Hi Detlef/Bogdan,

I appologise for not coming back on this earlier.
As a plant biologist and ecologist I contend that looking at plants with an engineer's glasses will lead to no knowledge at all. Plants are so complex and are affected by so many variants: temperature, saturation depth, NH/NO,nutrient soup, daylight length, growth stage, biological age, clonal age, genetic strain,disease succeptability......the list goes on and on.
To find out whether a plant is effective as a waste water evaporator, a good place to start is to look at dominant plants in habitats that have similar characteristics to the treatment site, use locally sourced species/strains and run a 1-2 year experiment to assess the effectiveness.
It would seem quite obvious that a plant with plenty of foliage such as the common reed (Phragmites australis) and Willow species(Salix spp.) would make good candidates for the Job, but that is not to say that there are'nt any others.

Bogdan: What is really interesting is the mentioned ability of those systems to notably and predictably transpire water in windy condtions so that we can use that feature for eco-engineering. Could you suggest any reliable reference what can be the figures in liters per square meter of planted area in relations to average wind speed, plant speceies and probably monthly average temperature?

Dear Bogdan,

You are right with you predictions on evaporation via leaves. I remember many years ago during my university times on the subject "Hydrology", as students we where calculating this evaporation figures based on solar radiations, temperatures & wind conditions. I can not remember properly on all, you may "dig" on the subject "Hydrology" and contact a proper Hydrologists direct.

During summer at least on "my" CW's evaporation via leaves is nearly 100%, as on the outlet of CW only drips of water leaving.

Good Luck
Detlef

Typical onsite wastewater treatment systems deal with lots of water per person per day (household greywater + full-flush toilet blackwater). In your case it's only number of visits x water volume per flush (incl. handwash) ...so calculating aeration tank volume to bring biological oxygen demand down to legal levels shouldn't be a nightmare.

The nutrients will indeed be concentrated in low-flush vermicompost effluent, even more so in clivus multrum leachate. Over here in this fellow rugby-playing nation nutrients don't need to be removed in the aerobic biofilter. The secondary treatment process is to get biological oxygen demand down and suspended solids down to levels suitable for safe surface application to vegetation, which would be the "tertiary" process that intercepts nutrients before they go into the water table.

I had assumed that you would have to discharge the leachate from a public clivus multrum. If you can indeed reliably fine tune the system using dehydration or some other method to avoid producing leachate discharge and without generating smells then you're probably on to a winner.

cheers
Dean

Hi Dean,

2 things about grey/black water in Ireland:

1. Our Rugby legend Brian O'Driscoll had once been quoted saying: "Knowledge is knowing a tomato is a fruit, Wisdom is not putting it in a fruit salad" and although he might have said it in a different context, it is very much relevant when it comes to Grey and Black water:
They are both waste waters but they are very different from both a biochemical ana d legal point of view. Grey water has at the very most a 10th of the N's and third of the P's of black water- probably a lot less when it is only a handwash basin, probably even less when you consider that the black water in question is undiluted by flushing water.
In Irish On-site waste water treatment regulations, any black water needs to be treated by a lot more than a biofilter to meet specs, the loading is calculated by the number of units and an arbitrary figure for visits in public places(I think it is 60 litres PPPD). So it is probably a territory that we do not want to enter if we can help it- as believe you me - it is a nightmare.

2. I believe a load-and-empty aerobic filter such as Clivus Multrum or Biolan produce can be very effective in neutralising nutrient loading comming from grey water as it is unactivated and typically will produce a very sharp biooxidation curve as a result. It may behave differrently with a very high activated leachate liquid - counteracting the success of grey water cleaning.
for those 2 reasons I believe it best to keep the leachate in the circle as much as possible and not to dilute it or discharge post treatment.

But including flush and other water will create an anaerobic mix not a compost.

Joe, you don't have to believe me, but having 10 years experience with wet composting of human excrement, I can categorically state that only where moisture content is beyond saturation (e.g. pooling of water) will anaerobic conditions cause problems. I'm not going to go into design details here, but drainage is the key, not the amount of water being added. Worms like the wet and efficiently produce humus in these conditions. Because it is wet, there are no bad smells.

Humus is better than compost, there is no active carbon left. My understanding is that earthworms significantly reduce levels of faecal pathogens (but not necessarily helminth nematodes) and once humified I'd suggest the "compost" is safe to handle. A resting period further reduces pathogens, but I haven't uncovered literature that quantifies such reductions over time. One can get carried away with expectations of fecal compost needing to be sterile and therefore safe enough to ingest... but the reality is that nobody wants to handle half-decomposed human waste, like what is often produced from dry composting, especially where there is a high volume of urine influent.

Thats the solid bit. Next liquids:

RonnieDeb, I'm interested to understand more about onsite wastewater treatment systems and your effluent quality standards. Is secondary treatment an option for you? If the washwater volume were instead filtered blackwater then I assume secondary treatment through an aerobic bioflter would also allow application to land. Secondary treatment of blackwater with solids removed is not a big deal in my mind, although overcoming the mindset of not wanting to add non-activated greywater to activated blackwater as a single treatment system might be...

cheers
Dean

Hi Joe & Dean

As I pointed out earlier in the conversation:
I was purposely using the term Decomposition rather than composting to refer to Cold Decomposition.
There is no doubt that by design we need to look at the worst case scenario in terms of what risks both environmental and health are created, Importantly however, we have to observe those risks in the context of the technology that they replace and what risks that carries and brings. so here's a little comparison:

Septic system:

High Coliform & Salmonella content preserved by nutrient rich anaerobic, gut - like acidic tank, then trickled out in an uncontrolled, unmonitored fashion into a percolation area which is supposed to be well away from the saturated zone but never is in a country with shallow soils and one of the highest rainfall levels in the world, then the excess trickles into ground water which then we drink and bathe in. Sludge in the tank forms a hotbed for all sorts of enteric pathogens and has to be pumped out by heavy machinery once a year to a highly expensive chip - composting plant in order to stabilise and sanitise the material. According to Irish EPA figures in 2015, 40% of all septic systems failed inspections on maintenance issues and technical malfunctions, not even looking at actual discharge quality, which has a 90% failure according to the same report.

Non flush, dampish, undecomposing closed chambers into which pee and poo goes(lets call it Clivus):

Excrement isolated from water cycle by plastic chambers where decomposition may or may not occur.
excess liquid is held in chamber until sump is full and then repumped into the solids with a backup of zero discharge evapotranspiration beds with under- surface irrigation. Much of the material returns to the atmosphere as water, CO2,NH4, N,Methane,SO2 etc. Much of the material remains infected with enteric pathogens but is handled so little that it does'nt form a risk.
In the extreme case that solid build-up is so fast that it outruns volume reduction in the 7 cubic metre tank it is either rested or emptied. in the case of emptying, the material is not completely dry but certainly not liquid and can be transported efficiently to a composting plant.
None of the material is used in any crop or foragable shrub to any extent.

Now you can make the judgement of which system is safer and less harmful to the water cycle.

We Cannot compare the existing technology with something that does'nt exist.
Irish law differentiates between solid waste and liquid waste in terms of biological indicators and treatment testing and is controlled by 2 completely separate pieces of legislation.
Livestock solids such as FYM can be left untreated so long they are covered from rain and do not leach into ground or surface water. Even Slurry from slatted units is considered solids even though it is sprayed on land...
The code of practice governing design and performance of on-site water treatment units is not relevant to dry toilets as it makes assumptions that are false for this kind of system.
I had been in this unchartered territory for quite a few years and to my understanding the best-fit is the agricultural waste of things which is regulated by the department of agriculture rather than environment(it is therefor easier to approve dry systems).

Grey water such as handwash basin can be treated in a small aerobic biofilter before being released into the sand. It requires no treatment system by law as it is considered negligent amount of pollution. I would certainly not add grey water, which is non activated to activated material such as leachate. Also you would'nt want to increase the volumes of liquid that you are hoping to remove by evaporation.

goeco wrote: Ronniedeb is right that hot composting is not viable using current technology in a public facility, because maintaining the very specific conditions required at all times to generate sterile compost isn't practical. I contend that composting does NOT need to be hot to be called composting.

Well I suppose what context it is that you are talking about. In the context of wanting to talk about composting systems which destroy faecal pathogens, then yes it really does have to be hot composting because all of the science suggests they're simply not destroyed in lower temperatures.

Humified compost that is produced non-thermophilically can contain viable helminth ova, but is that really an issue in Ireland? I would suggest important only if the compost is used around food crops, which doesn't need to happen in developed countries. Reasonable personal hygiene from those handling and disposing of the compost could be expected, such as rubber gloves and placement around suitable vegetation away from foraging children.

Let's be clear: people are talking about helminths because they're hard to destroy - and the thinking is that if it can be shown that helminths are destroyed then very likely all the other faecal pathogens are also destroyed (or more accurately reduced to safe levels). Helminths are probably not a public health issue in most places in most Western countries, and I'd be surprised if faecal treatment monitoring systems consider them in Ireland, the UK or elsewhere in Western Europe. But that's irrelevant - specific pathogens that are considered such as E.coli 0157 still require hot temperatures to be destroyed. And those conditions are only found in hot composting situations, therefore ongoing systems which cannot be shown to have met the temperatures are not considered to have been treated.

And I believe there is a lot of evidence to show that it is possible to get the temperatures in small systems. What is not possible is to have an isolated, unmanaged system in a wet, cold climate with variable amounts of carbon-rich material and then to suggest that this is treated - without any of the normal testing to show it. None of the evidence shows that this kind of system reliably kills faecal pathogens and there is a lot of evidence to suggest that it does not.

Of course, there may be other reasons to use these kinds of system - for example as simple collection vessels for faeces which is then treated further elsewhere. But it, in and of itself, is not doing any useful composting - as is simply proven by testing the end materials.

Joe, so only Ascaris lumbricoides is quantified when testing helminth ova content in wastewater, feces or sludge? In which case I am incorrect in assuming that all roundworm eggs are quantified, thus including Enterobius, Trichuris, Ancylostoma and Necator etc.

I don't know that Ascaris or other helminths are routinely tested in faecal treatment systems in any Western countries.

This document gives some information about the use and treatment of sewage in Ireland: www.meath.ie/CountyCouncil/Environment/S...nt/File,45832,en.pdf

According to that, the biological quality is measured via the presence of Salmenella and faecal colifoms, but I'm fairly sure a larger number of faecal pathogens are also routinely measured in the wastewater treatment plants and monitored by the regulators.

I also note that it says composting is only considered as a form of treatment when >55C for 3 days. This is because pathogens survive when this has not been achieved.

Studies looking at sanitation effectiveness in developing countries (particularly in South Africa) have looked at Ascaris and sometimes other pathogen worms. I don't recall ever reading that harmless worms were included in these studies - partly because the Ascaris work is so difficult to get right and costly.

C:N ratio and ammonia etc are only important with dry composting (i.e. no water added). Assuming that wet composting is anaerobic is the old paradigm.

Of course the moisture level has to be correct, as completely bone dry material will not compost either. But including flush and other water will create an anaerobic mix not a compost. Which is why I asked above about the dry matter of the material. If it is wet enough to be a slurry, it will not compost.

Ronniedeb is right that hot composting is not viable using current technology in a public facility, because maintaining the very specific conditions required at all times to generate sterile compost isn't practical. I contend that composting does NOT need to be hot to be called composting.

"cold composting" is of little relevance to sanitation

Humified compost that is produced non-thermophilically can contain viable helminth ova, but is that really an issue in Ireland? I would suggest important only if the compost is used around food crops, which doesn't need to happen in developed countries. Reasonable personal hygiene from those handling and disposing of the compost could be expected, such as rubber gloves and placement around suitable vegetation away from foraging children.

Joe, so only Ascaris lumbricoides is quantified when testing helminth ova content in wastewater, feces or sludge? In which case I am incorrect in assuming that all roundworm eggs are quantified, thus including Enterobius, Trichuris, Ancylostoma and Necator etc.

Mixed urine and faeces cannot compost on its own because of the high levels of nitrogen, so you have to add some kind of carbon source (sawdust, straw or something else) to get the material to have a C:N ratio of below 30:1.
And the moisture level is also important because too much water will produce anaerobic conditions in the material and will inhibit aerobic composting.

C:N ratio and ammonia etc are only important with dry composting (i.e. no water added). Assuming that wet composting is anaerobic is the old paradigm. Provided simple design criteria are followed, wet composting is indeed aerobic. The term "slurry" implies a mechanical process, because to generate slurry one needs to mix the solids and liquids together well. Simply "Pouring" toilet contents onto a heap with good drainage does not create a slurry. The presence of worms plus ventilation ensures the process isn't anaerobic, thus very simple and reliable.

Ronniedeb, how do you propose to deal with handwash water? By putting it down the toilet as flushwater the quantity of water doesn't increase, it just requires either disposal (e.g. underground soakage) or a secondary process before surface disposal. Putting it down the toilet allows you to use worms in a very reliable wet composting process. Sure, the liquid still needs to be disposed of but I am not familiar with your rules around disposal of secondary-treated effluent in high priority ground water protection areas. Perhaps handwash water can be deemed "greywater" and go straight into soakage untreated? Surely leachate from clivus-multrum would not be allowed to be discharged straight into the sand? Disposal of liquid effluent would seem to be an issue with both systems. There are a range of options for secondary treatment such as aeration, constructed wetlands etc...

Also, one needs to be careful when ruling out coniferous sawdust as a bulking agent. Generally, natural durablility of the heartwood is an indicator of species usefulness for composting, for example radiata pine is a non-durable conifer and the sawdust is fine.

Hi Ronnie,

Thanks for the mail. So the CM units are 7,000 litres (35 x 200 litres). Yes that does provide some leeway, but perhaps a tricky installation. I would make the point that the material can be taken off site to a composting facility and that onsite composting may not be a concern. Also you could have a number of toilets. On the soutis - after the 60 litres you just need to change the media but it's not a commercial size treatment unit. Please contact me on the website if you'd like any more information and I'd be delighted to provide. Many thanks - Patrick This email address is being protected from spambots. You need JavaScript enabled to view it.

Hi Toiletrevolution,

Thanks for the information.
I think a 200 litre tank will fill up in 2 days and would need a lot of backup.
The CM units are 35 times that size and therefor give some leeway.
The Biolan Soutis looks very interesting, particularly if there is a model that can handle more than 60 litres of leachate. Do you have test data for the Soutis that has been conducted with standard methods- I would be very interested to learn more!

Hi Ronnie,

This is a really interesting thread for us as we are a supplier of waterless toilets to the UK and Ireland. I think in this instance I would suggest the Biolan Populett as it has the advantage of being urine diverting if the user sits but also allowing males to stand. The other advantage is that there is no maximum amount of users as the bin can be changed over. The unit only required the 600mm of the toilet to be under the floor which is easier to work into the building than a CM system - in my humble opinion. Here is a link:

www.toiletrevolution.com/products/outdoo...-200-outdoor-toilet/

You could also add either a DC inline fan if you wanted to use solar or a cowl if you didn't. A self vented waterless urinal is also an option:

www.toiletrevolution.com/accessories/out...an-waterless-urinal/
www.toiletrevolution.com/accessories/out...-fan-non-electric-2/

If there is anything we can do for you let us know - Many thanks !

Hi Joe,

You are absolutely right about the Irish climate - not great for dehydration.
Actually Dry toilets are not about dehydration - they are called "dry" because they do not involve flush water and therefor produce little or no effluent.
I believe there is such thing as dehydration toilet but that is another matter.
I have to, again stress that we are not talking about"composting" here at the true and legal meaning of the word, however to state that the material remains unchanged forever more is simply not true and in my own experience I had seen it decompose and do so quite rapidly, despite there being no precise C:N ratio(at least not intentional).
You are right to say that the high levels of Nitrogen have an anti decomposing effect, however, Nitrogen, and particularly Ammonia are very prone to volatilisation and denitrification, particularly in a ventilated space and when in contact with Carbon, deeming that assumption to be temporary and local in A 7 cubic meter container. Many of the studies into composting refer to controlled conditions which cannot be replicated in a dry toilet situation - the only valid reference to these processes is experience and the toilets themselves.
I have attached a report in Swedish(which you can read with google translate) on the Susedalen Motorway rest area from the early days of the operation which shows a very poor standard of performance. The issues had been identified and addressed and the second report from 5 years later shows that the problems had been rectified and performance restored.

My point is: we have to learn as we go along and correct the process, we need to overdesign and be flexible and modular in our assumptions - there is enough evidence that the technology works and the more of it happens the more we learn - a good example is this forum.
We are not talking about a high risk operation or completely unchartered territory that we need to base our decision making on laboratory tests and desk studies!