Researching the Sludge Directive

A conference on sewage sludge

Brussels, 30 & 31 October 2001

Environment DG and UKWIR (UK Water Industry Research) organised a conference on sludge on 30 and 31 October 2001 in Brussels.

The aim of this two-day conference was to present the latest results from research studies carried out by UKWIR (the organisation that manages collaborative research on behalf of the water companies in the UK) as well as the results of the desk studies carried out by external contractors on behalf of the Commission. More than 200 European experts attended the presentations, participated into the discussion and shared their experiences.

The use of sewage sludge in agriculture is important in many Member States, but it is also becoming a very controversial issue. The Community policy in this field (as enunciated in the Urban Wastewater Treatment Directive 91/271/EEC and the Sewage Sludge Directive 86/278/EEC) is to promote the use of sludge in agriculture, provided that it complies with the applicable requirements in terms of monitoring, treatment and quality. The large participation at the conference produced a frank discussion between the different stakeholders involved in sludge use and a useful exchange of views.

After a general introduction by Mr David Grant Lawrence, Director of Sustainable Development in the Environment Directorate-General of the European Commission, the conference started off with a series of presentations on policy aspects. Mr Bernhard Berger presented some considerations on soil protection, as they are being developed in a draft Communication from the Commission. Mr Luca Marmo presented figures showing the current sewage sludge production in the EU and the work that had already been done with a view to revising the Sewage Sludge Directive 86/278/EEC. Mr Avelino Martinez of EUREAU outlined the point of view of the European water companies and stressed the importance of the agricultural outlet for sewage sludge.

The following session focused the attention on how to prevent the health risks linked with the agricultural utilisation of sewage sludge. Mr Bob Davis of WRc presented the results of a desk study on sludge treatments for killing pathogens. Some suggestions were made on the micro-organisms to be used in order to monitor the effectiveness of sludge treatment. Mr Alan Godfree of United Utilities showed the results of recent research carried out in the UK on reducing the risk from pathogens.

Session III on organic compounds started off with a presentation from Mr Kaj Henriksen of Aalborg University, who described some field experiments carried out in Denmark in order to assess the decomposition rate of compounds such as PAHs, LAS, DEHP and NPE. Mr Christophe Bonnin of Vivendi and Mr Alain Huyard of Ondeo presented the results of analyses carried out on French sewage sludge in selected urban waste water treatment plants. Mrs Cajsa Wahlberg of Stockholm Water outlined the concerns existing in Sweden for the presence of brominated flame retardants in sewage sludge. This session was brought to a close by Mr Andreas Prüeß of UMEG who presented the results of a literature study on the presence of organic compounds in sewage sludge and their toxicological significance.

The following session focused the attention on heavy metals and started with a presentation from Mr Jan Eriksson of the Swedish University of Agricultural Science, who presented the research carried out in Sweden on 61elements found in sludge (pdf ~800K). He underlined that metals such as gold and silver would double their soil concentrations within few years of sludge application. Mr Brian Chambers of ADAS talked about the field experiments being carried out in the UK in order to assess the what extent heavy metals are taken up by plants growing on different soil types. Mr Heinrich Langenkamp of the JRC of the Commission reported the results of the short term action for gathering the background concentrations of heavy metals in European soils. He underlined that data are not really comparable because of different methods used for sampling, extraction, analysis etc.

The last session of the conference dealt with management aspects related to sewage sludge, in particular with the issues of prevention of pollution and public perception of health risks. Mr Andrea Tilche of the Research Directorate-General of the Commission presented recent findings for effective waste water treatment systems producing less sludge and underlined the importance of pollution prevention for ensuring sustainability. Mr Radu Rautiu of ICON talked about the sources of pollutants in waste water and sludge and suggested some measures that could be undertaken in order to reduce pollution at source. Mr Eric Mugnier of Arthur Andersen presented some preliminary results of a cost-benefit analysis on disposal and recycling routes for sewage sludge. Although unavailable data prevents the production of a definitive conclusion, it appears that the use of sewage sludge in agriculture is the better alternative, in terms of global environmental effects. He also talked about the sociological acceptance of disposal and recycling routes for sewage sludge in Europe. The crucial point is that it is not the real risk that drives public opinion, rather it is the perception of the risk and this can differ significantly from the genuine risk. Mr Frédéric Dalimier of SEDE in his presentation suggested some technical improvements to sludge treatment and handling in order to improve its quality and therefore its image vis à vis the end user.

The discussions held during the conference and the exchange of views among the participants showed the need for a transparent and large debate among stakeholders about the threats and opportunities offered by the use of sludge in agriculture. The potential negative and positive aspects of sludge have to be put into perspective with similar materials, such as mineral fertilisers, compost, animal manure and slurries. There is a need for a global approach to soil protection in the Community.

Conference programme and presentations