Blog post by Brian Arbogast, Director, WSH Bill & Melinda Gates Foundation: Debunking Sanitation Myths


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  • christoph
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Re: Blog post by Brian Arbogast, Director, WSH Bill & Melinda Gates Foundation: Debunking Sanitation Myths

Dear Cor,

Just to give you a background. I use about 30% of my time to fix wastewater treatment problems of “western sanitation”, we operate about 80 WWTP plants and do consultancy for other 40 plants, therefore I know quite well about the operation and maintenance problems of this kind of treatment. This is one of the reasons I am a supporter of non-sewer service solutions.

My problem with the study is, that they do not mention that „western sanitation“ (due to their citation with eastern roots) is really a severe problem in many countries – I just would expect some question mark about the approach. To give you an example: Peru has 143 treatment plants, in a study (2008) only about 20% (don´t nail me for the exact number but certainly less than 20%) are working properly in a country with only 35% of treatment. That is a normal number in Lain America, from what I know it is not better in Africa or Asia. I could give innumerous examples where the treatment “western style” is NO or a very limited treatment. In my eyes you can not discuss the availability for investment, without discussing the sustainability of operation (I think we see that the same way).

You mention

(low-)flush toilet (which users prefer) + sewerage + wastewater treatment + resource recovery as a good viable alternative.

Could you give an example? I think you are mixing up aspects. Resource recovery - in very modern plants or simplified by using the sludge and energy?? – ok. Low flush and septic tank or pit – ok, but low flush with sewerage and treatment and resource recovery – never heard of that example and overall with economic viability? I really would appreciate an example (in scale)
(obs: I mixed up low flush and pour flush, but the point - I would like to know an example in scale for this combination remains)

I used a UDDT indoors for many years without the mentioned smell problems and therefore I am convinced that smell problems are ALWAYS design or maintenance problems – but not systematical problems of the technology. Even though I am therefore a supporter of non sewer services by UDDT, I would was not referring just to UDDT, but to non sewer service solutions in general.

The arguments you are putting up, are aspects to consider (in parts), but they are not fundamental problems – just aspects to be considered in an evaluation. I go by your arguments one by one.

- high communication/advocacy costs needed to gain user and policy-maker acceptance

The policy maker acceptance (decision maker acceptance) is certainly a severe problem, but not an argument against the technology, just a barrier to implementation. We have to work on overcoming this.

We NEVER had any problem with user acceptance. The very, very, very nice thing about non sewer solutions is… you don´t need to convince everyone. You just work with those who want to have the technology. The difference in costs in working with every third house is almost zero for non sewer solutions, for a sewer solution this would triple the cost for the sewer (transport). When we started in the settlements of Lima in 2008 we had to explain what is UDDT etc.etc. we worked just with those interested. Today I would say over 90% of the population in the area knows what are UDDT and how they do work. The technology is well known and approved as a clean and trustworthy solution. The time would be perfect to do a large scale example there – current barrier are the policy makers.

- Economies of scale (the report you mention is based on only 10,000 users)

Certainly that is a barrier which has to be overcome, but not inherent to the solution. I would be more than happy for examples with 10.000 toilets. Definitely there is a lack – but is that an argument against?

- access to finance / costs of finance

….as any system

- costs of certification, regulation and monitoring/quality control of multiple decentralised systems

Sure I agree for decentralized TREATMENTS, but as the treatment is centralized (sanitation on wheels) this is not more critical as in sewerage systems

- lack of successful examples of large-scale applications of non-sewered urban sanitation - the UDDT project in Durban which I assume you referred to showed "low levels of satisfaction with the facilities as well as an association between perceived smell in the toilets and malfunctioning of the pedestal, and low use of UDDTs when a pit latrine is present in the dwelling perimeter"

a) you are referring to the UDDT experience – I was referring to the example that the sanitation provider ethekwini takes responsibility even for non sewer areas – as well pit latrine emptying and container toilet blocks besides conventional sanitation with sewer and treatment..
b) the Durban people are well aware of the problems and the failures – they are working hard to get them straight – that is what I admire in them.

- Developments and successes in resource recovery from wastewater treatment plants,

I don´t understand why non sewer service has to solve all problems. It is great, that it might be possible to gain an additional value out of sanitation, but for me the main point is SAFE sanitation. Resource recovery is a plus, not a must.

@ Elisabeth – I don´t have anything against sewerage (I make my living with sewerage systems) – when there is enough money available for investment and operation. I have seen too many conventional systems fail - in coverage (how many people are you able to attend with a given sum) or in sustainability of operation and maintenance. Definitely my hope for sanitation for all is in non sewer service models. Maybe that some time from now this changes. But as long as there are not several large scale models which prove me wrong – I continue thinking that this is the way forward.

Hopefully we can discuss one day about real examples.

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  • christoph
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  • Sanitary engineer with base in Brazil and Peru, doing consultancy in other countries of LA
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Re: water necessity for a sewer and calc for a non sewer model

Just two more aspects.

1. Necessity of water to flush

For a properly functioning sewer you need at least 80 l/pe,d. About 40-50 l/pe,d will come from the flush.
Lima is located in a desert area. Currently 2,5 Mio of habitants live without sanitation. Water loss is about 30%. So serving these 2,5 mio of persons equals a necessity of an additional 3.310 l/s of which 1.650 - 2.070 l/s serve only for flushing purposes (not considering leaking toilets which are VERY comon in Peru). The additional water has to come from behind the Andes or will be produced by desalinization.
In my eyes the conventional sewer sanitation just enhances the severe water provision problems.
What would be your solution?

2. "Non sewer service model" calc.

We concluded a study recently for 750 houses (not really large scale but it it financeable in this size it is in larger size for sure) for a non sewer service model. The model is based on 100% service. Semi centralized greywater treatment, urine collection and feces collection – this due to high water tables.
Calculated service cost is about 3 U$/month,household, including (almost*) all costs for operation and maintenance. This is comes to a cost per use of 2,5 Cents (3 U$/month /30 days /4 users).


*almost as the urine is transported to the existing treatment plant and we did not put additional costs for the use of the plant.
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