Hanoi and Kampala: predictive models for TS (total solids) and emptying – and open sharing of data set (240 samples)


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  • CharlotteM
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Re: Hanoi and Kampala: predictive models for TS (total solids) and emptying – and open sharing of data set (240 samples)

Dear Linda,
Thank you for the detailed study. I have noted a lot of correlation of Kampala and various cities in Africa which will have similar characteristics. This will be based on the key parameters that are coming into play to come up with the models: Number of users, containment volume, truck volume and income level. In many instances as you have mentioned, the number of users would increase not only by being used as a public toilet or communally, but by households having many people (relatives) living together in one household. Hence, the septic tank or pit latrine that had been constructed to accommodate a specific amount of people will have to hold more waste within a shorter time. This will interfere with the emptying frequency which may now be higher. Income levels will also determine the type of sub structure that will be constructed especially in a pit latrine. It may end up being fully lined, partially lined or not lined at all. A scenario where the toilet is not lined at all may mean that there will be seepage to the soil and therefore may take longer to empty and also the emptying may require some introduction of water to help in mixing before emptying. They may also end up in abandoning the toilet altogether and constructing a new one. Of course, all these can still be factored in when making a predictive model. Thank you for this.
Charlotte Mong'ina Maua
Water and Sanitation Consultant

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  • Leader of the MEWS group (Management of Excreta, Wastewater, and Sludge) in Sandec (the Department of Sanitation, Water, and Solid Waste for Development) at Eawag (the Swiss Federal Institute of Aquatic Science and Technology)
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Hanoi and Kampala: predictive models for TS (total solids) and emptying – and open sharing of data set (240 samples)

Hi All,
We have used collected data from Hanoi and Kampala to investigate if predictive models can be built for total solids and emptying frequency. City-specific models were developed, and a cross-city model for emptying frequency of septic tanks. This first step opens the door to explore models across multiple cities and countries in able to support practitioners in making informed decisions.
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We have now made ALL of the raw characterization data collected during these studies freely available for anyone to use, 70 samples from Hanoi, and 180 samples from Kampala. The scripts are also available, providing a framework that people can use to
explore with their own data.
The data and scripts can be found here:
Open sharing of raw datasets should be encouraged, as sharing of raw research data will benefit the design of future studies, development of statistical methods, and reproducibility, transferability, and learning from results!!

Note by moderator (EvM): the conversation about open sharing of raw datasets continues in this thread .


The importance of faecal sludge management is gaining recognition. However, methods are still lacking to
reasonably estimate the quantities and qualities (Q&Q) that need to be managed, which makes the planning for
and implementing of management solutions quite difficult. The objective of this study was to collect and analyse
Q&Q of faecal sludge at a citywide scale, and to evaluate whether “SPA-DET” data (¼> spatially analysable -
demographic, environmental and technical) could then be used as predictors of Q&Q of faecal sludge. 60 field
samples and questionnaires from Hanoi and 180 from Kampala were analysed. Software tools were used in an
iterative process to predict total solids (TS) and emptying frequency in both Hanoi, Vietnam and Kampala,
Uganda. City-specific data could be predicted with types of “SPA-DET” data as input variables, and model
performance was improved by analysing septic tanks and pit latrines separately. Individual models were built for
TS concentrations and emptying frequency. In addition, a model was built across both cities for emptying frequency of septic tanks based on number of users and containment volume, indicating predictive models can be
relevant for multiple cities. Number of users, containment volume, truck volume and income level were identified as the most common variables for the correction function. Results confirm the high intrinsic variability of
faecal sludge characteristics, and illustrate the importance of moving beyond simple reporting of city-wide
average values for estimations of Q&Q. The collected data and developed scripts have been made available
for replication in future studies.
Linda Strande, PhD
Group Leader MEWS - Management of Excreta, Wastewater, and Sludge
Eawag - Swiss Federal Institute of Aquatic Science & Technology
Sandec - Department of Water & Sanitation in Developing Countries

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