Jovan Despotović

Further insight into the mechanism of heavy metals partitioning in stormwater runoff.

Various particles and materials, including pollutants, deposited on urban surfaces are washed off by stormwater runoff during rain events. The interactions between the solid and dissolved compounds in stormwater runoff are phenomena of importance for the selection and improvement of optimal stormwater management practices aimed at minimizing pollutant input to receiving waters. The objective of this research was to further investigate the mechanisms responsible for the partitioning of heavy metals (HM) between the solid and liquid phases in urban stormwater runoff. The research involved the collection of samples from urban asphalt surfaces, chemical characterization of the bulk liquid samples, solids separation, particle size distribution fractionation and chemical and physico-chemical characterization of the solid phase particles. The results revealed that a negligible fraction of HM was present in the liquid phase (less than 3% by weight), while there was a strong correlation between the total content of heavy metals and total suspended solids. Examinations of surface morphology and mineralogy revealed that the solid phase particles consist predominantly of natural macroporous materials: alpha quartz (80%), magnetite (11.4%) and silicon diphosphate (8.9%). These materials have a low surface area and do not have significant adsorptive capacity. These materials have a low surface area and do not have significant adsorptive capacity. The presence of HM on the surface of solid particles was not confirmed by scanning electron microscopy and energy dispersive X-ray microanalyses. These findings, along with the results of the liquid phase sample characterization, indicate that the partitioning of HM between the liquid and solid phases in the analyzed samples may be attributed to precipitation processes.

Some considerations of urban drainage design practice using experimental data

Abstract Two most frequently used procedures for obtaining design flow rates in urban drainage practice are design storm approach and historical storm approach. An alternative approach is possible if a series of measured flow rates at the outlet of urban catchment is available, so that the frequencies of flow rates are estimated directly. These three approaches are discussed using the measurements of rainfall and runoff at the experimental urban drainage catchment “Miljakovac” in Belgrade for the period 1981–1993.

Analysis of the Changes of the Streamflows in Serbia Due to Climate Changes

The effect of climate change on river flow trends in Serbia is analyzed. To reduce the impact of human activity on results, eight hydrological stations where human impact is negligible, or only minor, were selected. The chapter focuses on average annual river discharges and temperatures and total annual precipitation. The aim of the research is to document the observed trends of streamflow and air temperature, and assess and forecast average relationships between the changes in the streamflow and increases in air temperature in Serbia. Of the eight analyzed watersheds, the results obtained for the Pek and Resava rivers are highlighted to illustrate the range of departures of an individual watershed in our eight watersheds ensemble statistics.

Laboratory investigation of hydraulic characteristics of fly ash as a fill material from the aspects of pollutant transport

Depending on the usage of fly ash, it is necessary to determine its environmental parameters, such as the potential for pollutant transport/leaching after its built-in. This study presents a methodology for determination of transport parameters (filtration coefficient, effective porosity, longitudinal dispersivity, and the mean residence time) from experimental data collected from column experiments with a conservative tracer on different mixtures of fly ash with stabilizers (4.8% lime and 5% cement). The transport parameters are determined using (1) numerical model results and (2) an adapted analytical solution results against measured outflow tracer concentrations. The study shows that the addition of stabilizers decreases the filtration coefficient by an order of magnitude and the effective porosity by half. The longitudinal dispersivity is not influenced by the addition of lime to the mixture, and is increased by 40% by the addition of cement. The pollutant contact time with fly ash increases by six or nine times with the addition of lime and cement, respectively. The adaptation of the analytical solution agrees well with both the numerical solution and the experimental results, and it is anticipated to be of high value for determination of transport parameters for practitioners not familiar with numerical methods.

Fly ash and slag utilization for the Serbian railway substructure

Approximately 7 million tons of fly ash and slag are produced in thermal power plants in Serbia every year, only 3% of which is used in the cement industry. About 300 million tons of the ash-slag mixture are disposed in landfills, occupying an area of approximately 1600 hectares and generating environmental issues. Fly ash from Serbian power plants has pozzolanic properties and due to low concentration of calcium compounds (less than 10% CaO), they do not have self-cementing properties. According to the ASTM C618-15, this ash is from class F. According to the European Standard EN 197-1:2011, this ash is siliceous (type V) ash. From April 2014 to May 2015, an investigation of engineering properties of fly ash and mixtures of fly ash and slag from landfill (without or with binders of cement/lime) was conducted at the Laboratory of Soil Mechanics at the Faculty of Civil Engineering of the University of Belgrade (Serbia) and at the Institute for Testing of Materials – IMS Institute in Belgrade. The laboratory test results were showed in the study ‘Utilization of fly ash and slag produced in the TPP JP EPS thermal power plants for construction of railways’. Four kinds of waste materials from Serbian power plants were laboratory tested: (a) an ash-slag mixture from landfills at the ‘Nikola Tesla A’ thermal power plant; (b) fly ash from silos in the ‘Nikola Tesla B’ thermal power plant; (c) an ash-slag mixture from landfills at the ‘Kostolac A’ and ‘Kostolac B’ thermal power plants and ‘Srednje kostolacko ostrvo’ landfill; (d) fly ash from the ‘Kostolac’ thermal power plant. The following physical and mechanical properties of ash and mixtures were investigated: grain size distribution, Atterberg limits, specific gravity, moisture-density relationship, shear strength parameters in terms of effective stresses, California Bearing Ratio (CBR), and deformation parameters. The paper presents the results of laboratory tests of the materials with and without binders, and based on the laboratory results and previous research, the paper presents possibilities of using fly ash and slag for the construction of railway substructure in the planned construction and reconstruction of railway network in Serbia. The obtained results indicate that tested fly ash and ash-slag mixture have met the technical requirements and that they have the potential to be used in railway substructure. First published online 12 December 2016

Consequences of Non Planned Urban Development During Turbulent Times in Serbia — Case Study of Suburb Kumodraz Watershed in Belgrade

Development is usually based on numerous analyses accounting for planning, economy and population assessments as well as urbanism, architectural and civil engineering infrastructure planning and project design. The modern city planning begun during Napoleon in Paris, while modern urban planning in Belgrade started in mid nineteenth century. At the end of twentieth century turbulent times occurred in the area of ex Yugoslavia so that numerous plans of development started being misused or never completely respected. Actually, during 1990s urban development in cities of Serbia became rather uncontrolled. In addition, during 1990s many people moved from rural places to, to their opinion, more promising places, most frequently to the Capital city. This paper presents a series of consequences of non planned urban development on sewer infrastructure operation. Those includes high construction rate including increase of number of inhabitants at suburban part, namely watershed of the brook Kumodraz at the southern part of the city of Belgrade. Those changes were noticed during preparation of preliminary design for the reconstruction and upgrading of the combined waste water system at this part of the city. The design preparation included measurements of wastewater and rainfall runoff at the downstream outlet. During measurement period, which started in 1997, significant differences occurred in the both base flow, i.e. dry weather flow, as well as in peak flows during moderate and severe rainfall events.