Reúso de águas cinzas: análise da eficiência de filtro composto por materiais alternativos

Abstract

The negative impacts of human actions on the natural environment have caused serious risks to the survival of ecosystems; water demands, for example, are already scarce in several countries around the world. There are many reasons that lead to water scarcity, ranging from poor territorial distribution to the contamination of springs, thus requiring a proper environmental management and intelligent use of available resources. To this end, techniques and solutions are needed, such as the reuse of grey water or the use of rainwater for non-potable purposes such as irrigation, washing floors, car washes, and toilet flushes. The most common treatment for these effluents is the traditional sand filter, which despite being considered a low cost treatment, requires limited natural resources such as sand, limestone and coal. In order to combine the reuse of waste with the reuse of graywater, the main objective of this study was to evaluate the efficiency of an alternative filter with used sponges, biochar based on orange bagasse and construction waste to treat graywater from sinks. The research approach is hypothetical-deductive, starting from the hypothesis that the proposed treatment is sustainable and capable of filtering greywater for subsequent application as an alternative to comply with socio-environmental indicators. The materials that compose the filter were characterized, being the construction waste by X-Ray Fluorescence (XRF), sponges by Scanning Electron Microscopy (SEM) and the biochar by Brunauer, Emmett and Teller (BET) and SEM pointing them as porous materials and able to filter solids and undesirable substances from the graywater. The graywater samples for the study were collected from a men's bathroom located on the first floor of the biology and forestry engineering laboratory complex at UFS, São Cristóvão Campus, through a 50 liter tank installed below one of the sinks. The analyses performed before and after the treatment unit showed a 6.61% reduction in pH, a 41.62% increase in dissolved oxygen, a 71.56% reduction in turbidity, a 310% increase in electrical conductivity, and 100% removal of thermotolerant coliforms. Finally, as the final effluent is classified by NBR 13.969 for use in sanitary flushing and agriculture, a full-scale filter model was designed based on the production of graywater from sinks in the forum of Indiaroba/SE, with a capacity to filter 243.5 liters of graywater per day. The treatment met the hypothesis, although it did not produce effluent for reuse in gardens and car washes due to the average value of turbidity above 5 NTU, it proved effective in filtration, highlighting the sustainability of materials and their impacts, as well as proposing its application as a technology to meet the socio-environmental indicators of the Judiciary of Sergipe.