As climate change makes us more vulnerable to storms, floods and drought, scientists are working to protect our inner cities. Some look to nature-based solutions to tackle everything from flood risk to heat islands and from water wastage to pollution.

By Karen Thomas

As climate change makes us more vulnerable to storms, floods and drought, scientists are working to protect our inner cities to make them healthier, better places to live in. Some look to nature-based solutions to tackle natural and man-made disasters from flood risk and droughts to heat islands and from water wastage to air, water and soil pollution.

So-called blue-green synergies aim to redesign our inner cities to work with, not against, the natural environment. These can also transform the way we treat and use our water.

Conventional waste-water treatment plants (WWTPs) treat water by blowing large volumes of air into open, activated sludge ponds – a smelly process that takes up space. However, the latest generation of biology-based, engineered ecosystems uses metabolic network reactors, dynamic modelling and advanced software controls to create cleaner, more streamlined processes.

By building multifunctional bioparks around these ecosystems, we can develop WWTPs as urban oases that recycle every drop of wastewater.

Bioparks built around metabolic network reactors (MNRs) can have a much smaller footprint and offer lower capital and operating costs than conventional plants. They can be retrofitted into neighbourhoods’ metabolic hubs, designed to be aesthetically pleasing, to fit in with or even improve the local environment and architecture.

The Blue-Green Solutions (BGS) system is a Climate-KIC initiated paradigm. It unites academics, innovators, planners and technology delivery partners from across the European Union around the Blue-Green Consortium to pursue this approach.

Its aim is to rethink our waste-water treatment processes, instead recycling sludge and treated water effluent to conserve our supply, adding value and creating new business incentives.

But will water recycling – dubbed toilet-to-tap – catch on?

Thinking local

Third-generation MNR/BGS technology is the brainchild of a Hungarian inventor Istvan Kenyeres, see box, founder of the Blue-Green consortium member Biopolus. It uses fixed biofilm to concentrate the treatment process and a larger number, size and diversity of micro-organisms to clean waste water.

These more diverse organisms treat biodegradable matter in waste water more efficiently than conventional systems, shortening the processing time and delivering more efficient oxygen transfer.

This reduces the volume required, shrinking the plant’s footprint and needing about four times less energy to pump air resulting in better effluent quality at significantly lower operational costs.

The water quality is not fixed. Instead, the modular system uses a network of reactors to optimise the treatment process, adjusting the quantity and quality of treated water, from season to season, even over the course of a day, to meet changing needs in time and space.

Using fixed-film biological processes offers a cleaner approach, making it possible to incorporate WWTPs into neighbourhood bioparks that clean water in a garden-like environment.

Bioparks could make our inner-city communities greener, more pleasant place to live, says Imperial College professor Cedo Maksimovic, founder of the Blue-Green Dream project and a partner with Biopolus in the Blue-Green consortium.

The Blue-Green/Biopolus’ business model is to replace large WWTPs with a network of community-based plants, each treating and recycling water for urban clusters of between several thousand and several hundred-thousand people.

In addition to turning solid waste into energy or high-quality fertilisers for local growers, farmers and smallholders can use sludge processed at these plants into marketable products such as bio-polymers and industrial enzymes.

“The concept is, we decentralise our services – from waste-water treatment to energy and even food production – across our cities,” Prof Maksimovic says. “Using the principles of the circular economy, by positioning these plants as close as possible to the consumers, we can then recycle our waste water to absorb the useful contents of effluent.”

The plants will harness data and computer technology to optimise both water treatment and use. This cuts operating costs, enabling water-treatment firms to improve efficiency without having to charge the customer more, Prof Maksimovic says. Turning treated effluent into a resource should mean that not a single drop is wasted.

“If it costs about or slightly less than £1 per cu metre to clean water with current technologies, this system costs around 15p-20p,” he says. “In addition to using less spacefor new plants or vacating land when retrofitting the existing plants,these plants cost between 20-30 per cent less to build than conventional waste-water treatment plants and 40-50 per cent less to operate.”

Decentralised systems that use this type of WWTP achieve additional savings by doing away with expensive trunk sewers and high-capacity pumping stations.

“And so the main barrier remains infrastructure,” Prof Maksimovic says. “Although there are a few hundred first- to third-generation plants of this type successfully operating across the globe, UK water companies are reluctant to adopt this technology eitherbecause there is none operating in UK, or because they are not aware that you can retrofit to enable existing plants to make significant savings or a profit.

“I would love to see London retrofit at least one of its plant – perhaps a small one, like the one in Kingston-upon-Thames – as a teaser to show not only that this technology works but that it has multiple advantages over the existing outdated, smelly, inefficient and costly ones.”

Looking global

Examples of first- and second-generation MNT technology exist overseas. When a conventional WWTP serving 200,000 people in south Budapest was replaced with a plant using metabolic network reactors, the retrofit doubled the site’s treatment capacity and used just a quarter of the land.

“Because WWTPs can smell unpleasant, the authorities in Budapest imposed a ban on building houses on 5km2 around the plant,” Prof Maksimovic says. “So the area has been vacated for urban redevelopment.”

This example – and several others – demonstrate that retrofitting can deliver a lucrative business opportunity, he says.

In Japan’s Kyushu island, a property developer bought Kitakyushu treatment plant to redevelop the site as a metabolic hub. The new WWTP takes up 6 per cent of the original site, freeing up 4 hectares of prime inner-city real estate for redevelopment into apartments, a convention and fitness centre, commercial and green spaces. “It’s a big profit maker,” Prof Maksimovic says.

Another example, this time in the US, is a metabolic hub that is in the planning phase at the FAM University in Florida. This project is now in the final phase of detailed planning.

It features an innovative WWTP, fitted into an abandoned gym to serve the campus. This is a part of a metabolic hub that includes rainwater harvesting and recycling, fixed bio-film WWTP, use of secondary, treated effluent for aeroponicfood production.

The plant will support energy production, research labs, a communication and dissemination centre, computer centre and visitor centre.

And in The Netherlands, Trappist monks are getting in on the act, this autumn due to open an advanced WWTP in their brewery and abbey at Koningshoeven near Tilburg. The Biopulus hub will provide complete water recycling to irrigate the hop farm from which the Trappists brew their beer, along with organic waste management.

Growth markets

In Shenzhen, Apple needed to expand its electronic components production plant, bringing 60,000 more people to a 200,000-strong workforce. Expanding on this scale is equivalent to adding a small city. US-based Organica delivered a second-generation plant. This modular plant turns waste water into better-than drinking-water standard to meet that hike in production demand.

Prof Maksimovic and his partners see huge potential demand for third-generation MNRs from China and other Far East countries such as Singapore. In China, the Beijing 2 project plans brand new cities at Tongzhou and Xiong’an, to be completed in 2035, that could build in MNR plants from the outset.

A project of the size of Tongzhou’s suburban and rural neighbourhoods would need more than 120 WWT plants. Here, the MNR/BGS concept offers significant advantages over the conventional technology, Prof Maksimovic says.

And with Chinese contractors building new cities from Colombo to Cairo, successful uptake in China would position MNR/BGS technology to go global.

Meanwhile, the BGS consortium is working with UK Water contacts at a water and environmental consultancy industry in Tehran.

Iran’s dry climate makes it hard to maintain urban green spaces. The BGS consortium is looking to deliver recycled water to the city’s parks through a separate water network. Smart technology would switch from a gravity-fed water supply of the nutrients containing effluent in summer to replenish ground water in winter.

“You use waste water to irrigate the area’s green spaces and for food production, and recycle the nutrients present in this waste,” Professor Maksimovic says.

“When there is less pressure on water supply, as in winter, you release surplus treated effluent with nutrients removed to replenish ground-water stocks depleted in summer. It’s about incorporating all possible ways to reduce pressure on our drinking water resource.”

With more than 300 plants around the world adopting closed-loop water management systems, the technology is in its third generation, Prof Maksimovic says. “Unfortunately, none of these plants are in the UK.”

But urbanisation is increasing pressure on our established WWTPs. Prof Maksimovic points to Thames Water, which plans compulsory purchase orders of land and houses around its WWTP in Slough to build a larger plant.

It would be so much easier and cheaper, he says, to retrofit the existing site with space-saving metabolic network reactors. These could deliver better effluent quality at significantly lower operational costs, and release a huge chunk of land for local housing

“These technologies are proven – they are working today, in China and Japan, Canada and in Poland, France and Hungary,” he says. “There’s a conservative attitude here – a belief in being overly cautious when it comes to adopting technical innovation. But it’s also true that this technology is not yet known well here; we have to do more to promote it.

“This is the future. California has almost exhausted its natural water sources, the only viable options are to harvest storm water and to recycle treated waste water – our cities will have to go this way. There are few other possibilities to bring fresh water to big cities. We will have to recycle our water – we will no longer have the luxury of being able to throw water away.”

BOX: What is Biopolus?

Budapest-based chemical engineer and biotechnologist Istvan Kenyeres founded the Biopolus Institute in 2012, having sold an earlier waste-water treatment business, to find ways to make cities “more efficient, resilient and loveable”, he says.

Biopolus’ so-called BioMakeries are living factories blend IT and biotechnology to convert wastewater and other organic material into products to reuse or sell. They engineer the urban ecosystem to close loops for processing water, energy, food and waste, through a network of decentralised urban metabolic hubs.

Central to these are biorefineries that use Biopolus MNR technology to harvest clean water, energy, nutrients and minerals from waste water and organic waste. “The Biopolus system can be implemented in a stunning architectural form in a dense urban environment,” the company says.

Biopolus is an emerging innovator member of the Ellen Macarthur Foundation’s Circular Economy 100 group. It is also working on urban solutions to energy recovery, precision farming and food loops, and offers consultancy services on sustainable development to towns and cities around the world.

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