Atkins’ Mike Gardner and Dr Arthur Thornton provide an overview of the UK Water Industry Research Chemicals Investigation Programme.
The UK Water Industry Research (UKWIR)¹ Chemicals Investigation Programme (CIP) has provided an extensive set of monitoring data for a wide range of trace substances in the water cycle, which is helping to establish priorities with respect to the action necessary to ensure surface waters meet new environmental quality standards.
Recent EU legislation in the field of water and the environment, in particular the Water Framework Directive (WFD – EC 2000), has important implications for the scope and nature of pollution control measures required to protect surface waters.
Environmental Quality Standards (EQSs – EC 2008) are concentration limits that are used to define satisfactory water quality have been established for more than 30 substances, which hitherto have not been subject to detailed monitoring or control. In addition, individual national regulators have been required to set their own standards for a further group of potential pollutants. The combined effect of this legislation is to place increasing emphasis on pollution control measures.
While statutory regulatory bodies have formal responsibility for meeting these new regulatory demands, the UK water industry in its role as the most important provider of water and wastewater treatment will have an important part to play in assessing the contribution made by wastewater discharges to overall contaminant loads. Companies also need to prepare to fulfil their role in the progressive pollution reduction measures demanded by the WFD.
In order to address these new obligations, a clearer understanding is required of the occurrence, concentration and behaviour in wastewater treatment of the substances of interest. Given the variety of substances involved, obtaining the necessary information to a proven and adequate level of reliability is a considerable challenge.
To address this, the UKWIR has collaborated with the water industry, the Environment Agency and other UK regulators in the design of a £25 million programme of investigations – the Chemicals Investigation Programme, or CIP – into the management and control of a range of substances that may be present in wastewater treatment works’ discharges.
The overall aim of the CIP is to provide a sound and technically justifiable basis for future measures to be taken in order to achieve good chemical status for surface waters, as defined under the WFD.
The programme, which began in 2009 and is scheduled for completion in 2013, is intended to generate a national evidence base that will guide the selection of the cost effective WFD programmes of measures.
More than 50 chemicals are of immediate interest, including metals such as Copper, Zinc, Cadmium, Mercury, and Nickel, organic substances such as industrial chemicals, constituents of consumer products and the byproducts of combustion. In addition to the chemicals specifically named in the legislation, the CIP is being used to assess risks posed by other substances that can be present in wastewater effluents and for which future standards may be set. These substances include pharmaceuticals and detergents, and other metals such as Iron, Aluminium and Silver.
Surprisingly, little was known about the sources and extent of occurrence in wastewater and their behaviour in treatment processes. It is certain, however, that current wastewater treatment processes are not specifically designed to remove such chemicals from sewage.
The very low EQS concentrations for many substances raises the prospect that there might be a requirement for water companies to install specialist additional treatment, to attempt to remove chemicals at submicrogram per litre concentrations. Such technologies have, in many cases, not been proven at full scale operation. Furthermore, they tend to be expensive to operate and energy intensive, raising questions concerning the carbon footprint of water treatment operations.
A previous risk assessment carried out by UKWIR estimated the cost of compliance with the WFD to be several billion pounds, if tertiary wastewater treatment were to be found to be the only option for EQS compliance. An informed appreciation of key issues is therefore necessary if the most cost effective approach is to be identified.
Chemicals Investigation Programme
The CIP has been designed to address some of the key questions that face the water industry; for example:
1. What are the concentrations of different substances in effluents?
2. How do concentrations vary between treatment works in different areas and of different types?
3. Do these substances pose a compliance risk with respect to the new water quality standards?
4. What is the relative priority among contaminants for the implementation of control measures?
5. What is the most appropriate balance between different control measures; for example, source control, wastewater treatment, restrictions on substance use, and substitution – and how can the costs of such measures be made proportional to the benefits achieved?
6. How effective are current sewage treatment processes in controlling the concentrations of contaminants discharged, and do newer processes offer the possibility of improved control?
7. What proportion of contaminant load is currently derived from sewage effluent discharges and what arises from other sources?
8. What are the sources of different contaminant inputs to wastewater treatment works, which contaminants are derived from domestic sources and which from other urban sources, such as commercial areas, light industry and run-off?
The CIP covers more than 45 target contaminants including metals, industrial chemicals, biocides and pharmaceuticals, as well as including determinations of a range of supporting water quality parameters. The overall programme has three main components:
C1. Wastewater treatment works (WwTW) effluent surveys – Investigations to quantify risk of EQS non-compliance, such as the screening of WwTW final effluents to confirm the concentrations and loads of substances being released to receiving waters, and to assess their impact on achievement of WFD objectives. Participating treatment works were selected to represent the range of works across the UK. This was highly demanding and necessitated analytical performance requirements to be set, including limits of detection at or below current EQS values.
C2. Treatment process assessment – Investigations to assess the effectiveness of wastewater treatment processes in removing different chemicals. These investigations are currently evaluating a range of commonly used and advanced treatments. The element of collaboration means that each water company will not have to assess all treatment processes separately. Pooling of resources in this way offers substantial efficiencies in the identification of best practise for each substance of interest.
C3. Source investigations – Catchment investigations to assess upstream catchment sources of the specified chemicals discharged to sewers and alternative treatment options. These investigations are providing data on options for source control of substances discharged to sewers; for example, through marketing and use of restrictions or trader consenting, as well as providing information on possible advanced treatment technologies at a laboratory and pilot scale. Urban sewer catchments in nine towns are subject to investigations that will apportion the input treatment load between five different categories of sources: domestic, licensed traders, light industry and commercial, town centre, and run-off. Early indications are that most contaminants are detectable in all sources.
The C1 programme is now complete. A technical paper summarising the design and main outcomes has been published (Gardner et al, 2012). Figure 1 shows the range of values observed for the natural steroid Oestradiol. Similar outputs are available for a further 60 determinands.
While the effluent study did reveal some instances where particular chemicals were found at elevated levels in effluents from specific wastewater treatment works, these were relatively few in number and were usually already known. The overall picture was one of moderate variation within and between the treatment works but of no notable regional differences across the UK.
This is consistent with the initial findings of the C3 catchment studies, which indicate that sources of the majority of substances in wastewater are ubiquitous and domestic, rather than industrial. This leads to the observed picture of homogeneity at a national level.
Monitoring in the C2 programme at different stages in each process is providing information on performance that is being used to understand and optimise the effectiveness of removal of different substances: see Figure 2. It is clear from the initial results of this work that existing wastewater treatment processes are more effective in removing many substances than had been initially expected, on the basis that treatment processes are designed to remove bulk sewage constituents rather than trace chemicals.
The high quality data set that the CIP is generating represents a valuable platform for policy development. Successful execution of the overall project provides companies with a sound technical basis on which to approach future environmental quality requirements. The ability to differentiate between measures that can justifiably involve treatment and those that require other strategies, such as control of substance use, is critical to water companies and their customers.
The CIP is also providing regulators with a demonstrable technical rationale by which to justify its proposed actions for the next WFD planning cycle. The current sampling and analysis phases have fed into a process of options appraisal to assess the relative merits of strategies, such as source control versus wastewater treatment.
Cost effectiveness assessments and regulatory impact assessments have used the outputs from this project to identify effective programmes of measures to deliver good status under the WFD. The carbon footprint of measures has also been assessed in the light of the projected benefits to the water environment.
Gaining a view of how to prioritise future development of pollution control is a complex process. Selecting the best options to ensure that surface waters comply with quality criteria is complicated by at least two factors. Firstly, wastewater treatment is not the only approach. Indeed, it is likely that control on uses of certain substances, including some pharmaceuticals and personal care products, would prove to be more cost effective than removal of these chemicals from wastewater streams. For other substances, for example, naturally occurring chemicals such as steroids as well as essential drugs, wastewater treatment seems to be the only viable strategy.
Secondly, there is the issue of whether or not elevated concentrations of chemicals might occur at the same site and the assessment of the costs and benefits of the various treatment options, which might or might not be effective for one or more groups of substances. These considerations are currently the focus of a UKWIR sponsored project that aims to use the data generated by the CIP as a basis for an analysis of the most cost effective responses to new legislation.
Furthermore, one of the most important difficulties facing water managers is the lack of clarity in relation to the precise details of the legislative framework that is likely to be in place (EC 2012). The process of proposing standards and subsequent multiple levels of negotiation at EU level – any of which is capable of leading to potentially crucial decisions one way or the other – is a major cause of uncertainty in the standards that might have to be met. This in turn hampers the processes of planning appropriate responses in terms of controls of contaminants, or investments in upgrades to wastewater treatment. Such upgrades, when viewed at a national or EU level, very rapidly accumulate into total costs of billions of Euros.
Despite these potential difficulties, the extensive data set generated by the CIP together with similar data being generated in other EU countries (Clara et al, 2012 and Martinez Bueno et al, 2012), represents a valuable platform for policy development. Successful execution of the overall project is providing water companies with a sound technical basis on which to approach future environmental quality requirements.
We now have a much clearer idea of the concentrations of different substances that are present in effluents. This extensive monitoring programme has demonstrated that trace contaminant concentrations in wastewater treatment works’ effluents can exceed existing or proposed EQS values.
While some substances might present a challenge with regards to EQS compliance, it has been possible to rule out others as less important. This prioritisation is invaluable in directing investment on remedial measures and in ensuring best value for water consumers.
Current work is providing insights into the rates of contaminant removal achieved by current treatment processes. This has demonstrated the substantial positive impact of existing treatment processes.
Published: 27th Nov 2012 in AWE International