Can an ABR be done as a trench in clay with plastic sheets as baffles?
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TOPIC: Can an ABR be done as a trench in clay with plastic sheets as baffles?

Can an ABR be done as a trench in clay with plastic sheets as baffles? 27 Mar 2014 04:41 #7990

  • canaday
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Dear Detlef and others who know about ABRs,

Can you imagine making an ABR (Anaerobic Baffled Reactor) by digging a one-meter-wide and one-meter-deep trench in firm, impermeable Amazonian clay and making the baffles by stretching sheets of thin plastic across the trench? (The woven polypropylene cloth of rice sacks would likely be impermeable enough, would get more impermeable with dissolved solids and biofilm, and would be stronger than other plastics.) There would be roughly equal water pressure on each side of each baffle, so it seems this should work.

I have been asked to treat the sewage from two tourist cabins in the indigenous Achuar Community of Sharamentsa, which is reached by flying about 45 minutes in small planes, so every gram of material counts. One cabin is for 20 persons and 100 m away there is another cabin for 12 persons, so each cabin will require separate treatment.

They have successfully achieved infiltration of graywater into the soil, but not so with the blackwater from flush toilets, thus they called me.

My main goal for the ABR is to remove solids and greases before finishing the treatment with an upflow Vegetated Sand Filter.

The Compendium recommends a Hydraulic Detention Time of between 2 and 3 days. Any comments on this?

We might make two ABRs for each cabin in order for use to alternate and never have to remove fresh sludge.

I am also suggesting we build UDDTs and urinals that feed directly to the soil of banana plantations, to reduce the load on the ABRs and Constructed Wetlands, especially during moments of peak occupancy. I, of course, would have preferred they build UDDTs throughout, but the place is already built and they figured some visitors would not accept anything but flush toilets.

Sharamentsa is where we first built UDDTs among the Achuar in 2003 and they have been well received and are still in use. This work will allow me to do more follow up.

All suggestions are welcome.

Best wishes,
Chris Canaday
Conservation Biologist and EcoSan Promoter
Omaere Ethnobotanical Park
Puyo, Pastaza, Ecuador, South America
inodoroseco.blogspot.com

Re: Can an ABR be done as a trench in clay with plastic sheets as baffles? 27 Mar 2014 06:35 #7992

  • JKMakowka
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This sounds like a more up-market place so cost is probably less of a concern than durability and hassle-free operation.

If you want something light and durable, with final assembly on site I would suggest you look into foam-core composite materials. This is a technique from boat or airplane construction (or surfboards) that is actually not that hard to do by yourself.
Basically you manually shape the overall body out of a polymer foam (something like Styopor), reinforce critical junctions with a thin layer of glass or carbon fiber and then cover everything with a resin (epoxy probably preferred in this case as it is easier to work with and more durable against chemical degradation).

The result should be pretty similar to a FRP body ABR, but easier to make and equally durable.
Krischan Makowka
Technical Adviser at the Uganda Water and Sanitation NGO Network (UWASNET)
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Last Edit: 27 Mar 2014 06:52 by JKMakowka. Reason: link

Re: Can an ABR be done as a trench in clay with plastic sheets as baffles? 27 Mar 2014 07:30 #7994

  • AquaVerde
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Dear Chris,

Why not, if not

Do you use the biogas? I guess not.

Maybe for the hanging baffles and standing walls you might be better off with sturdy hard plastic. As the ABR "function" by just a small slop 5-10 cm between ABR inlet and outlet, you would have pressure by sewage and sludge between the baffles and walls. This pressure generates the needed up-flow velocity. Have a settler in front of ABR! Design 4 ABR-cambers (the spaces between the hanging baffles and standing walls) for the peak flow and have an up-flow velocity from approx. 0,6 m/h (not 1 m/h) and Hydraulic Retention Time (HRT) minimum 3 days to stay saver with your design. Keep the first camber larger to give more time for first stage, the hydrolysis (maybe 2x larger). To start the digesting process faster, put anaerobic sludge from other wwtp's on the ground of each camber. If not, it takes approx. 3 months for the ABR "to find its right way". Have on top a kind of flexible tunnel plastic as ABR cover and gas holder/reservoir. Keep rainwater away! Have a "Party-Filter" (effluent filter, e.g. from Tuf and Tite, USA) within the last ABR-camber outlet, to protect your CW against clogging by flushed out sludge.


I am only worried about the permanent sewage wetness of ??impermeable?? Amazonian clay. Have on side a separate trail for weeks with sewage before construction starts. Maybe you put 1 mm PE- foil on top of clay!?

They have successfully achieved infiltration of graywater into the soil...
I am guessing top soil.

We might make two ABRs for each cabin in order for use to alternate and never have to remove fresh sludge.
No need for two ABR's, you empty from time to time mineralized sludge from settler and after 3-4 years ("old") mineralized sludge from the ABR-camber grounds. Keep maximum distance to cabins!

The Compendium recommends...
Which compendium do you use, from BORDA (Sasse) maybe?

I hope my German-English was understanding enough.

Goooood Luck and let us (me only, if you like) know about your good and bad experiences made.

All the Best
Detlef
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Last Edit: 27 Mar 2014 08:02 by AquaVerde.

Re: Can an ABR be done as a trench in clay with plastic sheets as baffles? 28 Mar 2014 03:40 #8012

  • Marijn Zandee
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As a (former?) boat builder, I want comment a little on Julius' idea. I think you would need to use a more high quality foam (one that is resistant to the resin you are using). In boats this is usually a PCV foam. Also, you may need to at least clad both sides in glass fibre, to make the panels strong enough. Which will mean they will be fairly heavy, and they still need to fit in a small plane.

Chris,

I really like your thinking, some other things that come to mind:

-What will you use as a "roof", I think the most likely mode of failure of the pits would be water running in from the top eroding the walls.
-Are there local stones you can use to line the walls of the pit? You could just use clay as mortar between them. This would also give you a good anchoring point for the baffle walls.
-To make the baffle walls, I would also go for something more rigid than just rice sacks. Is there some sort local skill in making mats that are woven out of bamboo or tree branches that you can use to make some baffle walls that you make water tight with rice sacks?
- What materials and techniques did they use for the cabins? Can you use something similar to make the baffle walls and roof?

Regards

Marijn
Marijn Zandee
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Re: Can an ABR be done as a trench in clay with plastic sheets as baffles? 28 Mar 2014 05:29 #8013

  • canaday
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Dear Krischan, Detlef, and Marijn,

Thank you for your thoughtful and timely responses.

Rocks are hard to find at this site and mostly far away or deep in the ground.

My current thoughts are to:
1) Line the trench with rice sack material (which is also sold by the meter) to prevent slumping and clay getting into the water.
2) To try to find a broken plastic water tank or barrel (or potentially buy a new one) and cut pieces of it to form the baffles. I nonetheless still think that the rice sack cloth would work, and its propylene is reportedly very resistant to the acids that will form in the wastewater (and is mostly degraded by solar UV, which it would not receive). My Achuar counterpart's inclination is to make the baffles with planks from the hardest local wood, which involves deforestation and would not be feasible in other places.
3) I am not sure what to do the roof in. Maybe sections of ferrocement or wooden planks (which would not be rotting in the soil). Rain runoff would be kept out by making the edges higher with the excavated soil.
4) I am not planning to do anything with the biogas, especially since visitation by tourists would likely be fairly sporatic.
5) I am still thinking of potentially building two ABRs at each site, for alternating use, so that the community members would not have to scoop fresh sludge out. Maybe I need to make a gulper. Would alternation be bad for the microbiology of this?

Thanks for your help. More info soon.

Best wishes,
Chris Canaday
Conservation Biologist and EcoSan Promoter
Omaere Ethnobotanical Park
Puyo, Pastaza, Ecuador, South America
inodoroseco.blogspot.com

Re: Can an ABR be done as a trench in clay with plastic sheets as baffles? 28 Mar 2014 07:07 #8014

  • JKMakowka
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@Marijn: As this wouldn't have the same movement stress as a boat, I am pretty sure you could use a lot less fiberglass.

@Chris: Ok I see, that sounds a lot less "up-market" than I originally thought. A simple treatment pond is not an option? If it is used only sporadically an ABR might not work so well.

Is using some wood really that problematic? I think if you bring some surface treatment (maybe something like tung-oil?) any wood will last sufficiently long.

Your comment about old barrels also made me think that simple instructions for building an ABR out of old barrels (maybe even wood barrels?) could be something quite neat. Obviously you would need quite a lot of them, but as Detlef has mentioned, a larger first tank should be sufficient for some hydraulic buffer.
Krischan Makowka
Technical Adviser at the Uganda Water and Sanitation NGO Network (UWASNET)
www.uwasnet.org
Last Edit: 28 Mar 2014 07:22 by JKMakowka.

Re: Can an ABR be done as a trench in clay with plastic sheets as baffles? 28 Mar 2014 09:42 #8015

  • AquaVerde
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Dear Chris,

As already mentioned keep rain/storm water away from any ABR.

Your idea to use ferrocement as a roof is a very good one, do not forget to have an epoxy coating from inside. In general you could do onside the whole ABR from ferrocement, using the clay wall and bottom of trench as permanent formwork, even you could add to this camber walls and hanging baffles, or in a combination with sturdy hard plastic for camber walls and baffles. With ferrocement you could be very flexible.

I do not understand your plan for alternating use of two ABR's on each side, as you should never scoop fresh sludge out of ABR and visitors aren't permanent. There is no need to scoop fresh sludge out of ABR's. Or maybe I do not understand your intentions very well

Which ABR-compendium do you use?

All the Best
Detlef
www.aqua-verde.de
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Re: Can an ABR be done as a trench in clay with plastic sheets as baffles? 28 Mar 2014 14:51 #8020

  • canaday
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Hi,

I have been reading the EAWAG Compendium of Systems and Technologies for Sanitation (Spanish Edition). Are there other online texts I should see?

My goal for the ABR is obviously to give treatment, but especially to eliminate the suspended solids before the water goes to the Vegetated Sand Filter. So I want to apply the ABR as a very efficient settling tank, with its several slow up-flow chambers.

Standard flush toilets have been installed that discharge 6 liters per flush. Allowing for 3 flushes per person per day, 6 liters x 3 flushes = 18 liters, rounding up to 20. 20 persons x 20 liters = 400 liters per day for the one cabin. So the volume of the ABR should be 3 times this for allow for 3 days of detention, thus 1.2 m3. Taking into account that the porosity of sand is somewhere around one-third, the volume of the Vegetated Sand Filter should be at least 1.2 x 3 = 3.6 m3. Any comments or corrections on my calculations? (The staff needs to know to not flush and flush and flush during cleaning, and to not use toxic chemicals.)

Detlef, I do not understand why you say that fresh sludge would never have to be scooped out. Sludge does build up and eventually needs to be taken out ... and would only be as old as the last flush. This is not a huge volume, so there would be no problem in making two of each and alternating the use, in the same way as the two-chambered UDDTs that the community has been managing for 11 years.

I am thinking of getting inoculum from the bottom of a local lake or river.

The "Party Filter"
www.tuf-tite.com/ef4filter.html
seems great, but is not likely available here in Ecuador. I cannot quite see how it works, but is there a home-made alternative? How would a roll of plastic mesh do? (This could be pulled out and scrubbed with a brush periodically.)

Krischan, that Tung Oil sounds great, but I have never seen it in Ecuador. A little bit of wood would not be the end of the world, but most woods would rot in the water and those that do not likely come from very, very old trees. Sometimes there is the resistant heartwood of trees that have fallen in the forest decades ago; maybe we can find some of this.

My preferred plan is still to cut the baffles from an old (or new) water tank.

The roof might likely be wooden planks preserved with used motor oil.

Thanks for your help.

Best wishes,
Chris Canaday

We will make sure to keep rainwater runoff out.
Conservation Biologist and EcoSan Promoter
Omaere Ethnobotanical Park
Puyo, Pastaza, Ecuador, South America
inodoroseco.blogspot.com

Re: Can an ABR be done as a trench in clay with plastic sheets as baffles? 28 Mar 2014 15:06 #8021

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see: www.susana.org/lang-en/library?view=ccbk...p;type=2&id=1933

This book provides basic knowledge about the technology to non-technical project managers in order to enable them to adapt the technology locally.
The book wants also to help the technical specialist to understand where technical simplification is required in order to disseminate the technology in its typical decentralised context - and provides tables for dimensioning of treatment plants on the computer.
Also, the book is designed to assist senior development planners who need to understand the specifics of decentralised wastewater treatment technology sufficiently in order to select or approve appropriate strategies for its dissemination.

NOTE: This 1998 publication recommends for ABRs a maximum upflow velocity of 2 m/h, which is not recommended anymore by BORDA, the new value is max. 1 m/h (see page 80, first sentence, third line).

in short for an "improved septic tank":
- min. 1,5 h! HRT in Settler in front of ABR
- min. 4 cambers in ABR
- min. 3 d HRT in ABR
- max. 0,6 m/h (BORDA: vABR max. 1 m/h!) upstream velocity v in ABR-camber

May I suggest, have longer HRT's and provide just one unit for each house. You may construct one unit first and making your own experiences and improve from there your second unit. Just provide a Y-junction in your pipework for a possible parallel ABR. In my experiences, non permanent used parts of a sanitation system gets easily neglected (forgotten) long after you are gone. Please calculate very-very conservative the ABR size and secondary treatment CW even so as it is your first ABR you doing by your self. In your first ABR project do not go for -40% reduction of CW space. In GTZ/GIZ CW-review it is recommended -40% if ABR is doing the pre-treatment, but missing independent experiences made by well known scientific organizations.

"emergency" alternative to Tuf & Tite "Party-Filter": (second best)
Septic Tank Bristle Filter

You may "construct" your own home-made "Party-Filter"...

Do not use wood as ABR cover, I see danger for children long time after you left construction side.

To where is grey-water and kitchen-water going to?

All the Best
Detlef
www.aqua-verde.de
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Last Edit: 29 Mar 2014 10:17 by AquaVerde.

Re: Can an ABR be done as a trench in clay with plastic sheets as baffles? 28 Apr 2014 19:32 #8357

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Dear Chris,
Any developments on your first ABR?

FYI:
- see very small ABR's in Afg., Mr. Mang send me: www.borda-afg.org/news/newsdetails/artic...amiyan-workshop.html

- see simple & interesting link to this CH web page on biogas:
diy-biogas.org/micro.html

Regards,
Detlef
www.aqua-verde.de
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Re: Can an ABR be done as a trench in clay with plastic sheets as baffles? 30 Apr 2014 01:41 #8383

  • canaday
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Dear Detlef,

Thanks for asking.

Things are moving slowly. The community is still collecting the sand for the Vegetated Sand Filter ... and when I went out there I found all the available sand to be too fine, so my plan is to make charcoal from wood chips and chainsaw sawdust and mix this 50:50 with the sand, to make for more permeability and less clogging.

I also got some good news. There are several broken plastic water tanks present in this isolated community, so I plan to cut the baffles for the ABRs from these tanks.

I will post news on how things go.

Best wishes,
Chris
Conservation Biologist and EcoSan Promoter
Omaere Ethnobotanical Park
Puyo, Pastaza, Ecuador, South America
inodoroseco.blogspot.com

Re: Can an ABR be done as a trench in clay with plastic sheets as baffles? 30 Apr 2014 10:26 #8390

  • JKMakowka
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Yes good sand can be difficult to source in landlocked tropical countries. Have you had a look at the alternative laterite based planted filter that I linked here: forum.susana.org/forum/categories/35-bio...wats-technology#6463 ?
Krischan Makowka
Technical Adviser at the Uganda Water and Sanitation NGO Network (UWASNET)
www.uwasnet.org
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