John
Machell
*a,
Kevin
Prior
b,
Richard
Allan
c and
John M.
Andresen
d
aPennine Water Group, University of Sheffield, S1 3JD, UK. E-mail: j.machell@sheffield.ac.uk
bWater Science Forum, W1J 0BA, UK
cThe James Hutton Institute, Dundee, DD2 5DA, UK
dHeriot-Watt University, Edinburgh, EH14 4AS, UK
Water purity is a vague term. Applied to drinking water, the emphasis of pure can mean ‘free from all types of bacteria and viruses’ as defined by the United States Environmental Protection Agency, or as being ‘wholesome’ when defined within Great Britain. US and British standards are based on the protection of public health. Strictly enforced values for a broad set of physical, chemical and biological parameters, informed by expert evidence gathered from many countries over a long period of time, are applied in an effort to ensure a minimum purity is achieved regardless of geographical location within those areas. Other countries like Australia, Canada and New Zealand however, do not have such strict legal definitions. Instead, best endeavours under local circumstances, measured against ‘guideline’ values for a narrow set of parameters, are used to judge water quality, and hence purity. These discrepant definitions can lead to confusion so this brief has been created to clarify current understanding of the meaning of ‘water purity’.
Despite the truism that every human on this planet needs to drink water to survive, and that the water may contain harmful constituents, there are no universally recognized and accepted international standards for drinking water.1 Even where standards exist and are applied, the permitted concentration of individual constituents may vary by as much as ten times from one set of standards to another. Descriptions differ too; pure being replaced by words such as wholesome, healthy or potable.
Many developed nations specify country specific drinking water quality standards. In Europe, this includes the European Drinking Water Directive,2 and in the USA the Safe Drinking Water Act.3 For countries without a legislative or administrative framework for such standards, the World Health Organisation publishes guidelines on the standards that should be achieved. China adopted its own drinking water standard GB3838-2002 (type II) enacted by their Ministry of Environmental Protection in 2002.4
Most drinking water quality parameters are expressed in terms of guidelines, or targets, rather than specific requirements. Very few have any legal basis or are subject to enforcement.5 Two exceptions are the European Drinking Water Directive and the United States Safe Drinking Water Act, which both require legal compliance with specific standards.2,3
In Europe, the directive includes a requirement for member states to enact appropriate local legislation to mandate the directive in each member country. Routine inspection and, where required, enforcement is enacted by means of penalties imposed by the European Commission on non-compliant nations. Example countries with guideline values for their standards include Canada, which has guide values for a relatively small suite of parameters, and New Zealand, where there is a legislative basis but water providers have to make “best endeavours” to comply,6 and Australia.
Water supply companies purify water for drinking by identifying unhealthy contaminants and then reducing or removing them. In England and Wales, drinking water quality standards are enforced by the Drinking Water Inspectorate (DWI).7 Should consumers wish to treat to an even higher standard, or for a specific requirement, there is a plethora of commercially available methods and equipment. These range from simple particle filters, to technical multistage systems that might combine filtration, reverse osmosis and disinfection, for example.
Where drinking water is provided by desalination, minerals have to be added to the final product because it is so highly purified that it becomes corrosive, and therefore not fit for distribution or use by many conventional piped networks and fittings.
Even in a laboratory pure water is hard to come by, because bacterial contamination and algal growth can cause a deterioration in quality. Even if organic and inorganic chemical impurities are removed to levels below their limits of detection, bacterial growth can still occur. This is despite very pure water providing an extremely harsh environment with negligible nutrient content. To avoid metallic contamination of laboratory water, the purifiers are constructed using plastics. However, bacteria are able to utilise such materials for a carbon food source to sustain them. Then, when the micro-organisms die, they release further contaminants into the water. If this bacterial growth is not minimized, it can cause difficulties for analysts carrying out day-to-day testing within a laboratory.
In general, discussion about water quality can, and will most probably switch from the notion of ‘pure’ to that of ‘safe’. The Guidelines for Drinking Water Quality (Fourth Edition) states “Every effort should be made to achieve drinking-water that is as safe as practicable. Safe drinking-water, as defined by the Guidelines, does not represent any significant risk to health over a lifetime of consumption, including different sensitivities that which may occur between life stages”.8 Safe water is economical and attainable, whereas pure water is not.
Harmful contaminants, whether man made or naturally occurring, are constantly being identified. Disinfection by-products, harmful bacteria, metals and numerous chemicals have their removal thresholds legally set based on Best Available Technology principles. The WSF is striving to keep its members on the forefront of these developments as outlined in this brief.
Water destined for use by industry, agriculture or horticulture should be “fit for purpose” where the quality standards are determined for the most part by the user. In the case of environmental waters, they would be expected to have achieved satisfactory ecological status as described in the EU Water Framework Directive.2
In order to determine if water has achieved the required standards for a specific end use, evidence-based decision making is employed involving:
• Preventative risk management based on appropriate evidence-based quality standards
• Appropriate risk based monitoring and testing carried out by accredited laboratories
• Professional accreditations to develop competent technical staff
Examples of evidence based quality standards include the WHO drinking water standards,8 and UK Environmental Quality Standards.12
For example, the Australian Drinking Water Guidelines (2011) incorporates elements of a Hazard Analysis Critical Control Point (HACCP) system, ISO 9001 Quality Management and AS/NZS 4360:2004 Risk Management.13 These different regulations and guidelines recommend maintaining robust multiple barriers appropriate to source water condition, in recognition of the fact that no single barrier is effective against all contaminants all of the time. They encourage understanding of the entire water supply system, from catchment to consumer, including the hazards and events that could compromise drinking water quality, and the preventative actions required for safe and reliable drinking water. As a result, a holistic approach to water management is fostered which emphasises prevention and positions drinking water quality monitoring as a verification task. Implementation of such a framework has seen greater emphasis on river basin management, this being the first line of defence for safe drinking water.
While monitoring guidelines vary internationally, risk based emphasis has also been adopted elsewhere. For example the Australian Guidelines for Water Quality Monitoring and Reporting are applied to monitor system performance according to the hazard characteristics and risk profile identified for the particular water supply system. Overall, monitoring might be undertaken for catchment, treatment, and distribution; verification of drinking water quality; investigative studies; validation monitoring of new barriers; and incident and emergency response. Similarly to the UK, in Australia quality assurance of laboratory results is important and it is therefore recommended that accreditation by the National Association of Testing Authorities (NATA) is used whenever possible.
The Professional Registers consist of three designations:
Chartered Scientist (CSci) is a well-established award, with over 15000 scientists having achieved it since its launch in 2004. Candidates will typically be in senior scientific or managerial roles, qualified to at least Qualifications and Credit Framework (QCF) level 7, and applying their knowledge in their roles.
Registered Science Technician (RSciTech) is a new award to provide recognition for those working in technical roles.
Registered Scientist (RSci) is a new award to provide recognition for those working in scientific and higher technical roles.
Although there is no specific guidance for water reuse in the UK, internationally specific guidelines have been developed in regions where water scarcity has been a particular issue. For example, the US EPA 2012 Guidelines for Water Reuse (originally published in 1980) and the Australian Guidelines for Water Recycling: Managing Health and Environmental Risks 2006 (phase 1 – covering use of recycled water for commercial and residential irrigation, toilet flushing and industrial uses) and 2008 (phase 2 – covering recycled water to augment drinking water supplies, rainwater harvesting and managed aquifer recharge).
The US guidelines emphasise an integrated water management approach, where the focus is on broader water resources management, with reuse being a key factor in this more holistic strategy. Under these guidelines, opportunities to reduce the demand for freshwater are exploited. Alternative resources might include wastewater and greywater reuse, storm water use, rainwater harvesting, groundwater recharge, increased surface water detention, sewer mining, and the use of dual distribution systems to potable and non-potable water separately among others.
In Australia, as with drinking water, a risk management approach is adopted in order to anticipate potential issues and therefore implement strategies to prevent them from arising. The guidelines consider both risks to human and environmental health. Both US and Australian Guidelines emphasise the importance of public consultation. Sewer mining schemes have been explored in Western Australia, but there are currently no live systems.20 Indeed, public opposition to proposed recycled water systems has resulted in schemes of all kinds being rejected.
• Preventative Risk Management based on appropriate evidence-based quality standards
• Appropriate risk based monitoring and testing carried out by accredited laboratories
• Professional accreditations to develop competent technical staff
Building on these principles, the WSF is striving to promote secure, safe and affordable water.
Footnotes |
† Any opinions or views expressed in the following article are entirely those of the authors and do not represent the views of the journal, Environmental Science: Water Research & Technology, or the Royal Society of Chemistry. |
‡ This note was produced by a working party of the Water Science Forum of the Royal Society of Chemistry. The Society is a registered Charity. Its Royal Charter obliges it to serve the public interest by acting in an independent advisory capacity. In order to meet this obligation, the members of the Water Science Forum are drawn from a wide range of backgrounds, and serve on the committee as individual experts and not as representatives of their respective employers. The Water Science Forum welcomes comments on this note. Please send them to the Chairman, Water Science Forum, Royal Society of Chemistry, Burlington House, Piccadilly, London, W1J 0BA, UK. |
This journal is © The Royal Society of Chemistry 2015 |