Enhanced stormwater treatment performance by design modifications to the permeable pavement structure

Abstract

The aim of this doctoral study is to improve the pollutant removal capability of Permeable Pavement Systems (PPS) through design modifications, in order to fill the existing research gaps on PPS. Laboratory studies are carried out in this research, in particular, to understand the chemical kinetics (reaction time and rate – e.g., rainfall intensity, duration and pollutant concentration), appropriate conditions (e.g., pH, temperature, redox potential, oxygen and organic carbon availability), and essential catalysts (e.g., microbes and ion exchange sites) needed to optimise stormwater treatment processes in PPS that must be considered in order to make suggestions for realistic PPS applications under ideal conditions. The primary goal of this research is to improve stormwater treatment capability by modifying design variables in PPS, including subbase materials and design parameters. In this research, six PPS columns with different subbase configurations were tested for attenuation of pollutants commonly found in stormwater runoff. Column subbases were constructed considering the following hypothesis for enhanced physical, chemical and biological treatment of pollutants: (i) a layer of natural zeolite in the subbase of the PPS to enhance pollutants by ion exchange and adsorption; (ii) a layer of bark chips in PPS as a carbon donor for biodegradation; (iii) providing required moisture content and reduced oxygen level by maintaining a saturated zone in PPS and increasing retention time for enhanced biodegradation; and (iv) thin sand layers to limit oxygen transport and to create an anoxic zone. A series of experiments were carried out dosing with synthetic stormwater having different pollutant concentrations, while maintaining varying rainfall intensities to simulate extreme runoff conditions. The results of this study demonstrate the inefficiency of the traditional PPS structure on attenuation of nitrates, nitrites, heavy metals such as Al, Cr, Cu, Mo, Sr and phosphates. It also shows the attenuation performance of these pollutants by PPS further decreases in high rainfall intensities and for longer durations. An improved denitrification in the PPS is found when a saturated zone is maintained and an organic carbon source is added in the PPS subbase. It has been found that by maintaining a saturated zone, a thin sand layer and providing a carbon source in PPS subbase can improve metal attenuation by PPS. It has also been shown that a better total phosphorous and phosphate attenuation can be achieved by incorporating thin sand layers within the PPS structure.

Date of Thesis submission	2022
Original language	English
Awarding Institution	Western Sydney University
Supervisor	Ataur Rahman (Supervisor) & Chin Leo (Supervisor)