Changing demands on sewer and drainage systems imply changes for the professionals who work in this sector. Jeroen Langeveld spoke to The Source.
Professionals working on sewer and drainage systems make a crucial contribution to our modern, increasing high-density urban living, according to Dr Jeroen Langeveld, associate professor urban drainage and sewerage at TU Delft and chair of the IAHR/IWA joint committee on urban drainage. “Too many people take these systems for granted. Society will be completely disrupted if they don’t function.”
However, this contribution is being made by many people working in various professional fields with, to date, different outlooks. Langeveld sees that growing challenges call on the sector to develop in a number of different directions. Crucially, he also sees that this demands professionals adapt to build the integrated approaches that will be needed to meet these challenges.
Three directions for development
One current focus for developing sewer and drainage systems is on applying asset management approaches to minimise costs and maximise performance at acceptable risk. This focuses on the sewer as an underground asset to be maintained and operated for as long as possible to save money.
“In that field, the focus is on underground infrastructure,” says Langeveld. This drives a focus on aspects such as the development of inspection techniques and models that can predict survival age, he explains.
Another direction of development for the sector focuses on climate change adaptation and resilience. Here the view is that, while sewers and urban drainage are necessary, they cannot provide the total solution. Langeveld sees this leads on to approaches such as redeveloping urban areas to allow water to flow safely over the streets to where it is to be dealt with, infiltrating stormwater, or introduction of the ‘sponge city’ concept, where water is kept in the city for drier periods. In this direction, all the various ‘colours’ of urban infrastructure, whether green (urban green), blue (surface water), or red (built environment), and of water, whether black (toilet), brown (faeces), yellow (urine) or grey (household wastewater), must be included to create a robust and resilient system that benefits public health, says Langeveld.
The third axis of development is the concept of a circular economy that recovers energy, water, and all the valuable nutrients from wastewater. This approach challenges the interaction between sewers, urban drainage, and treatment plants. In particular, stormwater flows and extraneous water are seen as undesirable from an efficient recovery point of view, placing considerable requirements on the quality and performance of the sewer system.
Time for a rethink
These three approaches all pull in different directions, which is why the focus differs from place to place. “Nowhere is the full picture being covered properly,” says Langeveld. A real integrated approach towards urban drainage systems does not exist, he adds. This situation is reflected in the research world, where approaches, models and methodologies are very different in each direction, with research undertaken by different groups using different terminology. Rather, Langeveld believes that all three directions should be covered in an ideal situation.
The revision needs to start with basic thinking, even on the meaning of the term ‘urban drainage’, Langeveld believes. He notes that there are so many names for urban drainage or urban water systems that people are confused by what is meant and what such systems should do. The traditional term ‘urban drainage’ just means getting rid of stormwater as soon and safely as possible, he says, while it is now felt that limiting drainage only to that function is sub-optimal.
There are other terms, such as urban water systems, sustainable drainage systems, or low impact development, but Langeveld notes these “claim to be better in one or two directions than traditional urban drainage”. But such names are not enough in themselves to develop the field, he believes.
Part of the issue is linked to responsibility, especially what belongs to the water utility and what to the city, which can vary depending on the location. Langeveld observes that water utilities typically focus on asset management, whereas municipalities and urban developers focus on the blue-green and red aspects. Architects must also be involved, he stresses, because how they deliver their stormwater to the urban environment determines what can be done with it.
He adds: “They all have their idea about urban drainage, so a typical urban planner considers sewers as annoying rigid infrastructure that limit their creativity. And the wastewater treatment people would consider sewers as leaky infrastructure that gives too much dilution and stormwater peaks. So, they all have their perspective of what urban drainage is and how it performs.”
The subsurface sewer network can cope with storms to a certain magnitude, after which the urban environment – roads, green spaces, parks, and so on – has to cope with the excess water. This means the urban environment must be designed to ensure that when the capacity of the underground infrastructure is exceeded, the extra stormwater can be safely dealt with, which Langeveld stresses also means not building on flood-prone areas.
Beyond this, cities are set within catchments and river basins: spatial planning of flows is important and was a focus in the early days of urban drainage, Langeveld points out. Later, as cities developed, planning for water has had to follow the other functions.
Integration at the planning level
This links to a wider message of needing proper integration, of bringing more groups together and expanding the profession – for example, Langeveld says, ensuring spatial planners understand water takes the path of least resistance and take into account when planning that buildings should not be constructed in vulnerable locations, or should be modified to cope. He notes: “I think we are now at a stage [where] the blue-green transition helps to get more focus to reconnect the urban drainage to the urban planning.”
Examples of current best practice include Copenhagen, which is freeing up considerable space in the urban area for water by, for example, redeveloping the streets. “The focus internationally is on those climate change effects and the urban flooding, but at the same time, they want people to swim there,” says Langeveld.
Langeveld notes that in the big European cities, such as Paris and Amsterdam, there is an overlap between the ambition to consider climate change impacts and the need for clean rivers and seas. There is an entire dimension of integrating skills, he adds, with the biggest contribution being from the asset management aspect, in recognition of the need to minimise the money and effort expended. Digital technologies are being used to progress efficiency, Langeveld notes: “The use of sensors and smart systems is ideal to be able to get 99.5% performance out of your system.” Other issues, such as climate change, just need considerable adaptation in the urban area.
Looking at the urban groundwater community, the general view now is to infiltrate as much as possible, Langeveld observes, but if groundwater is not managed, other issues such as basement flooding arise. He therefore feels that these worlds need to be linked much more strongly. This reinforces further his message that integration, therefore, is a vital change required in the profession to meet future needs.