Conventional Sewer Systems Are Too Time-Consuming, Costly and Inflexible to Meet the Challenges of the 21st Century

Gunilla Öberg,Geneviève S. Metson,Yusuke Kuwayama,Steven A. Conrad

doi:10.3390/su12166518

Gunilla Öberg, Geneviève S. Metson + Show 2 more

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https://doi.org/10.3390/su12166518

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Abstract

There is an urgent need for innovation in the sanitation sector because the conventional model (toilet-to-sewer-to-treatment) is too time-consuming and costly, and alternatives are lacking. We estimate the challenge ahead by developing scenarios for 60 of the fastest-growing urban conglomerates in the World. We find that the majority would need to build out their sewer systems at a rate that is ten to 50 times higher than the highest rate for any project in the World Bank’s database, which is unrealistic. We also carry out a case study of Lagos, Nigeria, which suggests that, in any given year, 14–37% of Lagos State’s budget would need to be invested to provide sanitation to the presently underserviced population while keeping up with population growth, which also is unrealistic. Our study provides clear evidence that the conventional model for sanitation is unworkable for rapidly growing urban areas. We conclude there is an urgent need to encourage and fund projects that promote innovations that can tackle the three core challenges: can be built sufficiently quickly, are flexible, and affordable. This is not likely to happen unless the future generation is systematically trained and educated to creatively support innovation in sustainable sanitation.

Highlights

There is an urgent need for innovation in the sanitation sector [1,2,3,4,5]: while the conventional sewer system—i.e., water toilets connected to sewers discharging from a central treatment plant—is too resource-demanding and inflexible, none of the alternative solutions can realistically meet the challenges of the 21st century
We provide clear evidence that the conventional model for sanitation is unworkable in rapidly growing urban areas, drawing on officially available data from the World Bank and the United Nations (UN)
We estimate population growth rates, and collate data on sanitation coverage and the proportion of people living in informal settlements for the 20 fastest growing urban areas between (a) 300,000 and 5 million, (b) 5 million and 10 million, and (c) over 10 million

Summary

Introduction

There is an urgent need for innovation in the sanitation sector [1,2,3,4,5]: while the conventional sewer system—i.e., water toilets connected to sewers discharging from a central treatment plant—is too resource-demanding and inflexible, none of the alternative solutions can realistically meet the challenges of the 21st century. About a billion people live in such areas, and an increasing portion of urban population growth is taking place in informal settlements [6,7]. ‘Safe sanitation’ is commonly equated with the provision of water toilets and centralized sewers, drawing on experiences from the late 19th century in Europe and North America [11,12]. To further complicate planning and development, urban growth is often haphazard and takes place within unfavourable socio-economic structures, such as tenant–landlord relationships [14]

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