Gilbert Svensson

Variations of dissolved and suspended solid heavy metals through an urban hydrograph

Abstract Zn, Cd and Cu in stormwater runoff from an urban catchment are found to be present mainly in the dissolved phase, whereas Pb is most strongly associated with the suspended solid phase. High levels of metals, particularly Cu, are found in stormwater solids which may be due to the high percentage of particulate organic material in the runoff. The metal loadings over the storm event for the dissolved and suspended solid associated metals show similar distributions to the flow and suspended solids respectively. However, in some cases secondary peaks and deviations due to dissolved metal scavenging are observed.

Transport mechanisms and processes for metal species in a gullypot system

Abstract The measurement of soluble and solid associated Cd, Cu, Pb and Zn species within the immediate environment of a gullypot during storm events has enabled the identification of six major processes which affect metal mobilisation and transport through the gullypot system. These processes are described under the headings: (a) Atmospheric Fallout, (b) Acid Rain Mobilisation from Road Dusts, (c) Constant Metal Concentration Time Zones, (d) pH/Surface Area Dependent Suspended Solid Metal Transport, (e) Metal Increase in the Gullypot Liquor between Storm Events and (f) Contribution of Gullypot Liquor and Sediment to Metals in the Gullypot Outflow. The contribution of each of these processes towards controlling the form of the metal in the gullypot outflow is discussed and a number of theoretical concepts are established.

Modelling substance flows in urban sewer systems using MATLAB/Simulink

A model for simulation of substance flows in urban sewer systems has been developed in the computer programme package MATLAB/Simulink. The model is called SEWSYS and it handles fluxes of substances within an urban catchment. SEWSYS keeps track of each substance; where it originates and where it finally ends up. Some of the substances included are water, phosphorus, nitrogen, heavy metals and PAH. SEWSYS consists of a stormwater module, sanitary wastewater module and a wastewater treatment plant with nitrogen reduction. Verifications have been carried out both for each component separately and for the model as a whole. The results show that the modelling approach is valid, but further enhancements should be made.

Strategies for management of polluted storm water from an urban highway in Göteborg, Sweden

Stormwater from urban highways contains high concentrations of heavy metals, polycyclic aromatic hydrocarbons (PAHs) and other substances that are harmful to the environment. The choice of abatement strategies is not trivial. If the stormwater is brought to the municipal wastewater treatment plant (WWTP) in combined sewers, it will cause overflows at combined sewer overflow (CSO) points, accumulation of contaminated sludge that cannot be used as fertilisers on farmland, and sometimes disturbances of the operation of the WWTP. If the stormwater is discharged to a receiving water it will carry all the pollutants directly to the water body, most often a small urban creek not suitable for such discharges. If the stormwater is allowed to infiltrate, the groundwater and in some cases the vegetation will be effected. In an action plan for the improvement of the stormwater handling all these issues have to be taken into account. Abatement of pollutants at the source is one very important strategy that should have first priority. Thus, to improve the receiving water in a sustainable way the sources of the pollution have to be identified, quantified and reduced.

Substance flow analysis of the stormwater system in Vasastaden, Göteborg

A substance flow analysis of the stormwater system in Vasastaden in the city of Goteborg has been carried out using a substance flow model called SEWSYS. The model handles fluxes of substances within an urban catchment and keeps track of each substance; where it originates and where it finally ends up. The present sewer system has been studied and the status of sustainability evaluated. Different abatement measures to achieve a system with more sustainability have been modelled and evaluated. The measures include source control and end-of-pipe solutions. From this study it may be concluded that all the studied measures individually lead towards a very high reduction of the discharges of pollution to the water body, but the source control measures are recommended as a first choice since they by definition are sustainable.