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UNICEF Innovation

Latrine Additives Evaluation

The Challenge

UNICEF supports the construction and maintenance of pit latrines in both emergency and non-emergency settings. Though the latrines do effectively isolate faeces and associated illness-causing bacteria and viruses, the use and maintenance of latrines can be problematic. The following three issues are regularly raised by end-users and latrine owners:

  • Latrine odour is too strong to actually use the latrine

  • Flies and other bugs can be present in large numbers

  • The latrine pit emptying is expensive and required too frequently

In addition to these issues, it is also a concern as to where the sludge is being discharged after a latrine has been emptied as there are no formal disposal systems in many countries.

There has long been an interest in developing a latrine additive that could be used to compact and/or assist decomposition of faecal sludge while it is still in the pit latrine to reduce latrine emptying frequency. In addition, there is a need for smell reduction and fly control, in order to encourage more use of the latrines by individuals and communities. In 2013, UNICEF field experience with a specific micro-organism-based product in Uganda was documented as showing immediate results with smell reduction, as well as an observed sludge reduction in 16 of the study’s best performing school pit latrines, as recorded by the teacher/students out of a group of 40 school latrines. However, several products have been commercially available for years that claim to achieve the desired impact but actual field results have been mixed.

UNICEF's Response

To gather more rigorous evidence on potential solutions, the Innovation Unit and Water & Sanitation Centre at UNICEF Supply Division is conducted a double-blind randomized control trial in 2014. Three products and one placebo were tested in 155 school pit latrines in Uganda’s Jinja district over a period of 8 weeks. The products were evaluated on their ability to 1) reduce, or slow sludge accumulation rates, 2) reduce smell, and 3) reduce presence of flies. 

Results and Project Closure

Results show that the pits treated with microorganism-based latrine additive products were able to marginally reduce accumulation rates compared to the placebo with varying statistical significance.  All four product groups, including the placebo, showed positive impact on smell and flies.  As such the study does not provide evidence for or against additive impact on smell/flies. The full study results can be found here: https://intranet.unicef.org/denmark/danhomepage.nsf/0/13fbfd56199744c6c1257eeb0046eb2d?open&expandlevel=mainlevel1&expandlevel2=secondlevel6&expandlevel3=thirdlevel24 

In comparison to the case study by the Uganda Country Office, this study was not able to replicate the same impact on sludge reduction, and offers a much more conservative estimate of the additives’ impact on sludge. In addition, the previous case study reported the control group (where no product or placebo was added) reported no change in smell, whereas this study recorded a reduction in smell in all treatment groups, including in the placebo group.

However, it is impossible to extrapolate the results of this study to longer time frames, use in household latrines, latrines in emergencies, latrines with different designs (e.g., sealed) or latrines in different climates or with different geophysical conditions.

For governments or schools interested in purchasing commercially available latrine additive products, it is important to consider all costs of product application, including calculating the utility of initiating an additive project.  If this study is an indication, it is unlikely that the 5% reduction (the difference between the placebo and the additive) in accumulation would extend the life of a large, shared school pit enough to justify daily or weekly application of a product—which would include training, transport, and teacher staff time.

In September 2015, the project was closed as a UNICEF Supply Division Innovation project. While borderline statistical significance was shown in reduction in sludge accumulation rates, the reduction amount is not significant enough to warrant recommending the use of latrine additives for school pit latrines.  In addition, research on the use of latrine additives, faecal sludge accumulation, and emergency waste management is currently ongoing by other organizations.  



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