Assessing rainwater quality treated via a green roof system

• Published in: Clean technologies and environmental policy Vol. 24; no. 2; pp. 645 - 660
• Main Authors: Sá, Thomas Schatzmayr Welp, Najjar, Mohammad K., Hammad, Ahmed W. A., Vazquez, Elaine, Haddad, Assed
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.03.2022; Springer Nature B.V
• Subjects: Ammonia; Coliforms; Color; Containers; Crises; Disinfection; Earth and Environmental Science; Environment; Environmental Economics; Environmental engineering; Environmental Engineering/Biotechnology; Environmental policy; Experiments; Fecal coliforms; Green buildings; Green roofs; Health risks; Industrial and Production Engineering; Industrial Chemistry/Chemical Engineering; Nitrogen; Original Paper; Orthophosphate; Parameters; Prototypes; Quality assessment; Rain; Rain water; Recycling; Resource management; Roofing; Roofs; Sustainable design; Sustainable Development; Sustainable practices; Technical information; Turbidity; Wastewater; Water analysis; Water crises; Water management; Water quality; Water resources; Water resources management; Water reuse; Water sampling; Water management; Potential for reuse; Experimental study; Alternative for water supply; Water demand; Sustainability
• ISSN: 1618-954X; 1618-9558
• DOI: 10.1007/s10098-021-02144-6

The shortage of water worldwide is increasingly worrying. Studies in the field suggest that sustainable water resource management via water recycling is fundamental to alleviate the issue. The use of rainwater is an important alternative source that must be considered, mainly, in the water crisis facing the planet. When integrated with the concept of green roofs, the capturing and treatment of rainwater in these structures becomes an even more ecological and sustainable practice. The water drained by the roof can be used for non-potable uses, such as flushing toilet bowls. One of the main concerns when using rainwater, even for non-potable uses, is the quality of the water available, so as not to put users' health at risk. In this way, the present work proposes to experimentally analyze the quality of rainwater drained in a green roof prototype for reuse purposes. The green roof prototype was installed on an experimental bench. After each rain event (four in total), two water samples were collected in the following situations: rainwater captured directly by a container next to the bench and rainwater, drained by the green roof prototype, captured by a container through existing drains at the base of the prototype. The analyses of the collected samples were carried out at the Environmental Engineering Laboratory (LEMA/UFRJ) and performed according to the Standard Methods for the Examination of Water and Wastewater. Specifically, the experiments examine physicochemical and biological parameters following a rain event on a green roof prototype for sanitary use. Experimental results that were observed and analyzed include color, turbidity, pH, ammonia nitrogen, nitrite, nitrate, orthophosphate, total coliforms, and thermotolerant coliforms to indicate the rainwater quality from green roofs. The majority of parameters assessed were within the value thresholds indicated by the Brazilian standards, while the results of orthophosphate, fecal coliforms, color, and turbidity were not. The greatest divergence is in the concentration of orthophosphate, where a concentration of 10.88 mg/L was obtained in this experimental study, while other authors present values of 0.1 and 0.01 mg/L. Total coliforms also presented high values, but within the expected range. Comparisons with technical documents and international references related to water quality to identify possibilities of the use of rainwater were also conducted. Results indicate that the water quality has the same order of quantity for turbidity, nitrite, and ammonia nitrogen parameters across the standards. Based on such observations, filtration and disinfection processes are therefore required in the green roof system for the use of rainwater for sanitary. Finally, the experimental study of rainwater quality on the green roof presented similar results comparing with international references. The use of green roofs combined with the use of rainwater demonstrates the potential and benefits as an alternative to face the water crisis. Graphic abstract