It seems that some water in the flush is necessary to keep the heap from dehydrating, thus avoiding concentrations of urea building up. My own experience is with a Sealand 500 ml flush, which wasn't soapy water... but the GSAP microflush has proven successful using a minimal flush of soapy water. I also assume that in tropical countries some measures to mitigate buildup of heat would be wise. Such things as white paint and good ventilation... even some shade if possible.

I've found 600 mm height from the top of the bark to the inlet (or bottom of open microflush hinge) is sufficient, but that is for a family household. Generally increasing the width will achieve better breakdown with higher solids input than increasing height.

cheers
Dean

PS

I just dug out a very interesting (old) posting:

'Last questions re Update of Factsheet 11'; 20 Dec 2011 00:16 #767; by Ian Pearson
from which I quote the following paragraph:

"travel of contaminated groundwater = only 5m : tests were undertaken in South Africa where VIP latrines were installed in sandy soil - an area of very fine sand. Test pits were dug next to the pit and samples of the shallow groundwater taken and analysed. It was found that there were no coliform bacteria at a distance of 5m from the base of the pit. Of course there were higher nitrate levels, but the fine sand had effectively filtered out the bacteria and larger microorganisms. We are well aware though that in conditions of fractured rock travel of microorganisms can be extensive."

ciao Hajo

Dear H-A,

I am quite aware that sanitation effluent and rain water are of different quality. And I also agree that the topsoil may have the highest cleaning power due to the micro-organism.

But the research by Adane Molla (see the paper posted by Dean, 04.01.16) seems to indicate that only 1.5m of plain loamy, sandy or red laterite soils reduces the contamination of the effluent by min. 50%. Thus for me it is a question of soil distance between bottom of pit/soak-away and GWL that the effluent is effectively treated not to contaminate the GW.

Also the other paper quoted by me (Safe siting of sanitation systems) does not emphasise that sanitation effluent must pass through top soil for proper treatment. It rather builds on type of soil (sand, gravel, fractured rock, karst), on GW flow direction, on aquifer depths, on sub-soil layering and protection (impermeable top layer), etc.

Because of the complexity of influencing factors these ‘rule of thumbs’ exist which give a rough guide how far the well/borehole should be from a toilet, because also the horizontal flow of the sanitation effluent through subsoil constitute treatment as stated by this paper.

Therefore I find your judgement too cautious. It is the first time I hear that a school or communal toilet should generally have a leak-proof pit (cess-pit) and should be emptied by vacuum truck. Which does mean there may be cases where it is necessary, but not generally.

I would be interested whether forum users (kanalwolf?) have information about cleaning abilities of subsoil and whether more research has been done in that direction beyond what Adane Molla has reported. I believe subsoil will also treat sanitation effluent, it is only the question what distance/volume of soil is required to remove all contamination.

Ciao Hajo

Dear Dean and all,

It is a good idea to use the handwashing water for toilet flushing. But for Tanzania we will have to redesign the micro-flush system as Tanzanians prefer squatting pans. But it should be still possible. And I would prefer a system with goose neck, not only for fly and odour control but more for prevention of using the toilet as solid waste dump as it is the case with pit latrines.

Thanks for the hint with the required surface area to give enough room for the Tiger Worms to roam around for aeration and breakdown. On a 1sqm area what build-up of the heap would you allow for, spacewise and weightwise?

You mention ‘cool enclosure’. Remember that Africa may be a bit hotter than New Zealand and we cannot guarantee that not most of the filters/soakpits will be exposed to direct sun shine for most of a day and will become quite hot inside. Are the Tiger worms sensitive to heat? And are they sensitive to hand-washing soap?

Ciao Hajo

PS: And I would agree with Dean, I think it is one of the strong points of that microflush toilet that it uses very little water, and 'reuses' water from hand washing. But wouldn't these small quantities of water, probalby usually less than half a liter per use, be affecting the worms?

Hajo,

I don't think you can compare surface water (I suspect you are including rain water) with the discharge of unlined latrines or soak pits meters under the ground when it comes to ground water recharge - these are two completely different situations. What would be comparable to rainfall is irrigation - both are going through the complete strata of the soil. And concerning surface water like rivers, there also are natural cleaning mechanisms. Leach fields would also be somehow comparable if the piping is located just slightly under the surface. Unlined latrines and soak pits, however, are short cutting the upper strata, the top soil, in particular, which are the primary cleaning agents and where the naturally occurring microorganisms are located.

On the other hand, depending on the type of soil, mineral soil does have filtering and some iron exchange capacity, so that I wouldn't be too worried about small family toilets if they are located at a distance of boreholes (or wells). In Uganda, we used a ball park figure of 100 meters for the minimum distance from production boreholes, a figure which is certainly including a safety margin. But for larger toilets, like school toilets or communal toilets, I would certainly be worried. In my view, these should be lined so that they would require an emptying service, or alternatively discharge via a pretty large leach field, use wetland treatment or something like that.

Otherwise, success with your endeavors,

H-A

Hi Hajo,

What I like about the GSAP microflush is all the flush water is provided by handwashing, which is essential anyway for adequate sanitation.

I only copyrighted my drawing, and encourage design using the principles offered. One key to design is sufficient surface area of the basket floor. Each basket needs a surface area of approx. one square metre. What happens is the piles "spread" as the worms work on them, and this should not be constrained by having too little basket-width, otherwise aeration will not be sufficient inside the heap for rapid breakdown, even though the basket walls allow drainage. Reinforced concrete seems to be the material of choice for Biofil/GSAP constructions, keep in mind that the solids can weigh a fair bit and you want a cool enclosure in the tropics.

Tiger worms are good because they are "self-contained". I'd be interested to know whether black soldier flies complete their life cycle contained within the enclosure, or whether the adults need exit and entry. If they need an entry/exit point, then would other flies having access become a hygiene problem?

cheers
Dean

Dear Dean, H-A and all,

No question that the ground conditions must be appropriate for the soakage of whatever flush is used (low, pour or full flush). This condition should be established before any type of sanitation system based on infiltration is built whether vermicomposting, septic/soakaway or pit latrine.

Further, the groundwater level must be deep enough to allow for sufficient cleansing/filtration of the effluent before it reaches the ground water table. How much ‘deep enough’ should be? There is some indication in the paper ‘Subsurface infiltration presentation.PDF’ which Dean posted (above) which indicates that loamy, sandy or red laterite soils of 1.5m give already a quite good reduction of waste water quality indicators (BoD, CoD, TSS, helminths). Another source of information can be the paper ‘Safe siting of sanitation systems’ which is found on the SuSanA library (www.susana.org/en/resources/library/details/2155 ).

Therefore: about 200m3 of urine go into the ‘ground’ in Moshi daily but not necessarily into the ground water as part of it (how much we don’t know yet as we have not yet evaluated GWL or geological maps) is sufficiently treated by the over-laying soils before the effluent reaches the GW (remember: all GW is originally surface water filtered/treated by the soils and its micro-organism).

And I also see more problem of effluent from on-site sanitation affecting shallow water wells (5 to 15m) which draw water from shallow subsurface aquifer than in boreholes (20-100m) which draw water from deep aquifers where the sanitation effluent will be treated already when meeting the GW. And: Moshi has a sewer system of about 45km in the city-centre, that is not so much of our concern, rather the peri-urban areas.

I like the idea with two filter baskets on one soakaway pit and will think about how to convert Dean’s principal sketch into a design drawing considering fly protection and emptying service.@Dean: your copyright permits me to use your idea for further design?

Another question: Dean talks of Tiger Worms as the processing agents. I will have to look into what other worms could be used which are eventually available in Africa/Tanzania. Any ideas from forum members?

I agree with Dean to keep the system KISS and would possibly in a first try recommend not to use UD but keeping in mind that the urine can be a relevant fertiliser source and not ruling it out for good. At the moment I see the problem of collecting and storing (maybe for months) huge amounts (x.000 m3) of fluid if UD is introduced at scale. As Hanns-Andre points out, UD makes much sense if the toilet/plot owner re-uses the urine on the plot. But in a peri-urban/high density environment with small plots it is not feasible and a collection service must be provided for urine if UD to be used.

And we have to keep in mind that not ‘one stone kills all birds’: vermicomposting is a solution where people can and can afford to use water for flushing, because only about 60% of the Moshi population have house/yard connections. How far you want to carry water to flush your toilet? Thus, service chains for pit latrines and UDDTs have to be considered as well as possible extensions of the sewer system: city-wide sanitation planning!

Ciao Hajo

The forum software is reducing the size of images to 35kb, so to get around that I have attached a pdf of the diagram with readable writing...
forum.susana.org/media/kunena/attachment...posting-digester.pdf
cheers
Dean

Dear Hajo, dear Dean,

Thanks very much for your interesting contributions!

The use of urine as a fertilizer can work beautifully on your own plot if there is a) the land/cultures available, b) the time and interest, and c) some tolerance of the odors associated with the fertilizing activities. In that case, which may be applicable to a lot of small towns and villages in Africa, the cultures can even be used to recover some of the investments that have gone into the toilets.

In terms of storage, apparently you only need a couple of days in order to kill the urine born pathogens (bacteria), but what is recommended is a storage time of at least ten to fifteen days in order to reduce odor. That depends on the temperature, higher temperatures require less storage time.

Of course, not everybody is into the use of urine on his or her plot, so that in larger communities, some kind of collection system would be required. For that to be successful, there needs to be a local market for the urine fertilizer with people who are positive about that kind of fertilizer. In that case, you should be able to sell the fertilizer at a rate that is considerably lower than what artificial fertilizers cost (and these ones can only get more expensive in the longer run). In terms of storage time, what makes things a bit complicated is that you'd have to assume that some of the urine may be cross-contaminated with feces, which increases the required storage time to months, depending on the ambient temperature.

So, I think if the interest is there on the side of farmers urine separation and collection may be worth the trial. Especially since the alternative of having urine/effluents drain into the soil is not a long term alternative. Hajo, the currant situation in Moshi appears to be that close to 200 m3 of urine are going into the ground water every day - that basically makes it impossible to use that ground water for domestic uses apart from irrigation. In many parts of Africa, hand pumped bore holes are still used for water supply, so pit latrines, soak pits and the likes ought to be avoided.

For a town like Moshi, where I would presume there is a crowded center, at least for the crowded parts of town, and assuming the funds are available, the drainage of effluents via a small-bore (solids-free) sewer system with the aim of treating and using the effluents for irrigation would in my view also be a very nice option. In that case, all liquids (gray water, urine, pretreated black water) would all go into that sewage system, but care would have to be taken about commercial/industrial effluents. And for the biofill toilets, there wouldn't be an immediate need to divert the urine, apart from, possibly, protecting the worms from overdoses of ammonium and anaerobic conditions.

And concerning the textile we were using, Dean, that was inside the toilet, so there must have been another reason for it to get brittle than light. It could be elevated temperatures because we used black metal doors on the chambers in order to raise temperatures. It could also be the chemistry of the environment. Of course, higher temperatures are not what worms like, so we had plenty of other bugs, like black soldier flies. In that regard, and for the odors, the flaps that the biofill toilet design is including, would have been very helpful.

And Dean, unfortunately, the writing in your drawing is not readable, but the double chamber design is ok for larger toilets; that's what we also used. But, of course, it's also more expensive.

Cheers, H-A

Hi Hajo,

the key advantage with vermicomposting is that only the liquid effluent needs to be disposed of. With low flush "outhouse" toilets (I've found as low as 500 ml water per flush is enough dilution) the liquid effluent can be directed straight down into a simple soakaway so is simple and reliable. Not so good with piped effluent (indoor toilet) though, because enough water is needed to carry the solids. With full flush (indoor) toilets effluent fields are required because of the volume of liquids potentially contaminating the water table.

The double pit system would likely work if there was sufficient soakage. Insufficient soakage and the level rises and kills the worms. Remember, the pit will no longer fill with solids, so for longevity its all about soakage.

You can actually have one good pit (soakaway) with two baskets. I've attached a pic of what I do here in New Zealand, a twin basket system. Ideally the tiger worms can cross between baskets so a single chamber with twin baskets is best... but chambers would need to be constructed properly to be fly-proof etc and accessible for digging out compost.

There is no need to separate urine, so why do that? Follow the KISS principle...

Have a look at this video, it shows a simple low-flush toilet, vermicomposter and soakaway system (GSAP Microflush toilet).

Microflush toilet

I've attached an image that shows a full flush system for primary treatment. This includes a settling tank, which is not necessary for a simple low flush - soakaway system (I'm also into secondary treatment and irrigating with drippers).



(Also attached as a higher quality pdf)

cheers
Dean

Dear Dean, HAP and all,

I follow with interest the discussion about the (BioFil) vermicomposting technique and always try to compare its pros and cons with other alternatives we have, i.e. UDDT, VIP, flush and septic/soakaway, …

60-70% of the population in our town Moshi/Tanzania (200,000 E) use pit latrines (traditional or VIP) for which no proper service chains (emptying, transport, treatment, disposal/reuse) exist. And the authorities pacify them with the hope that ‘one day’ they all will have flush toilets connected to sewer or septic tank. Wishful thinking for the majority of them in my view.

Is vermicomposting a possible alternative if they have enough flush water and can afford to use it to flush shit? Therefore the question: does vermicomposting works with pour flush (by bucket) or low flush systems? I understand for the survival of the worms, the urine needs to be diluted by flush water. Is 2-3L sufficient?

I fully agree with HAP that a good alternative would be a UD interface where the urine is separated, collected, treated and used separately. But that requires a second service chain only for the urine which is also the reason why I am a bit sceptical about UDDTs: if 30% of Moshi (60,000 E) use UDDTs, every day about 60m3 of urine have to be collected, transported, treated (stored!) and reused. It is valuable fertilizer, but can it be processed economically?

I have the idea to use the vermicomposting with a ‘pour flush cum double pit system’ (S-6 of EAWAG Compendium). The ‘filter’ (basket, cloth, bark) sits on top of an ordinary soak-away pit. Of course the area must be appropriate for pit latrines and soak-away by ground water level and geology. The standard pour flush toilets sends the faeces (and urine) to the filter. Once the filter is full/clogged, the pipe from the interface is re-connected to the second pit.

The filter of the first pit is emptied once the latest excreta have been vermicomposted and the pit can be reused once the second pit is full. The flush water is percolated into the underground as with any pit latrine or soak-away after a septic tank (subject to favourable ground water and geological conditions). With this system the effluent (raw sewage?!) will not be re-used, but also has not to be handled.

The system will resolve three problems raised by Dean: 1) no handling of fresh sludge on top of the filter, 2) no overflowing of the effluent chamber (subject to ground conditions) and 3) once filter cannot handle inflow anymore the inflow is redirected to the other pit.

If the question of economical processing of large quantities of urine can be resolved the system can be upgraded with a UD facility.

If the underground is not favourable for infiltration of sewage effluent, the pits could be constructed as impermeable tanks (cess pit) and can be emptied regularly (bi-monthly only for black water?) with a vacuum truck (honey sucker), but that will be expensive, then the use of UDDTs may become more economical.

Looking forward to your comments and ideas,
Ciao Hajo

Happy New Year to all of you !!!