Off grid living, part five — effluent disposal

This is the last in a series of blog posts by the architect Mark Stephens on going off grid. The full series can be found here.


A flooded percolation area is a serious health hazard

Welcome to this final blog post on living off gird, which focuses on the safe disposal of any wastewater from a house not connected to a public sewer.

This topic is probably the one that Ireland has the most experience with (both good and bad), due to the lack of sewerage infrastructure once you leave the main towns and cities. There are currently around 500,000 on-site wastewater treatment systems in Ireland, and many are believed to be contributing to groundwater pollution due to poor design, maintenance and lack of regulation over the years. The EU recently ruled against Ireland for this, and the mandatory inspection of such systems is expected to start within the next year. 

This is also the one topic that will cause the most problems if you are looking for planning permission on a new house or more particularly the renovation of a ruin or abandoned house.

So let’s have a little look at the history of effluent disposal in modern times.

Septic tanks

The traditional septic tank would have been a concrete single chamber system — the outlet would have simply been piped out into a ditch that drained into the next field.

One problem arising with these systems is that frequently the farmer working the field would fill in the ditch, causing the effluent to start backing up. Then you could find yourself standing in a field slowly submerging in crap (this has happened to me on numerous occasions). A system like this also provides little treatment of effluent.

An article by Lenny Antonelli in issue twelve, volume four of Construct Ireland discusses precisely this problem and the bacterial hazards that are created.

The next stage on from a single-chamber septic tank was the dual chamber (again constructed in concrete). This system allows the solids to settle, with the second chamber taking the overflow which then exits the tank in a similar way. The same problem described above will also occur if the overflow effluent isn’t treated correctly. It’s therefore essential that a proper percolation or polishing filter system is designed and constructed within the curtilage of your own site.

Proprietary effluent treatment systems

A proprietary effluent treatment system utilises some form of aeration or mechanical purification/digestion before the wastewater exits the system. If properly designed for your site conditions, these systems can treat the effluent to a high standard, but consideration must still be given to what happens to wastewater when it enters the field. Most of these systems will require an electricity supply, which will add to your energy usage (and some may say goes against the off-grid ethos). One advantage of such systems is that it is possible to test and verify the quality of the effluent as most of the treatment is done in the unit itself, whereas with septic tanks more of the treatment takes places in the soil itself, making testing of final effluent difficult for these systems.

Composting toilets, reed bed systems etc

The principle of the composting toilet is straightforward — the solid waste goes into a separate section to the liquids, and the solids then dry and become first-class manure for the land. To create this compost requires a bit of time away from human contact which thereby breaks the cycle of the pathogens. Another option is rapid hot composting where usually sawdust or straw is added in order to kill all the known pathogens to humans in hours. But it will typically take about six months for compost to be available in dry conditions, longer if it is outdoors in a damp location.

Another popular way of percolating any waste in the ground is via a reed bed system, which is a natural solution that works ideally on a site with a fall where any effluent trickling through the reed bed is cleaned by micro-organisms living on the root system. Micro-organisms here break down the sewage in the presence of oxygen (ie aerobically). Your site will need to be physically suitable for a reed bed, and you may have difficulty convincing the planners that your system will work.

Planning

Any new effluent treatment system, either for a new house or a renovation will require planning permission. It is often thought that because a house was previously on the site (say for example, a wreck with no septic tank) you will have a better chance of obtaining planning permission. But I have seen many a dream quashed when planning is refused because the ground on site wasn’t suitable. The rules may be relaxed a little if the house already has a septic tank - a proposed upgrade may be acceptable if it improves treatment even if it doesn’t exactly meet the Environmental Protection Agency's Code of Practice. But you will find it harder to convince planners about any new system that falls outside the remit of the EPA Code of Practice.

If you're looking to install a new effluent treatment system for your new build or renovation project, start by contacting an experienced engineer or similar professional who can advise on the most appropriate system design for your site.

So that’s it, my take and discussion for living off-grid. With the country currently in economic turmoil, maybe living a simpler life not connected to electricity, water, sewerage etc doesn’t seem too mad cap after all.

Special thanks again to Nick Rosen's book How to Live Off-Grid.

Mark Stephens ARB RIBA MRIAI is a UK and Ireland registered and chartered architect specialising in sustainable, unique designs.