Department of Civil Engineering
Permanent URI for this collectionhttp://localhost:4000/handle/123456789/1927
Browse
11 results
Search Results
Item Investigation of urban water quality using artificial rainfall(Water Environment Federation, 2004) Goonetilleke, AshanthaAs the concept of sustainable communities is gaining increasing recognition around the world it is of critical importance to investigate the water quality of urban environments. The contamination of waterways in urban communities seriously affects the utility of water for different purposes and degrades the aesthetic value of natural watercourses. Research investigations in the past have generally focused on suspended solids and nutrients, which are relatively easy to monitor. Unfortunately the build-up and wash-off of micro pollutants such as polycyclic aromatic hydrocarbons (PAH) and heavy metals (HM) have received limited research interest in urban water quality research even though these can cause significant health and environmental impacts even at low concentrations. This paper describes how artificial rainfall, using a specially designed highly portable rainfall simulator was employed in order to generate water quality data from urban environments. This approach was adopted in order to investigate the wash-off of pollutants from paved surfaces and to overcome constraints due to the highly unreliable rainfall in South-East Queensland Australia. The rainfall simulator was able to demonstrate its ability to satisfactory simulate natural rainfall in the area. The results obtained confirmed that the rainfall simulator is a reliable tool for urban water quality research and can be used to simulate pollutant wash-off.Item Understanding the role of land use in urban stormwater quality management(Elsevier, 2005-01) Goonetilleke, AshanthaUrbanisation significantly impacts water environments with increased runoff and the degradation of water quality. The management of quantity impacts are straight forward, but quality impacts are far more complex. Current approaches to safeguard water quality are largely ineffective and guided by entrenched misconceptions with a primary focus on ‘end-of-pipe’ solutions. The outcomes of a research study presented in the paper, which investigated relationships between water quality and six different land uses offer practical guidance in the planning of future urban developments. In terms of safeguarding water quality, high-density residential development which results in a relatively smaller footprint would be the preferred option. The research study outcomes bring into question a number of fundamental concepts and misconceptions routinely accepted in stormwater quality management. The research findings confirmed the need to move beyond customary structural measures and identified the key role that urban planning can play in safeguarding urban water environments.Item Analysis of heavy metals in road-deposited sediments(Elsevier, 2006-07) Goonetilleke, AshanthaRoad-deposited sediments were analysed for heavy metal concentrations at three different landuses (residential, industrial, commercial) in Queensland State, Australia. The sediments were collected using a domestic vacuum cleaner which was proven to be highly efficient in collecting sub-micron particles. Five particle sizes were analysed separately for eight heavy metal elements (Zn, Fe, Pb, Cd, Cu, Cr, Al and Mn). At all sites, the maximum concentration of the heavy metals occurred in the 0.45–75 μm particle size range, which conventional street cleaning services do not remove efficiently. Multicriteria decision making methods (MCDM), PROMETHEE and GAIA, were employed in the data analysis. PROMETHEE, a non-parametric ranking analysis procedure, was used to rank the metal contents of the sediments sampled at each site. The most polluted site and particle size range were the industrial site and the 0.45–75 μm range, respectively. Although the industrial site displayed the highest metal concentrations, the highest heavy metal loading coincided with the highest sediment load, which occurred at the commercial site. GAIA, a special form of principal component analysis, was applied to determine correlations between the heavy metals and particle size ranges and also to assess possible correlation with total organic carbon (TOC). The GAIA-planes revealed that irrespective of the site, most of the heavy metals are adsorbed to sediments below 150 μm. A weak correlation was found between Zn, Mn and TOC at the commercial site. This could lead to higher bioavailability of these metals through complexation reactions with the organic species in the sediments.Item Mathematical interpretation of pollutant wash-off from urban road surfaces using simulated rainfall(Elsevier, 2007-07) Goonetilleke, AshanthaIn the context of stormwater quality modelling, an in-depth understanding of underlying physical processes and the availability of reliable and accurate mathematical equations, which can replicate pollutant processes are essential. Stormwater pollutants undergo three primary processes, namely, build-up, wash-off and transport, before accumulating into receiving waters. These processes are expressed mathematically by equations in stormwater quality models. Among the three processes, wash-off is the least investigated. This paper presents the outcomes of an in-depth investigation of pollutant wash-off processes on typical urban road surfaces. The study results showed that a storm event has the capacity to wash-off only a fraction of pollutants available and this fraction varies primarily with rainfall intensity, kinetic energy of rainfall and characteristics of the pollutants. These outcomes suggest that the exponential equation commonly used for mathematically defining pollutant wash-off would need to be modified in order to incorporate the wash-off capacity of rainfall. Consequently, the introduction of an additional term referred to as the ‘capacity factor’ CF is recommended. CF primarily varies with rainfall intensity. However, for simplicity three rainfall intensity ranges were identified where the variation of CF can be defined. For rainfall intensities less than 40 mm/h, CF varies linearly from 0 to 0.5. For rainfall intensities from 40 to around 90 mm/h, CF is a constant around 0.5. Beyond 90 mm/h, CF varies between 0.5 and 1.Item Understanding road surface pollutant wash-off and underlying physical processes using simulated rainfall(IWA Publishing, 2008-04) Goonetilleke, AshanthaPollutant wash-off is one of the key pollutant processes that detailed knowledge is required in order to develop successful treatment design strategies for urban stormwater. Unfortunately, current knowledge relating to pollutant wash-off is limited. This paper presents the outcomes of a detailed investigation into pollutant wash-off on residential road surfaces. The investigations consisted of research methodologies formulated to overcome the physical constraints due to the heterogeneity of urban paved surfaces and the dependency on naturally occurring rainfall. This entailed the use of small road surface plots and artificially simulated rainfall. Road surfaces were selected due to its critical importance as an urban stormwater pollutant source. The study results showed that the influence of initially available pollutants on the wash-off process was limited. Furthermore, pollutant wash-off from road surfaces can be replicated using an exponential equation. However, the typical version of the exponential wash-off equation needs to be modified by introducing a non dimensional factor referred to as ‘capacity factor' CF. Three rainfall intensity ranges were identified where the variation of CF can be defined. Furthermore, it was found that particulate density rather than size is the critical parameter that influences the process of pollutant wash-off.Item The importance of a triple bottom line approach for safeguarding urban water quality(Istanbul Technical University (ITU), Turkey, 2010) Goonetilleke, AshanthaWater environments are greatly valued in urban areas as ecological and aesthetic assets. However, it is the water environment that is most adversely affected by urbanisation. Urban land use coupled with anthropogenic activities alters the stream flow regime and degrade water quality with urban stormwater being a significant source of pollutants. Unfortunately, urban water pollution is difficult to evaluate in terms of conventional monetary measures. True costs extend beyond immediate human or the physical boundaries of the urban area and affect the function of surrounding ecosystems. Current approaches for handling stormwater pollution and water quality issues in urban landscapes are limited as these are primarily focused on ‘end-of-pipe’ solutions. The approaches are commonly based either on, insufficient design knowledge, faulty value judgements or inadequate consideration of full life cycle costs. It is in this context that the adoption of a triple bottom line approach is advocated to safeguard urban water quality. The problem of degradation of urban water environments can only be remedied through innovative planning, water sensitive engineering design and the foresight to implement sustainable practices. Sustainable urban landscapes must be designed to match the triple bottom line needs of the community, starting with ecosystem services first such as the water cycle, then addressing the social and immediate ecosystem health needs, and finally the economic performance of the catchment. This calls for a cultural change towards urban water resources rather than the current piecemeal and single issue focus approach. This paper discusses the challenges in safeguarding urban water environments and the limitations of current approaches. It then explores the opportunities offered by integrating innovative planning practices with water engineering concepts into a single cohesive framework to protect valuable urban ecosystem assets. Finally, a series of recommendations are proposed for protecting urban water resources within the context of a triple bottom line approach.Item Distribution of polycyclic aromatic hydrocarbons in urban stormwater in Queensland, Australia(Elsevier, 2010-09) Goonetilleke, AshanthaThis paper reports the distribution of Polycyclic Aromatic Hydrocarbons (PAHs) in wash-off in urban stormwater in Gold Coast, Australia. Runoff samples collected from residential, industrial and commercial sites were separated into a dissolved fraction (<0.45 μm), and three particulate fractions (0.45–75 μm, 75–150 μm and >150 μm). Patterns in the distribution of PAHs in the fractions were investigated using Principal Component Analysis. Regardless of the land use and particle size fraction characteristics, the presence of organic carbon plays a dominant role in the distribution of PAHs. The PAHs concentrations were also found to decrease with rainfall duration. Generally, the 1- and 2-year average recurrence interval rainfall events were associated with the majority of the PAHs and the wash-off was a source limiting process. In the context of stormwater quality mitigation, targeting the initial part of the rainfall event is the most effective treatment strategy. The implications of the study results for urban stormwater quality management are also discussed.Item Determination of a set of surrogate parameters to assess urban stormwater quality(Elsevier, 2010-11) Goonetilleke, AshanthaThis paper presents the outcomes of a research project, which focused on developing a set of surrogate parameters to evaluate urban stormwater quality using simulated rainfall. Use of surrogate parameters has the potential to enhance the rapid generation of urban stormwater quality data based on on-site measurements and thereby reduce resource intensive laboratory analysis. The samples collected from rainfall simulations were tested for a range of physico-chemical parameters which are key indicators of nutrients, solids and organic matter. The analysis revealed that [total dissolved solids (TDS) and dissolved organic carbon (DOC)]; [total solids (TS) and total organic carbon (TOC)]; [turbidity (TTU)]; [electrical conductivity (EC)]; [TTU and EC] as appropriate surrogate parameters for dissolved total nitrogen (DTN), total phosphorus (TP), total suspended solids (TSS), TDS and TS respectively. Relationships obtained for DTN–TDS, DTN–DOC, and TP–TS demonstrated good portability potential. The portability of the relationship developed for TP and TOC was found to be unsatisfactory. The relationship developed for TDS–EC and TS–EC also demonstrated poor portability.Item Analysis of build-up of heavy metals and volatile organics on urban roads in gold coast, Australia(IWA, 2011) Goonetilleke, AshanthaUrban water quality can be significantly impaired by the build-up of pollutants such as heavy metals and volatile organics on urban road surfaces due to vehicular traffic. Any control strategy for the mitigation of traffic related build-up of heavy metals and volatile organic pollutants should be based on the knowledge of their build-up processes. In the study discussed in this paper, the outcomes of a detailed experimental investigation into build-up processes of heavy metals and volatile organics are presented. It was found that traffic parameters such as average daily traffic, volume over capacity ratio and surface texture depth had similar strong correlations with the build-up of heavy metals and volatile organics. Multicriteria decision analyses revealed that that the 1–74 μm particulate fraction of total suspended solids (TSS) could be regarded as a surrogate indicator for particulate heavy metals in build-up and this same fraction of total organic carbon could be regarded as a surrogate indicator for particulate volatile organics build-up. In terms of pollutants affinity, TSS was found to be the predominant parameter for particulate heavy metals build-up and total dissolved solids was found to be the predominant parameter for the potential dissolved particulate fraction in heavy metals buildup. It was also found that land use did not play a significant role in the build-up of traffic generated heavy metals and volatile organics.Item WSUD application audit at gold coast city(Engineers Australia, 2012) Goonetilleke, AshanthaIn recent years, Water Sensitive Urban Design (WSUD) has been strongly promoted in South East Queensland to mitigate quantity and quality issues in relation to stormwater. Gold Coast City Council has implemented WSUD devices widely for stormwater management for a number of years and is planning to continue this practice into the future. According to the planning policy of Gold Coast City Council, the adoption of WSUD practices is now mandatory for any new development within the city. As a result, Council is expected to be in possession of tens of millions of dollars of these assets in the future and will be responsible for their maintenance and long-term management. Any shortcoming in the implementation of best practice can potentially result in substantial liability for the Council in the future. However, there has been limited evaluation of WSUD systems in relation to their performance, long-term maintenance, and current knowledge gaps. It was considered that periodical audits of WSUD applications on the Gold Coast is vital to ensure that Council’s WSUD policies are continually improved to new learning and best practice is implemented and risk to Council is mitigated. After a series of stakeholder interviews within Council to understand current practical issues (weaknesses and strengths) in relation to the implementation of WSUD on the Gold Coast, a field audit comprising of condition assessment of eleven WSUD systems within four suburbs was undertaken to identify weaknesses and strengths in WSUD implementation on the Gold Coast. The outcomes of this study are presented in this paper.