TRENCHLESS TECHNOLOGY
DEEP TUNNEL SEWERAGE SYSTEMS
Singapore’s success story
The City of Singapore (Credit: Darya Jum)
Singapore’s pioneering role in developing deep tunnel sewerage systems (DTSSs) serves as a prime example of what could be replicated by South African cities. Across the world, cities face similar challenges in terms of intensified urbanisation, poulation growth and the need to modernise decades-old wastewater infrastructure using best practice techniques. By Frank Stevens and Swen Weiner*
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ccording to the UN, 9.8 billion people will be living on the planet by 2050, with growth particularly coming from Africa and Asia. A total of 70% of that population will be urban, a 1.7-fold increase compared to 2015. Cities will have to invest massively in sewage handling capacity to serve this growing population, while climate change will further stress capacity. Additionally, extreme weather is confronting cities with high amounts of rainwater to be collected, discharged and – at least partly – treated within a short period. Diminishing surfaces for infiltration add to the problem by leaving fewer opportunities for rainwater to drain naturally. In
addition, many cities want to reuse sewage instead of discharging it into nearby rivers. In Singapore’s case, this sovereign island city-state has an area of 730 km² and a population of 5.7 million people. In addition to having the second highest population density in the world, this country boasts the second highest GDP per capita globally and Singaporeans enjoy one of the world’s longest life expectencies. Keeping up with economic growth is a clear priority and, with limited land space available, the installation of underground services is a preferred option. A DTSS is – especially from an operation cost point of view – a very cost-efficient solution to meet longterm needs for wastewater collection,
treatment and disposal. Deep sewer systems involve large-diameter main tunnels that convey wastewater by gravity to centralised treatment plants, mostly located outside cities. Smallerdiameter, often pipe-jacked, link sewers and deep shafts are further parts of these schemes. Construction of such large-scale schemes is quick and safe, with minimal impact on population and environment.
Water security
A key challenge facing Singapore is ensuring the security of its water supply, which is derived from three sources: • Imported water 40% of Singapore’s water is imported from the Johor catchment in Malaysia via a 1 km causeway. Singapore has an M AY / J U N 2022
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