Not sure why you'd need baskets. I'm thinking about something very simple and cheap... so you'd dig the pit(s), put a thick layer of rubble in (drainage layer), put the cloth over that after placing the two vertical aeration pipes into the rubble, then the layer of bark (refuge). The cloth needs to be pervious and non-biodegradeable. Rice sacks might decompose over time, I'd just use shadecloth/windbreak cloth, this should be very cheap.

The pile needs to be easy to dig out, but because you are making this under the ground surface level, you just need to make sure you can easily remove the latrine floor or digester lid to dig it out.

If dug as one pit and divided into two, there would need to be a baffle or wall between them, which should not be solid. You want the worms to be able to migrate between them... if the baffle were concrete this would need a pipe between chambers, or alternatively a pervious structure with cloth over it to stop solids transfer between chambers. Wood or steel are not the building materials of choice, plastic and concrete are good.

Dear Chris,

I am glad you like the idea since I know you from the forum as an Ecosan follower of Einstein’s ‘make it simple theorem’ finding the DVVC eventually not simple enough..

I would also prefer plastic over metal for the basket and binding several standard boxes together may be a good idea avoiding an expensive custom-made product.

Don’t you think flour or rice sacks may be too leak-tight and may eventually keep the worms’ refuge too wet? @Dean: any experience with rice/flour sacks for this application?

Chris, my idea was to have a door at the backside of the vault where the whole basket(s) can be pulled out for emptying like on UDDT vaults.

I assume that your proposed pipe is between the two vaults so that the worms migrate to the ‘new’ food once the first vault has been put to rest. I had been thinking how to facilitate this process and had the idea just to leave openings in the dividing wall between the vaults. @Dean: the worms will cross 5” of concrete block wall in their desire to reach ‘new’ food? Or do you have to carry them over from one vault to the other? I assume in the resting vault they will eventually die when no fresh ‘food’ is provided?

I don’t think we actually require a UD pan or pedestal. As long we provide an urinal for the males not too much urine will pass through the worms’ refuge and will be diluted by the flush water.

Percolating urine and black-water through perforated pipes into the soil under fruit trees (or bananas?) is a good idea. It serves a purpose and saves the further treatment. But we need to have the space for that on the plot.

Which may mostly not be available as we want to apply this system also in high-density peri-urban areas of Moshi. Users of the system can be any of the population in Moshi but I guess the core target group will be the low-income people in unplanned areas where sewers will never reach and even water services are limited, i.e. not every plot has its connection and many depend on neighbours or water kiosks.

Moshi Climate: 17–29ºC, 970mm in 6 months, see also en.wikipedia.org/wiki/Moshi,_Tanzania

Ciao
Hajo

Dear Hajo,

Looks like a great system.

I suggest making the basket with plastic, so it does not rust or rot. These could be disposable plastic fruit boxes (several tied together), lined with woven, polypropylene flour or rice sacks. Would there be small doors to open in order to empty the resting basket with a shovel? Would there be a pipe to allow worms to migrate back and forth?

It would be great to have a urine-diverting SATO squat pan. The urine + greywater for flushing could be dispersed in the soil via perforated buried below the surface among fruit trees.

Where will you do this? Who will the users be? What is the climate like?

Best wishes,
Chris Canaday

I apologize I use a speech to text system and sometimes miss a word like "Slusher" which was supposed to be "Flusher" which is my short form of any toilet that requires water to flush it largely because in most of these areas such as Africa and Central America where I am water is at a premium and it is easier to break down semi dried material than sludge.again I apologize for the misspelled word.

As to the acts the worms eat not only very small parasite eggs and the parasites themselves but they feed on virtually any living organism in the fecal matter, the UV rays from sunlight and I don't know if they're necessary as here in the United States we use Burma culture for processing several forms of sewage in agricultural areas and have never found a necessity to expose the material to UV rays however this is usually agricultural waste cattle sheet chickens livestock in general where the biggest problem is E. coli so I would suggest it, and I have used Worms for this purpose they work well, mind you I am a student not a waste water management engineer. And this is simply a topical suggestion I have seen it used also in human septic systems so I know it can be done. I do not know if the end product would require five or treatment which is why I mentioned exposing it to some sense anything the worms don't eat and kill the sunlight will.

Sincerely Kevin Arthur Cleveland

Hi Kevin,

thanks for joining in. I appreciate you are in favour of composting, but what means 'slusher'? I googled it but to no result, maybe 'sludge?

Do you have practical experience with vermi-(worm) composting? I don't think exposure to sunlight will kill ascari/helminth eggs which are my major concern. Any information about that?

And: this discussion is about finding ways that human excreta have not to be considered 'waste' but are captured and processed in a way that they can be reused!

ciao
Hajo

I am definitely in favor of composting toilets, as opposed to Flusher's of any sort in most situations. However this discussion seems to be more about what to do with waste. I don't really have a solution for all the problems brought but I have a solution that may minimize some of them. Worms in a composting toilet they will break the matter down to about 1/5 of its original volume, Increase the plant nutrients and removal of vast number of Pathogens (not all of them!)The worms eat human fecal matter digest it and leave us more amount of very dry fertilizer, this makes it lighter and smaller therefore easier to ship to farmers. I believe in Africa it would still be somewhat cost restrictive. It is easier to handle than simply dried fecal matter, and it does not require urine separation the worms I'm thinking of will consume the sugars in the urine and it to will become fertilizer.

It's a very simple process you build an improved composting toilet (should be improved as although the worms require only minimal oxygen they breed better if it is ventilated) you add the worms =Tubifex tubifex a.k.a sewer worm. It is a species of tubificid segmented worm (a family of clitellate oligochaete worms) that inhabits the sediments of lakes, rivers and sewers on several continents. they will speed up the breakdown of the fecal matter and give you a lighter more transportable and more sanitary fertilizer my recommendation is that the fertilizer be spread thinly and exposed to sunlight before it is shipped as a secondary method of removing pathogens.

Thanks, Dean !!!

Dear Peter, Dean,
Dear all,

As mentioned in my last post, I want to propose a double-vault vermi-composting toilet, please see the first draft attached and let me have your comments. Although it looks like a double-vault UDDT it is NOT a dry toilet because the composting requires a certain amount of moisture.

More details for better understanding:

1. Double vaults, used alternatively, 3 to 5 year cycle;

2. To be used with squat pan (why not SatoPan: designexpo.businessfightspoverty.org/sho...ed-from-safe-toilet/ ) or pedestal;

3. To be designed as urine diversion or mixed toilet (please take note: even as a UD it is a pour-flush toilet as worms need moisture);

4. If urine diversion then with outside urine tank or soak-away;

5. Urinal in any case: for ‘UD version’ urine goes to tank/soak-away, for ‘mixed version’ it goes into black-water channel under vermi-digester basket to protect worms from too much urine exposure;

6. Hand-wash basin can also be tippy-tap with bucket under for waste water, wash water should be used for pour-flushing as worms require a certain amount of moisture;

7. Black-water (i.e. pour-flush water, anal wash water, urine) goes along the channel under the digester basket to the waste pipe outside the toilet;

8. Black-water could first go through a settler (optional) to capture fine material which has passed through the digester with the flush-water;

9. Finally the black-water goes either into a soak-away (if ground water level and soil condition permit) or is captured in a tank (say 2m3) to be emptied every 2 to 3 months by a service provider for either further treatment and reuse or for disposal in central waste water treatment plant;

10. Both vaults have a common air pipe (is 110mm PVC sufficient or does it require the 200mm GI pipe which the Otji-toilet uses?), which ensures that the toilet is free of odour, flies and the digester is well aerated for the worms;

11. Each vault contains a digester basket ‘sliding’ on supports which keep it clear of the black-water channel under;

12. Digester basket (metal?, plastic?) is lined with a fabric which captures fine material, and filled with a layer of tree bark (20 cm high?) which serves as starter and shelter for the worms;

13. Excreta are pour-flushed in at the centre of the basket. As the worms work on it and digest it they spread it to the sides;

14. Therefore the basket should be wide and shallow, as they worms spread and digest the faeces the build-up is small and we require not much height as a rough calculation indicates:

15. i.e. for a household of 5, producing 0.4 L/d (faeces plus toilet paper), we require 0.4 m3 storage volume for 5 years (see Dean’s calculation) which results in a vault height of 1.0 m including all considerations: 2.5 safety, 1.6 m length, 1.2 m width, 0.2 m bark height, 0.2 m space under basket;

16. I see the advantage of this design in the fact that it is not so vulnerable to user mistakes: urine or wash water in the faeces are rather wanted than to be avoided;

17. On the other hand only human excreta and water in small quantities should go into the vault, chemicals or cleaning agents as well as solid waste are to be avoided (using a gooseneck in a pour flush squat pan or pedestal can help in this).

18. After 3 to 5 years resting the compost should be well hygienised, Dean even assumes that after that period the compost should be free of helminth eggs. Can somebody knowledgeable please comment on this?!

19. A service provider will check the compost activity frequently, empty the basket and change the squat pan or pedestal. The service provider will care for further treatment (if necessary) and reuse of the vermi-compost.

20. The responsibility for the service chain should be with the W&S utility who may be able to outsource the services to the private sector if the collection fees and the revenue from sales of processed excreta (urine, compost) guarantee some profit beyond cost coverage.

I hope for some comments and advice for consideration after which I will produce proper design drawings and post them here.

Ciao
Hajo

Hi Hajo,

If we have 0.4 litres of solids per person per day, and 5 people using the toilet, that is 730 l per year, which if reduced to 80 litres per year, would be 400 litres of solids over 5 years. Your prototype should be conservatively designed, perhaps with each digester basket having 1 m² space above the filter medium.

cheers
Dean

Dear Ross, dear all,

Thanks for your confirmation from the field that bananas are a good user of urine (and greywater as I know from own experience).

I want to emphasize again that we should discuss here options which are sustainable for peri-/urban areas in Africa (if elsewhere it is ok, but the target area is Africa).

And major criteria therefore should be:

1 the toilets are in congested areas with difficult access for larger trucks also due to poor road conditions;

2 the plots have no space to dig new pits when toilets are full;

3 the plots have not much (green) space for re-use of sanitation outputs;

4 also in vicinity there is no agricultural land for re-use;

5 which results in the requirement for sustainable service providers who collect safely whatever outputs the sanitation option produces;

6 which is also required for users who do not want to handle sanitation outputs by themselves in any other area of town;

7 and the option must be affordable for low-income households regarding investment and O&M.

Ciao
Hajo

Just a quick comment Hajo on the use of bananas for take up. I only make Urine Diverting pedestals now and the most frequent comment I get is where Bananas have been employed in the area of the gravel trench. The results of growth and fruit production (private owners) have been most notable. In many cases my UD pedestals have replaced mixed pedestals on top of existing Clivus or Eco Flo systems.
I do agree with your assessment that site considerations are paramount when considering the design of the system. To me water table height and whether re-use in the locality is available are the 2 top points.
Cheers Ross

Good afternoon Peter.

There is another alternative to moving the toilet pedestal and that is to centralise the pedestal over the dividing wall of the double pit and reduce the dividing wall in height by around 300mm. On the top of this lowered dividing wall is fitted a vertical shutter that operates in an arc via a hinge along the dividing wall edge. The purpose is to close one side of the pit until full to the height of the dividing wall and then pivot the shutter through a rod operation externally to open the second chamber.

We did this some years ago with the double vault being sealed all around to avoid soaking away, although if site suitable this would not be necessary. This was a completely dry and separated system with urine going to a gravel filled trench and access to the vault was via a front door at the bottom beneath ground level. The only moisture came from cleaning of the pedestal.
Unfortunately it was a one off and no records regarding decomposition were kept so I am unable to give the time between vault services, but I understand that servicing was simply shovelling due to the dry nature of the humanure.

Cheers Ross

Dear Hajo,

the pit latrine can be with or without Urine Diversion. We usually decide this together with the customer based on the number of users expected. Sometimes it is only for one or two workers and then we can skip Urine Diversion.

I agree with you that emptying a single pit latrine is not an optimal solution. It is rather the last option in case that the pit is full and no other solution is available. Better is clearly the double pit latrine with the pedestal moved. We have also designed this type - again as a Self-Build-Kit. In our case there is only one vent pipe which is connected to both chambers. But only one chamber is having air flow at a time since the other chamber is closed by then. The photo attached shows our double pit latrine with a hand wash facility attached to the building.

Greetings,
Peter