,650 L of freshwater
– at least 123 GL of water would be needed to produce 39 GL of algal biofuels (5% of U.S. demand for transportation fuels).
Sustainable Development of Algal Biofuels in the United States(2012), National Research Council of the National Academies
Recommendation:
Sustainable development of algal biofuels would require research, development, and demonstration of the following:
• The use of wastewater for cultivating algae for fuels or the recycling of harvest water, particularly if freshwater algae are used.”
Sustainable Development of Algal Biofuels in the United States (2012), Committee on the Sustainable Development of Algal Biofuels; Board on Agriculture and Natural Resources, Division on Earth and Life Studies; Board on Energy and Environmental Systems, Division on Engineering and Physical Sciences; National Research Council of the National Academies, pp344. Prepublication Copy available at http://www.nap.edu/catalog.php?record_id=13437
Inlet wastewater composition(Kingston on Murray; anaerobically pre-treated)
Parameter Mean (n)mg L-1
BOD5 204 (124)
NH4 -N 89.9 (120)
NO2-N 0.17 (120)
NO3-N 0.25 (118){28}
PO4-P 13.4 (118){6}
SS 109.1 (112)
Log10 (E.coli 100ml-1) 6.365 (123)
HRAP performance(Kingston on Murray)
• 1.5 to 3 log10 of indicator bacteria (E. coli)
• 60 – 95% of BOD5
• 60 – 90% of ammonia nitrogen
• 10 – 15% of reactive phosphate
• evaporative losses 12 – 17% compared with 30%
Comparison of HRAP with equivalent unmixed lagoon system
Treatment:
• in 8 -18 days compared with 66 days
• using 40 – 50% less surface area
• with only 11- 30% of the earthworks of lagoon system
• at 40 – 55% of the capital cost
Wastewater treatment: HRAP energy saving and reduced CO2 emissions
Adapted from Shilton et al (2008) WST, 58, 253-258
Treatment process
Energy Usage (kWh/ML)
*kg CO2-e/ML References
Conventionalactivatedsludge
40 - 230 31 – 18 Owen (1982), Green et al (1995)
Extended aeration AS
410 - 960 316 - 740 Owen (1982), Young & Koopman (1991), Green et al (1995)
Unmixed WSPs 0 0
HRAP 60 - 110 46 - 85 Fallowfield & Garrett (1986), Oswald, (1988), Green et al (1995)
CO2 emission factors for purchased electricity vary between states; 0.23 – 1.22 kg CO2-e/kWh (Tasmania and Victoria respectively); the value for South Australian of 0.77 kg CO2-e/kWh was used in the calculations (http://www.climatechange.gov.au/climate-change/~/media/publications/greenhouse-gas/national-greenhouse-factors-june-2009-pdf.ashx)
Biomass production
High biomass productivity.
Ken Baxter pers.com.
Biomass production in wastewater• Biosolids produced comprise
• algae• bacteria• zooplankton and• detritus
• Relative composition changes with organic loading.
• ‘Productivity’ (DW or AFDW) all include these components.
• Care needed when expressing and interpreting productivities since non-algal biomass might be significant.
Algae, bacteria, zooplankton and detritus –ALBAZOD(after Carl Soeder)
Cromar, N.J. & Fallowfield, H.J. (1992) The separation of biomass from high rate algal ponds using Percoll density gradient centrifugation. J. Applied Phycology. 4, 157-163.
Cromar, N.J., Martin, N.J., Christofi, N., Read, P.A. & Fallowfield, H.J. (1992) Determination of nitrogen and phosphorus partitioning within components of the biomass within a high rate algal pond: Water Science and Technology. 25, 207 -214.
Biomass and energy production: Kingston on Murray Study
• Biomass is mixture of algae, bacteria zooplankton and detritus.
• Productivity (g.m-2.d-1) may not all be algae.
• Estimated seasonal electrical energy production (median values) 7.5 – 46 MWh/ha.
• Potentially equivalent to 5.8 – 35.4 T CO2 –e/ha /season abatement via fossil fuel replacement.
Melbourne Water HRAP Pilot Plant Study
“zero net greenhouse gas emission by 2018”
“Smart investments in smart research for a water smart
future”
“inspiring achievement”
Research Service Provider
Industry Partner donating Land and providing
commercial expertise
Funding Agency on behalf of the Victorian Water utilities and
contract manager
The project is supporting Melbourne Water Corporation’s target of:
“zero net greenhouse gas emission by 2018”
Gwyneth Elsum pers.com.
Algae to energy at wastewater treatment plants
Melbourne Water WWTPS have some key attributes necessary for economic algae production:– Non potable water (raw to partly treated sewage through to
treated effluent)– Nutrients at low or no cost (contained in the partly treated
sewage through to treated effluent)– Land and surplus basins / lagoons / ponds (need
modification)– CO2 (biogas is ~12% CO2 at WTP)– Existing electricity generation plants ready to use additional
biogas– Heat (if required) from engine jacket water cooling &
exhausts– Operators familiar with water based biological processes
What do algae need?
Algae need: C : N : P 50 : 8 : 1
Wastewater has: C : N : P 20 : 8 : 1
Ken Baxter pers.com.
What do algae need?Algae need: C : N : P 50 : 8 : 1
Wastewater has: C : N : P 50 : 8 : 1
CO2 (exhaust or scrub water)Ken Baxter pers.com.
ASP PolishingCovered LagoonTransfer Outfall (PPB)
Blowers
Power Station
BiogasWashwater
WashwaterReturn
Nutrients (partly treated sewage)Water
CO2 richwashwater
CO2 rich exhaust
Heat Algae Growing
System
Harvest
Water return
Mid qualityreturn water
High qualityreturn water
Low qualityreturn water
Thicken-ing
WTP Algae Process Scenarios
Recycle
Exhaust
Ken Baxter pers.com.
Smart Water Fund ProjectAlgae for Energy: A wastewater solution
Project Aims• Design, operate and evaluate the performance of demonstration
HRAPs for the production of microalgae and wastewater treatment, using secondary wastewater influent.
• Data regarding the achievable microalgal productivities, yields and composition of algae grown wastewater in Melbourne climatic conditions.
• Development of plausible scenarios, using ‘real world data’ to assist the life cycle assessment of integrating this technology into wastewater treatment plants operated by water utilities.
Acknowledgements
• Melbourne Water Corporation• Smart Water Fund• AGL
– Craig Mayhew• Richard Gayler, Gayler Professional Services and Scott Campbell
Drafting,
Kingston on Murray Research:• The Local Government Association of South Australia• District Councils of Loxton-Waikerie, Lyndoch and Mt Barker.• Flinders Research Centre for Coastal and Catchment Environments
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