Re-thinking wastewater infrastructure in times of crisis and rapid urbanisation

Winston Churchill famously said that ‘we shape our buildings, and afterwards our buildings shape us.’ Past planning and investment decisions related to housing, transport, water or energy infrastructure helps determine how we live today. They shape how we manage current challenges and how we deliver infrastructure services like the treatment of water. However, past infrastructure decisions and choices on technology can result in lock-ins and path-dependencies that limit future development and hamper the flexibility to adapt to change. Inflexible infrastructure systems can leave cities vulnerable to unexpected crisis and established systems, when faced with unexpected events or fast-moving trends like urbanisation, can struggle to rapidly react to changes in emerging demands. However,

The case of wastewater infrastructure

One infrastructure challenge is the treatment of wastewater. In the developing world wastewater is discharged untreated into the environment approximately 90% of the time. Ancient clay-based drainage systems or roman home water distribution systems returned used water back to the environment. Today, digital simulation and planning software enables us to rapidly design concrete sewer pipe layouts, steel-reinforced manholes and pumping stations that transport sewage to distant treatment plants. However the basic approach on how we deal with wastewater has remained remarkably similar to ancient times, namely to transport waste away from the city. In OECD countries the centralised wastewater management approach has resulted in vast, capital intensive concrete based sewer systems over the last two centuries.

Persistent and systemic challenges related to construction and maintenance prevail. For example, in the US alone, an estimated US$271 billion is needed for wastewater infrastructure over the next 25 years and up to 75,000 sewer spills occur every year. Crucially, the imitation of such a centralised approach without regarding the local context results in various issues. In the UAE hypersaline groundwater infiltration compromises wastewater treatment stations and their ability to reuse water for irrigation. In Lebanon, international donors have invested in wastewater sewage treatment plants that have never operated as intended because the necessary sewage networks haven’t been constructed.

Decentralised technology as an alternative to centralised wastewater infrastructure

The ongoing data and sensing revolution facilitates novel decentralised infrastructure concepts and one such way to rethink wastewater infrastructure is decentralised wastewater treatment. Decentralised systems do not rely on expensive construction and maintenance of sewer networks. The modularity of small-scale and decentralised wastewater infrastructure is an opportunity for decision-makers to quickly address the sanitation crisis. BiomWeb is one such emerging technological example based on onsite treatment and smart monitoring that doesn’t depend on the availability of extensive sewer networks. We argue that re-thinking the conventional approach to wastewater management through decentralised, modular and small-scale systems has advantages which need to be properly evaluated. However, innovation in the wastewater sector has typically been slow and other sectors have been better in putting agility at their core and implementing policies for continuous replacement and reconfiguration or upgrading of subsystems.

We propose that actors in the traditional civil infrastructure sector need to compare the sustainability and resilience of both approaches for their geographic context and consider the feasibility and speed of implementation of their proposed solutions. Doing so will allow decision-makers to better assess policies and evaluate how a region or city can rapidly adapt to the urgent needs of rapid urbanisation and open the door to innovative emerging technologies.

About the authors

Ziad Hussami is an experienced sustainability consultant and co-founder of Mruna. Mruna is the developer of BiomWeb and winner of the GI Hub’s 2020 InfraChallenge. BiomWeb is an onsite wastewater treatment system that harnesses the power of nature and emerging remote monitoring technologies to decentralize and disrupt the sanitation infrastructure sector. He holds a graduate Planning degree from the University of Southern California (MPL High honors) and undergraduate degrees in Biology (B.S) & International Studies (B.A.) from the University of California Irvine. He is accredited and certified iconic projects under the following rating systems LEED, CEEQUAL, Esitdama, GSAS.

Dr. Sven Eggimann is an experienced researcher of next-generation urban infrastructure systems. His particular expertise and interest lie in sustainable transitions of current infrastructure systems, sustainable planning, geospatial analysis and next-generation infrastructures. He works as a Scientist at EMPA, Switzerland. He received PhD at the Swiss Federal Institute of Aquatic Science and Technology (EAWAG) and at the Swiss Federal Institute of Technology (ETH). In his PhD thesis he analysed the potential for a sustainability transition of decentralised wastewater treatment systems and the role of smart technology.

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