Esgoto como fonte de recursos

My name is Guilherme Castagna, and I want to talk to you today on the theme of Wastewater as a Resource. Over the past few years, decades . .

. centuries in fact, humanity has seen sewage as a problem that needs to be addressed. But this, I believe, is a wrong point of view, because sewage is not a problem, actually sewage can be a solution for a multitude of things.

If we stop and look, after all, what sewage is, it is nothing more than a constant flow of water with the presence of organic matter and nutrients, and embodied energy, which can be reclaimed. All of this is available on any scale we are working on, from a house to a municipality. The focus of this conversation is on the small scale, what you can do in your home, or in your small business to handle it more intelligently.

If we stop to look at a house or business as an organism, we will understand that there is an outflow, which is what we naturally call sewage (wastewater). This flow then consists of larger or smaller portions of water and a certain concentration of organic matter. What happens is that out of the total volume that is produced in a house, grossly 75% of it it is what we call gray water and the other 25% is what we call black water.

Only this 25% correspond to a volume that needs to be effectively treated. Within our own body, if we look at our excretory system we will see that we also have a flow of liquid resources, urine, and a flow of solid resources, the stool. People try to find ways to spend as little as possible to “solve this problem”, then they through it in a hole or in a “black pit”, in a stream or river, anywhere not caring who is ahead.

When we misuse this sewer and end up dumping it in inappropriate places, dealing with it inappropriately, we will end up contaminating the next user ahead. And it is always good to remember that behind us there are also people. So, it is time to see ourselves as part of a flow, as in a cycle, and be willing to enter and recreate a virtuous cycle.

A cycle where we produce resources that can be reintegrated into the production cycle. Throughout history, several peoples have known how to deal with sewage in a much more intelligent way than ours today, even in the middle of 2017. If we take the relatively recent example of several Southeast Asian countries in which rice cultivation areas were integrated with urban areas and where there was really a trade in people's excretions, nocturnal excretions - it even got a name, it was called "night soil".

There were traders who collected these materials and took them to the barges and where there was a trade where this material was taken to the cultivated fields around the city. So, through this, a direct relationship was created between the entry of nutrients into the field and the return of food to the city, that is, a closed cycle. In our cities, and even in the way of dealing with agribusiness, fertilizers are brought in from outside and the cycles do not close.

Not only does the sewage end up contaminating the water and does not return to fertilize the cultivation areas, but the rest of the food itself ends up being discarded, taken to the dump, and this opportunity to return to the fertilization cycle is lost. The population growth that we see as a problem, in fact, can be an opportunity, because the more people there are on the planet, the more fertilizer is being produced. Each person produces about 50 liters of solid feces per year and 500 liters of urine, and this liquid nature of urine facilitates the dynamic of nutrient conduction.

So, we wouldn't even need water to carry these nutrients wherever we want to take advantage of them. On the other hand, if we look at the total amount of nutrients produced by a person, we have the equivalent of fertilizer for about 230 kg of cereal production, per person, per year. When we look at the total amount of these nutrients made available by our liquid and solid stools, about 94% of the nutrients are present in the urine, and only 6% in the stool.

This means that our faeces can be used more as a soil builder than as a nutrient itself. Within the cycle of mobility of these nutrients, nitrogen is a nutrient that is available the atmosphere and that is simply recirculated in here. Now through the air, it is discharged into the soil through lightning streams, and this is incorporated, it is brought by the plants through their growth and, after death, it returns as a nutrient to the soil, or partly lost to the air And that has a cycle that is continuously recirculating on the planet.

Phosphorus, which is another key nutrient for plant growth, on which a good part of chemical fertilizers are based, is exploited in a mining process. It is available in phosphate rocks, from which mining takes this material and turns it into fertilizer that can be used in crops. A good part of these nutrients when applied on the soil is leached, it is carried by the rains, and then it is carried forward to the streams and rivers and, in the end, they all end up in the sea.

So the sea ends up being a final deposit for all this source of phosphorus that we have been extracting over the past good years. And, with the inadequate practices of agriculture, all this material has the tendency to return to the sea causing the overgrowth of algae, and a consequent deep change in the marine food chain due to this overgrowth while generating a shortage of phosphorus in the continents, in the long run. So, what we are exploring here is an opportunity to create ways to recycle phosphorus So, what we are exploring here is an opportunity to create ways to recycle phosphorus to you to grow the food or all the plants you want.

Before we talk about techniques it is important to talk about some issues that will guide us to choose those that are more appropriate for each context, because there is no such thing as the best technique there may be a handful more appropriate ones for each different context that each one of us is dealing with. The first fundamental aspect has to do with the culture, the culture of the place, the culture of the people who will use this system, who will eventually flush the vessel, and that will be using this infrastructure. The system has to have some degree of acceptance within the cultural standpoint of the people who will be using it.

In this image I show you the arm of a toilet seat in Japan where you see several buttons: one with music, one with a nozzle spray a bidet, a volume for the moment of flushing, a little background music. Imagine how these people would deal with a dry toilet, for example? How would them deal with the perspective of lifting the lid and finding no crystal clear water, no music, no nozzle of hot water.

. . ?

So, we need to adapt these techniques according to the local culture, not only of the people who are going to use it, but also of those who are going to operate it. Because here we are talking about the user, but there is the other end of the system where this material flow management will take place. Another important factor is the weather; you may achieve incredible results from using one technique in one place and suddenly, you may want to transport this technique to another place where will be completely inappropriate, simply due to the climate.

I will show you an example of a dry composting toilet later on that will make this clear. The type of soil also affects our choices, because if you´re counting with water infiltration in the soil after treatment, you need to check if your soil has greater or lesser infiltration capacity, as it will be more or less suitable for the system you are going to use. If you have a water table that stands near the ground you have to consider this as a determining aspect - ideally, there should be a minimum distance of 1.

5 meters between the point of application of the water after being purified, purified to the water table so that there is no risk of contamination. So, if you are in a place where the water table is very shallow, infiltration systems are more delicate because they will need the water quality to be much better (or you may not be able to count with infiltration, anyway). If you have more or less water, this will change the technique you are going to use, or better yet, it will change the list of possible techniques available for you.

The availability of space is relevant too, especially if you want to use large aquatic systems for fish production, for plant production as you will be more or less limited depending on the space. And, also, your goal. What do you want, after all, with this system of yours?

What do you want to do with these nutrients, with this energy, with this flow of water? The choice of technique will be made according to this combination of so many variables. For places where the water table is high, where the availability of water is eventually small and where you want to deal with its nutrients without water, the dry toilet is a great alternative.

The dry toilet allows you to rebuild the nutrient cycle on your property. It allows your food, which you may have grown in your property, to be returned in the form of nutrients to the soil through the process of composting. There are different ways for you to build a dry toilet, from a chamber model, which is perhaps the best known in Brazil, also called a compostable dry toilet.

In this model you have a composting chamber just below the seat, as you poop and add sawdust, all this material accumulates inside the composting chamber and, over time, it becomes a compost. But there is an important tip! Remember I talked to you about the climate issue?

The dry toilet is a classic case of this influence, and here I show you two images about it. . One of these images shows a dry bathroom with two people, Beira and Andrey, dealing with the material already quite well composted at the exit of the compost chamber.

On the right hand side you see a bathroom, also a chamber, with the black painted plate above, in Bahia, with Albertinho, a partner from Salvador, Bahia, presenting the system. The main difference that we see, not in technique and construction, is in the result of the composting process. This system in Bahia, was basically dehydrated, it was not fulfilling the function of composting - it had practically turned into a dehydrator bathroom.

And this is not what we want, because if we take a dehydrated material, it will have very little function as a real fertilizer for the soil. There are four important variables for our composting process: the carbon and nitrogen ratio, temperature, oxygen and humidity. So, after using the dry toilet, when you add some sawdust or ash, you are in fact throwing an amount of carbon that will regulate the amount of nitrogen present in your stool.

This will create an appropriate carbon-nitrogen ratio to accelerate the composting process. The sawdust is usually coarse sawdust. It is preferable to use coarse material, or even chopped straw or chopped leaves, as this will add volume and allow the oxygenation of this compost to happen in a more appropriate way and continue to promote an acceleration of this composting process.

It is also necessary to have a little moisture, neither too much nor too little. If it has less water it will dehydrate, as we saw in the photo from Bahia whereas if it has a lot of water, it runs the risk of entering into an anaerobic decomposition process, and it will smell bad. Anaerobic decomposition produces a gas that has sulfuric gas in its composition - and the smell of sulfur is very typical, a smell of rotten eggs.

So, if your compost has a very strong smell, you will already know that it is too moist and this has affected this dynamic of the composting process. Also, there is the issue of temperature. Even though we are trying to create conditions for composting to happen as quickly as possible, it is also important that this composting happens in an effective way!

We want a good quality compost, one that it is safe, We want a good quality compost, one that it is safe. Within the composting process there are different temperature phases, as the process is exothermic, that is, it releases heat. Right at the beginning it has a high temperature rise, and it reaches 60 ° C, sometimes 70 ° C, and remains at this temperature for a few days and, as we can see, the destruction of several of the most resistant pathogens happens after 60 minutes at this temperature, like E.

coli. So, if we have a good composting process, we guarantee the health of this compost. Nonetheless, the most recommended use for such a compost is that it should not be applied to vegetables, but rather, for other crops.

The suggestion is to leave the compost ideally resting for 6 months (shown in the image), because it will lead us to a condition of more safety of this compost, more than the very own increase of temperature. Well, since we already separated the feces inside the composting chamber (inside your dry toilet), we can also think about taking advantage of this urine, which as I said earlier, is a rich source of nutrients. How is this done?

It's simple! We all have a liquid outlet (different from the solids outlet), so the urine can be diluted in 1 part to 10 of water or can be preserved and stored for at least 6 months. These 6 months are a safety suggestion for some pH change processes to happen, which will cause any virus that could be present in the urine, to be killed.

In fact, the urine is sterile, unless the person is sick - only in this case it can have some virus transmission, but it is usually a very safe liquid. In addition to the collections at urinals, there are now some types of seats that allow separate collection of the solid flow from the liquid flow. In this image that you see on the screen, you see a toilet seat that is installed at the German Cooperation Agency, GIZ, where they do some studies to recover the nutrients in this building.

You also see images of a research carried out by a gentleman called Peter Morgan, which is available at the Sustainable Sanitation Alliance (SuSanA), in which he did a study on the application of different concentrations of urine for growing corn. The same corn seed, applied to the soil on the same day, under the same conditions of sun and watering, and you see the huge difference that the cobs present at the end of cultivation. The image on the right with very few grains, cultivated with zero urine, and the one on the left, with almost 2 liters of urine applied throughout the cultivation.

The tip is: if you are going to apply to vegetables, you have to be careful because there must be at least 1 month of separation between its application and the ingestion of the fertilized food. Also, if we remember that 75% of the total volume of wastewater produced in a single house is made out of greywater, which is that water used in the shower, washbasin, washing machine, and sink, we will realize that this water does not need to be treated since it (practically) does not contain pathogens - unless you have a high water table. This water can actually be used to fertilize different patches of your land.

Let´s imagine that, as you take a shower in every 1 minute of bath you produce between 10 to 15 liters of water, in other words, you produce at least 50 liters of water in 5 minutes, which could be used for the irrigation of a few fruit trees. In our tropical climate of Brazil we may think of Brazilian grape (jaboticaba), citrus in general, Brazilian cherry (pitanga), most of our typical native fruit trees of riparian forest like greywater because they thrive in humid and alkaline environment. So, make a study of fruit trees adapted to your climate and, from there, you will understand what trees you may be using along with your greywater.

Now, looking at the nature of these different sources of water, you realize that there are some sources of water that are suitable for direct reuse, it does not need a treatment. In this image you see the case of a municipal school in Ubatuba - at the time I was studying a project with a local NGO, ASSU, and there was a demand from the school direction, which was actually a complaint: on one side of the wall there was a sink where water was always being produced, kids washed their hands or drank water and forgot the tap open, and on the back wall there was an urinal. Our group suggestion was simply to install low-flow faucets and turn the water outlet towards the urinal, washing it away.

Each room in a house may be producing water to irrigate different places. So you can have your kitchen water irrigating some fruits in the west façade of house, for example, so that you shade the warmest side of the house (in the southern hemisphere of the planet) and, at the same time, you have a easily accessible production of fruits. In addition, if you start computing, considering that each person uses nearly 150 liters of water per day, the proportion of greywater would be over 100 liters per person.

So it's a lot of water that can be used for this application. One of the simplest uses that we can make for greywater, and in this case I’ll show you the water from a kitchen sink, is to direct this water that will have a little soap and food to irrigate fruit trees. So the simple fact that I wash a glass will cause this water here to irrigate a guava tree, a fig tree and some other ornamental plants, an arrowleaf elephant ear, and pineapple.

. So it's a choice that we make - this is not sewage, this is not a problem, this does not have to be treated, but it can be used. The only work I have to do here, or better said, the only two are to change or add more straw inside the pit, as this straw will slowly compost, and pick the fruits, in the case of guava, the fig that is still growing and the leaves of the arrowleaf elephant ear that I take for cooking.

So it's basically cultivation. I bring straw, let the water flow with nutrients and collect the food. It's that simple!

There was also something I did here to create a flexible system, in which I can choose to irrigate the fruit trees that I have here or, if I prefer, I can send them to the biodigester,, which you will see in a moment. So, I can connect this pipe that goes to the fruit trees or I can take it to the biodigester. In the same way, I could take it to another set of fruit trees.

It is important for us to understand the nature of these flows of the so-called wastewater. For example, let´s compare a shower, which has a steady flow (which is the volume of water that comes out over the time the tap is open), or even a tap sink which has a very similar flow rate. The washing machine, on the other hand, has a very different nature, because the machine stores the water and dumps this water with a pump, so whoever will receive this water needs to be designed according to this volume of water that is being produced at once.

We can make a direct application to a basin excavated around fruit trees or we can use the banana circle technique that is more appropriate for washing machines this is because it has a greater storable volume of water. All the dry matter placed inside the basin, such as straw, or firewood in the case of the banana circle, will make up the carbon composition with the nitrogen that is coming from the organic waste, soaps and cleaning products. This creates an aerobic environment, an environment where there is space, water infiltrates and, at the same time, we are creating a new type of soil, because all this material is decomposing and creating a very active space.

So, the amount of beneficial microorganisms present in the soil is enormous, reaching the range of 100 million microorganisms per gram of soil on the surface and only 1,000 to 3 meters in depth. What we are doing inside these basins is to simulate these surface soils so that not only does plants use this water being directed to them, but there is also a process of purifying this water as it infiltrates the soil. And, at the same time, we have this huge possibility of producing fruits and food that we saw.

When we talk about water purification processes themselves, it is not something we are inventing. These techniques use macros and microorganisms that already do this in nature. If you stop to think of any river that receives a load of sewage and that if it receives nothing but that initial sewage, it will purify itself along the way.

So, our challenge is to use techniques appropriate to our context and that use a strategy that creates appropriate environments for these microorganisms to act in a full manner. What we want is for them to be in the environment where they are happy, where they are fulfilling their role and that they do not need to go through any major effort to do so. From bacteria to microcrustaceans, each of them has a role to play and in addition there is a chain that interconnects each of these elements, that we can refer to as a hierarchy.

I mean, bacteria are those that act on the front line and as the water is being purified, microcrustaceans start to appear, ahead in this food chain (let's say so), this chain of breaking down these nutrients that are present in the Water. We simply have no idea of the amount of phenomena that are happening with the water when we look at a tank of zone of constructed wetlands, for example, from microalgae to microcrustaceans, protozoa. .

. there is a whole universe of life what's going on over there. When we start talking about the so-called black waters, the water generated at the toilet seat, one of the techniques that I really like is the vermifilter, because it adopts a completely different logic than everything you hear about today.

The vermifilter is a water filtration technique, it is not a technique that works with water retention, as is the case with septic tanks, evapotranspiration basins and digesters. It acts simply as a filter that has a support layer of 35 to 50 cm of sawdust, and that is the substrate for the development of Californian earthworms, which are worms that feed on fresh matter. When you flush, the solid matter stays in the substrate, the water goes through there and the worms digest it, so the water barely has time to be contaminated and this is one of the big draws.

In this flow, the water ends up taking some of the humus produced by the worms and, for this reason, it has a little color, but it is a water with low contamination content. You can complement this purification process using fruit irrigation, if you have a low water table or, if your water table is high, you can work with the constructed wetlands. Another approach to dealing with black water is the evapotranspiration basin, or banana pit - there are several names for this technique.

Its idea is to create a totally waterproof tank, where we have a receiving chamber for raw material. This chamber is hollow and, for this reason, the water flows from inside the chamber to the sides, where we have more coarse debris or broken tiles, which will serve as a support for the development of bacteria. As more sewage is deposited in the tank, the volume of water that is already inside goes up and flows through different layers of materials, from the roughest to the finest, until it gets closer to the surface, where bananas, arrowleaf elephant ear, or other plants that have a great potential for evapotranspiration receive this water, and the microorganisms associated with the roots and filter material transform these nutrients into nutrients assimilable by the plants and the plants evapotranspirate.

So, if you are in a dry environment, for example our semi-arid climate in Brazil, you virtually have the return of all the water back to the atmosphere. There is no effluent emission from this tank, there is no water outlet. But here in the Southeast, whoever is going to do an evapotranspiration basin has to deal with this outflow and, therefore, it is convenient that you have at least one infiltration tank (a banana circle for example), where we can do one more step of purification of this water.

And the fruits that are produced in this pit are healthy fruits, safe to eat. All of it! I am here in the integrated biosystem that is implanted in my house, the Almagestum space, in Pedra Bela, interior of São Paulo.

The integrated biosystem is an arrangement of different techniques that is done according to the objectives that, in this case, I wanted to achieve here, which are: energy production, nutrient recycling, biomass production and water purification. The main element of this biosystem in this case is a biodigester, which is a technique inspired by the functioning of the digestive tract of cows, which has 4 different stages developed from the entrance of fresh organic matter and, in the end, you have as a by-product the biogas (which is a composition of different gases in which methane is the fuel gas), and you also have the liquid effluent, which in our case is the effluent that comes from the wastewater in the house. Although our conversation so far has been related to sewage, your home's wastewater, has another source of resources that is generally discarded, which is kitchen waste, and which can help you increase your gas production.

All organic matter decomposing in water will produce gas; while some materials produce more or less gas, and the rest of grinded organic material (manually, in a blender or mixer, or even in a shredder like this that you couple under a sink) will offer you a volume of material with a very high potential for gas production. You can, as I said, attach this directly to the outlet of your sink or you can have another point where you simply place this material. In this case, I have access here, because my shredding at the moment is done in a blender, and after shredding I pour it (here).

This pipe leads this whole material to the biodigester, in a 75 mm pipe, with a steepness of nearly 3% and, from there, I have an increase in my gas production. If you have a restaurant or other business that produces a lot of organic matter, be it kitchen waste, or another business where you generate a lot of fresh organic matter, you can do that too. I'm sitting here on the top of the biodigester, next to me I have a gas outlet Beside me I have a gas outlet, this gas is going straight to a kitchen stove on the upper plateau, and I also have a lamp that lights up to illuminate the section below, in the biosystem, at night.

In the flow of the biosystem, after the biodigester, we have the hydraulic box (compensation chamber), which is where these papyruses are planted, on top of a hard wire screen mesh. The water flow is ascending vertical, that is, it is coming from below, from a 1 meter deep tank, and it flows upwards through the roots of the papyrus sedge. The function of the compensation box is to pressurize the gas inside the biodigester - o as the gas is being produced in the biodigester it presses this column of water that is inside the chamber, and this in contrast, presses back the gas column.

In this case, I changed the standard procedure, which was to plant the papyrus and the mini papyrus on top of the compensation box to already take advantage of this flow of water and already start the process of filtration and removal of nutrients. So, we can clearly see by the health of the plants and by the development of the roots in general, that it is clearly healthy and it is taking all this health precisely from the nutrients that are present in the wastewater. At the same time, the papyrus sedge allows the water to go a little more pure to the next stage, which is where I have a sequence of tanks, also of macrophyte plants.

Papyrus is a macrophyte plant that we call emergent, because it emerges from a substrate, the papyrus and the mini papyrus. Next, I have tanks with floating plants and the great thing about using the floating ones is because they grow very fast! I have a production, at this time of year, of 30 Kg of biomass in these 4 tanks, which should come up roughly to a total of 8 m².

Then, every 2 weeks, 30 kg; 2 weeks, 30 Kg. . .

This is because floating plants don't have to fight gravity, they just spread to their sides. So we can see that they start throwing the shoots to the side, and with each shoot, a new seedling leaves, and this whole space is occupied very quickly. And why do I want to produce biomass here?

Because our space was planted for many years with eucalyptus for cutting and transformation into coal, and the soil is very degraded! So I'm using this as a strategy so that I can retain and relocate the nutrients in the places I want. I can just take these plants and put them as soil cover wherever I want, it will decompose over time, it will turn into soil.

Due to its structure, which has the capacity to retain moisture, when it stays on the soil it will continue to retain moisture, so, in addition to bringing the moisture that is in the plant itself, it continues to retain moisture (from the rain) and will help to restructure the soil. I could also use it as animal feed, I could give it to cattle, if I had it, or to other animals, like pigs. There are other plants that we have here in our tank: salvínia, azolla and lemna as well.

However, in terms of production, because of the structure of the water hyacinth, we can see that it produces a much higher amount of biomass than other plants, which are somewhat smaller. We can compare it with salvinia, which has a very different structure, so even though it reproduces quite quickly, its biomass production potential by weight is relatively small. But, as I said, the importance of having diversity is not only due to the function it is playing in the system to help purify water, but also due to the macro and micronutrients, especially micronutrients, that it is able to assimilate.

Azolla, in particular, is a plant that fixes nitrogen from the air in the water, it is a plant that was traditionally used in the ancient flooded rice production systems in Southeast Asia, also with this function of fixing nitrogen. I have another experiment here which is a constructed wetlands with a floating structure. Traditionally, emergent plants are planted on top of aggregate substrates, stones of different granulometry, or even sand.

As you can see, we are dealing with emerging plants here, also macrophytes, and although they grow on the surface, they have a somewhat slower growth rate. The constructed wetland is a wastewater purification system, through which a series of microorganisms that are present in the water associate with the roots of the plants and transform this organic matter, which is in a slightly more raw state, into assimilable nutrients (by plants). So, what we see is a vigorous growth of the plants that are here.

I could be choosing different types of plants to make specific uses within the landscaping. Let's say I want to produce plants for cutting, so this is an ideal place for me to do this, as it has running water, with a constant flow of nutrients, especially since I am recirculating the water, and it has a very fast growth. So I could just cut it, take it for sale for example and, in a little while, I would have as many other flowers or stems to use.

Its growth is not as fast as that of floating plants because the floating plants are already on this nutrient solution, so it simply spread along the sides, while emergent plants grow against gravity, so it has an extra effort to transform these nutrients into fibers and this takes a bit of energy and the nutrients that are converted into all this biomass. So, if you want to produce fibers, then yes, emerging plants are a great asset in these sort of constructed wetlands. If you want to produce more mass, however, then you should work with floating plants, but always remembering that floating plants will require a lot more management.

They will require you to make periodic withdrawals and properly dispose of them. The constructed wetlands then is a water purification system that can be used not only for wastewater from a residence, or from any enterprise, but also for the purification of water in animal husbandry areas. If you have pig breeding, confined cattle breeding, and you want to help transform the stables' washing water into biomass you can use a sequence of aquatic plant tanks in this format that we showed earlier, which can help to purify all this water.

I hope this conversation has been inspiring and will help you to reflect and act towards rebuilding the way you deal with your sewage and come to look at it as a source of valuable resources. The address of Fluxus website is down there on your screen, so get in touch if you want to contact us. Thanks a lot, a hug and good work to everyonel!