Interdisciplinary study resulted in articles published in journals maintained by the International Water Association (IWA)
There is a growing concern in the world with sustainable development, which also involves the reuse of materials and resources. This is the scope of research carried out by professors from the Faculty of Civil Engineering, Architecture and Urbanism (FEC) at Unicamp, concerned with developing in future engineers an awareness of the need to search for sustainable alternatives, especially when it is known that civil construction It is one of the activities that use the most natural resources. It is within this perspective that interdisciplinary research is developed in which three professors from the Faculty of Civil Engineering, Architecture and Urbanism (FEC) at Unicamp are involved: the architect and urban planner Mariana Rodrigues Ribeiro dos Santos, the chemical engineer Adriano Luiz Tonetti, both today belonging to the newly created Department of Infrastructure and Environment, and civil engineer Gustavo Henrique Siqueira, from the Department of Structures. In the studies they developed, drinking water was 100% replaced by treated sewage in the production of interlocking concrete floors intended for paving. The work aims to provide support for techniques and processes that allow minimizing the consumption of treated water in concrete production.
The importance of the study is highlighted when it is known that in the country's densest centers, which therefore consume larger volumes of concrete, around 9% of the total water used in industrial activity is used in the production of this material. With the aggravating factor that, although Brazil has the largest reserves of fresh water on the planet, its distribution is uneven, which leads large centers in the southeast to water stress at certain times of the year, such as São Paulo, its most industrialized state and populous.
Work and publications
The study had three aspects. Initially, it was up to Adriano, as a chemical engineer, to evaluate the feasibility of using treated sewage, coming from the Sewage Treatment Station (ETE), operated by Sanasa, in Barão Geraldo, district of the city of Campinas, SP, for the manufacture of concrete blocks.
Afterwards, Gustavo, a civil engineer, monitored the production of the test specimens, consisting of cylindrical samples measuring 0,10 m in diameter and 0,20 m in height, which would be evaluated in relation to compressive strength and water absorption capacity. . The results obtained in the tests carried out in the Structures Laboratory using these specimens, in which the portable water was replaced by treated sewage water at 25, 50, 75 and finally 100%, were compared with each other and with the results from samples produced only using treated water. The parameters used in the comparisons were practically similar in all specimens and in the blocks produced with both treated sewage and drinking water. Initial indications suggest that reused water could prove to be a good alternative to reduce the consumption of drinking water in concrete production.
Finally, Mariana, with a background in architecture and urbanism and a role more closely linked to the area of environmental planning, impact assessment and related activities, stopped to check how people evaluate interlocking concrete blocks produced from 100% treated sewage. and applied, on an experimental basis, in a lane on the floor of the FEC parking lot, parallel to another made up of conventional blocks, in a section where vehicles that use it circulate.
A questionnaire administered at FEC among teachers, students and staff, which had around 240 participants, sought to verify the acceptance of the product made from treated sewage for use in homes. She considers acceptance to be good, as around 85% of those surveyed would use the material outdoors, a rate that dropped to 55% when considering its use indoors. The reservations were mainly due to two questions: wouldn't the material be harmful to health? And what is its durability? However, the researchers make it clear that these fears are not justified, as the floors do not cause any problems related to health or resistance.
The majority of users of the FEC parking lot did not notice any difference between the two ranges of blocks installed there, manufactured from 100% reused water and drinking water, even because the two series of blocks maintain the same appearance and the small difference Color is inherent to the production process itself. The majority declared themselves in favor of using this new product due to the reduction in costs and resources used, in addition to the benefits for the environment. It should be noted that, in this case, reused water costs much less than drinking water, which for concrete plants is certainly interesting, but it remains to be seen how they would receive the innovation.
The studies have, to date, resulted in two articles in journals maintained by the International Water Association, IWA Publishing, which denotes the interest of society and the scientific community in a topic that is on the agenda. At Water Supply, researchers address the "Environmentally friendly interlocking concrete paver blocks produced with treated wastewater”. No Journal of Water, Sanitation & Hygiene for Development the theme was “Water reuse in the production of non-reinforced concrete elements: An alternative for decentralized wastewater management”.
Impacts on the environment
Professor Adriano recalls that current standards still do not allow the use of treated sewage water for concrete production. However, the study of this feasibility is justified by the fact that the concrete industry is among those that demand the most water, which could compromise supply in regions such as the Southeast where there is water scarcity. In the Campinas region, water availability is lower than in the Northeast. So he asks himself: wouldn't there be a possibility of allocating less noble waters to the production of concrete? And he emphasizes: “In the future, if we do not use water in an innovative and conscious way, it will not be sufficiently available to serve populations and companies, which could jeopardize jobs and generate social problems. It is increasingly urgent to seek sustainable alternatives that will guarantee water for everyone.”
Although the tests carried out in the Structures Laboratory revealed, initially, the maintenance of mechanical properties in all blocks produced with treated sewage, and those installed in the FEC parking lot were applied eighteen months ago, there is still a need for monitoring of the material's behavior over time and also assessments of its microscopic properties. Professor Gustavo also makes it clear that the tests were carried out on non-structural elements and, therefore, without the presence of steel bars: “The study must advance to verify the absence of reactions in reinforced concrete parts or even changes in long term in simple concrete because it is known that treated sewage has organic components, although concrete does not favor the proliferation of microorganisms”.
As civil construction is one of the activities that consumes the most natural resources and causes negative environmental impacts on the environment, and given the increasing need to make use of sustainable processes, Professor Mariana considers it very important to develop civil engineering students' awareness of environmental preservation, especially because, “I think that most engineering courses do not incorporate this need and the emphasis on traditional production still prevails. Our study helps engineering professionals think about alternatives,” she says. Professor Adriano considers that this is facilitated by research that has an interdisciplinary nature, involving several engineering areas of the Unit. By the way, he adds: “The environmental issue must permeate the training of the engineer of the future who needs to be concerned about the materials he will use, where they come from, how they are obtained, what their characteristics are and what environmental impacts they cause as a result of their origins. , production processes and uses”.
Regarding health concerns, the group of researchers makes it clear that they do not intend for this reused water to be used in renovations or residential constructions where there would be direct contact with it. The objective of the study is its use in concrete plants and companies that produce concrete parts, in which there is no direct contact between workers and water. The concern is that it has suitable characteristics for the production of nature-friendly concrete. Once this possibility is confirmed, the company Villa Stone – Artifacts of cement and concrete, which produced the blocks and has collaborated with the researchers, is interested in this reused water for the production of interlocking floors as long as standards allow.
