Pitfalls and progress: a perspective on achieving sustainable sanitation for all

Abstract

Why is it that so many people in our world still lack access to a toilet? Many developing countries have met their Millennium Development Goal target for access to clean water but still lag far behind their goal for access to improved forms of sanitation, especially in the rural and unplanned peri-urban settlements that are inhabited by the poorest of the poor. A great deal of thinking, funding, and time has been invested recently in developing clever new toilets, but there is also a need to better understand and get the most out of the sanitation facilities to which many poor people already have access, such as basic pit latrines. There is an urgent need for longer lasting, sustainable sanitation solutions, but this should look beyond just new toilet designs and include providing sanitation services, enabling community leadership in sanitation programmes, and training the in-country sanitation specialists of the future. Achieving sustainable sanitation for all is not just an engineering challenge, nor is it only for economists and social scientists; multi-disciplinary efforts are critical to achieving successful outcomes. As sanitation needs expand and justification is sought for large-scale infrastructure projects, especially in booming urban areas, greater recognition is needed that investment in sanitation infrastructure is not only about improving health, but will also ultimately lead to significant economic returns.

---

Problems with pits

An estimated 2.5 billion people lack access to improved sanitation services¹ and roughly 1.8 billion people rely on basic pit latrines.² These latrines fill up over time, and 1.2 billion urban residents are in need of faecal sludge management services.³ This number will surely grow as urban populations in developing countries double in size to over five billion by 2050.⁴ Furthermore, access to improved sanitation and safe drinking water are linked; while basic pit latrines are effective at isolating bodily wastes from human contact, they can lead to pollution of groundwater with faecal pathogens and harmful chemical pollutants such as nitrate, especially in areas with high water tables. Countries that have so far done well in improving access to clean water may see future regression in this metric if improvements in provision of sanitation do not match their successes in provision of clean water.

Much of the world's population relies on basic on-site, decentralised sanitation facilities such as pit latrines, cesspits, and septic tanks. The problem with many of these is that they fill too quickly to be sustainable. This is especially true in areas with poorly drained soils, causing the liquid fraction of the waste to be held within the pits rather than infiltrated into the soil. It is not always an option to simply dig a new pit, especially in densely populated unplanned settlements, so full pits must then be emptied, which can be costly, inconvenient and hazardous.⁵ Emptying should ideally be undertaken by a vacuum pump truck, but tankers cannot gain access to narrow streets and alleys. Alternative small-scale emptying solutions have been developed to overcome these problems, but these technologies may not be effective for all sludge types.⁵ As a result, worldwide approximately 200 million latrines and septic tanks must be manually emptied each year by workers descending into the pits equipped with buckets and spades.⁵ The final disposal of faecal sludge by any of these methods is often simply by dumping into the immediate environment. This reintroduces pathogens into the environment which were previously safely contained in the pit or tank.

The pit design characteristics and other factors that cause some pits to fill more quickly than others are not well understood. Very little is known of the physical characteristics of the faecal sludge that accumulates in pit latrines.⁶ Sanitation experts often rely upon anecdotal evidence and resort to qualitative descriptions of pit contents to compare experience in different regions. There is a similar lack of knowledge of the factors that affect pit latrine fill rates and the rate of accumulation of the especially strong sludge which is difficult to extract.⁵ Latrine management advice such as “add an old car battery” is common, as are suggestions of using moth balls, kerosene, salt, sugar, ash, fertilizer, or even a dead cat, however there is no evidence that these, or commercially available pit additives, have any beneficial effect on reducing pit fill rates.⁷ People believe that round pits are better than square, deep pits better than shallow, and wet better than dry. Some tell of mystery pits that never fill up in 30 years despite being used every day by 20 people. In the absence of scientific data, sanitation experts are forced to rely on anecdotal reports and personal observations. The lack of data and understanding of the physical properties of faecal sludge is reflected by the common use of subjective terms such as ‘wettish’,⁸ ‘chocolatey’ and ‘sticky’⁹ to describe pit contents. This makes the objective comparison of pit latrines observed in different locations almost impossible. This is also reflected in the literature by the wide range of reported sludge accumulation rates, from 19 to 95 litres per capita per annum.⁷

A number of factors will affect how quickly a pit will fill. It is a common belief amongst householders who are reliant on pit latrines that the life expectancy of a pit is mainly related to its volume, producing a strong preference for large, deep pits.¹⁰ However, deep pits are expensive to construct, and the old consolidated sludge at the base of the pit becomes practically impossible to empty by any means other than a man climbing into the pit and using a shovel. There is clearly a trade-off to be made between pit volume, capital cost, and the ability to empty the accumulated sludge. However, without an understanding of how different design factors impact on the performance of the pit it is difficult to design a long-lasting pit with any confidence. The physical dimensions of the pit are expected to impact on water drainage rates and therefore pit fill rates. Modifying the aspect ratio to give a higher surface area to volume ratio increases the proportion of sludge exposed to the soil. A deep pit will have a higher static head, and both factors should improve percolation into the soil. If drainage becomes limited the fill rate increases by an order of magnitude and the pit quickly fills with water.¹¹ A complicating factor is that latrines are often built on marginal land subject to flooding and high water table; as the water table rises, so does the sludge in the pit. In the short-term, this produces seasonal peaks in demand for pit emptying services, although the majority of the material that must be removed is actually water that has flooded into the pit from outside. The long term impact of seasonal flooding on sludge accumulation rates is unclear, although it could in some cases be beneficial, which is somewhat counter-intuitive – as the surrounding water table subsides soluble organic matter is washed out of the sludge, reducing its volume. Additionally, the influx of groundwater may ‘back-wash’ the soil in immediate contact with the sludge, counteracting the effect of soil pore clogging over time.

There is a real need for the widespread collection of data on the physical properties of faecal sludge and rigorous investigation into the factors that affect pit filling. This information would directly lead to improved sanitation services, through better management of pits to reduce fill rates and the use of appropriate pit emptying technologies to suit the sludge type. There is also a need for relatively simple and inexpensive adaptations of pit latrines to achieve improved drainage and reduced filling rates.

Nature's garbage men

Sanitation technologies using composting of faecal matter by worms may present a solution to some of these problems. Worms are nature's rubbish collectors, being extremely effective in consuming faecal matter. The idea of using worms in sanitation systems is that the rate of filling of pits with solids can be reduced, because of the net loss of biomass when the food chain is extended by using worms. By reducing both the frequency of emptying and the size of the system, this approach could be particularly suitable for high density urban and peri-urban areas. Additionally, worms are known to reduce pathogen levels in sludge¹² and the by-product is a dry material, known as vermi-compost, which is easier to handle and transport than normal pit latrine sludge.

Worms have been previously shown capable of reducing sewage sludge,^13,14 dried or pre-treated faecal matter,^15,16 and wastewater mixed with organic bulking agents.¹⁷ Larger scale community worm-based systems have also been trialled in China for the treatment of sludge^18,19 and sewage.^20,21 Commercial on-site systems are currently available in several countries including Australia and New Zealand.^22,23 Recent research has proven that worm-based latrines connected to pour-flush toilets can also be designed specifically for the developing country context as a low-cost septic tank alternative, and they have so far shown promising results in dramatically reducing latrine fill rates.²⁴

Towards sanitation service models

In Kenya, an organisation called Sanergy is proving that sanitation is about more than just providing people with toilets.²⁵ Sanergy has applied a service model that accounts for the entire sludge management train, from the toilet construction, to the emptying and sludge transport, to final waste treatment and conversion of the sludge into renewable energy or fertilizer. Most of the team members are Kenyans who reside in the communities served, and Sanergy apply a franchising approach to facilitate financing, operations, and marketing.

Sanitation service models are attractive because they address the problems that commonly occur at each stage in the sludge management train, such as poor design and construction of latrines, unavailable or unsafe latrine emptying practices, improper disposal of emptied sludge into the environment, and wasted opportunities to recover valuable resources from the sludge. Neglecting or failing at any one of these stages can negate the benefits provided at the other stages. This type of more holistic approach to sanitation service provision is worthy of further exploration and emulation in other parts of the developing world.

Teach a man to fish

The Community-Led Total Sanitation (CLTS) approach was introduced in a rural community in Bangladesh in the late 1990 s.²⁶ Aiming to bring an end to open defecation in low-income communities, the CLTS philosophy makes people aware of the health hazards associated with open defecation and incentivizes them to take action to address the problem themselves. Community-led approaches are based on the notion that in order to change situations of disadvantage, social injustice, and poor health, top-down solutions are often insufficient. Instead, affected individuals are assisted to understand the root causes of their problems and then given the opportunities to develop their own solutions.

CLTS has now been widely applied in a number of countries worldwide, with many glowing success stories. That said, there have also been cases in which CLTS has not led to safe toilet construction, and a greater level of expert technical involvement may be needed in particularly tricky areas, such as those with high water tables or where there are shortages of general construction skills and materials.²⁷ However, this should be done whilst upholding the key principles of CLTS.

In addition to community-led approaches to sanitation, there is a serious need to train more sanitation specialists within developing countries. Many developing countries have meagre levels of in-country expertise in water and sanitation engineering or public health generally, in relevant government agencies, academic institutions and the private sector. More funding programmes like the recent Africa Capacity-Building Initiative of the Royal Society and Department for International Development in the UK²⁸ should be encouraged. That programme seeks to establish links between UK universities and three African institutions on each awarded grant and is focused on building in-country expertise in priority areas, including water and sanitation. Capacity-building should also be extended to include training below university-level, for example in trades that are relevant to safe pit construction, such as masonry, and the training of school teachers for delivering public health messages related to sanitation.

Ultimately, the challenge of achieving access to sanitation for all will not be met mainly by the invention of clever new toilets, but rather by training and enabling clever people within the affected communities. Community-led approaches, behaviour change programmes, and improved courses in relevant engineering, social science, governance, and public health subjects will go a long way towards allowing developing countries to select, design, finance, implement, evaluate, and maintain their own solutions.

Putting the pieces together

The word ‘prevention’ is a nice example of how experts from different disciplines can often have widely varying conceptions of how to approach the same problem. To a public health worker thinking about disease control, ‘prevention’ evokes vaccination programmes, but to a sanitation engineer ‘prevention’ means breaking the cycle of environmental contamination and exposure through the provision of clean water, toilets and hand soap. Indeed, both preventive approaches are vitally important, but controlling many diseases in the developing world requires that both types of interventions are applied together rather than in isolation.

In 2012 the London Declaration on Neglected Tropical Diseases²⁹ recognised that controlling and eventually eradicating neglected diseases including trachoma, river blindness, and sleeping sickness will take more than just drug delivery programmes on vast scales, but should also involve partnership with those in the ‘WASH’ community (where WASH stands for water, sanitation and hygiene) to implement combined activities targeting these diseases.³⁰ For many of these diseases, the routes of transmission are different from those of the faecal-oral diseases that are more commonly associated with lack of adequate sanitation, and for some diseases, such as schistosomiasis, there is a need for evidence of which types of WASH interventions are most effective at reducing disease prevalence when implemented alongside drug delivery programmes.³¹

Health is not the only intended outcome of improved sanitation, with other objectives including ensuring personal dignity, safety, and a cleaner environment. However, narrowly focused funding programmes which support sanitation interventions on their own will have only limited health impact compared to studies that incorporate complementary multi-disciplinary solutions across all the health-relevant disciplines. Further funding should be provided to support multi-disciplinary research and interventions, to increase the chances of effective and sustainable health protection and to demonstrate the added benefits of working together.

Thinking bigger

Sanitation in urban areas presents special challenges. Increasing population densities from rapid urbanisation mean that there is often insufficient space to dig new pits when latrines are full, forcing residents to resort to unsafe manual pit emptying or open defecation.⁵ As peri-urban slum populations boom, decentralised on-site sanitation solutions may increasingly represent only short-term, ‘band-aid’ solutions. While the ‘small is beautiful’ philosophy, advocating implementing appropriate local solutions, is still relevant in providing rural sanitation and for addressing the immediate needs of the poorest urban slum dwellers, there is also a growing urgency to plan and invest in sanitation projects on much larger scales, for implementing the urban sanitation infrastructure (i.e. sewers, wastewater treatment plants, pumping stations) that will be the ultimate long-term solution to sanitation for millions of urban dwellers in developing countries.

Many in development circles are somewhat wary of this suggestion, and rightly so, given that the history of international development is littered with ‘white elephant’ projects, installed when technocrats decided that big infrastructure was the silver bullet for sanitation but neglected the necessary maintenance, in-country operator skill base, and financial and management structures required to sustain such systems in the long-term.³² However, these should be viewed as lessons from which to learn, rather than held up as evidence against attempting big infrastructure projects in the developing world.

A good return on investment

An important report published by the World Health Organization in 2012 (ref. 33) presented calculations of the benefit-to-cost ratios of water and sanitation interventions in the developing world. Such calculations inherently require many assumptions, and the report's authors took a relatively conservative approach, however a key take-home message was that every dollar invested in sanitation leads to an average of 5.5 dollars of benefit in return. Economic paybacks from improved sanitation accrue through reduced healthcare costs and more productive uses of time, for example. This is a powerful message, signifying that governments who are under-investing in sanitation in their countries are incurring a massive opportunity cost.

The conclusions of the WHO report make a lot of intuitive sense to most people, but the message that investing in sanitation is a wise economic strategy is still a slow one to be understood and taken up by many policy makers in the developing world. Multi-disciplinary demonstration studies, involving economists, policy analysts, engineers and public health experts and aimed at rigorously quantifying the benefits of sanitation at different scales (household, community, regional), in various settings (rural versus urban/peri-urban), across a range of countries, and over several time scales would re-enforce the WHO's important message and grow the evidence base for convincing policy makers that investment in sanitation really pays.

It's not a pipe dream

To summarise, sanitation for all is achievable, but it will require information gathering, innovation, and approaches that go beyond just technologies. A lot of mileage can still be got from today's common forms of basic on-site sanitation, such as pour-flush latrines, but more information is needed about how to optimally design them and manage their contents. Innovative new sanitation technologies might be required in cases where existing latrine designs cannot do the job safely or sustainably. However, sanitation technology selection and implementation should always be seen as only one part in a much wider strategy that includes community involvement in sanitation decision-making, training of the in-country sanitation leaders of tomorrow, and active participation in sanitation programmes by experts from all the relevant disciplines. These principles need to also be kept at the heart of the planning and implementation of larger scale sanitation infrastructure in booming urban areas in the developing world. Only then will access to sanitation be effective in sparking and then sustaining an upward spiral in the quality of the lives of our planet's poorest people.

Acknowledgements

The perspectives expressed in this paper are mine but have been shaped by many discussions with colleagues and students, and I wish to especially acknowledge Mansoor Ali, Tom Bond, Moussa Boukari, Serigne Faye, Dick Fenner, Claire Furlong, Walter Gibson, Jack Grimes, Wendy Harrison, Jean Patrice Jourda, Feroza Kassam, Nik Papafilippou, Jamie Radford, Steve Sugden, Yoke Pean Thye, Lindsay Todman, and Sabitri Tripathi.

References

1. WHO/UNICEF JMP for Water Supply and Sanitation, Progress on drinking water and sanitation, 2012 update, New York, USA, 2012.
2. J. P. Graham and M. L. Polizzotto, Environ. Health Perspect., 2013, 121, 521–530.
3. BCG, Omni Ingestor global market sizing project: Final deliverable part B: Complete compendium, Boston Consulting Group, 2012.
4. UN-DESA, World urbanisation prospects: The 2011 revision, Highlights, United Nations, New York, USA, 2011.
5. Y. P. Thye, M. R. Templeton and M. Ali, Crit. Rev. Environ. Sci. Technol., 2011, 41, 1793–1819.
6. J. Radford and R. Fenner, J. Water, Sanit. Hyg. Dev., 2013, 3, 375–382.
7. D. Still and K. Foxon, Tackling the challenges of full pit latrines, Volume 1: Understanding sludge accumulation in VIPs and strategies for emptying full pits, WRC Report no. 1745/1/12, Gezina, South Africa, 2012.
8. D. Still and M. O'Riordan, Tackling the challenges of full pit latrines, Volume 3: The development of pit emptying technologies, WRC Report no. 1745/3/12, Gezina, South Africa, 2012.
9. J. Harrison and D. Wilson, Towards sustainable pit latrine management through LaDePa, Second International Faecal Sludge Management Conference (FSM2), International Convention Centre, Durban, South Africa, 2012.
10. S. Sugden, Reflections on business models and technology designs for pit emptying service, Second International Faecal Sludge Management Conference (FSM2), International Convention Centre, Durban, South Africa, 2012.
11. L. C. Todman, M. H. A. van Eekert, M. R. Templeton, M. Hardy, W. T. Gibson, B. Torondel, F. Abdelahi and J. H. J. Ensink, J. Water, Sanit. Hyg. Dev. DOI:10.2166/washdev.2014.082.
12. B. R. Eastman, P. N. Kane, C. A. Edwards, L. Trytek, B. Gunadi, A. L. Stermer and J. R. Mobley, Compost Sci. Util., 2001, 9, 38–49.
13. P. M. Ndegwa, S. A. Thompson and K. C. Das, Bioresour. Technol., 2000, 71, 5–12.
14. A. Parvaresh, H. Movahedian and L. Hamidian, Iran. J. Environ. Health Sci. Eng., 2004, 1, 43–50.
15. K. D. Yadav, V. Tare and M. M. Ahammed, Waste Manage., 2010, 30, 50–56.
16. K. D. Yadav, V. Tare and M. M. Ahammed, Waste Manage., 2011, 31, 1162–1168.
17. M. Taylor, W. P. Clarke and P. E. Greenfield, Ecol. Eng., 2003, 21, 197–203.
18. M. Y. Xing, J. A. Yang, Y. Y. Wang, J. Liu and F. Yu, J. Hazard. Mater., 2011, 185, 881–888.
19. L. M. Zhao, Y. Y. Wang, J. Yang, M. Y. Xing, X. W. Li, D. H. Yi and D. H. Deng, Water Res., 2010, 44, 2572–2582.
20. M. Y. Xing, X. W. Li and J. A. Yang, Afr. J. Biotechnol., 2010, 9, 7513–7520.
21. L. Wang, F. Guo, Z. Zheng, X. Luo and J. Zhang, Bioresour. Technol., 2011, 102, 9462–9470.
22. Simple Waste Water Solutions, http://www.swwsnz.co.nz (accessed Nov 2014).
23. Biolytix, http://www.biolytix.co.za (accessed Nov 2014).
24. C. Furlong, M. R. Templeton and W. T. Gibson, J. Water, Sanit. Hyg. Dev., 2014, 4, 231–239.
25. Sanergy, saner.gy (accessed Nov 2014).
26. K. Kar, Subsidy or self-respect? Participatory total community sanitation in Bangladesh, Institute of Development Studies, Sussex, UK, 2003.
27. N. Papafilippou, M. R. Templeton and M. Ali, Int. Dev. Plann. Rev., 2011, 33, 81–94.
28. Royal Society and Department for International Development, Africa Capacity-Building Initiative, https://royalsociety.org/grants/schemes/africa-capacity-building/ (accessed Nov 2014).
29. Uniting to Combat Neglected Tropical Diseases, The London Declaration, http://unitingtocombatntds.org/resource/london-declaration (accessed Nov 2014).
30. WHO, Accelerating work to overcome the global impact of neglected tropical diseases, a roadmap for implementation, Geneva, Switzerland, 2012.
31. J. E. T. Grimes, D. Croll, W. E. Harrison, J. Utzinger, M. C. Freeman and M. R. Templeton, PLoS Neglected Trop. Dis., e0003296 , in press.
32. European Court of Auditors, European Union development assistance for drinking water supply and basic sanitation in sub-Saharan Africa, Special Report no. 13, Luxembourg, 2012.
33. WHO, Global costs and benefits of drinking-water supply and sanitation interventions to reach the MDG target and universal coverage, Geneva, Switzerland, 2012.

---