UTN Concepción del Uruguay Exhibition
On October 21, at the Civil Engineering Final Project Chair, engineers German and Dino Raffo shared their experience abroad and their knowledge about sustainable solutions for wastewater treatment. 💧🌱
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Informative talk on Sustainable Technologies for Wastewater Treatment
Informative talk
Sustainable Technologies
Wastewater Treatment
In this article, we present the words of Germán in an informative talk in the community of Puerto Escondido, Oaxaca, Mexico. In which he discusses wastewater issues, treatment solutions at a domestic scale, treatment solutions at different scales, possible solutions for growing municipalities such as Puerto Escondido, among other things.
This informative talk was held at Elephant Garden on Saturday, October 15, 2022, thanks to the support and organization by SOS Puerto Escondido.
Following are Germán’s words
“
Hello good afternoon, my name is Germán Raffo. I am part of a family of engineers with self-sustainable horizons, with many years of experience in solid waste treatment and wastewater treatment. Mainly, it is Fernando Raffo, my uncle, who has been in the wastewater treatment business for more than 15 years, with a lot of experience in treatment systems.
With my twin brother, Dino, we studied together Civil Engineering at the UNC, and also in Italy, at the Politecnico di Torino, he with a master’s degree in Architecture, and a master’s degree in Hydraulics in my case.
After this, after two years of development, we started a new project here in Mexico, to make people aware of the problem of wastewater. Dedicating ourselves to designing treatment plants and advising people, to contribute to the solution from our technical experience, thanks to the constant advice and support for and by our uncle and our father, with whom we have been working on this for some time.
This project is called The Wave, where we also have a creative team with whom we are working on creating audiovisual content to raise awareness of this problem.
THE WAVE – A Family of Engineers with self-sustainable horizons
Introduction to the problem
Today, here in Mexico, only 4% of the wastewater is treated correctly, as established in the NOM-001 of the SEMARNAT ( Ministry of Environment and Natural Resources).
In localities such as Puerto Escondido, we can observe a great tourist and real estate development, which is generating a great increase in the amount of water used, and, therefore, a great increase in the amount of wastewater produced.
It is very important, for this reason, to be aware of the conditions in which we return these waters, and the impact that this problem is having on the environment, demanding as citizens that something be done about it to avoid an almost irreversible deterioration of water resources, as we can notice in municipalities that have faced this type of growth, such as Tulum, Acapulco, among others.
Photos of wastewater problems in Acapulco and sargassum proliferation on Quintana Roo’s coastline
I would like to talk mainly about possible solutions and not so much about the problem, what can we do, from our position, regarding this problem.
Starting with the different solutions we can find to treat our own wastewater, thus becoming part of the solution and not part of the problem.
What types of systems can we implement on a domestic scale?
Depending on what water purification status we want to achieve, and where the wastewater is directed to, we can opt for different solutions.
First it is necessary to understand and differentiate between a primary system, a secondary system and a tertiary treatment system.
A primary system is a system in which anaerobic wastewater treatment takes place. This means a system that operates in the absence of oxygen, where anaerobic bacteria proliferate, which are responsible for diluting and reducing the organic load contained in the water.
This type of system is usually a tank with a volume proportional to the flow to be treated, where the water is pre-treated.
They are essential prior to a secondary or tertiary system, since in these types of primary systems, the fast sedimentation solids are retained, and the organic load in the water is diluted, homogenizing the load and eliminating the solids that can clog the secondary or tertiary treatment system.
As an example of these systems, we can find Septic Tanks, commercial Biodigesters, etc.
Example of primary system : Septic Tanks & Biodigester
A secondary system, however, is a system in which aerobic treatment takes place. That is, a system that acts in the presence of oxygen, where mainly aerobic and photosynthetic bacteria operate, which, together with plants, close the cycle of pollutants by transforming them into nutrients for the plants.
An example of these systems are constructed wetlands, or large-scale forests of afforestation.
We will go deeper into the functioning of these systems later on.
Example of a secondary system : Constructed Wetlands
A tertiary system is a system of infiltration of water into the ground. In this type of system, water is absorbed through an absorption surface between the system and the ground, where the water infiltrates into the ground.
An example of a tertiary system is an absorption well or infiltration trenches.
In these systems, an aerobic treatment takes place in the pores of the soil, where aerobic bacteria act and fungi proliferate, which finish treating the pollutants before they reach a groundwater aquifer.
Example of a tertiary system : Absorption Well & Infiltration Trenches
What do the standards recommend?
The standards that regulate the pollutant status of wastewater differentiate between two different requirements in terms of the pollutant parameters contained in wastewater when it is returned.
One requirement is for water returned through a tertiary system of infiltration into the ground, and another requirement is for water discharged directly into rainwater drains or water bodies.
Recommended discharge parameters : Differentiating whether the water is directed to an infiltration system, or if it is directed to a pluvial gully or water bodies.
So, which system is recommended to solve the problem?
It depends on where our wastewater goes, but whatever the case, a primary treatment system is essential.
If a tertiary system is in place, only a well-designed primary system may be sufficient to achieve the water pollutant parameters required to comply with Table 1.
In cases where the treated water is to be reused for direct irrigation or returned to a surface watercourse, a secondary system is required in addition to a primary system to achieve the values established in Table 2.
Which system should I choose?
In order to implement a primary treatment system, one can opt for treatment using a well-designed septic tank system or commercial biodigesters.
The main differences between these two systems are maintenance and cost. On the maintenance side, both systems, when performing anaerobic decomposition, produce a sedimentation of sludge at the bottom, which must be removed after a certain period of time. In the case of the biodigester, they are usually removed twice a year, and in the case of septic tanks, this time is usually between 3 and 5 years, depending on the volume and height of the tank. From the point of view of cost, from our experience, we always ended up being more economical to opt for septic tanks.
For a secondary treatment system, you can opt for an constructed wetland, or any other aerobic treatment technology.
As for the tertiary system, infiltration trenches can be chosen, if space permits, because of their lower cost. Otherwise, absorption wells can be used.
In both cases, for proper sizing, a soil infiltration study is necessary, which you can do yourself with a simple technical manual.
What is a constructed wetland?
An artificial wetland, also called a biofilter, is a secondary treatment system for sanitary effluents.
This system is mainly composed of a granular media and plants. The granular medium serves as a base for the surface life of plants, and also the contaminated water flows through it so that the pollutants are filtered through this medium, deposited around the roots of the plants, which, through phytoremediation, end up being transformed into nutrients for the plants.
So the pollutants end up transformed into plants, while the water passes clean to a system for irrigation reuse, an infiltration system, or a surface course.
What these types of systems do is to replicate what happens spontaneously in nature on wetlands, therefore their name.
Scheme of wastewater treatment system with primary and secondary system
Why is it the best solution?
- They have clear economic advantages, due to their low construction and maintenance costs and reduced or zero energy consumption.
- They have excellent purification performances, especially for parameters such as BOD, COD, suspended solids, bacterial load and nitrogen.
- They are easy to operate.
Optimal oxygenation of treated water. - Optimal landscape integration.
- Environmental reclamation of degraded sites.
- Opportunity to reuse treated water and biomass, developing the logic of recycling, closing the cycle of some nutrients, such as Nitrogen and Phosphorus.
- Possible construction by growth stages.
- Optimal solution for variable hydraulic loads.
Different types of Constructed Wetlands
This can be of different types in terms of its style of operation.
It can be a subsurface horizontal flow wetland, where the water flows under a certain height of granular soil, and where the water flows horizontally, entering from one end of the system, and exiting at the other end.
Another type of these systems is a subsurface vertical flow wetland, which like the previous one, the water flows under the granular soil, but in this one the water flows vertically, entering from the top and exiting from the bottom.
There are also free-flow wetlands, where the water is in contact with the surface, which are usually used as a tertiary system after a subsurface wetland.
Architectural Solution Ideas
The biofilter design can be adapted to have a more aesthetically pleasing architectural design.
Analogous large-scale solutions
In situations of a high quantity of wastewater with a high organic load contained in it, mega systems of this type have to be made to solve the problem.
In the following images we can see the treatment system of a meat processing plant that slaughters 80,000 chickens per day, using about 2,000,000 liters of clean water per day, and returning that amount in wastewater with a BOD of 1500 to 2000 milligrams per liter.
For this case, a primary system using facultative lagoons and a secondary/tertiary system using afforestation forests.
Fadel poultry processing plant, which uses about 2,000,000 liters of water per day.
Also, we can find scales of urbanizations, also treated using facultative lagoons and forests, such as the following examples of communities of 6,000 and 80,000 inhabitants.
Ejemplo plantas de tratamiento mediante lagunas facultativas y bosques de forestación en dos localidades de Argentina
Possible solution to wastewater problems in communities such as Puerto Escondido
To conclude, I would like to talk about a possible solution for a growing locality such as Puerto Escondido.
Parallel to the solutions that have to be found through state financing, in maintenance, repair, creation, of sewage systems and treatment plants, a more short-term solution can be proposed, without state financing of the treatment systems.
The solution consists of an ordinance that requires an effluent treatment system that meets certain effluent parameters, such as those discussed in this article, from every developer who does not have access to the public sewer system, prior to approval of building permits.
This ordinance consists of three main parts. The Ordinance, which legally speaks of the conditions to be met, to whom it is addressed, sanctions and more. A Technical Annex, where the parameters for the discharge of water pollutants are required. And, finally, a Technical Manual, with general and detailed information on the treatment systems described, which will be associated with training courses for professionals, builders and the general public.
We have this type of ordinance, since we participated in the elaboration of the same for a municipality in Argentina, similar to Puerto Escondido in terms of its active tourism and growth”.
Up to here came the words of the engineer, with the respective images that he used in his presentation.
We will expand more on this last subject with respect to the solution of the problem through Ordinances in the Municipalities in this article.
We want to thank the beautiful community of SOS Puerto Escondido and Elephant Garden for making this possible. Also all who came to the event, raising awareness for the problem that involves all of us from our main element, Water.
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Domestic wastewater teatment
The UNC Civil Engineer, Dino Raffo, presents his Thesis of Laurea Magistrale in Ingegneria Edile with courses at the School of Architecture, Castello del Valentino, at the Politecnico di Torino, in Italy.
Dino shares in his final thesis a complete analysis of the solutions for domestic wastewater treatment.
Shared here in Italian, English and Spanish.
Wastewater Treatment Ordinance to be applied in a Municipality
Wastewater Treatment Ordinance to be applied in a Municipality A solution for municipalities with low infrastructure budgets In small towns, which are facing a great growth in real estate and development, and which