christian.rieck wrote: @Julius, could you share pictures from the artifial fish breeding areas under the floating villages of Halong Bay in Vietnam?

Here you go:


Edit: I *think* they are used for fish breeding, but maybe someone knows better? Might be for mussels?

Dear Analiza and Julius,
Thank you for this valuable input. I agree with you that UDDTs, Terra Preta and similar dry sanitation technologies are not suitable for this flood-prone area. That is why we have so far settle on pour flush toilets with a water-tight septic tank. However the discharge of effluent from the septic tanks is yet unclear. I thought to infiltrate it into the ground which would automatically happen during low tide, however I am not sure if the ground has the capacity to soak water. There was also an option mentioned in this discussion with a floating pipe to the sea, but that seem technically not easily feasible.

The suggestion from Julius on the aquaculture option seems very promising to me. We could use the pre-treated effluent from the septic tank and use it in a fish pond or artificial reef. In Darumawang they told me (I was there myself) and the other colleagues that they once had something like a fish pond, but somehow this project has failed. Not sure why, but a reasonable option to follow up.

@Julius, could you share pictures from the artifial fish breeding areas under the floating villages of Halong Bay in Vietnam?

I am attaching a sketch of the proposed toilet setup for the school. Please feel free to comment on it.

Best,
Christian

HI Christian,
Thank you for this option..

Terra Preta is wonderful, but i am still into pour flush with a water proof septic tank since charcoal is very much limited in island areas...


Thanks..

Analiza

Hi Christian,
I just visited Duramawang Elementary School, in the Philippines, which is a flooded area and I think you visited there as well...(i am not sure if you are the same Christian who visited there).

When I saw the area, i came to realize that UDDT is never a best or better option due to the difficulty of procuring resources within the area for maintaining and operating the UDDT...besides it's difficult to transport materials(e.g. sawdust, charcoal, etc) needed for daily operation for UDDT.
On the other hand, toilets with simple or conventional septic tanks is never an option as well since it is really a flooded area...
My opinion as better sanitation facility option for flooded area would be:
1.constructing a pour flush toilet
2. have a water proof septic tank
Treatment option: once the water proof septic tank is full, it will be locally desludge and placed in the pit which is lined with a thick plastic lining or tarpaulin to avoid groundwater or sea contamination. Once the sludge is already in the pit, it will then be treated through raising pH to 14 .

The problem I see with any kind of composting solution is that as far as I understood there is no substantial agricultural activities on these islands, and thus little motivation to acquire good organic fertilizer.
A bucket toilet might work just fine, however I really wouldn't be surprised if after a short time people just start dumping the contents into the backyard/ocean again.

Therefore my idea to implement an artificial reef for fish breeding. In north Vietnam I have seen a quite interesting way of making artifial fish breeding areas under the floating villages of Halong Bay. Basically they hang a lot of sand filled buckets under their floating rafts, and due to the high nutrient (the water is completely green from algae), shallow and calm waters of that area, it becomes a perfect breeding ground.

Well... sure this is probably not the perfect reuse of human remains, but one of the few where I actually see some benefit for the communities, and as the fish are (usually) not consumed directly/immediately, the negative health impact is probably relatively low.

Dear Analiza,
I am looking forward to the response from the engineer of your university. I am sure there are more option we can look at. During my work I have just come across the Terra Preta approach which could in theory also work for this school. As they use firewood and charcoal as well for cooking there is enough supply of grounded charcoal available. Please have a look at the presentation by Jan Spit held at the workshop on emergency sanitation in Delft a few weeks ago www.susana.org/lang-en/working-groups/wg...therlands-june-2012-



Would Terra Preta be a future option?

Regards,
Christian

Considering that Philippine is an archipelago, this is just one of the many schools or areas challenged with same issue.
I spoke with an engineer in my university when i saw this topic under discussion, and he is willing to come up with a design for areas like this.
Zandee,yes, i would agree to come up pilot project in responding to situation like this...

thanks.

Sincerely,
Analiza

Why diarrhea is not a problem? I will get some more data about this in the health statistics of the village via the village health worker or the school division nurse. Just an idea, maybe the children's internal organs/conditions are very strong already from repeated infections to withstand bacterial infestation (or those who cannot survive die early).

With regards the septic tank design elements, maybe a "floating" septic tank composed of airtight 200-liter drums tied together in bamboo frames is an option. Then we can just transport/float the loaded drums to higher ground for storage and eventual re-use and replace the tanks with new empty ones?

Dear Marijn,
Thank you for your suggestions. I also see this school project as a perfect case to showcase sustainable solutions. Apart from the technical solutions I would like to first get a clear understanding why there is no diarrhea problem in the community as stated earlier and dicussed with Julian. People poop in the water (maybe 50 meters outside the villages in drop-to-water body toilets or even within the villages), there are pigs and chicken, there is solid waste floating around and lot more pollution is also streaming in from the mainland , but obvioulsy diarrhea is not an issue. Once we have clearly understood why this is the case or if this is a wrong information, we can think about the final technical solution. Are dilution, hostile saltwater environment (if that is true) and washing out of tidewater to the ocean reliable conditions to continue in a similar direction or should there be new ways of dealing with toilet waste.

Cheers
Christian

Dear all,

This is an interesting case study, partly because if there is no need for plant nutrients an important pillar below the ecosan concept is removed (assuming it is impossible/very costly to transport the "products" to the nearest agricultural area).

The suggestion of a pipe to sea, that is discussed is similar to so called "outfall pipes" used in Europe still in some places. I would say that with those it is indeed important that sewage is take far out to sea, otherwise it will just float back into the village if wind and current are wrong. Also in shallow waters you may get algae blooms is nutrients are not washed away effectively. Further, can shell fish get contaminated with for instance salmonella hyphi under water?

I think you can not work with a floating pipe to sea, as that would be prone to damage in storms and be in the way of (fishing) boats. Submerging and stabilizing a pipe on the seabed would be an interesting but challenging proposition. To do this on a small scale would require a high amount of trial and error and improvisation in engineering. If dumping is indeed the only option, I think having drums that can be put on fishing boats and emptied far from shore would be the most economical option.

There are of coarse some interesting moral aspects to this solution. Apart from the question of whether this solution would be legal in the Philippines. As Elmer indicates, there are many communities with a similar situation, do we want to pilot and thus promote a "solution" that actually means just dumping the waste into the oceans? If we do this on the basis that it is only one small community, do we not set an example for all those other coastal communities?

Kind regards

Marijn

Hi Julian,
Thanks for this scientific background. I hope the Philippine colleagues will be able to clarify the health status of people and if indeed they have no problems with diarrhea and why. I am still puzzled. I agree that it would be best get the wastewater far outside, but laying pipes in such a tideland environment might be tricky due to being exposed during low tide. We will keep you updated.

Cheers
Christian

Well, sadly you are right, the scientific literature is a bit contradicting is that regard. It is clear that the use of E.coli as an indicator bacteria might be misleading as it dies off relatively quickly in sea water as opposed to some real pathogens. That is why enterococcus is generally recommended as the indicator bacteria for testing water at beaches.

www.springerlink.com/content/v235710vl5506161/
hydrobio.icbas.up.pt/documents/4_Bordalo_Ratiwun.pdf (see discussion part)

Give an overview, the latter should be quite close to what you will find in the philippines.

To me, it seems that it is mostly the predatory factors (marine protozoa, bacteriophages etc.) present in natural seawater that have the sometimes reported strong effect on pathogen die off in sea water (and those studies not showing it probably used artificial seawater etc.). In addition it is probably likely that the saltwater has a negative effect on non cyst forming protozoa (mainly amoebae) that are responsible for many kinds of diarrhoea.

Never the less it is advisable to try and get the sewage out as far as possible, so that the seawater dilution (pathogens need a certain concentration in order to overcome the immune system) takes full effect. In addition some literature reports strong die off rates after a few days, so making sure the sewage "stays out" that long is probably also a good idea.

The flush out system was just an idea that came to my mind when reading your post, not sure if it has been done before, but I think it should be relatively easy to construct.
Maybe you have an construction engineer in your team who can have a look into this?