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Sewer system

From sewers to sludge: the revolution has begun

Civil engineers Chloe Underdown and Jamie Radford are frontline activists for faecal sludge management (FSM) as a practical cost-effective alternative to waterborne sanitation. To mark World Toilet Day, they celebrate the recent gain in momentum, as nations increasingly recognise the need for cheaper, faster waste disposal.

Currently, 2.7 billion people globally benefit from a form of faecal sludge management (FSM), whether a pit latrine or septic tank, emptied by vacuum tanker or manually with a bucket. Even so, this on-site sanitation has traditionally remained low priority in the minds of policy makers compared to gold standard sewerage projects. Turning on the taps and fitting a flushing toilet in the city centre has carried more political kudos than emptying latrines in the slums.

But no longer. Why? It comes down to bums on seats. Due to the high cost of building a city’s first sewers, typically only 5-10% of residents get connected and benefit. The remaining 90-95% in the city, and everybody on the outskirts, are no better off. Sewers are not the equitable choice. With rapid population rise already putting urban centres under pressure, FSM provides a far quicker, cheaper and more sustainable solution. Bringing 80% whole life cost savings and 15 times lower capital costs compared to sewerage, the figures for FSM are hard to ignore.

The World Bank estimates that for every dollar spent on sanitation, states can expect returns of $6 in terms of wider benefits across, for example, reduced illness, loss of economic productivity and early child death. A decade ago, FSM was the sideshow, not the main focus. Today, the culture has changed as the clear economic benefits of sanitation have risen up the agenda. As technologies become more cost-effective and the advantages of FSM are more widely communicated, we have seen policy shifts from both the World Bank and Asian Development Bank. FSM is turning from backwater to mainstream, from any other business to business as usual.

Government ministries are also recognising mass sanitation as a burning issue. Countries from Kenya, Uganda, Zambia and Ghana to India, Indonesia, Bangladesh and Nepal have recently taken steps to integrate FSM within their sanitation policies. We have seen investments in sludge strength testing, pump performance and financial modelling in recent years.

Our challenge is one of logistics. How to get the right system in place and the business models to make FSM work? The private sector increasingly involved in turning good ideas into working facilities on the ground, as entrepreneurs wise up to the commercial opportunity that this growing market presents. The prize is significant, with up to five billion people worldwide predicted to use FSM by 2030.

Waste management will become an even bigger concern within small towns: the rapid growth areas over the next 30-50 years. With no funds for expensive sewerage systems in these new hotspots, the government is faced with a choice. Does it marginally grow the system for the wealthiest in the capital, or provide baseline health standards for millions of people in the small towns? Better insight on the urban environment is also making the case for FSM. For example, a city needs to achieve around 80% coverage of community waste management to really unlock the full benefits of sanitation. Wastewater is not a feasible option.

As engineers in this specialist field, we’re more optimistic than ever that we can play an important role in addressing the basic lack of sanitation that affects 60% of the world’s population. There’s a collective drive to do the right thing. The Millennium Development Goals failed to achieve the turnaround on sanitation that they set out to do. To capitalise on the momentum that’s building behind the Sustainability Development Goals, we must act now.

The good news is that we have the tools and means to get on and do this.

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