A HYDROLOGICAL MASS-BALANCE SIMULATION FRAMEWORK FOR ENVIRONMENTAL ENGINEERING EVALUATION OF LOW-IMPACTDEVELOPMENT STORMWATER TREATMENT TRAINS

Abstract

Urban stormwater management is an environmental engineering discipline concerned with controlling both runoff volume and pollutant load from developed catchments, addressed through low-impact-development (LID) treatment trains combining bioretention cells, vegetated swales, and constructed wetlands. Published literature documents that facility sizing calculations vary inconsistently across jurisdictions and are sometimes applied incorrectly, motivating a transparent, parameterized alternative. The present work proposes a hydrologic mass-balance simulation model of a three-facility treatment train – tracking TSS, COD, total nitrogen, and total phosphorus – coupled to a real-time interactive visualization, letting a user adjust rainfall intensity, infiltration capacity, and treatment-train composition and observe the resulting change in runoff and removal efficiency. Key engineering challenges included preserving conservation of mass in the hydrologic computation, correctly routing serial treatment-train capture without double-counting, and sustaining real-time rendering performance. Experiments confirmed that removing the treatment train collapses removal efficiency to zero while engaging it restores 72-93% removal, and that rising rainfall intensity exceeds fixed hydraulic capacity, driving TSS removal from a 96% peak down to 25%.