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).

Christoph

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

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.

Cheers
Christoph

Yes, sorry that was not explained well.

Let me just give the government regulations in the UK for the use of treated human faeces:

Treated sewage sludge is also known as ‘biosolids’. There are two different forms of treatment - conventional and enhanced.

In conventionally treated sludge at least 99 per cent of pathogens have been destroyed. If you’re using conventionally treated sewage sludge there are rules that cover its use on:

• grazing land - you cannot surface spread. Instead, you must deep inject the sludge into the soil and leave at least three weeks until it is grazed
• land growing vegetables - there must be at least 12 months between treatment and harvest

You can apply conventionally treated sewage to the surface of grassland - or to forage crops such as maize - which will then be harvested. However, there can be no grazing on any regrowth or aftermath in the season in which you applied the sludge.

Enhanced treatment - also known as Advanced Treatment - virtually eliminates all pathogens which may have been present in the original sludge. When using enhanced treated sludge, you must:

• wait at least three weeks before grazing animals or harvesting forage crops
• wait at least ten months before harvesting fruit and vegetable crops that have been grown in direct contact with the soil and are normally eaten raw

This is for well-tested material from working treatment works. I think this advice, based on the risk of pathogen transfer in food, is good.

I hope you were not talking about "spreading faeces on food", Joe.
Just to be precise: it would be "spreading treated faeces on soil as a soil conditioner or fertiliser to grow crops of various kinds." Sorry for being pedantic, but I think it's important in case newcomers read on this forum and get totally confused.
But I think we basically agree.

By the way, SOIL in Haiti do use such compost also on cabbage, see here:
forum.susana.org/forum/categories/91-pro...icultural-activities

But that's a topic for a different thread, not for this one.

Elizabeth, that was me talking about spreading faeces on food.

I'm not sure what I think about trees, but I was mostly thinking about leafy plants that you are going to eat that may not be properly sanitised before consumption - such as cabbage, lettuce etc. I don't have any problem at all* with using it on non-food crops or on food crops with adequate controls regarding direct transfer of pathogens in food.

*well, only that there should be some agronomic need for it. And the sludge might not be particularly well balanced in terms of the needs of the crop and soil. If the soil is just being used as a dump for sewage, I'd rather see it used as a fuel, personally.

Dear all,

I have enjoyed reading this discussion and hope that the author of the blog post, Brian Arbogast, has also followed it (and perhaps wishes to comment?).

Let's not fall into the trap of having a polarising debate on sewer systems versus non-water based excreta management systems. It is not about having one or the other in my opinion. It's about having sewers and treatment plants where they make sense. And having other options where sewers and treatment plants don't make sense.

Looking back at the blog post by Brian, he wasn't totally clear what his definition of Myth # 2 is. This is what he wrote:

It would seem then that improving wastewater treatment plants and connecting them to toilets through a more reliable sewer system is the way to bring sustainable sanitation to 2 billion more people, which is a Millennium Development Goal. But that’s actually Myth No. 2. The fact is that there are simply not the resources — human and financial — to properly build and run all of the plants this approach would require.

I read it as saying:
"It is a myth to think that the ideal scenario would be that all those 2.5 billion people currently lacking access to sanitation should be connected to sewers and treatment plants as the only and ideal solution - because this would be too resource intensive."
(note he didn't talk about financial resources only but also human resources - here he is referring to all the non-technical aspects, such as operation and maintenance issues, revenue collection, management issues and so forth).

Brian, did I interpret this correctly?

Oh and so which fraction of the 2.5 billion people should rely on something different than sewers and treatment plants? I think here we should think about those people living in poverty in dynamic dense urban slums, or scattered rural areas, or people living in flood-prone areas, rocky soils etc. - all those difficult conditions that require systems that are not necessarily "buried infrastructure" like sewers and pit latrines.
What fraction of the 2.5 billion this will turn out to be, I am not sure, let me just take a wild guess and say more than 50%.

Short comment towards Jürgen Tümmler: Just because "outflow from proper sewerage & purification plants is a proven technology" doesn't mean it is necessarily good. Many cities might be on the coast but not with a vast ocean around them but e.g. a bay-type situation. Not everyone is as lucky as Sydney where there is "nothing around you", and even they are moving more towards treatment plants instead of simple ocean outfalls (partly due to intentions of reusing treated wastewater).

Jürgen also said "Where water for flushing is lacking, one might look at the use of sea water for flushing and sewerage". Sea water for flushing? I don't think so. You would get corrosion and salt build-up everywhere in the system. Plus you would first have to pipe and pump the sewater to some reservoir, then you would need a separate water distribution system to the houses just for flushing their toilets. Doesn't sound sensible to me.

Regarding your comment "Personally I would never spread any kind of treated faeces on plants that you are going to eat, and would take care when spreading it on soil that will be used to grow root crops.": we had lengthy discussions about this on the forum, see e.g. here: www.forum.susana.org/forum/categories/17...le-plants-preferably. You might enjoy reading the different positions there.

Personally, I do think that excreta-derived fertilisers make a lot of sense (with respect to long-term sustainability issues; phosphorus being a limited resource) and we are seeing more and more larger scale examples of this.
For example:
Urine for apple and cherry tree plantations in China:
www.forum.susana.org/forum/categories/91...-successful-business

Urine and faeces compost for coffee plantations in Burundi:
www.forum.susana.org/forum/categories/91...antations-in-burundi

Treated blackwater user in agriculture in Sweden:
www.forum.susana.org/forum/categories/91...a-farmer-of-the-year

Fortifer - a fertilizer manufactured from faecal sludge
www.forum.susana.org/forum/categories/98...e-1-and-2-iwmi-ghana

Yes, I know these are still "experimental" but I would say the trend to larger scales and more professional operations and businesses is clearly obvious.

And a comment towards Cor Dietforst, who said:

I believe the SuSanA forum would benefit from inviting (more) WWTP resource recovery experts and practitioners to its discussions.

Yes, please, we are very happy to have anyone on this forum who is interested in sustainable sanitation issues (be it developing countries or not). People who are working on wastewater treatment plants are very welcome. I just don't know if they have perhaps their own fora already? And if they perhaps don't have too much of a need for discussion because it's all more straight foward and nothing much to discuss (except fine engineering points, such as which alpha factor to use when designing fine bubble diffuser systems)? There are Excel spreadsheets (e.g. this one which Marcos von Sperling recently posted: www.forum.susana.org/forum/categories/39...reatment-performance, computer models, plenty of good consulting firms, contractors, lots of people with experiences... Do you have any suggestions how these people could be invited specificially and which topis they would want to discuss on such a forum?
Thanks for highlighting to us this new IWA cluster on resource recovery:
www.iwahq.org/26z/communities/clusters/i...ecovery-cluster.html
Sounds interesting. One of their objectives is:

To promote links with complementary organisations to find proper ways to build value chains where waste is converted to resources in a well-managed and beneficial way.

So there could be some synergies with SuSanA. I don't know how such a cluster would work in practice and will follow this with interest.

Regards,
Elisabeth

Juergen wrote:
Well, living and having lived before in quite a few major cities around the globe, including Delhi, Cotonou, Manila, or Ouagadougou, I can assure that the failure of decentralized system may not look spectacularly catastrophic, but has the same effects, as a failing centralized system in terms of impact on citizens' living conditions and health in those agglomerations. The absence of reliable data about the effects and the lack of GIS-based representations of those does by no means indicate there are no threats.

That's true, but not really what I meant.

If you have a large sewerage system which fails, a large number of people are affected.

If a decentralised system fails, it is more likely that individual parts of that system can be improved.

Of course, decentralisation does not mean that the system is for-certain better than a well-performing centralised system, but the risk must be lower, just because the problem is dispersed around multiple individual treatment centres.

I would always opt -with due regard to the ever increasing number of city-dwellers in most parts of the world- to put economy first, for it's the family-economy that decides in the end about the spreading rate and progress in sanitation. Where water for flushing is lacking, one might look at the use of sea water for flushing and sewerage (many, if not most of mega-urban settlements are sited along the coasts) and appropriate purification connected before letting the residues going back into the sea.

Oh I agree that economy is important, no question. All I am saying is that a lack of regard to governance and political issues is a cause of failure of centralised systems.

Use of human faeces as fertilizer is a no-go in many cultures and bears risks of some dimension, whereas an outflow from proper sewerage & purification plants is a proven technology. I do not doubt the needs of fertilizers now or in the foreseeable future, but KPN can be brought on as mineral ("chemical") fertilizer as well - the plants do not mind the difference between fertilizer and politically correct fertilizer. Problems of human nutrition will have to be solved by developments in agriculture & related technology - with greetings from a country with an official population growth rate above 3% ...

Well that is a complicated issue. I aceept, of course, that other sources of NPK fertiliser exist. In fact, I'd argue that safe disposal of faeces is more important than the actual fertiliser effect of the nutrients within the material. Personally I would never spread any kind of treated faeces on plants that you are going to eat, and would take care when spreading it on soil that will be used to grow root crops. There are plenty of good ways to land spread sludge which avoids this.

I agree that outflow of a sewerage treatment plant is a proven technology, but of course this is usually spread to agricultural land (in many European counties, at least) - albeit with tight regulations regarding the use and timing of operations.

joeturner wrote: ...The fact is that centralised systems carry with them tremendous risks. The systems require ongoing political commitment, regular and ongoing investment of capital, human resources etc. There are examples of centralised systems, recently installed, which have failed due to lack of consideration of these factors.

....

You are not wrong about the additional, perhaps uncalculated, costs of non-centralised systems, but the one thing they have in their favour is that there is no risk of catastrophic failure.

...

Well, living and having lived before in quite a few major cities around the globe, including Delhi, Cotonou, Manila, or Ouagadougou, I can assure that the failure of decentralized system may not look spectacularly catastrophic, but has the same effects, as a failing centralized system in terms of impact on citizens' living conditions and health in those agglomerations. The absence of reliable data about the effects and the lack of GIS-based representations of those does by no means indicate there are no threats.

I would always opt -with due regard to the ever increasing number of city-dwellers in most parts of the world- to put economy first, for it's the family-economy that decides in the end about the spreading rate and progress in sanitation. Where water for flushing is lacking, one might look at the use of sea water for flushing and sewerage (many, if not most of mega-urban settlements are sited along the coasts) and appropriate purification connected before letting the residues going back into the sea.

Use of human faeces as fertilizer is a no-go in many cultures and bears risks of some dimension, whereas an outflow from proper sewerage & purification plants is a proven technology. I do not doubt the needs of fertilizers now or in the foreseeable future, but KPN can be brought on as mineral ("chemical") fertilizer as well - the plants do not mind the difference between fertilizer and politically correct fertilizer. Problems of human nutrition will have to be solved by developments in agriculture & related technology - with greetings from a country with an official population growth rate above 3% ...

dietvorst wrote:
A (low-)flush toilet (which users prefer) + sewerage + wastewater treatment + resource recovery, is a sustainable, advanced sanitation service.

Calculations for non-sewered approaches need to take in account:
- high communication/advocacy costs needed to gain user and policy-maker acceptance
- economies of scale (the report you mention is based on only 10,000 users)
- access to finance / costs of finance
- costs of certification, regulation and monitoring/quality control of multiple decentralised systems
- lack of succesful 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" - washurl.net/nf9bie
- developments and successes in resource recovery from wastwater treatment plants, see for example www.ch2mhillblogs.com/water/2013/11/01/resource-recovery/ and the Dutch experiments mentioned earlier on this forum: washurl.net/c2qdyo

Well, yes - but the sustainability of a centralised sewerage system is not only related to the questions of whether it is theoretically affordable. It is not just a question of engineering and economics.

The fact is that centralised systems carry with them tremendous risks. The systems require ongoing political commitment, regular and ongoing investment of capital, human resources etc. There are examples of centralised systems, recently installed, which have failed due to lack of consideration of these factors.

And a failed centralised sytem is not worth having.

You are not wrong about the additional, perhaps uncalculated, costs of non-centralised systems, but the one thing they have in their favour is that there is no risk of catastrophic failure.

At present the 'sewer and treatment plant' model looks very attractive, particularly given the obvious benefits to the countries which have had them for decades - who are usually financing new systems. Who knows how effective they'll turn out to be in a future where even those countries struggle to find the finances and political will to keep them running.

In the end this comes down to politics and philsophy much more than engineering or economics.

Dear Christophe,

The study by Hall and Lobina links sewerage to safe disposal throughout the text, so I assume they include wastewater treatment in their calculations.

To judge their report properly, I think you should replace "sewerage" with "advanced western sanitation services". The development industry has been telling developing countries that they can't afford "advanced western sanitation services", which in many cases, as Hall and Lobina argue, is not true.

A (low-)flush toilet (which users prefer) + sewerage + wastewater treatment + resource recovery, is a sustainable, advanced sanitation service.

Calculations for non-sewered approaches need to take in account:
- high communication/advocacy costs needed to gain user and policy-maker acceptance
- economies of scale (the report you mention is based on only 10,000 users)
- access to finance / costs of finance
- costs of certification, regulation and monitoring/quality control of multiple decentralised systems
- lack of succesful 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" - washurl.net/nf9bie
- developments and successes in resource recovery from wastwater treatment plants, see for example www.ch2mhillblogs.com/water/2013/11/01/resource-recovery/ and the Dutch experiments mentioned earlier on this forum: washurl.net/c2qdyo

I believe the SuSanA forum would benefit from inviting (more) WWTP resource recovery experts and practitioners to its discussions. In September 2014 IWA plans to launch a new Cluster on Resource Recovery - www.iwahq.org/26z/communities/clusters/i...ecovery-cluster.html - at the IWA World Water Congress & Exhibition. Are any SuSanA members planning to attend this congress?

The real myth is that WWTP effluent, biosolids and septic systems are actually a sanitation solution when they are a major source of microbial and nutrient pollution.

Mixing waste with water is akin to deforestation, altering "old growth" ecosystems in bodies and bodies of water.

Dear Cor,

thanks for posting the study of Hall and Lobina. I did not know this study. This study the classical example, on how to do a good and well thought study, but unfortunately based on the wrong assumption. To make it easier to the people to follow the argument I will cite some aspects of the study, but it is worth reading it, although the base is wrong in my eyes.

The authors describe very well why improved sanitation does not mean anything.

3.1.1_What is “improved”?
This means that urban households can be counted as having “improved’”sanitation, even without a sewer connection. It also means that the health benefits of achieving the MDG on sanitation are much reduced. Evenif the MDGs are met, it has been estimated that 76 million people will die by 2020 of preventable water-related diseases.

in this regard they are in accordance to what Brian Arbogast writes

So while toilets are necessary to solve the sanitation challenges we face, they alone are not sufficient. Additional systems are necessary to prevent harmful, untreated waste from being released into the environment.

But the study just focusses on the sewer (some may say the word sewerage includes treatment – the results worldwide show the opposite). I counted. The word sewer or sewerage is present 485 times, the word plant (from treatment plant) 6 times. The study simply forgot the treatment.

But that is not my main point. The study argues

4.3.2_The ancient South Asian tradition of urban sewers
It is important to respect and use local traditions and knowledge in all countries, but this is not a reason for avoiding the development of sewerage systems. In urban environments, sewers are the traditional technology – a technology that was first developed in the ancient cities of South Asia 4,000 years ago. The first urban sewerage systems were built around 2,000 BC by the inhabitants of the great cities of the Indus Valley civilisation at Mohenjo-Daro (now in Pakistan).

When I read this I could not stop smiling – seems like the argument of not to use cars – as we always rode horses, not to use phones – as they are of the devil. There are arguments for sewers in certain situations, but certainly not the argument “we always did it like that”.

The main flaw of the study is ignoring that other ways of doing sanitation are necessary. Why do professionals ignore experiences as in Durban?

I think Brian Arbogast is more than right to write that the lack of money is a myth. We had some discussions on the forum about other ways, other approaches to calculate sanitation. We showed in a publication in 2007 that conventional sanitation is far more expensive than non sewer solutions (with complete sanitation service). (www.susana.org/lang-en/library?view=ccbktypeitem&type=2&id=961)

When you concentrate just on the most harmful part (feces) the gap between conventional sanitation and a full service model for dry sanitation (feces) comes to a factor 10 in savings for the non-sewer service solution.
There has been a discussion as well on concerning “what is affordable for poor people? – the 5% question”. As well focusing on the question sewer or non sewer services.
forum.susana.org/forum/categories/55-wg-...asonable-target#5717
forum.susana.org/forum/categories?func=v...6098&limit=1000#7274

Hall and Lobina come to the conclusion:

The need for sewerage in cities, in particular, is so fundamental that it should be incorporated as a new target in the MDGs: “To halve by 2015 the proportion of the urban population without household connections to a sewerage system.

Again – I could agree with most of the study, if it would be sanitation system instead of sewerage system.
I think the thinking in sewerage systems is the most critical barrier for the development of new approaches and therefore a barrier for the development of “fast track sanitation”.

Yours
Christoph