Water Recycling
Climate change, increasing population and environmental pressures are impacting on the resilience, sustainability, quality and security of existing sources of raw water to be treated for drinking water purposes. To improve the reliability of drinking water supplies and to ensure future provision of sufficient safe drinking water, new and alternative raw water sources will need to be developed.
A number of alternative sources of drinking water are currently being considered as part of the water companies’ water resource planning. One of the options being considered is recycled water, also known as water reuse. This source of water would be blended with and augment existing raw water sources and could supplement the raw water supply to drinking water treatment works.
What is water recycling?
The water cycle is a description of how water is in continuous circulation from the atmosphere to the Earth. In terms of drinking water supply and the water cycle, water precipitates from the atmosphere to the Earth and water is then abstracted from various sources, such as rivers, reservoirs and aquifers to be treated and supplied for human consumption, food production (for instance drinking water, bathing, or cooking) and other uses. Once used this water is then sent for treatment via a wastewater treatment works before being discharged back to the environment where it evaporates to the atmosphere and the cycle starts again.
Water recycling can provide a continuous and sustainable source of water, which is less prone to cyclical shortages such as droughts as it reclaims the most dilute portion of treated wastewater which would normally be returned to the environment.
The water element of that process which is reclaimed is then subjected to further advanced treatment at a water recycling plant before it is either sent to an existing water treatment works (known as direct water recycling) or discharged to a river, reservoir or aquifer (referred to as an environmental buffer) where it blends with other sources of water before being abstracted and further treated at a drinking water treatment works (known as indirect water recycling). Currently there are no proposed direct water recycling schemes. However some water companies will be developing indirect water recycling to help ensure a sufficient and sustainable supply. Indirect recycling is shown in the diagram below:
Indirect Recycling Scheme Diagram
The most common advanced water treatment processes that would be utilised at a water recycling plant would adopt a multi barrier approach which typically includes membrane filtration. Membrane filtration technology comprises membranes with an extremely small pore size, through which water is forced at high pressure to leave behind contaminants commonly found in treated wastewater including viruses, bacteria and other chemical contaminants.
How is water recycling regulated and is it safe to drink?
Water recycling schemes provide a safe source of drinking water. As with all water treatment facilities, they need to be designed appropriately and managed effectively. Water companies planning to utilise water recycling to supplement their raw water are required to ensure that all regulatory requirements in the drinking water quality legislation are met at all times.
The Drinking Water Inspectorate, as the independent drinking water quality regulator for England and Wales, has powers and duties to ensure that water companies are meeting the obligations relating to drinking water quality and sufficiency under the Water Industry Act 1991 and that water companies meets their regulatory duties as set out in the Water Supply (Water Quality) Regulations 2016 (as amended) and The Water Supply (Water Quality) Regulations 2018 (Wales) in full. These regulations cover water intended for human consumption and other domestic purposes (for example washing and laundry).
Drinking water that is supplied by a water company must be ‘wholesome’ and this is defined in law by having standards for a wide range of substances, organisms and properties of water in regulations that must not be breached. There is an additional requirement to make sure that it does not contain anything else that might be a potential danger to human health. The standards are set to be protective of public health and the definition of wholesome includes factors that might affect the look, smell or taste of the water. There is good agreement amongst experts worldwide on the science behind the setting of health based standards for drinking water and this expert evidence is documented by the World Health Organisation in its Guidelines for Drinking Water Quality. The legal standards in England and Wales are based on those which were set in Europe in the Drinking Water Directive 1998 and subsequent revisions, together with national standards set to maintain the high quality of water already achieved. The standards are strict and include wide safety margins. They cover:
• micro-organisms
• chemicals such as nitrate and pesticides
• metals such as lead and copper
• the way water looks and how it tastes
The requirements for water companies to ensure that the water supplied is wholesome and safe to drink applies to all sources and systems that supply drinking water, and this includes recycled water. This is achieved by understanding the risks all the way from the source to your tap, and making sure that the process contains multiple steps to address all risks so that the water produced does not rely on any one measure or process. This typically involves measures taken in the water catchment, managing how and when water is taken from the environment for treatment, and the treatment processes themselves.
There is a fundamental regulatory requirement for water companies to adequately treat and disinfect the water before it is supplied to consumers. The risk assessment should also include sufficient safeguards and failsafes which can detect and divert or prevent water entering supply before any of the standards or operational limits are breached.
The Inspectorate has set out how the existing regulatory framework applies to water recycling schemes to water companies in more detail in an Information Letter. Companies will have to demonstrate that they have met these requirements before any schemes are put into use.
Further information on the drinking water standards can be found here.
Is recycled water used elsewhere?
The use of recycled water to provide drinking water is a recognised practice internationally and has been successfully and safely used for a number of years in Singapore, Namibia, Australia and several locations in the USA.
How will I know if I am receiving recycled water?
Water companies that are proposing water recycling schemes will be consulting on their proposals as part of the water resource management plan process. The Inspectorate has been clear that engagement with consumers is a key stage when considering developing new sources of water such as recycled water and that consumers should be notified in advance of any changes of their water supply arrangements.
Will my water supply taste different if I receive recycled water?
Any change of a water source has the potential to affect the taste and feel of the drinking water supply for consumers. Water companies routinely move water around drinking water networks and introduce different sources of water to meet changes in demand, therefore they understand the challenges and how to manage them.
Recycled water which goes through membrane filtration is highly treated. Even the usual mineral content is reduced so there is the potential for recycled water to taste and feel different to the water supply consumers are typically used to. It is usual though for consumers to become accustomed to the characteristics of the new supply within a short period of time. Water companies can help make changes less noticeable by remineralising the pure water and/or blending it with existing sources of treated water and/or gradually introducing different sources.
What are the long-term implications of drinking recycled water?
Appropriate treatment of water sources reduces the presence of harmful properties, organisms and substances to provide a safe source of drinking water. As noted in a previous section companies supplying water for domestic purposes must meet the requirements of the Water Industry Act 1991 and the Water Supply (Water Quality) Regulations 2016 (as amended) and The Water Supply (Water Quality) Regulations 2018 (Wales) in full.