Assessment of sediment traps for controlling stormwater quality in a heavily urbanized area

Abstract

Raised awareness of environmental constraints in recent decades has led stormwater management to incorporate quality components and focus on the treatment of urban runoff water through solutions at source, such as sediment traps. This study evaluated the impact of a developed type of sediment trap, installed into sewer inlets, on the total suspended sediments (TSS) load of an urban Finnish catchment through a modelling approach, as well as the contribution of different landuses on the TSS load.

The study utilized a Storm Water Management Model (SWMM) parametrization of the Taapelipolku catchment in Lahti, Finland with streets, parking lots, pavement, roofs, green areas and other (miscellaneous) defined as landuses, and literature Event Mean Concentrations (EMCs) were used to define the generation of TSS for each landuse individually. A method to implement the sediment traps in SWMM was presented, and the model was run for a 6 month period using the PySWMM module in Python.

The catchment sewer inlets were ranked according to the maximum potential removal of TSS, when installed with sediment traps, to determine the optimal set of locations for the sediment traps, and the influence of landuse on this ranking was analyzed. Additionally, the effect of regular maintenance intervals on the catchment TSS load, given a maximum storage capacity of the traps, was explored.

The results showed a large variation in TSS removal, depending on the inlets chosen for the sediment traps, highlighting the need for an informed decision when selecting trap locations. Streets and parking lots were the largest TSS contributors, with sewer inlets located on streets likely overall to be the optimal sediment trap locations. The results, however, were found to be highly dependent on the EMCs, adding some degree of uncertainty to the findings of this research.