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From toilet to tap - the future of Cambridge’s drinking water?

Fancy drinking a cup of treated former sewage water? That could be the future for Greater Cambridge’s tap water as our growing population means water demand is increasing.

The toilet-to-tap suggestion is tucked away in a sustainability report for the emerging Local Plan which will take effect in 2023 and cover how much housing development is permitted for the next 20 years.

But without the water recycling project or other schemes such as piping the water from another county or building a new reservoir, it is still unclear how a large population growth could be supported.

Currently, drinking water is pumped from the chalk aquifer under Cambridgeshire, a natural underwater reservoir that contains the purest water source in the world. But it is running out, causing huge environmental impact on the River Cam.

Anglian Water treatment works North Cambridge. (27585362)
Anglian Water treatment works North Cambridge. (27585362)

The report states: “There is no environmental capacity for additional development in the new Local Plan to be supplied with water by increased abstraction from the chalk aquifer.

“Even the current level of abstraction is widely believed to be unsustainable, potentially causing environmental damage… and pressure is building to reduce abstraction rates significantly, safeguarding natural river flow. Future water demand and supply will need to be balanced in other ways”.

The plan being worked on by Cambridge City Council and South Cambridgeshire projects the building of between 3,900 and 26,300 extra homes by around 2041, which together with homes currently in the pipeline would lead to around 40,300 to 62,700 additional homes over that period.

Research into the new local plan includes an Integrated Water Management Study, published this month. It moots the possibility of recycling waste water - including water flushed down the toilet - to keep up with demand.

“Treated effluent (waste water) could… be used for potable (drinking water) supplies subject to quality standards and infrastructure,” says the report.

But it adds the “reuse of effluent” would need to be assessed to make sure rivers receiving the “treated flow” are not “detrimentally impacted by reduced river flows below sustainable levels”.

Cambridge Waste Water Treatment Plant (CWWTP) shortlisted sites for relocation. Picture: Anglian Water (40478296)
Cambridge Waste Water Treatment Plant (CWWTP) shortlisted sites for relocation. Picture: Anglian Water (40478296)

More worryingly, there were also concerns that public health is not impacted by introducing “treated effluent” into the food chain.

If the recycled water is allowed, the report considers whether they could allow water recycling centre “discharges” to fill up a Fenland reservoir. The author adds: “Water Resources East are actively investigating these options.”

Other places around the world facing severe drought, such as Toowoomba in Eastern Australia tried introducing recycled waste water into the local tap water but the scheme was met with disgust from the local population, who voted to reverse the decision in a referendum.

To treat the effluent, first, you have to filter out all of the solids. Then, in a process called reverse osmosis, you filter out small particles. Water is sometimes also sterilised with ultraviolet light.

It is assumed that significant decreases in licensed groundwater abstraction rates will not be feasible until alternative drinking water sources are available, which means that even without the huge house building schemes proposed for the region the River Cam will continue to suffer low water levels.

In the interim, the report suggests a limit could be placed on how much water is used per household.

Anglian Water treatment works North Cambridge, settlement tanks. (26175194)
Anglian Water treatment works North Cambridge, settlement tanks. (26175194)

Pete Aspley, wholesale director at Cambridge Water, said: “We recognise that there are challenges in the Greater Cambridgeshire region around the amount of proposed growth and ensuring that water supplies are both environmentally sustainable and secure, now and in the future. We are working with the planning authority and regional water resources partners to ensure that we manage water supplies over the long term and we are considering all options to remove pressures on chalk streams without impeding the economic growth of our region.

"We have all got a part to play, increasing the volume of water that is recycled within new developments is high on the planners’ agenda. We should also ensure that we minimise waste and use water wisely.

"We are fully engaged with Water Resources East (WRE), which will produce a Regional Water Resources Management Plan containing multiple options for water supply, demand management and minimising environmental impact. Along with WRE we are committed to solving the problem across the region. Within Cambridge we are currently re-introducing sources that do not abstract from the chalk aquifer and investigating bulk imports from neighbouring water companies. Longer term, we will potentially support the development of new reservoirs that will ensure there are sufficient supplies to meet everyone’s need whilst protecting our precious natural environment.

"Invariably, we’ve all got a part to play in this. We all need to recognise that water is a precious resource and that we often take it for granted. So each and every one of us needs to avoid, wherever we can, any waste or misuse of water to ensure that water is available now and in the future.”

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