Combining wastewater treatment and willow biomass production in the UK - establishing a demonstration project

Transcription

1 Combining wastewater treatment and willow biomass production in the UK - establishing a demonstration project Lisa Avery, Matteo Tamburini, Peter Randerson, Claire Abel, Craig Thomson and Rupert Hough

2 WP 2.2 has a Systems approach The supply and demand of water, energy and nutrients are intimately related How can we manage resources for a larger population, in an energy, water and green-house gas efficient way without compromising critical ecosystem goods and services, and in a socially equitable manner? Water Behaviour & Attitudes Nutrients (land use) Energy Policies dealing with managing natural resources often in conflict The future management of closely linked themes of water, energy, and land requires an integrated approach

3 Background to the Project Scottish Government's Rural and Environment Science and Analytical Services Division (RESAS) Theme 2: Strong and resilient sources and supply chains for water and energy Work package 2.2 Technologies and management approaches to deliver multiple benefits while minimising disbenefits Overarching systems approach (LCA, CBA, MCA, CEA) to evaluate a broad range of approaches and how they work in different environments what is the best appraisal method Mainly data based but feed-in from specific projects such as this one!

4 Woody Biomass Uses: Fuel Chipped stems; pellets More efficient energy conversion from biomass- AD, fermentation, efficient combustion Animal bedding pellets Production of paper, chipboard, charcoal (Pulford and Dickinson, 2005).

5 How? Irrigated Plots vs. Constructed Wetlands Land based Willow systems CW Willow systems reduced hydraulic conductivity Build up of salinity/sodium Water logging Leaching to GW Non-saturated conditions Better P-adsorption capacity (?) HC easier to manage Flow regime must be suited to plant tolerance Liner integrity Plants reliant on nutrients from wastewater HLR must be balanced against nutrient and water uptake Soil ameliorates some nutrient imbalances

6 How Effective is SRC at treating wastewater? Parameter Treatment Efficiency Reference Mant et al. (2003) Ansola et al. (2003) Ansola et al. (2003) HRT (days) System type NH 4 -N (%) Influent Fill and drain (tidal). S. viminalis; gravel pots; settled 1 O effluent (mg L -1 ) FWS pond planted with Typha and SSF with Salix atrocinerea; raw municipal wastewater 98 7 (mg L -1 ) 59 7 (mg L -1 ) TP (%) Influent (mg L -1 ) 68 2 (mg L -1 ) PO 4 -P (%) Influent (mg L -1 ) BOD (%) Influent (mg L -1 ) (mg L -1 ) (mg L -1 )

7 Why Combine Willows and Wastewater? Willow SRC well known energy crop Flood tolerant High growth rates (high nutrient uptake) Marginal Economics for biomass alone. Saved treatment & fertiliser costs; enhanced yield, alters the economics (Roseqvist and Dawson (2005) - Ireland Policy Context - EU water framework directive;eu Renewable Energy Directive, which includes a UK target of 15 percent of energy from renewables by So produce energy and save money using waste

8 Buonocore et al (2012) Enköping LCA 20,000 inhabitants Wood based district heating 100 ha Willows Septic tank sludge into ponds ~ 1 yr; applied to Willows via irrigation system Plant nutrients supplied Provides % biomass burned (rest brought in) 24 MW electricity 45 MW heat 50 % electricity requirement 85 % heat requirement 30% increase in biomass yield Harvesting 3-5 yrs. Replanting yrs. Photo: L. Christersson -

9 Enköping

10 Demonstration Site our approach Demonstrate the feasibility of willow based CW for wastewater polishing in Scotland (UK) An analysis of benefits vs. disbenefits of using willow instead of reeds Feed into higher level energy and carbon footprint assessments of technologies Improve an existing WWTP?

11 The site and its challenges Site Plan

12 Bunded wetland area Grass plots Fence line (grass plots lie beyond here) Soak away area Community Septic Tank

13 Soil type - brown earth developed on fluvioglacial sands and gravels.

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15 System Individual willow mesocosms with rainwater, septic tank effluent. Four willow varieties including S. viminalis. Little effect of Salix clone type. S. alba in soil lysimeters in the field Soil-willow systems vs. unplanted soil treating landfill leachate. S. amygdalina L. in soil-plant systems 3-month old willow spouts Increase in evapotranspiration (compared to baseline) Reference Up to 9 mm Curneen and Gill (2010) m 3 willow -1 Day mm Guidi et al (2008) x greater than bare soil Potential to evapotranspire the bulk of incoming water/wastewater times greater than an average precipitation rates Extrapolating up to 0.2 m 3 per day Bialowiec et al (2007) Hasselgren (1998) Agopsowicz (1994)

16 Effluent quality could be further improved NH4-N Total N mg L Septic Tank Effluent Soakaway Herringbone PO4-P Tot-P 5.00 mg L Septic Tank Effluent Soakaway Herringbone

17 Design: Septic Effluent Water Quality Parameter Concentration (mg L -1 ) BOD (5) TN NH 4 -N 7-13 NO 3 -N TP 7-14 PO 4 -P 5-10 ph ~7.3 Na 37-88

18 Design

19 Constructed Wetland Design Up to 20% of septic effluent ~ 22 pe ~ 3300 L d -1 Tidal flow (but readily adapted to HF) Shallow beds (~0.5m) 1% slope Floating outlets 6 x 3m (x 2 beds one willow, one reed)

20 Media

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22 Outlet

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24 Future Direction connection and monitoring Treatment performance: BOD 5, NH 4, N0 3, P0 4, S0 4, Na + SS, ph, EC, coliforms, E. coli) in order to monitor treatment performance Establishment and maintenance requirements - written notes of activity and time taken Provides info for WLC/LCA Growth parameters - potential biomass yield Plant health indicators - signs of disease, chlorosis etc. Biodiversity indicators - birdlife Greenhouse Gas Emissions NO X, Methane, CO 2 Provides info for LCA and pollutant swapping Oxygen status of bed DO 2 profiles link to operation and GHG emissions. Determination of pollutant build up (P) on substrate materials; Fine sediment accumulation indicators of lifespan.

25 Hopefully. Results shortly On-going research site

26 Acknowledgements Scottish Water site provision and funding Dr Sean Tyrrel (Cranfield University advice) RERAD (Scottish Government) funding THANK YOU!