Sanitation systems, what should they acomplish and what does it mean for re-use and disposal

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  • rcsindall
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Re: Sanitation systems, what should they acomplish and what does it mean for re-use and disposal

I'm really enjoying following this thread so first of all thank you to everyone taking part!

A couple of things that I have noticed in the last couple of posts:

1) There has been some discussion about what nutritional deficiency exist in different places. This is always going to be dependent on the soil type, the crop being grown and the farming history of the area. We know that nitrogen and phosphorus are both present in high quantities in faecal sludge (including urine) and there is general agreement that recovering those for reuse is beneficial. The exact process for doing that is never going to be one size fits all because of the variation in requirements. We don't want to have farmers using a product that is deficient in the key nutrient for their soil and crop types. We also don't want to be overloading soil with a nutrient that isn't required and will therefore leach off into watercourses when it rains. This is a great example of the need to localise sanitation and reuse systems. In an attempt to keep this post on topic, I agree that there is still a need for basic ground rules to ensure that localised reuse is done in a safe way.

2) Developing countries wanting to emulate developed countries concerns me. I agree that this happens (not all the time, but frequently) and I certainly don't blame consumers, engineers, planners and politicians in developing countries for this approach. You see something that works and that is better than the (sometimes non-existent) system that you currently have and you want that "upgrade". However, it's a really dangerous mindset and one that we all need to work to change. We have seen time and time again that developed country solutions are not guaranteed to be the right solution in developing countries. Hence the focus in Africa on FSM in an attempt to shift focus away from sewered sanitation for all. It's vital that people see good solutions that are relevant in their context. By all means, set some ground rules for what those systems are trying to achieve (as this thread is trying to do) but don't prescribe the system. With limited water resources, the effects of climate change and a need to move towards a circular economy to protect resources such as phosphorus, the developed country approach to sanitation also needs to change and adapt. Sanitation is an area where developing countries have the opportunity to leapfrog developed countries by moving towards dry sanitation systems and localised reuse systems without ever passing through the water-intensive and relatively linear economy model of sewered sanitation currently in use in developed countries.

Thanks,

Becky
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  • goeco
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Re: Sanitation systems, what should they acomplish and what does it mean for re-use and disposal

Hi Marijn,
Phosphate levels in urine are too low for use as a balanced fertiliser. On the other hand, water with very low levels of pathogens and containing high levels of balanced NPK is potentially a valuable product for agriculture. The leachate from my domestic vermifilter grows plants exceptionally well in my phosphate deficient (worse, phosphate retentive) soils.

In developing nations, consumers, engineers and planners tend (on majority) to want to emulate the lifestyle of OECD countries. This means that if we want non-sewer and re-use oriented technologies to become widely used in developing countries they first need to become widely used in developed nations.


I don't agree fully with this comment. I'll use recycling as an example... here in New Zealand recycling is very poor, with little interest from local authorities or government on reducing the huge volumes of waste going to landfill. I compare this with what is happening in India , which in my mind closely compares with ecological recycling . The problem is that huge volumes of untreated sewage are currently being used for fertilising food crops in developing (but not developed) countries because that is what is available... and there is a "market" for it. contrast this with the unsustainable mining of mineral nutrients by developed countries because they are "cost efficient".

My concern is whether we can safely assume that decentralized (or semi-centralized) solutions can reliably generate a waste water quality that is sufficient for re-use.


For me reinstating the nutrient cycle is imperative. The solution is to reuse effluents but ensure this is done safely. This doesn't have to mean burying "partially treated sludge and plant trees on top", but re-use of both liquids and solids in food crops using technological solutions. For example the added cost for twin digesters, just like twin pits, is minimal, but ensures a safe soil amendment. In my view this could be part of your "simple and relatively strict guidelines", especially "where there is a government that can enforce building standards successfully".
cheers
Dean
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  • rcsindall
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Re: Sanitation systems, what should they acomplish and what does it mean for re-use and disposal

Marijn,

As Krischan said, the Sanitation Safety Plans Manual from WHO is a good place to start. Downloadable here is a handful of languages: www.who.int/water_sanitation_health/publications/ssp-manual/en/

Becky
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  • JKMakowka
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Re: Sanitation systems, what should they acomplish and what does it mean for re-use and disposal

Marijn Zandee wrote: Do you have an introductory text on applying your risk based approach to sanitation. I would like to get my head around it a bit better.


I think she is referring to the WHO guidelines:
www.who.int/water_sanitation_health/sani...water-guidelines/en/

and maybe:
www.who.int/water_sanitation_health/publications/ssp-manual/en/
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  • Marijn Zandee
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Re: Sanitation systems, what should they acomplish and what does it mean for re-use and disposal

Dear Becky,

Do you have an introductory text on applying your risk based approach to sanitation. I would like to get my head around it a bit better.

Regards

Marijn
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Re: Sanitation systems, what should they acomplish and what does it mean for re-use and disposal

Dear Dean,

By "convenience/aesthetics" I mean the desirability of the toilet for the user. If it stinks or is not clean then people would be far more likely to avoid using it. This is a perception thing and I see it as an important function of the sanitation system and more than just a selling point.


It seems we are simply confused about what we mean with the word function. For me (as a non-native speaker) function means “What should it achieve”. In that sense I stand by my idea that lowering pathogen levels to a point where re-infection can be easily controlled with occasional use of medicine is the primary function of sanitation systems. (Note, with sanitation systems, I mean the whole system including conveyance and treatment).

When it comes to sustainability, I think there are a few different takes that all need attention.

- Social sustainability (I am not sure that is the correct term). This would cover convenience/aesthetics, but also whether the system fits with local cultural practice and whether it is aspirational enough (i.e. does it fit with people’s sense of progress and modernity).

- Economic sustainability (especially for conveyance and treatment, but also for user O&M for stand-alone systems).

- Technical sustainability. This includes durability of construction materials, availability of skilled repair workers in case something goes wrong, robustness to environmental shocks to the treatment process, etc.

-Ecological sustainability. Prevention of pollution, and recovery of nutrients, water or energy.

My interest is in onsite systems, not sewer pipes. Clearly reuse is not always an option, depending on the site. However, I just can't see that strict rules should be only around reuse and not also around discharge/disposal.


I am not saying there should not be any rules on discharge or disposal. See the discussion above on when population density is so high that simple (pit) or improved (septic tank) systems that rely on infiltration are not feasible without causing pollution. However, when water is re-used in agriculture there are higher re-infection risk then when it is soaked away. This should be reflected in how strict you make the rules.
By the way, I think the work you are doing is very good. Just to add another little pet argument of mine. In developing nations, consumers, engineers and planners tend (on majority) to want to emulate the lifestyle of OECD countries. This means that if we want non-sewer and re-use oriented technologies to become widely used in developing countries they first need to become widely used in developed nations.

If the treatment technology is simple and inexpensive and resilient (to varying loads) then provided the principle is adhered to (for example settling for removal of helminth eggs or even residence time for pathogen reduction) then risk is significantly reduced for reuse. Compare that with the current situation in many developing countries - high levels of reuse with no treatment at all... people will continue to ignore strict rules if raw or partially treated sewage is what is available.


No-one suggested that the disposal or re-use of untreated sewage was acceptable. My concern is whether we can safely assume that decentralized (or semi-centralized) solutions can reliably generate a waste water quality that is sufficient for re-use. I am not convinced we can, but I will admit that there are locations where water is a scarce enough commodity that re-use should be considered. However, for me, the default would be not to promote re-use of effluents from a better safe than sorry perspective.

There is also "fully treated" solids. Resting time can determine that and design can ensure it. For example twin vermi-digesters that rotate every 5 years when one side fills. Wait for it to fill before removing fully treated solids from the other side. Simple, reliable and safe as a soil amendment for food crops.


Yes, however, is the added cost justified for a developing world consumer considering the very small amount of soil amendment?

Soil fertility is not so much about what the soil contains, but what it is lacking - the so-called "limiting" nutrients. In most cases phosphate is the limiting nutrient for plant growth (see " peak phosphorous "), whereby it doesn't matter how much nitrogen or potassium you throw at the plants - they do not grow unless you also add phosphorous. Urine is useful only where phosphorous is not the limiting nutrient because the phosphorous in our food ends up in our feces. Feces + urine = balanced plant nutrients. The phosphate in feces is dissolved into the wastewater as treatment takes place. This is not the same issue as adding organic matter as a soil amendment.


I am aware of basic plant nutrition theory. In my experience, it is quite rare to see signs of phosphate deficiency in plants in Nepal. This indicates that phosphate is not the only nutrient that is limiting plant growth. However, I understand the risk of nitrogen only fertilization. Your comment implies that phosphate is not excreted in urine which is not true. P is both found in urine and feces. In the table attached, the properties of urine stored under field condtions in Nepal are given.
This table can be found in the following report: www.susana.org/_resources/documents/defa...thdripirrigation.pdf . It would be interseting to see the composition of the effluent of the vermi based systems to see how much closer to a “perfectly” balanced fertilizer it is.

Note, my suggestion to bury partially treated sludge and plant trees on top (for rural areas) is specifically so because it will allow the tree to use the phosphates and other remaining nutrients.

Regards

Marijn
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  • rcsindall
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Re: Sanitation systems, what should they acomplish and what does it mean for re-use and disposal

Hello,

I agree that Durban is a relatively unique environment in terms of governance but the risk-based approach still has a value elsewhere. I believe that there is a need to identify and involve government players wherever possible if they are to be involved in the long-term solution. However, in terms of applying risk-based approaches, this can be something that is done at a number of levels. In a slightly different field (flood risk), I am involved with an organisation that facilitates communities to carry out drowning risk assessments. This requires facilitation and some expert guidance to dispel myths (e.g. the river steals our children because of the spirits that live there) but the ultimate aim is for the community to identify the risks that they face and then select ways to mitigate those risks that are within their ability to implement. This sort of approach is not uncommon in disaster risk reduction and I think that similar approaches could be trialed as an extension to CLTS. It's not a perfect solution as we know that CSOs have different levels of power in different regions and even from village to village, the success of these approaches can vary based on who is involved and their level of interest. However, that is true of any project that is repeated in many locations.

I like the idea of adopting recycling to deal with MSW and would suggest that more needs to be done to consider this (both informal and formal sectors) when we talk about sanitation!

Becky
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Re: Sanitation systems, what should they acomplish and what does it mean for re-use and disposal

Hi Marijn,
By "convenience/aesthetics" I mean the desirability of the toilet for the user. If it stinks or is not clean then people would be far more likely to avoid using it. This is a perception thing and I see it as an important function of the sanitation system and more than just a selling point.

My interest is in onsite systems, not sewer pipes. Clearly reuse is not always an option, depending on the site. However, I just can't see that strict rules should be only around reuse and not also around discharge/disposal. I heard recently that even India is implementing stringent rules around effluent disposal, as strict as here in NZ.

If the treatment technology is simple and inexpensive and resilient (to varying loads) then provided the principle is adhered to (for example settling for removal of helminth eggs or even residence time for pathogen reduction) then risk is significantly reduced for reuse. Compare that with the current situation in many developing countries - high levels of reuse with no treatment at all... people will continue to ignore strict rules if raw or partially treated sewage is what is available.

Sure, some knowledge of system design is required for any system. A bit like some knowledge of diet is required to be healthy. Not insurmountable. Simple rules of thumb like a capacity of x litres per person.

There is also "fully treated" solids. Resting time can determine that and design can ensure it. For example twin vermi-digesters that rotate every 5 years when one side fills. Wait for it to fill before removing fully treated solids from the other side. Simple, reliable and safe as a soil amendment for food crops.

Soil fertility is not so much about what the soil contains, but what it is lacking - the so-called "limiting" nutrients. In most cases phosphate is the limiting nutrient for plant growth (see " peak phosphorous "), whereby it doesn't matter how much nitrogen or potassium you throw at the plants - they do not grow unless you also add phosphorous. Urine is useful only where phosphorous is not the limiting nutrient because the phosphorous in our food ends up in our feces. Feces + urine = balanced plant nutrients. The phosphate in feces is dissolved into the wastewater as treatment takes place. This is not the same issue as adding organic matter as a soil amendment.

cheers
Dean
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  • Marijn Zandee
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Re: Sanitation systems, what should they acomplish and what does it mean for re-use and disposal

Dear Becky,

I agree with am lot of what you write. I think the idea of a minimum distance between systems that rely on filtration is an interesting one.

Regarding the idea of a risk based approach. Who would asses the risks? Sanitation entrepreneurs, the local government involved in planning approval or the government level that sets standards. It is great to hear that so much research and quality/capacity improvement is going on around Durban. I think in your context it should be feasible to use a more detailed risk based approach. However, most of the people that urgently need sanitation live in areas with much weaker government and private sector capacity. (Or in places where the incentives to look the other way are stronger than those to enforce the rules :( ). How do we balance safety, affordability and re-use in a very weak governance context dominated by "cowboys"?

For fecal slurry/sludge. I think my proposals for burial are only valid for low density rural areas. For (peri) urban area's some form of (semi) centralized treatment will be needed.

Finally, regarding solid waste management. Establishing markets for recyclables (and local recycling capacity) should become a matter of priority in my view.

Regards

Marijn
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Re: Sanitation systems, what should they acomplish and what does it mean for re-use and disposal

Dear Dean,

My focus on public health comes from answering the “what should sanitation achieve” question rather than “what is a sanitation system that is in all aspects sustainable”. Convenience and aesthetics are not a function of sanitation, though I fully agree that desirability is an important selling point.
Whether my thinking will fall or not, we will see. In many ways I hope so, as I also think that nutrient recovery is important and that we should very seriously work on getting rid of the need for all these expensive sewer pipes.

The reason I am not happy to prescribe re-use of liquid effluent for irrigation is that I have become convinced of the need for very simple (and somewhat conservative) rules regarding re-use. For any sanitation technology to make a real impact, it will have to be implemented at a massive scale. This means that it will be replicated by many not very well trained masons and entrepreneurs. In this context, we will have very little control over the sizing units, etc. Obviously, this also means that treatment efficiencies will vary. Perhaps, in a country where there is a government that can enforce building standards successfully one could promote re-use of the liquid effluents.
The distinction between “fresh” and “partially treated” sludge/solids is by no means there to suggest that partially treated sludge is safe. It is there to make a useful decision about how many protective measures are needed for those working with it. Yes, helminths will survive much longer than 6 months. This is why I think the slurry/sludge (in a low population context) should be used for tree planting or burial in a forest area (if available). I see this as a reasonable compromise between some re-use value for the organics and some nutrients, and the intention to separate the helminths from the population.

I am not at all convinced by your statement that urine is that much worse a fertilizer than effluent. Any fertilizer should be used together with a certain amount of organic material to keep soils healthy. Perhaps you can start trying to convince me by comparing the nutrient values of effluents (treated to a safe standard) with those of urine.

Regards

Marijn
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Re: Sanitation systems, what should they acomplish and what does it mean for re-use and disposal

Hi Marjin;

In all my years of working in water and sanitation, I have far to often seen people not pay attention to sustainability when it comes to sanitation. By this I mean four things:

1. All domestic wastewater whether from toilets, bathrooms, kitchens or washing areas must be collected and treated. It makes no sense to focus only on toilets as that leaves dirty greywater with its own loads of health issues flowing down streets and streams potentially creating space for mosquitoes and other diseases to spread. Further putting toilet wastewater in the ground via soak pits is incredibly stupid as all it does is collect the solid and leave the untreated liquid to contaminate nearby water sources - remember it's not a case of just a couple of litres or less per use but that same water mixes with the larger amount of greywater soaking into the ground and then can affect a larger area. Also in the monsoons the solids can also liquify again, a fact often ignored, and create a even larger problem.

2. The beneficiaries must be able to operate the system installed both technically and financially. If this is not done we are looking at beneficiaries continuously forced to seek handouts whether via Corporate cCR or Government. Not an ideal solution by far.

3. The treated water must be reusable for at least agricultural field irrigation in rural areas as this can in essence augment available resources throughout the year. In urban areas, landscaping use is possibly the best option.

4. Finally the solution deployed must be a community based solution and not individual based. By this I mean while individuals can have their own toilets/bathrooms, the community must be responsible for the network and treatment solution used. this has a major advantage as it is much more difficult to revert to outdoor defecation if your community is watching you.

Do all this and I think the rest is easy...

I say this with confidence as we did just this side by side with the Nalanda Foundation (IL&FS) at a tribal village and you should see how happy the villagers are today. It is by the way 100% ODF as well and not by the government definition of just toilets build but 100% recycle and reuse of all domestic wastewater. By the way cases of Diarrhea have dropped to zero over the last year.

With regards,
Sanjay
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  • rcsindall
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Re: Sanitation systems, what should they acomplish and what does it mean for re-use and disposal

Hello,

I think this is an interesting discussion. WHO defines sanitation as follows: "Sanitation generally refers to the provision of facilities and services for the safe disposal of human urine and faeces. ... The word 'sanitation' also refers to the maintenance of hygienic conditions, through services such as garbage collection and wastewater disposal." Therefore a sanitation system would be a system that provides for the safe disposal (or re-use) of human urine and faeces. The aim of sanitation is certainly one of removing causes of disease and having a positive impact on health at household and community level.

However, "safe" can only really be defined used a risk-based approach. As you quite rightly point out, water that is safe to put on the garden is not guaranteed to be safe to drink. That means that we need to understand the potential uses of the products that come from a sanitation system before we decide whether they are safe.

With liquid effluents, the suggestions that you make are sensible. You have accounted for the height of the water table (variations due to season should be considered here too), and the proximity of water systems. The proximity of other infiltration systems that you allude to with critical population density is very important and a way to look at this may be the minimum distance required between infiltration systems. If you cannot cater for a community whilst maintaining those minimum distances, a sanitation system that does not rely on infiltration is likely to be a safer option.

In terms of the secondary treatment of liquid effluents, I am not clear what you are referring to. Would this be something like a DEWATS? There is a lot of work going into the safety of irrigating crops for human consumption with DEWATS effluent here in Durban. The results look promising so far but there will always be some crops that are safer to irrigate with treated water than others. Back to the risk-based approach!

As for your comments on private sector operators, this is where policy is important. eThekwini Municipality are currently in the process of writing a policy for construction and operation of DEWATS. It will detail the stages that private operators need to go through in the design and construction of the systems and minimum staffing requirements and O&M capacity that must be in place. That helps to reduce the risk of private operators acting like cowboys.

For solids and sludge, emptying "fresh" faecal material using a vacuum tanker may not always be an option. In Durban, pits tend to be very dry and the rheology is not conducive to pumping out unless you add huge volumes of water first (not a popular option in a drought-prone area). The other challenge with pumping out pits is trash, which is where the other part of the WHO definition of sanitation is useful. If we had an effective trash collection service for all of Durban, we would remove a large chunk of our sanitation problems! Once again, we need to consider the risks. In Durban, pits are emptied manually so pit-emptiers are trained on the safest way to do the job and given the equipment and PPE to do the job in accordance with that training.

Finally, I think that limiting partially treated sludge to reuse for soil amendment is too simplistic. There are many options for solid products depending on the treatment process and extent of treatment, as well as the local market. Soil amendment is one option, bioenergy products or animals feeds are also being considered here in Durban and elsewhere. As Dean says, cost efficiency of a system is key and that may rely on selecting the right product for the local market.

Broad guidelines for sanitation are always going to be a challenge. There are too many variations in context for solutions to be straight-forward and easily copy-pasted from place to place. However, by moving away from these kind of broad guidelines to a risk-based approach we can improve existing systems and ensure the design of new systems are fit for purpose.

Looking forward to further views or comments on this!

Thanks,

Becky
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