Dynamic Release of Solutes from Roof Bitumen Sheets Used for Rainwater Harvesting

Abstract

Bitumen waterproof sheets are widely used to seal building roofs. Previous works have focused on the mechanical-physical properties of bitumen sheets, as well as their aging and degradation processes, and their impact on sealing properties of the buildings. Due to a growing need over recent years to use rooftops in urban environments for rainwater harvesting purposes, it is highly important to better characterize the quality of the harvested water from the bitumen covered roofs, and to shed more light on the impact of bitumen degradation processes on the release of various components to the harvested roof water. In the present study, the extracted organic and inorganic solutes from bitumen-covered roofs by water flow on the bitumen sheets were examined through a series of experiments, including measurements from the roofs of buildings in the center of Israel during the winter of 2019–2020. The results indicated high levels of organic and inorganic solute loads in the roof water during the first flush of the first rain of the winter, with maximal electric conductivity readings at the order of 4 dS/m. However, it was shown that following the first flush, a ~20 mm of cumulative rainfall was sufficient to wash off all the summers’ accumulated solutes from the roof. After this solute flushing of the roof, harvested rainwater along the winter was of good quality, with electric conductivity readings in the range of 0.04–0.85 dS/m. Moreover, it was shown that bitumen sheets which were exposed to direct sun radiation emitted greater loads of solutes, likely a result of elevated aging and degradation processes. The findings of the present research point to the need to find efficient ways to isolate roof bitumen sheets from direct sun radiation and to design rainwater harvesting systems that will not collect the water drained from the first flush.

A Comparative Analysis of Rainwater Harvesting System and Conventional Sources of Water

“…The runoff coefficient is equal to 0.9, based on the study of (Stang et al, 2021). The first flush (from the first rainwater event) is used to wash away the organic/inorganic contaminations present in the rooftop area (Nachshon et al, 2021). It is assumed in this study that the first flush (equal to 1 mm) from the first rainfall event of each month is washed away.…”

A New Method for Selecting the Geometry of Systems for Surface Infiltration of Stormwater with Retention

“…In recent years, there has been an increase in the vulnerability of some areas to the changing climate [1], with many aspects related to the hydrological cycle [2]. Urban areas are a particularly vulnerable environment as a result of rapid urbanization, population growth, and increased demand for water [3].…”

Hydraulic Issues Concerning Injection of Harvested Rainwater to the Subsurface Through Drywells: Insight From Numerical Simulations of Flow in a Realistic Combined Vadose Zone‐Groundwater Flow System

“…A way to deal with both floods and water availability in urban environments is based on rainwater harvesting (RWH) from impermeable surfaces (e.g., roof‐tops, roads) and using this water for MAR operations (Nachshon et al., 2016, 2021). Groundwater recharge in urban environments through shallow infrastructures such as vegetated systems, pervious pavement, and infiltration ponds or trenches, is widely discussed in the literature (Ahiablame et al., 2012; D'Aniello, Cimorelli, Cozzolino, & Pianese, 2019; D'Aniello, Cimorelli, & Cozzolino, 2019; Duchene et al., 1994; Fletcher et al., 2015; Newcomer et al., 2014; Thompson et al., 2010; Zhang & Chui, 2019).…”