A Comprehensive Monitoring and Evaluation Framework for Hybrid Stormwater Treatment Systems in Tropical Urban Environments

Abstract

Urban stormwater pollution is an increasing challenge in rapidly developing tropical cities, where high runoff volumes, ageing drainage infrastructure, and mixed contaminant sources place growing pressure on receiving waters and conventional treatment systems. This paper proposes an integrated monitoring and evaluation framework for a hybrid stormwater treatment system which combines Continuous Deflective Separation with Nature-Based Solutions (CDS-NbS). The method includes CDS pre-treatment, followed by a vetiver floating wetland and biochar filtration media, with natural zeolite adsorption units. The performance of the system was assessed through staged sampling, independent third-party verification, accredited laboratory analysis, and real-time Internet of Things (IoT) monitoring under representative tropical urban operating conditions. The integrated procedure showed progressive improvements in water quality, reductions in suspended solids, organic pollutants, and selected contaminants, while nutrient behaviour was observed to vary depending on operational and seasonal conditions, and stable gravity-driven hydraulic performance. Besides efficient treatment, it also offers opportunities for water reuse, biomass recovery, and circular-economy applications for non-potable water not used for irrigation. This pilot project illustrated the potential of a hybrid CDS–NbS system which can be adopted to deliver practical, scalable solutions for resilient stormwater management in tropical cities while advancing broader sustainability, circular-economy, and water-security goals.