Great idea. your point could be taken up by the team then. i am also interested in working on something like this.

Those white sacks degrade in sunlight. Shadecloth/windbreak is uv stabilised and a much more durable material.

Constructed wetlands might remove helminth parasites and would be good to see helminth count at the other end of the canna bed comparing effluent from urine-diverting toilets with flush vermicomposting toilets. A simpler solution to achieve sanitary standards might be to drip irrigate nutrient rich raw effluent on high growing crops such as trees.

I understand that diverted urine would be free of helminths, but wouldn't treatment still be required to be free of other pathogens (lepto, typhoid etc)? Storage (time alone) surely wouldn't be enough for all urine-carried pathogens for use as fertiliser on crops? Also, wouldn't stored urine require aerobic treatment leading to loss of nutrient (volatilisation of N)?

Simplicity is what is so appealing about flush-vermicomposting. No problems with subsurface soakage fields feeding crops using raw filtered effluent (apart from cost of the fields or where the water table is too high), this is a much improved primary treatment system from traditional septic tanks. The technical challenge is to cost-effectvely get the liquid component from the full flush system suitable for surface application. Biofilcom are supposedly working on this, as are other funded bodies such as GSAP, LSHTM etc. Adane Molla seems to have uncovered opportunities with his research on secondary treatment of the liquid effluent (attached) with a significant reduction of helminthic parasites using filtration through red lateritic soil media, suggesting innovation holds the key, with the lowest cost and simplest method winning the day.

cheers
Dean

Interesting! I tried an HDPE fabric in combination with a gravel drainage when I was GIZ advisor in Uganda, so something similar to the Biofill treatment, but the fabric didn't last. It was what is used in the typical white sacks. Perhaps the temperatures in the chambers were too high and was making the plastic brittle.

As for the control of pathogens, I'd go with urine diversion as explained earlier. In that case, most of the nutrients would be either in the urine derived fertilizer and thus free of pathogens after some little storage, or in the worm compost, thus also strongly reduced in pathogen counts after some months of storage. The effluents would be easily treated in a Canna bed or something like that.

Cheers, H-A

Hi H-A,

there are a range of fabrics available (windbreak and shadecloth), these are very cheap. They are either knitted or woven and made from polypropylene or HDPE into monofilament or tape yarn. Thus the hole size varies dramatically and thus so too does the filtration capability. For example:

From my experience, of greatest importance is to discharge the flush on top of the pile. The pile sits on a layer of coarse bark and this acts as a kind of filter, with the cloth underneath to catch finer solids that filter through the bark.

This system requires flush toilet input to dilute the urine which otherwise will be too strong for the worms to thrive. Tiger worms will thrive and proliferate with nothing more than blackwater (water, human waste and toilet paper) influent, provided the environment is conducive for their wellbeing (i.e. appropriate temperature, drainage, humidity and moisture). Low flush toilets work, I've used the Dometic Sealand,
Dometic Sealand
...but because these don't have a trap and water seal there is a risk of flying insects that are part of the fauna in the chamber flying out when you flush. Biofil's "patent pending" microflush valve does not appear to overcome this problem.

Although producing pathogen-free effluent is the silver bullet, I'm not sure if that is always necessary. Of course every pathogen is different and some only require skin contact to infect, whereas others need to be ingested. Therefore methods of handling the effluent and the choice of crop would need to take into account the pathogens present, secondary treatment method, their persistence after treatment, how long they last in the environment, climatic factors, and what the vectors might be. The requirement in New Zealand and Australia for surface application of treated effluent is a biological oxygen demand of less than 20 g/m3 and suspended solids of less than 30 g/m3. No mention of pathogens.

Of interest to me is how well vermicomposting deals with pathogens, especially helminths. The literature is interesting in that results are conflicting, but most studies indicate significant reductions in the solids. Given that this technology is simple, inexpensive and likely to be effective at reducing pathogens (i.e. "win win"), I'd suggest 3rd party research is required into domestic vermicomposting flush toilet systems to quantify:

1. pathogen yields in the humus; and
2. pathogen yields in the effluent for full flush systems.

That would resolve the question around pathogen yields and potentially encourage further innovation in secondary treatment leading to irrigation of crops.

cheers
Dean

Thanks, Dean, that makes it a bit clear. Even though it is not so obvious to me that your point # 4 can be easily resolved. This is because the effluent would be carrying pathogens if people using the toilet are sick.

What do you call shade cloth? What kind of material would that be?

Kind regards,

H-A

Hi Elizabeth,
to answer some of your questions from 27 August (see in this thread here ), vermicomposting digesters work very simply. The effluent flushes from the toilet in through the top and adds to a "heap" sitting on filtration media. The liquid drains away through the media and is discharged to land. It is aerobic because the heap composts in an aerobic environment and the worms introduce air into the heap. They are very effective at reducing bulk and with sufficient worms present the heap grows only very slowly. Thus the system is aerobic and is a "digester".

Vermicomposting digesters are being used around the globe for municipal sewerage treatment and here in New Zealand have been commercialised for on site household sewage treatment for a number of years. These systems incorporate flush toilets and filtered effluent disposal to land.

Having experience with vermicomposting digesters I would suggest that the comments in the video that the system never needs to be desludged and that the sludge turns to sand are not factual. Solids do build up, albeit slowly, in the form of vermicast humus. Also, importantly, suspended solids will remain in the liquid outflow even if the filter media is very effective. The more effective the filter media is, the more likely it will clog over time or require maintenance. A filter media that lets more solids through will require lower maintenance. The biofil system uses porous concrete, whereas we use wire baskets, shade cloth and bark as the filtration media on which the pile sits. Small amounts of solids do make it through and although further filtration is an option for the liquid, maintenance and cost become an issue with secondary filtration.

The vermicomposting system deals with the solids very effectively and virtually without odour. The question in my mind is around the liquid effluent. This is still raw sewage being discharged, just with the solids mostly removed. Here in New Zealand local authorities are accepting that this may be discharged as primary treated blackwater, thus application to land via effluent trenches under the soil, just as with septic tanks. The question remains about longer term clogging of effluent lines from buildup of solids which only time will answer.

Although its difficult at this point to know what Biofil are doing because of the lack of information forthcoming, it appears that before mass deployment some simple design improvements may need to be made so that:

1. fresh fecal matter does not need to be handled when removing the humus (every couple of years);
2. flooding of the chamber cannot occur when inflow volume exceeds outflow capacity (i.e. soil infiltration);
3. filtration flow does not decrease from buildup of organic matter (i.e. maintenance); and
4. the nutrients and water are utilised for irrigating useful vegetation (the required cycle for environmental sustainability).

None of these issues are difficult to resolve, The question remains around what the most cost-effective methods are. The technology is low-tech and eminently suitable for application in third world countries seeking low cost solutions for hygienic effluent recycling.

Cheers!
Dean