A new paper entitled “Hydraulic and biotic impacts on neutralisation of high-pH waters“ has just been published online and in open access on the journal Science of the Total Environment. This paper is available here.
Our research showed that cascades lower pH and alkalinity more successfully than ponds, and that configuration should be adopted, if possible, in the passive treatment of high-pH waters.
We could also observe that biofilms promote neutralisation due to CO2 from respiration. In fact, photosynthesis and respiration in biofilms induce a diurnal effect at high pH. The pH variation in biofilm colonized systems shows a diurnal cycle of 1 to 1.5 pH units due to CO2 uptake and release associated with respiration and photosynthesis. However, the hydraulic configuration has more influence on neutralisation of alkaline waters than biofilm.
The management of alkaline (pH 11-12.5) leachate is an important issue associated with the conditioning, afteruse or disposal of steel slags (an important by-product of the steel industry). Passive in-gassing of atmospheric CO2 is a low cost option for reducing alkalinity, producing calcium carbonate.
View of the biofilm colonized systems used in the experiments
The field trial at the Scunthorpe British Steel plant started this month. We are currently monitoring the existing wetland for passive treatment of the steel slag leachate. We are aiming to understand better what happens to vanadium (plant uptake / partitioning) and also to determine the treatment buffering rates. We hope to be able to publish some exciting results soon!
As part of the R3AW research we are interviewing a wide range of stakeholders to understand how they view the prospects for deployment of the remediation and resource recovery technology that we are developing here at the University of Hull.
Dr Pauline Deutz at Coatham Marsh
So with that in mind Dr Pauline Deutz and I set off up to Tees Valley Wildlife Trust to find out about their experiences of managing a site which was formed by the legacy of Redcar’s industrial past, but is affected by leachate from historic steel slag. After having driven over the spectacular North York Moors we pulled up outside the Trust’s offices and were warmly welcome with an offer of a much-needed cup of coffee. Our interviewee, who heads up the team at the Tees Valley Wildlife Trust, spoke to us for over an hour about the issues pertaining to managing such a complex site, which is bordered by Redcar town on one side and Redcar Steelworks on the other. Coatham Marsh is home to a myriad of wildflowers and over 200 species of birds as well as providing a haven for small mammals and invertebrates . Protecting sites such as this from the effects of legacy steel slag while recovering valuable resources is fundamental to the approach being taken by the R3AW research team. The experiences and thoughts of stakeholders like Tees Valley Wildlife Trust are helping us to understand how the current policy and regulatory environment is working and what other factors influence the way in which areas impacted by historic and legacy steel slag off being managed.
Looking out from Coatham March to the steel works
After we had to finished the interview we were given directions on how to get to Coatham Marsh so we could see for ourselves the work being done by Tees Valley Wildlife Trust and understand the interesting geography of the site which is bisected by a railway line! Once we found our way to the site, we were greeted by steel sculptures including, reeds and even a pair of walking boots and a rucksack. Despite dullness of the day and the ever threatening prospect of a downpour the site itself provided us with ample colour with displays of wildflowers, ponds and reed beds. Looking east out over the sea provided us with a dramatic view of offshore wind turbines and the view to the north the Redcar Steelworks. We explored the site for over an hour seeing the variety of flora and fauna that Coatham Marsh is home to. The impact that the legacy from the steel slag that surrounds site is something that the research of the R3AW project will hopefully be able to resolve so that sites like this can continue to provide a home for wildlife and a resource for local people into the future. Coatham provides a dramatic illustration of the way in which industry has shaped the environment and is continuing to do so, juxtaposing the rich and biodiverse Marsh with the Redcar Steelworks and Teesside Offshore wind farm.
Example of the art work found at Coatham
We would like to thank Tees Valley wildlife trust for sparing the time to talk to us, the contribution of stakeholders and their willingness to talk to us as part of this research project is much appreciated by everyone on the R3AW team.
Written by Dr Helen Baxter, University of Hull.
Water, sediments and invertebrates sampling in Coatham Marsh, Redcar