Nature provides valuable sanitation services, says study

Nature’s role is difficult to quantify, say researchers

March 04, 2021 07:12 pm | Updated March 05, 2021 09:57 am IST - HYDERABAD

Representational image.

Representational image.

Should disposal of human waste be allowed into nature or modern engineering solutions of waste water treatment plant? A global multi-city study claims ‘Nature’ can (and does) take the role of sanitation infrastructure and strengthening natural sanitation ecosystem services may be more cost effective than equivalent investments in engineered sanitation infrastructure.

“While we are not marginalizing the vital role of engineered infrastructures, we believe a better understanding of how the engineered and natural infrastructures interact is a promising topic for further research and may allow adaptive design and management, reducing costs, and improving effectiveness and sustainability,” said researchers after studying disposal systems in 48 cities across the globe.

Prajna Paramita Mishra and Kongala Venkatesh of University of Hyderabad’s School of Economics, Simon Willcock and Indunee Welivita from the School of Natural Sciences, Bangor University, Alison Parker, Charlotte Wilson, Tim Brewer, Sarah Cooper, Dolores Rey and Paul Hutchings of the School of Water, Energy and Environment, Cranfield University, Dilshaad Bundhoo and Kenneth Lynch, School of Natural and Social Sciences, University of Gloucestershire, Sneha Mekala of Fresh Water Action Network South Asia, Hyderabad, were part of the research team whose report was published in the Journal — One Earth.

One billion people or 14% of the global population used toilets where the waste matter is disposed in situ and a further two billion people (>25% of the global population) did not have access to basic sanitation facilities with 673 million of these defecating in the open. While some of this waste may present a danger to local populations, it is likely natural processes contribute to reducing this risk.

However, nature’s role in sanitation is poorly understood and difficult to quantify due to data deficiency and hence, nature’s role in sanitation is likely “underappreciated”, is their contention. About 711 million people (~9% of the global population) have sewer connections that do not connect to wastewater treatment plants with majority of them (>90%; >640 million people) living in urban areas.

Those connected to wastewater treatment plants do not provide effective treatment or comply with effluent requirements, so at least some wastewater ends up in water courses. Here too, nature may fill a gap by transporting the high-risk sewage away from human populations, acting as a conduit for untreated sewage into wetlands or the sea, which then further dilutes and treats the waste, the report said.

It is important to understand impact of human waste on pollution-carrying capacity of various ecosystems and ensure they are not overloaded like, for example, pit latrines safely manage human waste in rural areas yet, may not be safe in urban areas where they cannot be moved and need emptying.

It also needs to be looked at what population density can nature no longer be relied upon to safely treat all the human waste produced like what quantities of human waste per unit area can mangrove, natural wetland, and marine environments safely treat? And, at what levels does the human waste risk damaging the natural environment?

Rough estimate is that nature is treating ~41.7 million tons of human waste per year worldwide worth up to US$ 4 billion a year. However, to sustainably manage this service, more research is necessary for improved collaboration between ecologists and water, sanitation, and hygiene researchers to achieve this, researchers said.

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