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Remediation of Diffuse Water Pollution
Treating diffuse agricultural pollution
1) Lena McAuley is researching "pollution swapping" to compare the nitrogen removed from agricultural runoff by buffer strips and wetlands with the powerful greenhouse gas, nitrous oxide, that may be emitted by these systems. Gaseous and aquatic nitrogen fluxes are being measured in a wetland and field buffer strip experiment at Nafferton Farm (University of Newcastle). To understand the processes that control nitroegn removal and nitrous oxide emission from wetlands and buffer strips, laboratory soil core experiments are being conducted, including detailed measurements in sediment cores using the novel membrane inlet mass spectrometry (MIMS) system at the University of Newcastle.
2) Fabrice Gouriveau conducted a detailed 2-year assessment of the ecology, hydrology and water treatment performance of two constructed farm wetlands (CFWs) in the Scottish Borders. The research also included a wider evaluation of the economic costs and benefits and farmer perceptions of CFWs throughout Scotland. Anthony Maire tested a wetland model to model TN and TP from these CFWs. To view Anthony's report click here.
3) Sunitha Rao Pangala conducted field and laboratory experiments to assess the effectiveness of iron ochre and gypsum at reducing emissions of the powerful greenhouse gas, methane, from constructed farm wetlands.
The CFWs monitored reduced concentrations of BOD, suspended solids, nitrate/nitrite, ammonium and reactive phosphorus between inlet and outlet, although the concentration of some contaminants at the outlet frequently exceeded river water quality standards. Water treatment efficiency varied seasonally, being significantly lower in winter, mainly due to lower temperatures, increased volume of inputs and reduced residence time.
Despite significant costs associated with construction (£20 000-£50 000 ha-1) and maintenance (£900-£1500 ha-1 yr-1), CFWs may still represent a more cost-effective alternative than conventional methods. However, their adoption, implementation and sustainable use by farmers are conditioned by land availability and suitability, existing farm infrastructure, detailed information on limitations and maintenance requirements, and adequate financial support for both construction and aftercare.
To ensure a long-term, consistent and efficient water treatment, and to enhance biodiversity and landscape, well-maintained, large, vegetated, multi-cell CFWs with shallow overflows are recommended.
Iron ochre was found to be effective in reducing methane emissions from a constructed farm wetland. Addition of ochre at 5 t/ha resulted in a % reduction in methane emissions and had no apparent adverse effect on sediment and water quality, nor on the nitrogen removal performance of the wetland. This use of ochre represents a sustainable use of a waste material from mine water treatment in reducing greenhouse gas emissions.
Kate Heal and Fabrice Gouriveau co-authored the Constructed Farm Wetlands (CFW) - Design Manual for Scotland and Northern Ireland published in 2008.
Carty, A., Scholz, M., Heal, K., Keohane, J., Dunne, E., Gouriveau, F. and Mustafa, A. (2008). Constructed Farm Wetlands (CFW) - Design Manual for Scotland and Northern Ireland. Belfast/Stirling, Northern Ireland Environment Agency/Scottish Environment Protection Agency, Oct 2008, 61p.
Heal, K.V., Vinten, A.J.A., Gouriveau, F., Zhang, J., Windsor, M., D’Arcy, B., Frost, A., Gairns, L. and Langan, S.J. (2006). The use of ponds to reduce pollution from potentially contaminated steading runoff. In: L. Gairns, K. Crighton and B. Jeffrey (Eds.), Agriculture and the Environment – Managing Diffuse Agricultural Pollution, Proceedings of the SAC and SEPA Biennial Conference, 5-6 April 2006, Edinburgh, pp.62-70. ISBN 1901322637.
Sustainable Urban Drainage Systems (SUDS)
Specific research projects include:
1) Investigating the fate of organic and metal traffic-related pollutants in SUDS.
2) Monitoring long-term sediment accumulation and sediment quality (potentially toxic metals, nutrients, hydrocarbons) in SUDS ponds across Scotland, including at the Dunfermline East Expansion Area (DEX), Dunfermline, the first large-scale development in the UK which incorporated SUDS.
3) Assessing the performance of retrofitted SUDS and recommending management approaches.
4) Examining the benefits of the treatment train for sediment removal, water treatment, aquatic ecology and maintenance costs at the Hopwood Motorway Service Area, England.
5) Developing tools for rapid assessment of sediment accumulation and quality (in SUDS ponds. We are testing the use of ground penetrating radar for measuring sediment depth in ponds. Detailed sediment surveys have been conducted to determine whether there are any relationships between sedimentation patterns and composition which could provide a means of rapidly assessing sediment quality without the need for expensive and time-consuming sampling and analysis.
6) Modelling the long-term performance of SUDS ponds of different designs, taking account of climate change.
Sediment accumulation rates in SUDS ponds draining residential catchments are c.1 cm/year, although rates depend on catchment characteristics and are lower where there is an upstream treatment train. It is estimated that sediment removal from the SUDS ponds studied is required every c.25 years. Sediment from SUDS ponds draining residential catchments normally contains pollutant concentrations lower than aquatic sediment standards and therefore could be spread in designated areas close to the pond, without necessitating landfilling.
Using a generic modelling approach we demonstrated that the methodology used to design urban stormwater ponds, i.e. whether they are designed for flow attenuation or for water quality enhancement, has a significant effect on pond performance. Ponds designed for flow attenuation are more successful in terms of both flow and pollutant attenuation (measured as removal of suspended sediment) and are more resilient to climate change. The use of multi-level outlet devices for urban stormwater ponds can also improve flow attenuation.
Heal, K.V., Bray, R., Willingale, S.A.J., Briers, M., Napier, F., Jefferies, C. and Fogg, P. (2009). Medium-term performance and maintenance of SUDS: a case-study of Hopwood Park Motorway Services Area, UK. Water Science and Technology, 59, 2485-2494.
Jefferies, C. and Napier, F. (2008). SUDS Pollution Degradation, SNIFFER UEUW02 Final Report. SNIFFER, Edinburgh, 33p.
D’Arcy, B.J., McLean, N., Heal, K.V. and Kay, D. (2007). Riparian wetlands for enhancing the self-purification capacity of streams. Water Science and Technology, 56(1), 49-57.
Morgan, C.T., Heal, K.V., Wallis, S.G. and Lunn, R.J. (2007). Assessing the effects of design and climate change on sediment removal in urban stormwater ponds. In: Webb, B. W. and de Boer, D. (Eds.), Water Quality and Sediment Behaviour of the Future: Predictions for the 21st Century, IAHS Publication no. 314, pp.71-78.
Jones, A.J., Heal, K.V., Stuart, N., Wallis, S.G., Lunn, R.J. and Barbarito, B. (2007). Quantifying sediment deposition and the spatial variability of sediment-associated metals in ponds treating urban diffuse pollution. In: Webb, B. W. and de Boer, D. (Eds.), Water Quality and Sediment Behaviour of the Future: Predictions for the 21st Century, IAHS Publication no. 314, pp.173-180.
Heal, K.V., Hepburn, D.A. and Lunn, R.J. (2006) Sediment management in sustainable urban drainage system (SUDS) ponds. Water Science and Technology, 53(10), 219-227.
Wallis, S.G., Morgan, C.T., Lunn, R.J. and Heal, K.V. (2006) Using mathematical modelling to inform on the ability of stormwater ponds to improve the water quality of urban runoff. Water Science and Technology, 53(10), 229-236.
Wilson, C., Clarke, R., D’Arcy, B.J., Heal, K.V. and Wright, P.W. (2005). Persistent pollutants urban rivers sediment survey: implications for pollution control. Water Science and Technology, 51(3-4), 217-224.
Heal, K.V., Scholz, M., Willby, N. and Homer, B. (2005). The Caw Burn SUDS: performance of a settlement pond/wetland SUDS retrofit. In: Newman, A.P. Pratt, C.J., Davies, J.W., and Blakeman, J.M. (Eds.), Proc. 3rd National Conf. On Sustainable Drainage, pp.19-29. ISBN 1846000076.
Heal, K.V., McLean, N. and D'Arcy, B.J. (2004). SUDS and sustainability. In: Newman, A.P., Davies, J. and Blakeman, J. (eds), Proc. 26th Meeting of the Standing Conference on Stormwater Source Control, pp.47-56. ISBN 1846000017.
Heal, K.V. and Drain, S.J. (2003). Sedimentation and sediment quality in sustainable urban drainage systems. In: Pratt, C.J., Davies, J.W., Newman, A.P. and Perry, J.L. (Eds.), Proc. 2nd National Conf. On Sustainable Drainage, pp.215-225. ISBN 01903818273.
Jefferies, C., Heal, K.V. and D'Arcy, B.J. (2001). Performance of sustainable urban drainage systems for urban runoff. In: Pratt, C.J. (ed), Proceedings of the First National Conference on Sustainable Drainage Systems, 18-19 June 2001, Coventry University.
Heal, K.V. (2000). SUDS Ponds in Scotland - performance outcomes to date. In: Pratt, C.J. (ed), Proc. 20th Meeting of the Standing Conference on Stormwater Source Control, pp.1-8. ISBN: 0905949994.
Heal, K.V. (1999). Metals in sediments of sustainable urban drainage structures in Scotland. In: Ellis, J.B. (ed), Impacts of Urban Growth on Surface Water and Groundwater Quality, IAHS Publication no. 259, pp.331-337, IAHS.
Investigating the variability in Phragmites australis (Cav.) Trin. ex Steudel in reed beds for habitat enhancement and water treatment
The implications of the research are numerous. Variation in seed production and morphology may affect wildlife communities and large genotypic differences between populations may have implications for seed selection for new reed bed establishment. In addition, morphological differences may have economic implications, such as the choice of reed used for thatching and CWS.
Remediation of mine spoil and mine drainage
1) The effectiveness of the remediation of Benhar Bing, an ironstone mine spoil heap in central Scotland. The acidic was amended with peat, dried pelleted sewage sludge and limestone (powdered and chippings) to create a medium suitable for tree growth. Acidic, metal-rich drainage was diverted into a settling pond and a surface-flow wetland in which Typha latifolia were planted in a substrate of spent mushroom compost.
2) The role of microalgal biofilms for removing iron and manganese from mine waters was investigated by exposing substrata for different lengths of time in a mine water settlement pond. In addition to determining the metal content and periphyton community composition of the recovered substrata, scanning electron microscopy/electron dispersive spectroscopy (SEM-EDS) was used to identify the processes of metal accumulation by biofilm.
3) How maintenance affects the performance of a scheme for reducing iron and aluminium concentrations in mine spoil drainage using RAPS (reducing and alkalinity producing system), settlement ponds and a wetland.
Iron removed by microalgal biofilms is mainly associated with extracellular polymeric substances (EPS) in the biofilm matrix than in cells. Our finding of no apparent association between Fe accumulation and biofilm community composition or function, suggests that bioremediation schemes for metal-contaminated waters should be designed to maximise biofilm colonisation in general rather than introducing “designer” biofilm communities. Iron and manganese removal rates by biofilm in the settlement pond studied were 35 and 0.7 mg m2 day-1, respectively, but biofilms might only account for c.1% of the iron and manganese removed in the settlement pond.
The use of iron ochre from mine water treatment plants to reduce point and diffuse phosphorus pollution
Carr, S.T.D., Dobbie, K.E., Heal, K.V. and Smith, K.A. (2009). The use of phosphorus-saturated ochre as a fertiliser. In: Ashley, K., Mavinic, D. and Koch, F. (Eds.), International Conference on Nutrient Recovery from Wastewater Streams, pp.623-633, IWA Publishing, London. ISBN 1843392321.
Heal, K.V., Dobbie, K.E., Bozika, E., McHaffie, H., Simpson, A.E. and Smith, K.A. (2005). Enhancing phosphorus removal in constructed wetlands with ochre from mine drainage treatment. Water Science and Technology, 51(9), 275-282.
Dobbie, K.E., Heal, K.V. and Smith, K.A. Assessing the performance as a fertiliser and the environmental acceptability of phosphorus-saturated ochre. Soil Use and Management, 21, 231-239.
Heal, K.V., Younger, P.L., Smith, K.A., McHaffie, H. and Batty, L.C. (2004). Removing P from sewage effluent and agricultural runoff using ochre recovered from mine water treatment. In: Valsami-Jones, E. (ed) Phosphorus in environmental technology: removal, recovery and applications. IWA Publishing, London, pp. 320-334.
Heal, K.V., Younger, P.L., Smith, K.A., Glendinning, S., Quinn, P. and Dobbie, K.E. (2003). Novel use of ochre from mine water treatment plants to reduce point and diffuse phosphorus pollution. Land Contamination & Reclamation, 11, 145-152.
Ochre use seminar, National Coal Mining Museum for England, Wakefield, 14 February 2005
Seminar aim: to evaluate ways of using ochre from mine water treatment plants in a sustainable manner
Presentations from the seminar are available below:
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