A question for all caravaners

[PeterS2018]

Hello all.

Please forgive my ignorance, but let me start by saying I am not (currently) a caravaner. My background is as a services engineer and I am looking to develop what I see as an improvement in sewage treatment in tiny house design, an issue you all have to deal with in your caravaning lives I presume.

My idea is to create what on the surface looks like a regular flushing toilet you would get at home, but once flushed would treat the sewage at source. Upon flushing, the mix of solids, paper, urine and water would be centrifuged to separate the urine/water mix from the solids. This leachate, as it is known, would be treated by passing through a reverse osmosis filtration system, which produces water that is of drinkable quality to be re-used in flushing the toilet the next time. The mix of solids and paper, having been dried substantially in the centrifuge would be passed into a composting system for turning into dry compost that is safe to put onto the garden etc.

I understand that this would mean having to deal with the compost, but to me it would be preferable to deal with clean smelling compost rather than raw sewage. Obviously, when moving there would have to be some system to cap the water in the bowl/U bend to stop any splashing at the same time as maintaining the water seal to prevent smells.

I would greatly appreciate any comments, good or bad as I don't want to spend months on the design and testing of this only to find some problem further down the line that someone with more experience might be able to spot straight away.

Thank you for your time reading this - happy caravaning!

PeterS2018

 

[camel]

How does your system compare weight wise with a Thetford cassette or any other system, caravanners do have a thing about keeping in the pammeter on weight we don'the have much to play with.

 

[CustardAvenger]

Hi Peter,
Interesting idea. I've seen a few documentaries on "Tiny Houses" that were designed with composting toilets and were intended to be moved, but were not truly mobile. I guess the main concern from a caravaning perspective is weight. In the standard cassette toilets used in caravans, the flush tank and waste cassette are emptied prior to towing so keeping liquid contained is not a concern. I have no idea how much a cetrifuge and reverse osmosis system would add to the MiRO (unladen weight) of a caravan but it may be prohibitive. Also would the composting of solid waste be onboard or dumped (no pun intended) into an external receptacle? As this would technically be classed as payload and would need to be factored into the caravan MTPLM (Maximum weight) if it needed to be left to properly decompose.

Paul.

 

[VicMallows]

The situation where such a system might be useful to caravaners/motorhomes would be for camping 'wild' away from on-site facilities. However this scenario leads to two problems:

1) You will need fairly substantial power for both the centrifuge and the reverse osmosis. In the absence of mains electricity, power is always a precious resource, even today with PV.

2) I am rather surprised that reverse-osmosis would work satisfactorily with the leachate, but presumably you have investigated this. However surely copious amounts of clean water will still be needed for reverse-flushing the osmotic filter? ..... and again this is a precious resource when 'wild' camping.

 

[PeterS2018]

Hello Camel
Thanks for your reply - to be honest, at this stage I would assume that the first version of the system I'm envisaging would be heavier than the current cassette, however the aim would be first to do a proof of concept, followed by revisions regarding the weight if it were to be used within the caravaning field.
PeterS2018

 

[PeterS2018]

Hello CustardAvenger
Thank you for your reply. As with my reply to Camel before I would assume the first version of the system would be heavier than the current cassette unit, but if it passes proof of concept, then I may look at some form of miniaturization to maybe reduce weight. In my case the end goal is going to be the fact that I'm designing a "large" tiny home that will be based on a 40ft HighCube trailer. Since this will be pulled by an Artic, weight in my case won't be too much of a concern. The final siting of the house will be in Greece as temporary accommodation whilst having a permanent house being built. As such I would be composting in place.
PeterS2018

 

[PeterS2018]

Hi VicMallows
Thank you also for your reply. To your first point, I would agree that it will probably be fairly power hungry, however again for my own project, the intention is to cover the roof of the mobile house with PV, which should give a 40ft x 24ft surface area, and with the addition to wind and possibly a small packaged power plant will supply more than enough power to run the intended equipment.
As regards the second point, RO can be used to treat leachate satisfactorily. Flushing may be an issue, but one of the separate technologies I'm testing out is using solid state condensation of water from the air using Peltier plates, which will also provide Heating and Cooling (Hence all the PV).
PeterS2018

 

[PeterS2018]

Thanks to everyone who's replied so far and to everyone else who've taken the time to read the posts. As you can my own case is rather a special one, however off the back of the work I'm doing I may be able to create something of use to the caravaning industry as a whole. To date the issues raised are
1. Weight of suggested equipment (twice)
2. Power requirements
3. Quantity of water to back flush filters.
If anyone else has any comments please feel free to post. In the meantime I will research the points raised and keep you all posted on progress.

Thanks again for your time and help

PeterS2018

 

[otherclive]

Whilst your system isn’t currently focussed on caravans I’d be interested to know how you get on and what you end up with. Keep us posted please. Good luck.

 

[ProfJohnL]

...If anyone else has any comments please feel free to post.

In the following series of points I refer to hazards. This should be considered in the context of being more haradous than current equipment or practices.

Can these systems be left for several months between use or is there any regular maintenance activity required to keep them functioning?

Will any special chemicals be needed, and are they toxic or hazardous?

How would the system cope with freezing conditions? One of the perennial problems with most caravans is freezing during storag winter storage. Most years we get some questions on the forum resulting from frost range because water containing systems have not been correctly drained. Issues such as burst tanks, and damaged valves, damaged water filters etc.

Will it be smelly? Caravans are small enclose spaces, and any smells quickly pervade the whole caravan.

How noisy will it be? Caravans are more like guitars than brick out houses, they transmit and have a tendency to amplify vibrations both inside and out. So noise and vibrations must be kept as low as possible.

Is it going to be easy to keep clean? Cleanliness is obviously important from a hygene point of view, but also the emptying and refilling of any aspect needs to be manageable with the minimum of special equipment.

How often will it need emptying? I know that will depend on how much it's used, but it would need to match or more the capacity of the current competition . If it's bigger and lasts longer, will the weight of the stored waste become a problem, not only for manhandling, but also the additional mass being carried in the caravan. As has already been mentioned we are very weight sensitive, especially if the load is at the rear of the caravan which can affect towing stability.

Will it be dangerous in the event of a road traffic incident when towing? The media love caravan smashes, they are spectacular because of the way caravans tend to disintegrate splaying their content across the highway. If this happens and the closest losses it's integrity, can it release any hazardous materials, or pose any other threat to people or the clearance of the incident.

Cleaning or replacing filters etc? Will this be required, how often and how expensive. What about disposal of used filters? Are the classed as hazardous?

Cost? Obviously that is an unknown at this stage but as with weight caravanners tend to be cost sensitive.