Why have you constructed a rainwater reservoir in Hombeek, near the city of Mechelen?

Flanders has typically a high grade of urbanisation with a serious disorganised urban planning. Our water system is heavily modified to drain water as fast as possible, due to our landscape and historical practices. With increased paving of open area, the water system often can’t cope with the amount of runoff from a rain event. Water drains too quickly, and floods occur downstream. To cope with this common problem in Flanders, retention ponds are built, giving space to excess water during peak flows. Since we face drought related problems in the water scarce Flanders, capturing water in ponds only to discharge it afterwards seems wasteful.

A separated sewer system was constructed ten years ago in the Bankstraat in Hombeek. The local water authority (the province of Antwerp) demanded in the building permit to build a rainwater reservoir of 2170 m³ to prevent flooding. During the planning phase of the reservoir, the idea arose to use the collected water for a good purpose. Because the groundwater levels in the surrounding fields had fallen sharply due to the drought, the idea arose to infiltrate the water into nearby agricultural fields. One of the first hurdles was to ensure that the overflow from the existing sewer system could no longer be discharged with the stormwater runoff.

The retention basin as it exists now functions as a reservoir from which water will locally infiltrate in the surrounding agricultural area. This way flooding is prevented, local water is kept local, and it is used in a responsible way for the benefits of the agriculture, water- and ecosystem.

What is innovative about the reservoir?

There are quite a lot of innovations. The most impressive is the use of a weather steered gate valve to empty the reservoir in the river only when a certain amount of new rain is forecasted and there is no capacity to store it. Other innovations are:

• Coupling automated drainage level control to the need for drainage or sub-infiltration in the field, and evacuation of excess rainwater in the buffering pond. When water is available and infiltration is possible, the level is set acceptable for the crops and infiltration will occur gently until the set level is reached. When water in the rain pond must be evacuated, the drainage level control will close, and water is pumped in the fields at maximum rate. When drainage is necessary, the level control will lower, infiltration stopped, and water can drain.
• Linking of the sub-infiltration to the available water and predicted rainfall.
• A sand filter as water treatment to remove the contaminants expected in the stormwater (from pavements, roads, and roofs).

What is the current state of the reservoir?

The reservoir is ready and since December 2023 the weather steered gate valve is operational too. This is a quite a new system, not only technological, but also operational. At the start of the project the city of Mechelen was responsible for the sewer system. During the project this responsibility was transferred to the sewer utility PIDPA (public drinking water company in Antwerp). The weather steered gate valve will be the first sewer real time control implementation of PIDPA.

There are two challenges in the next six months. The first is to tackle “teething pains”. The second is the cooperation between PIDPA who is responsible for the real live operational issues (no floodings) and the three R&D partners (Aquafin, Vito, PSKW). It is a real Living Lab!

We also hope to be a leading example for the rest of Flanders. There is potential to repurpose existing and redesign planned retention basins to serve a sustainable, responsible, multifunctional purpose. The disorganised urban planning is a challenge as well as a chance. While creating the problems which ask for retention ponds, beneficiaries of rainwater storage ponds are never far off due to the mix of land use.

How is the B-WaterSmart project connected to this?

There are quite huge amounts of money involved to adapt the reservoir to make these innovations possible. It’s only because of the EU funding, that these adaptations were possible in the budget of the city of Mechelen. Also, the B-WaterSmart project makes it possible to test such adaptations to a basin with the right mix of partners. Without the support of the project, these innovations would have taken a lot longer.

What else has been done in the Living Lab in Flanders that could be considered successful?

We’ve tested a straw container to de-ironise the water that was pumped away during the building phase. The results were quite impressive. It could be interesting to reuse this kind of water e.g.  for farming in other projects. We also minimised the amount of this water to 20.000 m³, while the studies suggested we would have to pump up to 60.000 m³. This is a reduction of 66%. We measured this precisely with the use of an online flow meter on the outlet pipe. This raises awareness of the importance of the influence of construction water.

This was not an original B-WaterSmart goal, but a good example of the advantages of having an active Living Lab. It’s only by doing it in real life and real scale, that you encounter the real problems and solve them. We also have shown the benefit we can achieve by infiltrating water through a drainage system. Especially in dry periods we measured significant higher yields. This kind of experiments are important to convince farmers to cooperate in projects like B-WaterSmart.

The interview was held with Sander Bombeke (Research station for vegetables, researcher sustainable water management), Joris De Nies (Research station for vegetables, coordinator soil & water division) and Stijn Van Goethem (City Mechelen, project coordinator).

In urban areas, inland and paradoxically also in coastal regions, water constitutes an increasing challenge, due to possible scarcity and increased demand driven by economic and population growth, and quality of life. It is therefore necessary to accelerate the transformation into water-smart economies, reducing the consumption of potable water through the reuse of water in non-potable uses, among other aspects.

The Tejo park, irrigated with reclaimed water

To support urban management institutions and water utilities in making smart and climate-resilient water decisions for an efficient water-energy-nutrient balance in the cities, including safe water reuse, the Living Lab Lisbon of the B-WaterSmart (BWS) project developed methods, algorithms, and software for a smart allocation of water, delivering the following tools for integrated use:

1. Water-Energy-Phosphorus balance planning: A user-friendly solution for matchmaking water sources (potential supplies) and water demands, enabling the design of supply chain solutions (the shorter and more circular the better) to a set of potential users of non-potable water, namely, reclaimed water and other water sources alternative to those currently in use. The supply/demand alternative combinations (matches) over a target period are assessed through a range of performance and cost metrics, for supporting strategic and tactical (aligned) planning; examples of these metrics are satisfied demand, reclaimed water used, carbon footprint of energy consumption, phosphorus fertilizer production avoided, total cost.

2. Reclaimed water quality model in the distribution network: A complete hydraulic and water quality simulation model for pressure flow networks. By modelling the (bulk and wall) decay of the residual chlorine, the key barrier for water microbial stability, it aims primarily at mapping and quantifying risk in reclaimed water distribution networks.

3. Risk assessment for urban water reuse: A user-friendly solution for carrying out human health and environmental (groundwater and surface water) risk assessments, requiring a basic knowledge of risk management and the legislation applicable to water reuse. The process adopted for the qualitative risk assessment is based on relevant ISO standards and EU Regulations. A methodology for building hazard exposure scenarios was developed from scratch.

4. Environment for decision support and selection of alternative courses of action on non-potable water supply: The supply/demand alternative combinations are assessed and prioritized through a subset of standardized and user-selected key metrics.

This year, the World Youth Day (WYD), which is an international encounter with the Pope, was celebrated in Lisbon, in August 1-6, 2023. Over one million pilgrims participated in this event. The main event took place in a new green area specially developed for this occasion. This 38-ha park (built on a landfill site decommissioned in the 1990s), located near Parque Tejo (an initial Lisbon Living Lab pilot) and Beirolas Water Resource Recovery Facility, was irrigated with reclaimed water to promote faster meadow growth. Therefore, it was used as an additional pilot for demonstrating the use of three of the above mentioned BWS tools. The Lisbon municipality intends to now use all four tools to support urban management in making smart and climate-resilient water decisions for an efficient water-energy-nutrient balance in Lisbon.

The World Youth Day 2023. Credits: Carlos Silva (CML)

But the citizens of Lisbon can do their part to make Lisbon a water-smarter city too. This includes the involvement of different stakeholders in the provision and use of water, and citizens being key players in water efficiency and use. Citizens need to know their water consumption and where can they save water, and they need to know and accept that several types of source waters exist to safely satisfy the city’s needs. Sound information easily accessible and initiatives to build the citizens’ trust and acceptance of water reuse are pillars of the right decisions the citizens need to make to improve urban water sustainability. Thus, the Living Lab of Lisbon is focused on the development of software tools to facilitate safe water reuse and improve water-energy-phosphorous efficiency in non-potable uses, improving Lisbon’s climate resilience to water scarcity. Additionally, with the Lisbon Urban Water Cycle Observatory, citizens’ awareness is being increased by providing easy-to-read information on the city’s water cycle. Furthermore, the use of the Climate-Ready Certification Tool will provide improvement measures that leverage the development of water-resilient and climate-adapted buildings, contributing to the sustainable climate transition of cities. Finally, the citizens’ trust on water reuse safety is being worked out by offering VIRA beer in AdTA’s events, a beer produced with reclaimed water, and for which a protocol is being developed within B-WaterSmart. With this action we intend to help change the mindset and the perception of water reuse safety.

The information in this article were given by Pedro Teixeira (Lisbon Living Lab owner) and Maria João Rosa (Lisbon Living Lab mentor).

According to reports from the European Parliament, the European Union generates more than 2.5 billion tonnes of waste per year, a high figure that puts pressure on the environment and contributes to the consequences of the climate crisis. It is therefore essential to abandon the current linear waste management model and move towards a circular one.

In this context, and focusing on sustainable water management, Cetaqua and Aguas de Alicante are participating in B-WaterSmart to convert wastewater treatment plants into biofactories. These plants aim to obtain reclaimed water for reuse, produce renewable energy and recover nutrients in the form of fertilizers that can be reintroduced into the value chain. These objectives are being pursued at the Rincón de León Wastewater Treatment Plant (WWTP), managed by Aguas de Alicante, which is in the process of being converted into a biofactory.

Among the different processes, the anaerobic digestion of sewage sludge generates biogas, a renewable energy source that contributes to mitigating the energy crisis and reducing greenhouse gas emissions. After the anaerobic digestion, the mechanical dewatering of sludge by centrifuges generates a solid stream and a reject water stream. At Rincón de León, the use of this rejected water is being validated using an innovative treatment train to produce struvite, a phosphate mineral with numerous environmental advantages, which can be used as a fertilizer in agriculture.

Faced with the raw material supply crisis and the scarcity of fundamental elements, such as phosphorus, as well as the environmental impact derived from importing these minerals from outside the European Union, Medifer is committed to the sustainability of its products and is convinced of the potential industrial symbiosis with Aguas de Alicante to take advantage of the struvite generated from wastewater for its production of sustainable and local fertilizers.

This by-product has attracted the attention of a fertilizer producer near Rincón de León. Medifer is a leading Spanish company in the production and distribution of fertilizers that has been committed to sustainable and efficient agriculture for more than 50 years, markets more than 200,000 tons of fertilizers annually to more than 15 countries and has an annual turnover of more than €70 million.

Medifer actively participated in the first CoP (Community of Practice) meeting, organized by the Alicante Living Lab, where the company first learned about the B-WaterSmart project and the objectives pursued in Rincón de León. In addition, last December 2022, Aguas de Alicante visited the Medifer plant to explore potential synergies and collaboration opportunities within the framework of the project.

Water supply is a complex matter. The Oldenburg-East Frisian Water Board (OOWV) in Germany therefore wants to find out more about demand patterns and is using modern technology to do so. Therefore, smart metering technology is hidden under a 30-kilogram lid: in three districts in the city of Lohne, the OOWV has been measuring the flow in drinking water pipes since May as part of the EU project B-WaterSmart. A total of five probes have been installed.

„We want to create the basis for predicting water demand for a day in advance with hourly accuracy,“ explains Julia Oberdörffer, project manager at OOWV. „This will allow us to optimally control our drinking water treatment plants in future and build up water reservoirs in line with demand. So even in very hot summers with high water demand, sufficient drinking water is available at all times.“

For the OOWV, the city of Lohne is a coherent location for the project. In the past, the town’s citizens experienced pressure loss in the drinking water network, especially when consumption was high. On the one hand this is a result of the specific topography. Lohne lies higher above sea level than the rest of the supply area. Thus, the water has to be pumped uphill. „On the other hand Lohne is located exactly between three of our drinking water treatment plants and thus at the edge of the respective supply areas,“ explains Kay Schönfeld, OOWV regional manager for the district of Vechta. The drinking water therefore has to travel long distances before it can flow out of the taps in Lohne, and long distances mean high pressure losses.

The OOWV has already taken measures to deal with these challenges, which occurred especially in the hot and dry summers of recent years. A system to increase the pressure in the drinking water network has been installed and a new drinking water supply pipeline is under construction. In 2023, an additional drinking water reservoir with a volume of 1,500 cubic meters will also be built in Lohne, which will be filled at night to release its contents into the local network during the day.

The flow measurements are accompanied by an online questionnaire on socioeconomic and demographic data, which can be filled out by the citizens in the respective districts. Lohne’s mayor, Dr. Henrike Voet, welcomes the project: „This is a great opportunity to help the OOWV to better understand local requirements in our city. With these new insights we hope that our local drinking water supply system can be further optimized in a targeted manner.“

The installed probes will now record the flow, pressure and temperature of the drinking water for a year. This data will be linked to the data from the survey. In the fall of 2023, the results will be presented to the public.

The OOWV also employs merpeople.