[iacopo.russo (OP)]

Jil from New Zealand wrote to us to ask:

One thing that concerns me is the amount spent on infrastructure to deal with sewage. This whole idea of using water to shift sewage around in pipes to treatment plants, seems the wrong way to deal with it, in a world that moves, has earthquakes and floods.  And now the trend is to regard sewage as a resource to extract water and nutrients from.

Would it not make more sense to render sewage harmless as soon as possible (using enzymes, heat, light treatment or whatever? ) and then put that neutralised product back into the local area, rather than transport it to a processing plant?

I know there are some domestic sewage treatment options out there which a minority may be able to afford or develop. I understand sewage in space is dehydrated and brought back to earth. The future has to have something less risky than piped sewage. Effluent overflow is such a major problem in times of disasters. I am sure there are brilliant minds out there with solutions.

What do you think?

[alancalverd]

The "earth closet" has been around for hundreds of years. It works brilliantly to provide useful compost but is impractical in an urban society - "nightmen"  used to collect poo and pee with a horse and cart, but then somebody had to clean up after the horse and London streets were often rendered impassable. After The Great Stink (1858) Bazalgette was commissioned to upgrade the old Roman cloaca system and reintroduced waterborne sewage disposal as the standard in all modern conurbations. HIs descendants still deal in sh1t, but as television producers rather than civil engineers.

[evan_au]

I heard that some people were experimenting with separating urine and feces at source, as they are much easier to process separately.
Apparently, they each have a unique set of nutrients, and when you put them together, it is very nutritious for the wrong set of microbes. If you keep them separate, you can produce more useful products, and the processing time is much shorter.
But it requires a urine-separating toilet (and presumably, a good aim).

By the way, this was one driver for the recent research on the "Moo Loo".
https://www.abc.net.au/news/2021-09-15/nitrous-oxide-levels-reduced-if-cattle-toilet-trained-research/100460510

[Colin2B]

Apparently, they each have a unique set of nutrients, and when you put them together, it is very nutritious for the wrong set of microbes.

A friend in special forces says the army learnt this the hard way. On patrol they put waste in sealed bags so as not to leave trails, if urine and faeces are in the same bag they explode   

[Bored chemist]

One big problem is the infrastructure.
It would be great to have separate waste systems for the toilet, the bath, industrial waste and the run-off from the roads.
But they are all mixed together.

We would need to rebuild our city drain systems with 3 or 4 times as many pipes.

[evan_au]

We would need to rebuild our city drain systems with 3 or 4 times as many pipes.

In Sydney, rules were changed long ago to require separate pipes for stormwater runoff (eg from the roof) and sewage (eg from the toilet/bath). This has greatly reduced instances of sewage plants overflowing in heavy rain (which then dumps lots of raw sewage into the nearest creek). Some old houses still have them combined.

More recently, it is now required to have onsite storage for storm water, which reduces flooding of creeks, and reduces consumption of drinking water for watering lawns during droughts.

Some newer houses are separating "grey water" from bath & sink, and using that for watering the lawn. But this is not legislated (last time I looked).

[alancalverd]

Ever wondered about the distinctive smell of genuine Harris tweed? The traditional dye mordant is human urine - an ecologically sound use for stuff that would otherwise go to waste. Apparently it was exported in bulk from Yorkshire pubs and returned as bolt cloth to the factories in Leeds, one of the finest examples of a circular economy.

[Bored chemist]

The Romans were keen on urine too, as a laundry detergent.
More recently, it was used as a raw material for gunpowder.

It's not a great source of nitrogen for plants; there's too much salt in it.

On a tangentially related note, some big buildings have "surge ponds" to collect the rain from sudden storms and let it into the drainage system more slowly.

[alancalverd]

On a tangentially related note, some big buildings have "surge ponds" to collect the rain from sudden storms and let it into the drainage system more slowly.

Also, as I discovered by experiment, very handy if the building catches fire whilst containing radionuclides. The fire brigade does a fine job of washing any soluble stuff into the drains, and we were able to contain it on site for several half lives in a series of ponds. Not quite Chernobyl but a very interesting few months.

[Petrochemicals]

They are beginning to deal with sewage in different manners, all new houses are ideally built with different systems

Black water, - toilet water basically into the standard sewer
Grey water - showers and washing machines retained to be used for toilet
 flushing garden watering, supplented by rain water. Not sure how the biological clothes powder will sit with the grass
Rain water, - retained as grey water if needed or into a seperate sewer for local discharge, at this time it can be put straight into the standard sewer as infrastru ture is not present to deal with it but all new UK houses are now supposed to be built with dual sewers.

This is very informative

https://www.bbc.co.uk/iplayer/episode/m000t8zl/the-secret-science-of-sewage

[Bored chemist]

all new UK houses are now supposed to be built with dual sewers.

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