Author

Fabrice Gouriveau

Date

2009

Project Type

PhD

Subject

Ecology

Datasets

Ordnance Survey collection

Related Subjects

Geosciences; Geography; Agriculture; Engineering; Water pollution remediation

Sources: Digimap

Dates/Editions: All available from Digimap.

Scale: Variable.

Publishing Institution

University of Edinburgh

Summary

Farmyard runoff is a major source of water pollution that affects bathing water quality, causes eutrophication and degradation of aquatic ecosystems, and incurs considerable costs. Constructed Farm Wetlands (CFWs), systems made of vegetated ponds through which water flows and gets cleaned, are recommended for remediation of farmyard runoff. However, many questions remain on their long-term treatment efficiency, optimal design and cost-effectiveness.

The main aims of this study are to: 1) evaluate the treatment performance of CFWs, 2) assess their ecological value; 3) assess their cost and 4) propose guidelines for their design, construction and aftercare.

Research is focusing on two CFWs built in south-east Scotland and receiving runoff from farmyards, roofs, tracks, middens and silage pits. The removal or storage of pollutants such as nitrate, phosphorus or bacteria is assessed by monitoring flow and water chemistry at the inlet and outlet of the wetlands and by analysing sediments. The ecological value of the ponds is evaluated y monitoring vegetation and aquatic invertebrates. Moreover, q questionnaires are given to farmers to collect data on farm practices, wetland maintenance, and assess farmers’ acceptance of these treatment systems. Finally, the real costs involved in the construction of wetlands are being detailed.

This study will provide recommendations for the design and maintenance of constructed farm wetlands to increase their water treatment efficiency, enhance their ecological value and reduce their cost.

Aims & Objectives

Constructed Farm Wetlands (CFWs), semi-natural systems made of vegetated ponds through which water flows and gets cleaned, are recommended for decontamination of farmyard runoff in Scotland.

This study investigates their water treatment performance, ecological value and cost, involving water and sediment sampling, vegetation and invertebrate surveys and interviews with farmers and experts.

It will provide recommendations for the design and maintenance of constructed farm wetlands to increase their water treatment efficiency, enhance their ecological value and reduce their cost.

Methodology

I used Digimap mainly to create maps of my field sites, locate constructed wetlands, locate places were interviews with farmers were carried out, study the hydrology of the catchments, map water sampling points, etc.

Results/Outcome

Conclusions from the CFWs - Paper for SAC SEPA Conference 2008:

"CFW 1 receives a lightly polluted runoff, discharges a good quality effluent meeting river water standards, except periodically for nitrate and faecal coliforms and has good ecological value. However, its effectiveness is limited because not all farmyard dirty water is conveyed properly to the CFW and inputs of field drainage and groundwater decrease residence time and treatment (e.g. denitrification), especially in winter. In addition, preferential flow occurs in the system due to improper levelling and biomass build-up, reducing the residence time and area of exchange between dirty water and biota. CFW 2 receives significantly polluted runoff, achieves some treatment but discharges a poor quality effluent which does not meet river water standards. It has only a moderate ecological value. The poor efficiency and ecological value are mainly due to the lack of vegetation, the small size of the system, the lack of subdivision into several cells, and subsequently a very reduced residence time. However, shallow fully vegetated cells could be added to the system to enhance water treatment.

To consistently achieve water quality targets, CFWs should comprise a sedimentation pond followed by several wetland cells, shallow, large enough, fully vegetated and properly levelled to provide sufficient residence time and contact between water and biota. Although the cost of CFWs is lower than the cost incurred by conventional dirty water management options, they represent a significant investment for farmers. Appropriate external funds and support schemes are therefore recommended to promote more widely their adoption and proper management."

References & Acknowledgements

Project Supervisors: Dr Kate Heal and Dr Graham Russell, University of Edinburgh; Dr Andrew Vintan, The Macaulay Institute

Generously supported by the David Kinloch Michie Studentship, the Torrance Bequest, the University of Edinburgh Development Trust, the Scottish Environment Protection Agency (SEPA), The Macaulay Institute, Scottish Agricultural College (SAC), Edinburgh University Small Project Grants and the Elisabeth Sinclair Grant.