Brown water ahead; climate change impacts on water quality and treatment

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Peat soils are a large terrestrial store of carbon and if they destabilise it will provide a positive feedback on climate change. Surface waters draining peat systems are brown from high amounts of dissolved organic carbon (DOC), which, if not removed effectively, can form potentially carcinogenic compounds during water disinfection. I’ve been taking peat soils from UK research catchments, simulating different climate scenarios and looking at the DOC released and how easy it is to treat.

Instead of just treating the water, there’s interest in looking at things that can be done in water catchment management to improve the water quality

Tell me more!

I’m looking at problems surrounding organic carbon-rich peat soils and drinking water treatment. Drinking water companies need to know if the dissolved compounds will be hydrophobic, high molecular weight compounds, which you can remove quite easily with standard drinking water methods, or low molecular weight, hydrophilic compounds which may require new treatment processes.

One of the things we’ve been looking at is what happens if there is an increased frequency and severity of droughts through climate change; it’s more likely the water table will drop and the peat will become oxygenated leading to increased organic carbon flux.

Peat systems also have a large number of Sphagnum mosses which are difficult to decompose — one of the reasons why this carbon stays in the soil for thousands of years. With climate change and also atmospheric deposition of nitrogen, there may be a shift away from these mosses to grassland species. Our work and that of other researchers suggests that if this substitution of mosses for grasses occurs, you won’t see as much new sequestration of carbon occurring in peatlands.

Why is this so important

Since peat systems are one of the main terrestrial stores of carbon, there is a lot of interest in them and whether they will continue to be a sink of carbon in the future. There’s also a public health aspect to our work as drinking water companies must minimise any potential carcinogens in their water and do this in the most cost effective way possible.

Instead of just treating the water at the treatment plant, there’s interest in looking at things that can be done in catchment management to improve the water quality before it gets to the treatment works. One approach is to keep the water table high in peat catchments so oxygen cannot penetrate into the soil and so that Sphagnum mosses have the conditions they need to thrive.

Biography

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I am a PhD candidate at Imperial College, working on a Grantham Institute for Climate Change project investigating the impact of climate change on surface water quality and drinking water treatment, with further funding from Welsh Water and South West Water. I won ‘Best Thesis 2010/11’ for my King’s College MSc research on lead contamination in Sub-Saharan Africa, worked as a sustainability consultant with CarbonPlan Ltd and as an applications specialist with Industrial Tomography Systems.

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Social and Commercial opportunities

Some of the drinking water companies in the UK are now looking at what they can do with catchment management to improve water quality and support Sphagnum mosses. They are doing it mainly for the carbon sequestration, as this angle has been proved, while the drinking water quality aspect is still under debate as we don’t know quite the kind of impact it’s going to have.

 Catchment management definitely works for some water quality issues; pesticides for example. It's expensive to remove pesticides at treatment works, whereas you can pay a farmer to farm organically near rivers or not to use a certain pesticide. We’re hoping our research will provide evidence for whether similar schemes could work for keeping DOC manageable.

My dream for this project

I think the next step is to scale up my research and link it with other work looking at land use changes, hopefully developing a larger system of catchment modelling to figure out the best way of managing catchments to produce sustainable water. Ideally, if you can improve water quality in the catchment rather than spending a lot of money and energy at the treatment works, it may be a lower carbon and more sustainable way of producing drinking water.

My expertise

Dissolved Organic Matter, Peatland Systems, Disinfection By-Products, Water Quality, Biogeochemical Cycling, Vegetation, Biogeochemistry