Occurrence and Analysis of Pollutants in Stormwater from an Urban Catchment
Tutor / director / evaluatorMalmqvist, Per Arne
Document typeMaster thesis (pre-Bologna period)
Rights accessRestricted access - confidentiality agreement
The occurrence of metals and organic compounds such as phthalates, nonylphenols (NPs) and its ethoxylates (NPEs) in urban stormwater runoff makes it a large contributor of pollutants to receiving waters, the pollutants’ toxicity can severely affect the aquatic life. This study focuses on the analysis of stormwater from an urban catchment area of 25 ha in Kärra, northern Göteborg. An automatic sampler, controlled by a flow meter, was installed in the separate sewer system pipe that conveys the stormwater from the catchment area to the river Göta Älv without any pre-treatment. Flow-proportional stormwater samples were collected during four rain events. Sediments from the side of the road and from a ditch draining of the catchment area were also collected. The stormwater samples were analyzed to find the total metal concentrations and eight conventional water quality parameter, whereas the sediments were screened for organic compounds. The substance flow model SEWSYS (Sewer System), developed in MATLAB/Simulink, was used for simulating stormwater volumes, finding pollutant concentrations in runoff and identifying the main pollutant sources. Two versions of SEWSYS were used, the second being an adaptation including organic compounds in the simulation. The simulated site mean concentrations (SMCs) were compared with the concentrations found in the analysis of stormwater. It was seen that the main sources were roofs for zinc (Zn) and atmospheric deposition and pollution from diverse areas for lead (Pb) and copper (Cu), SEWSYS tends to underestimate the loads of Zn and Cu but overestimates Pb. The metal concentrations and organic compounds in sediments were compared with results from other studies. It was found that in Kärra concentrations were comparably lower than those found in Gårda and Järnbrott stormwater treatment facilities. The organic substance fluxes from the sources to the sampling catchment were calculated using the SFA methodology. The loads of organic substances were calculated using factors describing the emission of phthalates and nonylphenols from different sources in urban areas together with results from the detailed classification and quantification of sources in the area. The flow analysis showed that annual fluxes in stormwater of the phthalates DEHP and DINP were ~ 2000 g respectively. The annual loads of Nonylphenols were ~100 g. The comparison with the SEWSYS simulation for the month of November and the calculated fluxes for a month showed lower values for the simulation of phthalates but extremely higher results for the simulation of Nonylphenols. Sediment samples verified the occurrence of these compounds and a comparison with results from other studies showed that concentration levels are low. The sediments from the detention dike were found to be more polluted than the sediments collected from the side of the road.
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