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Subject: search.filters.subject.combined sewer systems

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    PublicationOpen Access
    Optimal control of urban sewer systems under enhanced water quality modeling
    (5th International conference on Sustainable Built Environment, 2014) Rathnayake, U. S
    Agricultural lands usually carry a considerable amount of phosphorous and nitrogen. This is due to the routinely added chemical fertilizers. Phosphorous is identified as a non-point source pollutant that causes eutrophication in surface waters. Even though, phosphorous is less mobile than nitrogen, soil erosion in agricultural lands leads to increase the phosphorous levels in surface water. Therefore, it is always better to consider phosphorous concentration when considering the receiving water quality due to combined sewer overflows (CSOs). Rathnayake and Tanyimboh’s optimal control model for urban sewer systems is capable of assessing water quality in receiving water due to CSOs. However, it only includes the concentrations of total suspended solids (TSS), chemical oxygen demand (COD), nitrates and nitrites (NOX), five-day biochemical oxygen demand (BOD) and total Kjeldahl nitrogen (TKN). Therefore, there is a necessity to improve the water quality analysis in Rathnayake and Tanyimboh’s optimal model. This paper presents an enhanced water quality approach, including phosphorous concentrations, in control of urban sewer networks. The enhanced model is applied to a real world combined sewer network. Results show that the enhanced model produces better approach compared to the existing Rathnayake and Tanyimboh’s control model.
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    PublicationEmbargo
    Two consecutive storms and optimal control of urban sewer networks to minimize the pollution load of combined sewer systems
    (Springer International Publishing, 2017-03-01) Rathnayake, U. S; Azamathulla, H. M
    Combined sewer overflows (CSOs) are a burdened environmental issue. Structural measures are not the best solution to cope with or to minimize these adverse impacts from CSOs. Non-structural measures, if possible to implement, would be the best solution in sustainable development. Controlling of existing urban sewer networks is a potential non-structural measure to minimize the adverse impacts of CSOs. Several algorithms to control urban sewer networks are in literature; however, there is little literature in minimizing the environmental impacts from CSOs. Rathnayake and Tanyimboh (Management 29:2715–2273, 2015) have successfully developed a control algorithm to minimize the environmental impacts or to enhance the quality of receiving water in an event of CSOs. However, this control algorithm is based on single-peaked runoff hydrographs. Not only for the research in control of urban sewer networks, but also in most other researches, single-peaked runoff hydrographs are generally applied. This is due to the modeling simplicity. However, in real world, these conditions may not be applicable. It is very common to have a second peak after the first peak in the hydrograph. The second peak may or may not be high as the first; however, it is important to consider these peak flows, when it comes to design and control of combined sewer systems. Therefore, this reach was carried out to improve Rathnayake and Tanyimboh’s optimal control algorithm (2015) for two consecutive storms. Runoff hydrographs due to two consecutive storms and pollutographs were developed in improving the Rathnayake and Tanyimboh’s control algorithm. Results manifest the benefits of using multi-objective optimization in controlling combined sewer networks under two consecutive storms where many sets of feasible control settings can be obtained. A desired control settings can be implemented to the sewer system according to the available resources.
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    PublicationOpen Access
    Optimal control of combined sewer systems using SWMM 5.0
    (Southampton: WIT Press, 2012-04) Rathnayake, U. S; Tanyimboh, T. T
    Combined sewer networks carry wastewater and stormwater together. Capacity limitation of these sewer networks results in combined sewer overflows (CSOs) during high-intensity storms. Untreated CSOs when directly discharged to the nearby natural water bodies cause many environmental problems. Controlling urban wastewater systems is one possible way of addressing the environmental issues from CSOs. However, controlling urban sewer systems optimally is still a challenge, when considering the receiving water quality effects. In this study, a multi-objective optimization approach was formulated considering the pollution load to the receiving water from CSOs and the cost of the wastewater treatment. The optimization model was tested using an interceptor sewer system. The results demonstrate the benefits of the multi-objective optimization approach and its potential to establish the key properties of a range of control strategies through an analysis of the various tradeoffs involved. Keywords: combined sewer overflows, effluent quality index, evolutionary computing, genetic algorithm, multi-objective optimization, combined sewer systems.