Contaminants of Emerging Concern
Nottingham Trent University 31 October 2013
Mike Waite and Maxine Forshaw
We joined a group of about 50 delegates for this meeting. Despite some presentations causing UAO (Unexplained Acronym Overload) the meeting was very informative and worthwhile! The presentations were packed with information - selected key points are described below.
Caroline Whalley (Defra) opened with a presentation on ‘Chemicals and the Water Framework Directive’. She referred to the 2013 list of priority substances under the Directive, which is expected to be revised around 2017, and outlined other relevant Directives. An accompanying watch list of substances that may warrant inclusion in the next revision of River Basin Management Plans is due in September 2014.
On behalf of UKWIR, Arthur Thornton (Atkins) spoke about ‘Researching the Problem’ and described the UKWIR Chemicals Investigation Programme (CIP) intended to assist the water industry and others in identifying and assessing the significance of contaminants of potential concern. When defining criteria for inclusion of substances it is necessary to have an appropriate weighting system which also includes non-scientific aspects such as the value to society of the contaminant. The CIP looked at the full range of potentially relevant substances, the ability of current treatment processes to remove or inactivate them, and likely amounts to be encountered in the environment. The CIP has not addressed multiple threats or the more sociological/economic aspects.
Chris Sinclair (Food and Environment Research Agency) described a UKWIR project ‘Prioritising Pharmaceuticals in the Environment’. There are some 4000 active ingredients of which around 1000 are prescribed in the UK. Prescription data enables an assessment of the total amount used but there are 22 relevant substances available in over-the-counter medicines, and use in both hospitals and prisons is not easily quantified. In addition, much information is commercially sensitive and cannot be obtained. When total use is calculated, the top three active compounds are paracetamol, metformin (anti-diabetic drug) and ibuprofen. The project also identified 66 compounds in seven classes considered to be of high hazard concern (rather than for quantities used). Amounts (after metabolism) likely to reach surface water were calculated, together with the significance of any metabolites and the impact of treatment processes. As degradation in the environment cannot be predicted it was not included although it could be important. There is a serious lack of information on the aquatic toxicity of many contaminants and metabolites.
‘A Regulator's Perspective’ was presented by Pete Marsden (Drinking Water Inspectorate) in which he summarised current legislation and outlined relevant research commissioned by DWI. He referred to the current European standard for pesticides still being set at 0.1μg/l as a surrogate zero with the exception of four pesticides, while in the US individual pesticides have specific standards based on toxicology and many are set well above this level. The Water Supply Regulations (2010) introduced a requirement to minimise disinfection by-products whilst not compromising disinfection. A desk study reviewed pharmaceuticals and a formula for predicting concentrations in drinking water was developed. Predicted concentrations in drinking water were less than one thousandth of the therapeutic dose for all but ten substances and of these, four were illegal drugs. DWI concluded that there is no risk from pharmaceuticals in drinking water. A further monitoring programme at four sites, measuring removal in treatment, confirmed this. Very low concentrations of N-nitroso dimethylamine (NDMA) were detected at three works and, although at the time of the study there was no WHO Guideline value for the substance, further investigation led to the recognition that the source was certain ferric coagulants and DWI issued Guidance to Water Companies which was updated in 2012.
Steve Tennison (MAST Carbon International) talked about 'Development of Novacarb' (or Novocarb the two names being used interchangeably), a novel polymer-bound carbon, and its ability to remove metaldehyde, a widely used molluscicide and a substance highlighted by Anglian Water as being of concern. Novacarb outperformed GAC (granular activated carbon) in lab-scale studies although some limitations were apparent and the material is not yet available in sufficient quantities to allow work at demonstration or pilot plant scale.
'United Utilities’ (UU) approach to tackling Priority Substances' was outlined by Carolyn Heath. Following a study to assess the contribution of wastewater discharges to Priority Substances in the aquatic environment, UU identified that 112 of 550 sites would fail environmental quality standards (EQSs) when in force, for one or more of seven selected Priority Substances. All 112 would fail for tributyltin. A review of the effect of various conventional treatment processes showed that, apart from membrane filtration/reverse osmosis, for which data was not fully available, no treatment was effective against all the selected Substances. Control at source was generally not possible. UU also established that there was a need for advanced Total Phosphorous Removal technology, and the BluePro© process (which uses ferric chloride in a continuous moving bed sand filter) was able to reliably achieve over 95% removal when trialled at Windermere. Modifying the process by adding ozone (BlueCAT©) enabled significant removal of a wide range of Priority Substances.
Ruth Barden described how Wessex Water had set out to develop a 'Standard design of reed bed/controlled wetland'. Tests using six different substrate beds for bulrushes showed steel slag to perform best overall in terms of substance removal, especially for orthophosphate, but no substrate was ‘the best’ for every substance monitored. None of the substrates could remove Diclofenac.
‘Do we have an answer for emerging pesticides?’ asked Barrie Holden (Anglian Water). He explained that emerging pesticides (eg clopyralid and metaldehyde) have caused compliance issues and that an immediate cost effective solution is not available. Catchment management is a long-term solution; treatment provides more immediate action. Many treatments have been tried with varying results. A low carbon and cost effective treatment is the present challenge for technology companies.
Pascal Martin (Veolia) considered the 'Evolution of treatment and the development of the ActifloCarb® process'. With the drivers of drinking water quality and achievement of good ecological quality of surface waters, efficient removal of micro-pollutants is essential. The Actiflo process uses powdered activated carbon (PAC) and microsand ballasted flocs in a continuous process. Pilot and industrial prototype plants have been tested at wastewater treatment plants in a number of countries. Testing three different PACs showed that none was superior for every substance tested but while two achieved an average 69% removal, the other only achieved 55%. The process reduces endocrine disruptors, pharmaceuticals and biocides in wastewaters. Pilot plant trials at North Mymms drinking water treatment works in north London, alongside a competitor treatment plant, showed reduction in turbidity of generally around 90%; for metaldehyde, a molluscicide of particular interest and present at approximately the permitted concentration in the raw water, removal was variable, between 50% and 90%.
The presentations finished with Karin Helwig (Glasgow Caledonian University) outlining the multinational 'European study PILLS (Pharmaceutical Input and Elimination from Local Sources)' which looked at hospitals as sources and loadings of pharmaceuticals at wastewater treatment works. The study focussed not on concentrations in hospital effluents but on total loadings at the plants and the ability of these to reduce or remove them. Key conclusions were that membrane bioreactors, while good at removing COD, nutrients and bacteria, were not efficient for some pharmaceuticals, while granular activated carbon with reverse osmosis leads to high removal of all compounds. Although treatment at point sources could be effective it would be very expensive with high energy costs, so reduction of inputs should be explored. The successor ‘noPILLS’ project will look at campaigns to raise awareness of the impact of discharges of pharmaceuticals, together with an assessment of the results of these campaigns on loads to treatment works. It will also look at removal efficiencies of existing treatment facilities, plus the effect of diverting surface water away from treatment plants via SuDS (sustainable urban drainage systems).