Development of a systematic approach to assessing proprietary stormwater filter chamber performance under simulated conditions

Abstract

Graphical overview of the study framework and key findings. The study begins with a comparison of three major stormwater treatment test protocols (BW CoP, NJCAT, and DIBt), leading to the selection and adaptation of the DIBt protocol. The adapted protocol is applied under controlled laboratory conditions to evaluate both filter chamber performance (particle and hydrocarbon removal) and filter media performance (metals and nutrients). Results indicate strong removal of suspended solids (TSS), hydrocarbons, copper (Cu), and phosphorus (P), while zinc (Zn) shows fluctuating behaviour and nitrogen (N) exhibits negative removal. The findings highlight the influence of hydraulic conditions and cumulative loading during consecutive sub-tests, and emphasize the need for harmonized, region-specific testing frameworks for compact stormwater treatment systems. Urbanization increases impervious surfaces, generating higher stormwater volumes and pollutant loads that challenge conventional drainage systems. While nature-based solutions (NBS) are widely used for stormwater management, compact stormwater treatment systems (CSTS) provide a decentralized alternative suited to space-limited urban areas. However, their evaluation is hindered by inconsistent international testing protocols. This study compares three major CSTS performance standards, the British Water Code of Practice (BW CoP), the New Jersey Corporation for Advanced Technology (NJCAT) program, and the Deutsches Institut für Bautechnik (DIBt) protocol, to identify methodological differences and testing implications. Based on this comparison, a modified DIBt protocol is developed, expanded to include nutrient (phosphorus and nitrogen) tests, was applied to a filter chamber under controlled laboratory conditions. Results showed particle removal ranging from 25% at high flow to 97% at low flow conditions, hydrocarbon removal remaining consistently high (98–99%), and metal removal efficiencies varying with flow, copper increasing from 19 to 95% and zinc from slightly negative (release) to 88%. Nutrient tests indicated phosphorus removal from 32 to 84% and negative nitrogen removal rates. These findings highlight the need for harmonized testing frameworks reflecting regional conditions to improve CSTS evaluation and implementation.