It’s time to change how we think about water within housing developments, towns and cities, reversing our dependence on using water only once.
For too long, the linear model of ‘take, make, consume, and waste’ has dominated, with water abstracted from the natural environment, ‘made’ drinkable through treatment, used by humans and then discharged back to the environment. Currently, over 80% of wastewater generated by society flows back into the environment without being treated or reused.
This model is increasingly unsustainable. On a global level, the United Nations predicts that demand for fresh water will exceed supply by 40% by 2030 if current practices continue. Closer to home, 2022 saw England experience its driest July since 1935 and these drought events are set to repeat as the effects of climate change intensify, bringing higher temperatures and increased evaporation. Concentrated rainfall will become more frequent, but the parched soil won’t be able to absorb such large quantities of water, leading instead to runoff and flash flooding.
In April, the government publshed its integrated plan to deliver clean and plentiful water, in which it pledges to transform the whole water system to make sure it is fit to deliver for water supply and the environment by addressing the sources of pollution in our water bodies and closing the 4 billion litre a day supply-demand gap in public water supply whilst also contriuting the to the recovery of nature, achieving Net Zero and provding addiitonal public health and wellbeing benefits.
The natural environment is going to struggle to support our single-use water approach, so what’s the alternative?
A step change to circular water management
We need to disrupt the current unsustainable linear model and introduce a circular economy water framework that emphasises reusing and recycling water. This is a considerable task, requiring a rethink of the entire water cycle and a shift in our relationship with resources to one of stewardship, where resources are reused for as long as possible.
Martin Lambley, Product Manager for Urban Climate Resilience, Wavin sums up the value of water reuse: “water reuse tackles both flooding and shortage, working with our ‘up-down’ water cycle whereby reservoirs run low every summer, but we drain this water away in the winter. By reusing water, drainage capacity issues are circumvented – reducing flooding and stormwater discharges - while also addressing shortages in useable water for communities”.
The idea of a circular water economy is well established; European Union policy identifies the use of treated wastewater as one potential solution to water scarcity, and the International Water Association has taken this further, developing the 5Rs approach to water management:
• reduce: reduce water losses and boost water efficiency
• reuse: reuse water, with minimal or no treatment
• recycle: recycle resources and wastewater (treated by membrane or reverse osmosis to a very high quality)
• restore: return water of a specific quality to where it was taken from
• recover: take resources (other than water) out of wastewater and put them to use.
The future will be blue-green
The good news is that the growing blue-green infrastructure movement is the ideal environment to nurture water reuse and recycling.
It moves away from grey infrastructure, that’s heavily focused on concrete-based drainage designed to take water out of the built environment as quickly as possible, with no options for reuse or recycling. The era of grey is ending because systems such as surface water gullies, culverts and channel drains are easily overwhelmed by periods of extreme heavy rainfall, leading to flooding. There’s also growing momentum for a more sustainable approach to managing the built environment – one that preserves biodiversity and minimises the depletion of resources such as water.
In contrast, blue-green infrastructure uses blue elements, like rivers, canals, ponds, wetlands, floodplains, and water treatment facilities, and green elements, such as trees, forests, fields and parks, in urban and land-use planning. In a blue-green world, developers use green spaces to take a more natural approach to urban drainage, enabling water to be controlled closer to the source. Increasingly, sustainable drainage systems (SuDS) are being used to address urban water challenges and generate environmental and societal co-benefits.
“Blue-green infrastructure is a term we’re going to see more and more, and it’s really important that this idea starts to lodge with people, particularly in terms of sustainable drainage systems (SuDS). There are three drivers in the immediate term: developers are recognising how attractive buyers find a green housing area, the cost of installing SuDS is now no more than those of traditional drainage, and policy makers are strengthening their approaches.”
Martin Lambley, Product Manager for Urban Climate Resilience, Wavin
At their core, blue-green infrastructure projects integrate environmental components and natural assets into an urban landscape to create and promote more sustainable ecosystems. The key focus is on holding water within the immediate environment by storing, infiltrating and harvesting it for reuse. Ultimately, blue-green infrastructure will allow the whole water cycle to occur within the urban setting. It will reduce pollution in the air, irrigate parks, provide local drinking water and prevent harms like flooding. Plus, it will provide natural cleaning agents, reducing the amount of contaminants and sediment in surface water runoff through settlement or the biological breakdown of pollutants.
Although the concept is far-reaching, blue-green infrastructure is already a practical part of new developments through the incorporation of SuDS schemes into sites. The regulatory environment is tightening, encouraging greater use of SuDS to promote infiltration (where runoff naturally soaks into the ground), evaporation from surface water and transpiration from vegetation (evapo-transpiration). Across the UK, rain gardens, bioswales and wetlands are in action, collecting rain and filtering contaminants out into the soil, and urban trees, small parks, green roofs and green walls are all contributing to reducing surface water runoff.
Regulations encourage water reuse and recycling
The next frontier for blue-green infrastructure is to embed water reuse and recycling into new developments, keeping more of the whole water cycle in the urban environment, and reducing the calls on freshwater supplies.
In the UK, legislation has opened the door for this change. Part G of the Building Regulations introduced a requirement that, for any new dwelling, the potential wholesome (or potable) water consumption should not exceed 125 litres per person per day. To help achieve this, the regulations allow for the use of non-wholesome water – defined as rainwater and greywater - for toilet and urinal flushing, washing machines and irrigation, provided an appropriate risk assessment has been carried out. The risk assessment should ensure that any rainwater or greywater system does not cause waste, misuse, undue consumption or contamination of wholesome water.
Further guidance comes from BS 8525-1:2010 on greywater systems, giving recommendations on the design, installation, alteration, testing and maintenance of greywater systems utilising bathroom greywater to supply non-potable water in the UK. And BS EN 16941-1 discusses rainwater harvesting systems, specifying the requirements and giving recommendations for the design, sizing, installation, identification, commissioning and maintenance of rainwater harvesting systems for the use of rainwater on-site as non-potable water.
The Environment Agency is also supportive of rainwater use, stating that it won’t regulate harvested rainwater provided its use doesn’t harm the environment – either alone or combined with other abstractions or transfers. It only stipulates that rainwater harvesting within a catchment mustn’t affect the normal watercourse flow.
Think greywater recycling
The environmental potential of reusing greywater – the wastewater from baths, showers, washing machines, dishwashers and sinks – is huge. Greywater typically makes up between 50-80% of a household’s wastewater. If recycled properly, greywater can save approximately 70 litres of potable water per person per day in domestic households.
Greywater reuse systems vary significantly in their complexity and size, from small systems with very simple treatment, to large systems with more intricate treatment processes. However, most include a tank for storing the treated water, a pump and distribution system to move the treated water to where it’s needed, and a method of treatment. Any system that stores greywater must include some sort of treatment to avoid rapid deterioration in quality due to the bacterial growth that occurs when organic matter (such as skin, hair, soap and detergent) is mixed with warm water.
The BSI defines the range of greywater systems according to the type of filtration or treatment they use:
• direct reuse systems, with no treatment and minimal, or no, storage
• short retention systems, using a rudimentary filtration or treatment method, such as skimming debris off the surface and allowing particles to settle to the bottom of a tank. They tackle smell and water quality issues by not storing the greywater for long
• basic physical or chemical systems, filtering out debris and using chemical disinfectants to stop bacterial growth
• biological systems, using aerobic or anaerobic bacteria to digest any unwanted organic material in the collected greywater
• biomechanical systems, combining biological and physical treatment, and encouraging bacterial activity by bubbling oxygen through the collected greywater
• hybrid systems, that mix the above approaches.
Think rainwater harvesting
Rainwater harvesting is also a strong option for developers wanting to reduce potable water use in their housing. Harvested rainwater is collected from roofs and other above-ground surfaces via a system of above ground pipes and tanks. The water captured is separate from inland waters or groundwater.
The process involved is standard, involving channelling the rainwater that falls onto a roof through guttering and downpipes into a storage tank, via a filter that prevents any leaves, moss or debris from getting into the tank. The clean rainwater is stored in the tank, ready to be pumped to its point of use – an outside tap, a toilet or a washing machine.
In many developments, the decision between installing a greywater reuse system or a rainwater harvesting option will be the size of the roof available and the space that can be found to hold the necessary storage tanks.
Build circular water management into future developments
Although the blue-green infrastructure movement is gathering momentum, wholesale transformation will require a culture change. There must be a shift from seeing water and its supply, transport and drainage as add-on infrastructure, to viewing it as an integral part of our living environment.
The stakes are high. Blue-green infrastructure has the potential to help urban communities adapt to the impact of climate change by managing flood risk, mitigating the urban heat island effect and reducing the drought risk.
But realising this potential, and valuing water as a finite resource, will take government backing, whether via mandates, introducing new national or local standards, or changes to planning policy.
Spearhead the transformation with a water performance certificate
Introducing a water performance certificate for every home could be a strong starting point for increasing awareness of the importance of water management.
Martin Lambley, Product Manager for Urban Climate Resilience at Wavin has long been an advocate: “When you buy or rent a house, you have to have an electricity performance certificate, so why not have one for water efficiency? There are lots of things it could be based on – is it on a combined sewer or a separate sewer? Are there SuDS on site? Are there low-flush toilets fitted? The critical thing is, this needs to be driven nationally. It needs to become part of standard house-buying documents.”
There’s a growing movement of support for such a simple, yet transformative measure. Taking away the assumption that every home will use potable water for everything could shift thinking among the water use chain – the water and construction industries, regulatory bodies and citizens - towards a more circular water economy.
In many ways, it’s about thinking bigger.
Vicki Westall, Flood and Water Management Co-ordinator – Strategy, at Hampshire County Council highlights grassroots activity: “Why aren’t we putting tech in so that when we have water, we keep it and use it when we need it? Why are we dumping clean water? Grey water reuse is essential. [Some organisations have looked] at producing a flood certificate, similar to an energy certificate. It’s coming out in water utensil markets already, but we want to do this for homes”.
So, given how critical it is that we reverse our dependence on using water only once – what changes can you make to your construction and development practices?
