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Has files: YesSubject: search.filters.subject.Combined sewer overflows

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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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    PublicationOpen Access
    OPTIMAL CONTROL OF URBAN SEWER SYSTEMS–WHERE DO WE STAND TODAY?
    (SAITM, 2014-04-26) Rathnayake, U. S
    Combined sewer overflows (CSOs) are identified as one of the major environmental concerns at most of the cities to date. These untreated combined sewer overflows are directly discharged to the nearby natural water bodies and cause many environmental problems because of the increased pollution levels at natural water bodies. Constructing additional storage facilities, increasing conduit capacity, expanding pumping capacity and application of controlling strategies to utilize the existing storage in sewer network are the common mitigation solutions of CSOs. This research paper targets to present the state of art of control of combined sewer systems, including the author’s current research work in developing a holistic optimal control model for combined sewer systems.
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    PublicationOpen Access
    Integrated Optimal Control of Urban wastewater Systems
    (2012) Rathnayake, U. S; Tanyimboh, T. T
    Sewer networks are designed to collect and transport wastewater to treatment plants. However, during wet weather periods stormwater runoff flows into these sewers and combined sewer overflows (CSOs) occur. Damage to the nearby natural waters from these CSOs is noticeable. This is because of the high pollution concentrations in CSOs. Controlling urban wastewater systems is one possible way of addressing the environmental issues from CSOs. Therefore, this research explores the development of a holistic framework that is intended to be used for the multi-objective optimization of urban wastewater systems, considering water quality in both sewers and receiving waters and the economics of wastewater treatment. Dry weather flows (DWFs) and stormwater runoff water quality compositions were considered. Temporal and spatial variations of the stormwater runoff were incorporated using pollutographs for different land-uses.
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    PublicationEmbargo
    Enhanced water quality modelling for optimal control of drainage systems under SWMM constraint handling approach
    (IOS Press, 2015-01-01) Rathnayake, U. S
    Phosphorus and nitrogen are two important nutrients to plants. Therefore, fertilizers usually used in agricultural lands hold a significant amount of phosphorus and nitrogen. Even though these two are essential for plants, they are treated as pollutants when they are contaminated to the fresh waters. Therefore, phosphorus in stormwater runoff is a concerned topic for combined sewer overflows (CSOs). Rathnayake and Tanyimboh's optimal control model was capable of handling five different water quality parameters (chemical oxygen demand, bio-chemical oxygen demand, total suspended solids, total Kjeldhal nitrogen and nitrates and nitrites) in CSOs. However, the enhanced approach is capable of integrating phosphorus concentrations into the analysis of water quality from CSOs. The new optimal control model for drainage systems was run and compared against the previous work by the author. Promising findings are illustrated from the newly developed model in controlling drainage systems.