Fresh water is a finite, non-renewable resource. A limited supply becomes available each year as a result of rainfall. Climate change and air pollution lead to less rainfall each year. Land use and municipal sewage policy lead to unnecessarily wasted water. Together these factors mean that our limited water supply is shrinking each year, and becoming an existential threat to global civilization. A few areas are already practicing some limited water reuse by repurposing grey water from sink and shower runoff for things like flushing toilets and watering subsistence crops. While this is an excellent way of extending the limited supply, it does not address the core of the issue and it does not increase the still-shrinking supply of fresh water.
At the scale of individual homes as well as communities, it is currently illegal to reclaim black water for radical water-reuse. (Smoliński) In fact, even in Taos where the Earthships are, homes are required to use archaic septic systems rather than composting their solid wastes, capturing biogas, and reclaiming the fresh water from sewage. There are already water wars around the world and they are only going to grow and spread as our limited fresh water supplies continue to shrink each year.
The cost of access to fresh water is enormously high for many of the most impacted populations in our society. The fact that we require them to dump their black water into the ground and buy new fresh water is a moral outrage. There is just no reason the ban on the centuries-old bioremediation and water conservation techniques that indigenous societies from Mexico City to Thailand have used to subsist for millennia. (Levy) Nor to ban the modern science of biogas capture which is both a great source of energy and a powerful way to lessen the impacts of climate change.
Black water comes out of toilets and goes into urban water remediation plants. These plants use enormously water-intensive processes to dilute and sterilize black water before dumping it into rivers and oceans. I spoke with the chair of the American Conference of Mayors who said that the typical city adds thirty to thirty-six times more fresh water to sewage in order to dilute it before sterilizing it and then dumping it into the rivers. This method of remediation compounds the problem of water scarcity by wasting even more water in order to safely dispose of sewage. An alternative method would be to reclaim the sewage without dumping it into the oceans. Sewage contains fresh water plus waste products. These waste products can be extracted to produce safe and valuable compost, leaving behind fresh water which can then be reused indefinitely.
The process of reclaiming sewage is exactly what the earth is doing with our diluted sewage when we dump it into the rivers and oceans. The water later evaporates from the oceans and precipitates as our limited and shrinking annual rainfall. We can skip this step and choose to reclaim the water directly. There are many safe and effective reclamation methods available to cities which would save them an incredible amount of money and water. The dream of water sovereignty is within reach for cities around the globe.
After cities dilute their sewage, it is sterilized using a two-step process. First, they deprive the mixture of oxygen resulting in what’s called an anaerobic stage of processing. All bacteria can survive either with oxygen or without oxygen but not in both situations. So the anaerobic process kills those bacteria that need oxygen. The next stage of the process exposes the sewage to lots of oxygen. This is called the aerobic stage of processing, and it kills the remaining bacteria which can not survive in the presence of oxygen.
During the anaerobic process, enormous amounts of methane are released. This is extremely dangerous for the environment. Methane is 100x worse than carbon dioxide as a greenhouse gas. Methane is also what natural gas is made of, and so it can be captured and used as a fuel source. This process of capturing methane during the anaerobic process is called biogas digestion. Biogas digesters are already in place all over the world providing an enormous amount of power to communities, while also safely processing their sewage into compost. In one case study, a test farm in California is using a biogas digester to process their sewage. They produce enough power from this process to run all their buildings, tractors, and even their vehicles. The potential value from capturing biogas is huge. We could be powering our cities this way. To reiterate, burning that methane reduces its impact on climate change by 99%.
Next is the question of separating the solids from the liquids after they have been processed. There are several techniques. Perhaps the most interesting is the swirl filter technique. There is a property in fluid dynamics where a fluid forced to rapidly change direction will drop any particles it holds in suspension. This is how non-filtering masks work to prevent covid transmission, and it’s also how existing aquaponics systems remove fish wastes from water. These filters are a perfect match for the challenge of removing any solids from the water coming out of the biogas digester. (Kramer) Additional stages of permanent filtration can remove any microparticles and produce completely pure water. There are even simple and straightforward processes available to eliminate any drugs, hormones, or other complex organics. (Faul) Any solids removed from the now-pure water can then simply be composted with wood chips and other material to produce fertile compost. These solids form an enormously beneficial soil additive which actually improves the quality of the soil over time as it is applied. (Halecki)
There is a lot of discussion around the world about what to do with the pure water that we have reclaimed from sewage. It’s now perfectly pure water, (Mazuki) but pure water that did not pass through the Earth’s precipitation cycle after its last trip through the human body. It therefore carries a stigma. In one case study, Israel is using this pure water to replenish aquifers through bioswales. (Abbo) Bioswales are a far better alternative to septic systems for many reasons; they can also handle storm water, they use bioremediation to put the water back into the ground rather than simply storing it in a tank which must eventually be emptied, and they let sun light in to keep the transfer medium sterile in the bioswale. (USDA) Bioswale aquifer replenishment seems like an ideally suited solution for California in particular where aquifer depletion is so extreme. (Abbo)
I interviewed the president of the Taos Earthship Biotecture Academy about the potential for simply returning this pure water to a home’s holding tanks. He explained that this is actually illegal at present, and they struggle with a great deal of legal challenges to even far simpler sustainable technologies like composting toilets. (Center for Environmental Research Information) The civic policy front has a great deal of catching up to do in order to legalize these kinds of proven, straightforward solutions to the many existential threats we face. Until then, we are likely limited in the short-term to things like aquifer replenishment as a use for this kind of reclaimed water. It’s also unclear how legal biogas digesters are across America, but again they are a far superior alternative to current standards which have already shown they can power whole communities off the pollutants currently being emitted by their sewage. There is a wide range of solutions and systems to address these issues at every scale. They have been thoroughly studied for thousands of years in some cases. (Levy)(Wang) These solutions have already been proven at the scale of the city as well as the scale of the community or the individual home. (Ham) It’s not just the right thing to do morally and environmentally, but this system also stands to earn enormous profits for the first-mover who implements it on a wide scale, and for those homes and communities which adopt these changes and reap the benefits. (Axelrad)
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