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The safe and effective treatment of sewage is one of the
hallmarks of civilization. Human population rise,
increasing
urbanization and concern for public health demand more
capacity and efficiency from treatment facilities.
There are a few standard methods of treating sewage. As
far as I
can tell, the first step is to filter out the big
chunks, boulders, bits of tree, alligators - that sort of
thing. Then, water is allowed to settle, so the finer
particulates have time to fall through the water column
to
the bottom. That gives you a sludge, which is usually
carted off as someone else's problem. The next step is
usually some kind of microbial digestion. This may be
achieved by spraying contaminated water over pebble
beds
which house myriad species of aerobic bacteria that use
air
to oxidize organic compounds in the water. The organic
compounds largely end up as CO2 and biomass, i.e. the
bacteria use the organics as fuel to make more of
themselves.
The biomass created can be a problem, it has to go
somewhere. There are some attempts to dry and burn it
for power generation, but there are problems with
efficient harvesting and drying.
To increase the Organics>CO2 conversion and reduce the
biomass problem, it would be helpful if the bacteria
were
less efficient. This would lead to bacteria using far more
organics to stay alive and having much less overhead to
divert into cell growth.
To make the bacteria less efficient, we add chemicals
that
make the cell membranes selectively permeable to
common ions. A good example is 2,4-dinitrophenol which
is
a protonophore. It allows H+ to easily travel through the
normally sealed phospholipid membranes. Now the
bacteria spend an awful lot of energy moving H+ in one
direction only to have it flow back through the 2,4-DNP.
On
a large scale this can create a lot of heat. That's no
problem, however, there are plenty of thermophilic
bacteria that digest sewage. In fact there are
thermophilic
aerobic digesters <link>, which can need a lot of heating
but are great at breaking down some difficult
substances.
The DNP should dramatically reduce any heating
requirement, in fact there may well be enough medium
grade heat for power generation.
All that remains is to get all the DNP out of the water...
Aerobic digester
https://en.wikipedi...i/Aerobic_digestion
[bs0u0155, Feb 25 2019]
Living Machines
https://en.wikipedi...wiki/Living_machine
[2 fries shy of a happy meal, Mar 01 2019]
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Annotation:
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It goes without saying that genetically engineering composting bacteria to have leaky membranes could also work. |
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//genetically engineering composting bacteria to have leaky
membranes could also work.// |
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You'd have to include a fairly robust selective mechanism,
otherwise, the environment will favor mutations that inhibit
the uncoupler, and your population will be wild-type in
short order. |
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I think evolution would be a problem anyway. Sooner or later
you'll just evolve a bug that pumps out the DNP, or has a
protein that binds it and stops it acting as a protonophore. |
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//bug that pumps out the DNP// That's OK. There's a whole
lot of protonophores, then we can start on Na+, K+, Ca2+
and so on. You can even do non-lethal electroporation
cycles. |
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//You can even do non-lethal electroporation// So, a typical
EP voltage is about 1kV/mm. If your sewage bed is 10m
across... Arcing is going to be an issue. |
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//Arcing is going to be an issue.// |
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If by "issue" you mean feature... |
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Why not just replace the bacteria that have gotten too good
at life with ones freshly engineered to be bad at life? |
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//If by "issue" you mean feature...// Well, putting a few MV
across a rich organic soup that is bubbling with methane
would definitely feature in some way. |
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I've been looking into a system called Living Machines you might be interested in, which quite elegantly deal with shit the way I think it should be dealt with. There is an entire office building using one of these prototype systems where the contents of all of the sewage produced within the building is treated and filtered using settlement ponds and plants down a man-made river, and here's the kicker... the waterfall feature in the lobby is the end result of the cycle before the water is then re-used.
[link] |
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As for anaerobic bacteria creating methane and stench the obvious solution is not to constantly turn a compost pile so as to aerate it but instead to use the waste heat to heat water for in-floor heating while a stationary pile decomposes with a methane digestor at its core providing natural gas as a byproduct. |
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I am planning to purchase or build a small campground/cabin rental property and have been looking into these things for a bit now. (+) |
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So in that office building, if you drink from a drinking
fountain, you're drinking water that's been exposed to
people coughing, sneezing, and dropping things in it? |
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//Living Machines// I don't see the advantage in having each
building deal with its own sewage. One of the advantages of
being a communal species is that we can specialize. It has to
be more efficient in every way to have sewage dealt with
centrally. |
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//It has to be more efficient in every way to have sewage
dealt with centrally.// |
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I was halfway through writing up this exact point, only I
was making a poor job of it. It's begging for problems to
entangle a sewage plant throughout a building. It's only
function is greenwashing, which with algae blooms will be
successful. The same priorities are seen with skyscrapers
with wind turbines in them. They work poorly, because
airflow is always going to be complex, and they often
generate nasty oscillations that make the adjacent
occupants complain so much they end up turned off. |
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Nature did everything locally but just not at the scale we need today. We will need to shrink that process to the locally safe scale for space stations, starship development and colonising, out there, earthly nooks. |
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Starting with office buildings seems fertile ground. |
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As for the manipulation, Is the process known 100% ? because allowing nature free reign on an excess of resource because one species is inefficient usually has unknown consequences. |
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//So in that office building, if you drink from a drinking fountain, you're drinking water that's been exposed to people coughing, sneezing, and dropping things in it?// |
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Only non-potable water in the system, but I believe it is reused as gray water. |
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//I don't see the advantage in having each building deal with its own sewage. One of the advantages of being a communal species is that we can specialize. It has to be more efficient in every way to have sewage dealt with centrally.// |
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I was thinking mostly about off-the-grid applications but it would be great if individual buildings were autonomous, producing their own energy and dealing with the waste created.
Compost gives off the same BTU's as burning the material but over a longer time. If that waste heat can be used to augment power generation then it would ease a lot of burden on existing systems as we grow. |
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//Is the process known 100% ?// |
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It's supposed to be the way nature already takes care of things... just sped up by maximizing conditions for plants bacteria and critters to do their thing. |
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//I was thinking mostly about off-the-grid applications //
Good. |
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//but it would be great if individual buildings were autonomous, producing their
own energy and dealing with the waste created.//
No, it would be terrible, and an environmental disastrophe. It's inefficient,
wastes resources, and is hazardous. Treating water so that it's safe to be put
back into rivers or the sea (which is where it tends to end up) is a serious
business. Do you really want a city with 2000 different treatment systems, all
discharging water that may or may not have been properly remediated, and which
will be almost impossible to regulate or police adequately? When it turns out that
your local river is seething with mycobacteria, who do you go and talk to? I want
potentially hazardous waste to be handled by professionals, who can use
economies of scale to add more treatment steps and who constantly monitor
what's going on, and who can be prosecuted if it goes wrong. |
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The idea of everyone being responsible for everything they need or do is a terrible
idea. It's incredibly wasteful of resources and just makes people feel that they're
helping the environment when more often than not they are harming it. |
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From what I understand, unlike conventional treatment plants, absolutely none of the gray water goes back into our streams and rivers at all.
What isn't expelled as water vapor gets recycled for evaporative cooling, to water plants in the building, and re-flush the toilets.
The leftover biomass from the plant matter and residual sludge composted properly becomes the soil for ornamental plants throughout the building and none of it goes back into the environment. |
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It beats the hell out of current septic systems and is potentially far more efficient and environmentally friendly than our waste treatment facilities. |
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//The idea of everyone being responsible for everything they need or do is a terrible idea. It's incredibly wasteful of resources and just makes people feel that they're helping the environment when more often than not they are harming it.// |
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I think that designing architecture for self sufficient systems is the future so I guess we should probably figure out how to make it harmless and less wasteful. |
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// is potentially far more efficient and environmentally
friendly than our waste treatment facilities// |
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I flatly don't believe that, not even remotely. Do you have
numbers? And if you have numbers for efficiency, do they
include build cost, land cost, space cost and operational costs
and maintenance? And how are they more environmentally
friendly than a modern sewage treatment plant that doesn't
use chemicals, produces near-drinkable water, and makes
fertiliser? |
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They discuss the differences between living and conventional treatment systems on the link. Numbers are kind of lacking but construction and maintenance costs are all well documented in the external links on that page.
They claim the systems become so efficient that the caretakers "shock" the ecosystem periodically to keep them from becoming unresponsive to change. |
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Basically;
-Reusing water until it evaporates entirely is better than pumping (almost) drinkable water into our rivers.
-Turning the sludge into biomass is better than burning since heavy metals and such are dealt with and waste heat can be recouped.
-It allows us to expand further without so much reliance on centralized systems. |
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In nature's way, fecal material didn't need a pool of water unless it was a species already in water. The natural resource had to be used before drying out or being too mixed with soil. Water is man's effort to made it easy, cheap to deal with and easier to centralise. |
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True. We've got quite a problem with out-houses in our parks and on our trail systems with the shear volume of people using them. The latest solution is to build suspended toilets rather than out-houses, (for airflow), above a deck large enough to let them be re-positioned every so often, with a large bucket of wood-shavings next to the toilet paper for when you're done, and once in a while somebody tosses a bag of worm-castings down there. Human waste turns back to soil very quickly this way and with minimal odor. |
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That doesn't work in a city so we need to use water, but decentralization of this process just makes sense. |
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But is there a historical inertia? There isn't really any need to look for other city solutions. |
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I suppose economics rather than sense will force change if grey water is useful as a source for the potable gold. |
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