Browsing by Author "Karunarathne, HDSS"

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item: Article-Abstract
Applicability of pressure retarded osmosis power generation technology in Sri Lanka
(2015-08-18) Karunarathne, HDSS; Walpalage, S
In this study the applicability of pressure retarded osmosis power generation was investigated in order to fulfil current electricity demand in Sir Lanka. Pressure retarded osmosis (PRO) process is a renewable and green technology with zero carbon emission to the environment. Salinity gradient through a membrane is the key parameter in osmotic pressure development. Theoretically it is a pressure increment of 26 bar which is equivalent to 270 m high water column for fixed volume of salt water compartment. This hydrostatic pressure can be used to generate electricity by sending pressurized water through a turbine. According to the literature, 1 MW electricity generation requires 1m3/s flow of fresh water. Sri Lanka has a great potential to develop this technology as it is surrounded by sea. Subsequently the country is having 103 number of water rich river basins over the country. Currently the electricity demand of the entire country is about 2100MW and it is already being supplied by both hydro and thermal power plant. The country spends an immense amount of money for the thermal power generation in every year. This can be reduced by introducing PRO power generation. Calculations over the PRO power generation reveal that it is possible to generate 7.84% of country energy requirement via some selected river basins through this technology.
item:
Applicability of pressure retarded osmosis power generation technology in Sri Lanka
(2014-06-27) Karunarathne, HDSS; Walpalage, S
In this study the applicability of pressure retarded osmosis power generation was investigated in order to fulfil current electricity demand in Sir Lanka. Pressure retarded osmosis (PRO) process is a renewable and green technology with zero carbon emission to the environment. Salinity gradient through a membrane is the key parameter in osmotic pressure development. Theoretically it is a pressure increment of 26 bar which is equivalent to 270 m high water column for fixed volume of salt water compartment. This hydrostatic pressure can be used to generate electricity by sending pressurized water through a turbine. According to the literature 1 MW electricity generation requires 1m3/s flow of fresh water. Sri Lanka has a great potential to develop this technology as it is surrounded by sea. Subsequently the country is having 103 number of water rich river basins over the country. Currently the electricity demand of the entire country is about 2100MW and it is already being supplied by both hydro and thermal power plant. The country spends an immense amount of money for the thermal power generation in every year. This can be reduced by introducing PRO power generation. Calculations over the PRO power generation reveal that it is possible to generate 7.84% of country energy requirement via some selected river basins through this technology.
item: Article-Abstract
Fixed bed adsorption column studies for the removal of aqueous phenol from activated carbon prepared from sugarcane bagassa
(2015-08-18) Karunarathne, HDSS; Amarasinghe, BMWPK
Fixed bed adsorption has become a frequently used industrial application in wastewater treatment processes. Various low cost adsorbents have been studied for their applicability in treatment of different types of effluents. In this study, the potential of activated carbon derived from sugarcane bagasse was studied for the removal of aqueous phenol in a fixed column. Sugarcane bagasse was thermally activated under 600 °C in absence of air. A series of batch experiments were performed in order to identify the appropriate adsorption isotherm. Both Langmuir and Freundlich equilibrium isotherms were analyzed according to the experiment data and related parameters were estimated. Results revealed that the Langmuir isotherm provides the best fit with experimental data. Fixed bed experiments were performed and, breakthrough curves were drawn by varying activated carbon bed height. Accordingly the ideal breakthrough curves (IBC) were prepared and bed capacity (BC), length of the unused bed (LUB), the time required for full bed exhaustion at infinite rapid adsorption TS and the breakthrough times Tb were calculated for each scenarios.
item: Article-Full-text
Fixed bed adsorption column studies for the removal of aqueous phenol from activated carbon prepared from sugarcane bagasse
(2014-06-26) Karunarathne, HDSS; Amarasinghe, BMWPK
Fixed bed adsorption has become a frequently used industrial application in wastewater treatment processes. Various low cost adsorbents have been studied for their applicability in treatment of different types of effluents. In this study, the potential of activated carbon derived from sugarcane bagasse was studied for the removal of aqueous phenol in a fixed column. Sugarcane bagasse was thermally activated under 600 0C in absence of air. A series of batch experiments were performed in order to identify the appropriate adsorption isotherm. Both Langmuir and Freundlich equilibrium isotherms were analyzed according to the experiment data and related parameters were estimated. Results revealed that the Langmuir isotherm provides the best fit with experimental data. Fixed bed experiments were performed and, breakthrough curves were drawn by varying activated carbon bed height. Accordingly the ideal breakthrough curves (IBC) were prepared and bed capacity (BC), length of the unused bed (LUB), the time required for full bed exhaustion at infinite rapid adsorption TS and the breakthrough times Tb were calculated for each scenarios. Â© 2013 The Authors. Published by Elsevier B.V.
item: Conference-Abstract
Investigation of stability of anaerobic digestion of food waste in a plug flow reactor using mathematical modeling and simulation
Karunarathne, HDSS; Rathnasiri, PG
Anaerobic treatment has gained wide acceptance as a sustainable technology for treatment of solid wastes and waste water. Recently, novel plug flow reactor system has been installed at few local institutions to treat semi solid wastes with improved efficiency. However lack of understanding of operational parameters and functional units of this reactor system has led to suboptimal operation and thereby low gas production and methane yield. In this study, plug flow anaerobic reactor is modeled using two modeling scenarios. For this task, Anaerobic Digestion Model No. I (ADM1) implemented in the simulation software package called AQUASIM 2. If is used. Under first scenario, advective diffusive reactor compartment followed by two continuous stirred tank reactors for collection of slurry and gas used to model the plug flow reactor. Under second was scenario, series of CSTR reactors were used to model plug flow reactor and biogas was collected into a common head space via diffusive link. Simulation was performed for the different hydraulic retention times and feed flow rates for the substrate of food waste. Simulation results from advective-diffusive reactor model revealed that accumulation of gasses in the slurry causes an inhibition in methane production. In series of CSTR model, when the food waste alone was used at low hydraulic retention times, pH decreases drastically and causes to process inhibition in the first reactor. This inhibition propagates towards the other connected CSTR reactors and after a certain periods of time total methane production ceases.
item: Thesis-Abstract
Investigation of stability of plug flow anaerobic digester using mathematical modeling
(2015-06-26) Karunarathne, HDSS; Rathnasiri, PG; Bakke, R
Anaerobic treatment has gained wide acceptance as a sustainable technology for treatment of solid wastes and waste water. But in the local context this technology is not rapidly advancing due to process failures and poor technology management. Most of the failures are reported in the anaerobic solid waste treatment than waste water treatment. Recently, novel plug flow reactor system has been installed in few local institutions to treat semi solid wastes with improved efficiency. However lack of understanding of operational parameters and functional units of this reactor system has led to suboptimal operation and thereby low gas production and methane yield. Objective of this study is to develop dynamic mathematical model for plug flow reactor system and propose new strategies to enhance the methane yield and stability of the process. The anaerobic digestion model No. 1 (ADM 1) developed by the international water association (IWA) task group for mathematical modeling of anaerobic digestion process is the most sophisticated model established for full- scale industrial applications. In this work ADM1 was implemented in the simulation software package called AQUASIM 2.1f and advective diffusive reactor compartment was initially used to model the plug flow reactor. To be able to model the actual plug flow reactor system as installed two scenarios are introduced i.e. advective diffusive reactor compartment followed by two continuous stirred tank reactors for collection of slurry and gas. The simulation was done for the different hydraulic retention times and feed flow rates for the substrate of food waste. As second scenario, series of CSTR reactors was used to model plug flow reactor and simulated as before. Simulation results on advective-diffusive reactor model reveal that accumulation of gasses in the slurry cause an inhibition in methane production. In series of CSTR model, when the food waste alone was used at low hydraulic retention times, pH decreases drastically and cause to process inhibition in the first reactor. This inhibition radiates towards the other connected CSTR reactors and after a certain periods of time total methane production terminates.
item: Conference-Abstract
Sugar cane bagasse based activated carbon as an adsorbent for Phenol removal from aqueous solutions
Karunarathne, HDSS; Amarasinghe, BMWPK
In this study, applicability of activated carbon derived from sugar cane bagasse to remove phenol from aqueous, solution by the technique of adsorption was investigated. The adsorbent was prepared from bagasse by therm.i I activation at 600°C in the absence of air. Batch adsorption studies were carried out to determine the factors affecting adsorption by varying experimental conditions; contact time, initial phenol concentration (50-150) mg/L, adsorbent dose (g/L) and initial solution pH. Adsorption Isotherms and kinetics were studied. Approximately 90(ih removal ()J phenol was observed at solution pH lto 9 and rapid decline in removal % was obtained beyond pH 9.5. Till experimental data were analyzed according to the Langmuir and Freundlich isothermal models. The equilibrium d.u.. were best fitted to Langmuir model with a maximum adsorption capacity of 35.71 mg/g. Kinetic studies revealed that the pseudo-second order model was the best interpreter for the experimental data. Activated carbon prepared hI sugar cane bagasse is an efficient adsorbent material for removal of phenol from aqueous systems.