Assessing rainwater quality treated via a green roof system

Abstract

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 analyzes 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 10.88mg/L was obtained in this experimental study while other authors present values of 0.1 and 0.01mg/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.

Economía circular mexicana

“…Se destaca la capacidad de reducir la huella de carbono y ser eficiente al reutilizar residuos de construcción en la composición del sustrato (Kuoppamäki y Lehvävirta, 2016; Xue y Farrell, 2020), así como la necesidad de estudios detallados sobre el impacto de los materiales en la calidad del agua de lluvia (Baryła et al, 2018;Sá et al, 2022) y los acv (Gargari et al, 2016;Shafique et al, 2020) respaldan la adopción de materiales alternativos. Sin embargo, aún no se han documentado ejemplos claros que muestren una integración efectiva de la economía circular en la optimización de los techos verdes.…”

Disinfection of Rainwater for Economic Purposes

“…Zhang et al [62] found that in strains of Escherichia coli and Pseudomonas aeruginosa, after exposure to UV radiation, cell membranes remained intact even at UV doses of 300 mJ/cm 2 . Moreover, dead cells are a source of additional portions of nutrients for living cells [63,64].…”

Effect of Combinations of Green Roof Substrate with Vegetation Coverage on Rainwater Quality Improvement

“…Examples include low-impact development (LID) [7], sustainable urban drainage systems (SUDS) [8], water-sensitive urban design (WSUD) [9]. An important strategy in the WSUD system is to control the source of runoff to improve the quality of stormwater runoff and reduce the amount of water [10,11]. The installation of green roofs is considered to be the best management measure for reducing peak urban runoff and improving the quality of stormwater runoff [12,13].…”