Lost revenue from tourism, impaired recreation, poisoning⦠⢠Current wastewater effluent standards not being met. ⢠$54 billion to meet new US target ...
Cultivation of Natural Algal Assemblages for Wastewater Nutrient Remediation Erica B. Young Department of Biological Sciences University Wisconsin-Milwaukee
Acknowledgements Kristine Schiman, Anirban Ray, John Berges (UW Milwaukee) Linda Graham, James Graham, Brian Pfleger, Benjamin Smith, Reese Zulkifly (UW Madison) Jun Yoshitani (AlgaXperts)
• • • • •
University of Wisconsin System Wisconsin Energy Independence Fund Milwaukee Metropolitan Sewerage District Great Lakes Bioenergy Research Center NOAA - Sea Grant
Outline • Current problems • Algae offer solutions • An experimental wastewater-algae cultivation in temperate climate • Conclusions
Problems - coastal dead zones and eutrophication Wastewater effluent, agricultural and urban runoff - nutrients to aquatic ecosystems
Mississippi Delta, NASA
Problems – algal blooms
Ulva prolifera bloom Qingdao, China, July 2013
Problems • Eutrophication and degradation of freshwater ecosystems and resources
Lake Ontario, Jay Ross
Murray River, Australia Daily Telegraph
Eutrophication costs • Higher costs of treating drinking water for humans • Algal blooms (green tides, HABS) • Lost revenue from tourism, impaired recreation, poisoning… • Current wastewater effluent standards not being met • $54 billion to meet new US target
Another important issue… e.g. Mississippi River watershed catchment
• ~150,000 tonnes P flushed into Gulf of Mexico annually - 5% of 3 Mt P-fertilizer sold (Whittall 2008) • Gulf coastal eutrophication and loss of valuable P • Annual global P flux to oceans – 22 Mt (Bennett et al. 2001)
Nitrogen cycle
SLOW WWTP
loss
Phosphorus is a limited resource Global Rock Phosphate supply
Phosphate Rock manure
Solutions - Retaining Phosphorus Sustainable Phosphorus network sustainablep.asu.edu/home
Organic fertilizers from sewerage Capturing P from wastewater – struvite – P fertilizer Ostara - "We've got to do something to close the loop on phosphorus. If we continue to send it off into the oceans ... we're going to run out." capitalpress.com/idaho/JO-Struvite-011813
Solutions • Algae can remediate waste water – reduce eutrophication, retain nutrients • Can be coupled with addressing global energy challenges (concurrent session S3 Global Change)
Algal Biofuels • Traditional approaches use microalgal bioreactors – High maintenance – Indoor facilities require lighting – 20 – 30% of cost is harvesting (Molina Grima et al. 2003)
– 80 – 85% energy in dewatering (Lardon et al. 2009)
• Outdoor open ponds increasing – free light, water supply and harvesting still problematic
NASA’s OMEGA project: ‘offshore membrane enclosures for growing algae’
Lake Michigan, Milwaukee WI
Lake Mendota, Madison, WI
Lake Michigan
Lake Mendota
Filamentous freshwater algae growing in waste water treatment plant (WWTP) pond
Bloomington Normal WWTP Image M. Cook
Local Solutions! • Algal nutrient remediation not new (e.g. Mulbry et al. 2010) • Natural local algal assemblages - taxa well-adapted to local climatic conditions • Algae don’t naturally grow in monocultures! • Higher nutrient uptake and more stable growth in diverse consortia (Ptacnik et al. 2007, Cardinale 2011) • Select algae from eutrophic waters (WWTP)
Aim: Grow naturallyoccurring temperate lake algal assemblages in wastewater
Examine in the lab
Grow in WWTP pilot plant
Lab: Cladophora grew well in wastewater effluent • High nutrient uptake capacity • Sequester substantial N and P from effluent water e.g. SRP drawn down from 0.05 to < 0.005 mg/L (25 (should be P-limited) • P saturated! • N and P incorporated into algal growth • Next… – Increased water sampling frequency – Also measure organic N – Shallow trickle system = higher light, higher biomass:water ratio, can be scaled up
Diatom Lipids
Graham et al. 2012.
Fatty acids in Synedra and Aulacoseira
Cellulose in wastewater-grown algae 8 – 30% cellulose by mass
Calcofluor-stained cellulose cell walls (UV-excitation)
Biofuels potential – biodiesel and cellulose from waste-water grown algae
Algal Biofuels – Microalgae Session CS12 tomorrow
• ‘Traditional’ microalgal bioreactors – High maintenance – Harvesting problematic – expensive and energy-demanding
• Use of outdoor open ponds increasing ̶ free light, water supply ̶ harvesting still problematic
Advantages of natural algal assemblages in wastewater • Filamentous algae plus epiphytes readily harvested with screens • Grow year-round in wastewater – adapted to climate • ‘Free’ water and nutrients • Cultivation in wastewater - can offset costs of algal biofuel feedstocks (Clarens et al. 2010, Pitman et al. 2011) • Biofuels production with nutrient remediation
What to do with the algal biomass? • Anaerobic digestion – electricity production (Milwaukee municipal WWTP) • Organic fertilizer ? • Biofuels production – biodiesel and cellulose potential
Conclusions • ‘Weedy’ WWTP macroalgae and diatoms offer advantages for wastewater nutrient remediation • Potential for biofuels products • High nutrient loads challenging • Need larger scale, in situ WWTP optimization of nutrient uptake, harvesting, processing (physiology and engineering) and infrastructure for using biomass
Thanks!
