UWU Repository :: Browsing by Author "Weerasekara, W.B.M.L.I."

Browsing by Author "Weerasekara, W.B.M.L.I."

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Assessment of the Impact of Azolla pinnata at Demodara Water Treatment Plant Intake Reservoir
(Uva Wellassa University of Sri Lanka, 2019-02) Jayasinghe, N.S.; Weerasekara, W.B.M.L.I.; Udagedara, T.; Weragoda, S.K.
Demodara Water Treatment Plant intake reservoir is located in between Demodara and Badulla cities about 12 km upstream in Badulu Oya from Badulla. An invasive growth of floating macrophyte was observed from third week of January 2018. Water quality of treatment plant intake reservoir was studied by analyzing the reservoir water with the presence and the absence of the Azolla mat, to find whether there was any change in the water quality with the mat. Water quality close to the dam, lake at about 1 km upstream from the dam and upstream flowing water (about 500 m upstream from the lake) were analyzed in different depths (close to the dam 6.5 m and upstream lake 1 m depth). pH, turbidity, electrical conductivity, dissolve oxygen was analyzed on site and NO3-, Total PO₄ 3- , SO42-, Cl- and F- was measured using Ion Chromatograph and relative abundance of phytoplanktons were estimated using plankton nets (20 μm) and microscope with the presence of A. pinnata mat and following day of removal of A. pinnata mat. As a part of the study, two models were observed inserting 20 l of intake reservoir water and 22 g of Azolla for one model. pH, turbidity, conductivity was monitored for seven weeks. pH was decreased in the model with Azolla. Conductivity and turbidity did not show a significant change. pH decrement and Total PO₄3-, Phytoplankton increment was observed with the absence of the mat in Demodara reservoir. All the water quality parameters in treatment plant raw water were within the drinking water standards (SLS 614:2013), with the presence of Azolla mat. The Azolla didn’t appear after manual removal. Therefore, further studies and implementing a Water Safety Plan by proper catchment management is needed.
Effect of Catchment Characteristic on Formation of Trihalomethane along the Kelani River in Sri Lanka.
(Uva Wellassa University of Sri Lanka, 2019-02) Bandara, H.R.L.C.; Weerasekara, W.B.M.L.I.
Kelani River is the fourth longest river in Sri Lanka which starts its journey from the Sri Pada Mountain range and meet the ocean at Colombo. In upper catchment area there are plenty of tea and rubber plantation land and in down catchment there are huge number of industrial zones. Therefore, it carries more Dissolved Organic Carbon (DOC), inorganic and suspended solids. In drinking Water Treatment Plants (WTPs), can be removed mainly Total solid. As a result of remaining DOC in filtered water Disinfection by Products (DBPs) such as Trihalomethane (THM) formed after the chlorination. THM is carcinogenic. Present study aimed to investigate the effects of catchment characteristic on THM formation along the Kelani river. Water samples were collected from the WTPs located at Seethagangula, Hatton, Maskeliya, Morontota, Ruwanwella, Yatiyantota, Pugoda, Biyagama and Ambatale. Four THM species, Trichloromethane, Bromodichloromethane, Dibromochlomethane and Tribromomethane were measured using Gas Chromatography (GC) system and finally Total THM (TTHM) were calculated. The lowest TTHM concentration was reported in Maskeliya (9.34 µg L-1) WTP. Catchment area is mostly covered with tea plantation in Maskeliya area. The TTHM concentration at Morontota and Ruwanwella WTPs were 42.96 ±7.00 µg L-1and 65.70 ± 16.12 µg L-1, respectively. The main catchment characteristic of these area is rubber plantation. However, highest TTHM value of 67.19 ± 4.50 µg L-1was reported in Biyagama WTP which is located in highly industrialized area. Even though both Ambatale and Biyagama WTPs are located very close, TTHM value of the Ambatale (21.33 ± 2.41) µg L-1WTP is significantly lower than Biyagama. However, all the recorded TTHM values were below the United States Environmental Protection Agency (USEPA) maximum contamination level of 80 µg L-1. Finally, it can be concluded that THM formation is lower in tea plantation area and high in industrialized area.
Investigation on the Manganese Phase Diagram when Manganese is Reacting with Calcium Hypochlorite
(Uva Wellassa University of Sri Lanka, 2019-02) Abeysinghe, S. A.; Weragoda, S. K.; Weerasekara, W.B.M.L.I.; Udagedara, D. T.
Oxidation Reduction behavior of different substances highly contributes to the condition of water and phase diagram express the relationship between Eh and pH of a particular substance. When Manganese is in water, it can exist either as suspension matter or as dissolved matter and exact speciation can be determined by investigating the Manganese phase diagram. The objectives of this study were to investigate a suitable method to reduce excess Manganese from water by flocculation and filtration process and identify the different species of Manganese from phase diagram which can be removed from water as insoluble form. Excess concentration of Manganese was reduced by oxidizing to an insoluble form using Calcium hypochlorite and resulting insoluble form was removed by flocculation and filtration. Behavior of the Manganese species fluctuates with different pH and Eh values. The pH values of the samples were measured directly by pH meter and Eh values were determined by both calculated value from Nernst equation and measured value as oxidation reduction potential. After 30 minutes of time residual Chlorine values of all the trials were zero. Manganese rich water was synthetically prepared by adding MnSO4 in to raw water sample collected from Maguru Oya, Wariyapola. Manganese was removed as a brown color deposition which was confirmed as Mn3O4 (Hausmannite) by Manganese phase diagram. This deposition can be removed by using suitable filtration process and removal efficiencies were 33%, 22%, 11% and 0 with concentration of Calcium hypochlorite of 0.6 ppm, 0.7 ppm, 0.8 ppm and 0.9 ppm respectively. That need to be confirmed by further studies because raw water sample may have different cations and anions.
Optimization of Pre-Treatment Process of Iron Removal from Groundwater
(Uva Wellassa University of Sri Lanka, 2018) Manathunge, M.D.R.M.; Weragoda, S.K.; Weerakoon, W.M.D.S .; Weerasekara, W.B.M.L.I.
The presence of iron is one of the major issues experienced by groundwater consumers. The rural water treatment plant located at Bolagala area in Kandy treats water mainly for iron removal. The available half treatment process of this plant removes 83.20 - 93.06 % iron from natural water. As the raw water iron concentration is high, the removal percentage is not adequate to bring the iron concentration down to the recommended standards (SLS 614: 2013). The study was carried out to optimize the existing pre-treatment process with the purpose of bringing the treated water iron concentration under 0.3 mg/l. Two oxidation processes a) Aeration b) Chlorination were experimented to select an optimum oxidant. Aeration was tested for different time periods. 6 min aeration time showed approximately 50% removal of dissolved iron concentration. Chlorination was tested for different doses. 5 ppm chlorine dose was effective in 99% removal of the dissolved iron. The final dissolved iron (DI) concentration reached 0.03 mg /1 which is ten times lower than recommended level. The plant pre-treatment step should include a chlorination step with aeration to achieve the optimum removal of dissolved iron in raw water.
Risk Assessment and Health Based Evaluation on Rural Water Supply Schemes: Case Study in Kotiyakumbura, Mawela and Kandewaththa
(Uva Wellassa University of Sri Lanka, 2019-02) Edirisinghe, E.P.M.; Rajapakse, R.M.S.M.; Weerasekara, W.B.M.L.I.; Weragoda, S.K.
Provision of safe drinking water and sanitation facilities are cited as the highest social priority to communities. In Sri Lanka, rural water supply schemes are not subjected to substantial concern. This research was to focus on health-based evaluation on treated water from rural water supply schemes. Hazards and hazardous events were identified at the water source, treatment process, distribution system and the consumer end of three rural water supply schemes. The risk assessment was carried out following semi quantitative approach. 40% of the identified hazards were recorded as high risk. Turbidity, Electrical conductivity, pH, Temperature, Alkalinity, Hardness, Nitrate, total phosphate, Phosphate, E. coli and total coliform were measured in raw water, treated and water from consumer end. Residual Chlorine was measured in treated and consumer end water samples. Tested water quality parameters were within the limits of Sri Lankan Standards except the pH of treated water in Kotiyakumbura, turbidity of Kandewaththa. Kotiyakumbura and Mawela treated water is microbiologically unsatisfactory. The pH of water in Kotiyakumbura ranges between 5.98 and 7.40. 90% of the turbidity of water at the consumer end in Kandewaththa exceeds 2 Nephelometric Turbidity Unit. Questionnaire survey was done by covering the income levels, education backgrounds and location. Kandewaththa consumers do not use this water for drinking. Currently, none of the consumers are suffering from waterborne diseases. 82% of Kotiyakumbura and 78% of Kandewaththa consumers practice domestic water treatments such as boiling and filtering. Due to these domestic treatments they may be free from water-borne diseases currently. As a recommendation it is necessary to implement Water Safety Plans on rural water supply schemes. Further studies are required on rural water sector to improve the quality of treated water.
Social Impacts on Rainwater Harvesting – A Case Study in Anuradhapura and Kegalle
(Uva Wellassa University of Sri Lanka, 2019-02) Rathnayake, K.A.I.L.; Weragoda, S.K.; Weerasekara, W.B.M.L.I.; Udagedara, D.T.
Water scarcity is a global issue with the increasing population. Rainwater harvesting is considered as an environmental friendly, sustainable source of water which can be used for domestic and drinking purposes. Sri Lankan government has framed rules and policies supporting the installation of rainwater harvesting systems, however, implementation and operation of these require the acceptance and willingness of general public. This research focuses on the social impacts on the rainwater harvesting systems installed in dry and wet zones in Sri Lanka. Both, water quality (Physical, Chemical, Bacteriological) and factors affecting it were assessed through the study. The samples were collected from rainwater harvesting systems at Kegalle and Kebithigollewa regions, 30 from each while conducting a questionnaire survey simultaneously. pH values were varied between 5.53- 7.19 in Kebithigollewa and 6.49 – 9.55 in Kegalle, may be due to the reactions in the tank material, ferrocement and plastic. All the tested chemical parameters of rainwater samples were within the limits of SLS 614: 2013 guidelines. Total coliform was detected in 50% of Kebithigollewa samples and 100% of Kegalle samples, which may be due to wrong water quality and quantity management practices. Social survey analysis revealed that microbiological parameters were affected mainly by the cleanness level of roof catchment area and atmospheric conditions, such as dust in the environment. Consumers in Kegalle region hesitate to drink rainwater due to lack of confidence as a drinking source. Harvested rainwater can be of consistently high quality through the selection of appropriate catchment, storage materials and the application of post-cistern treatment. A water safety plan should be implemented on rainwater harvesting systems to identify the risks, to improve the water quality and to mitigate quality degradation. A social awareness programs can be recommended to increase the rainwater consumption and willingness.

Browsing by Author "Weerasekara, W.B.M.L.I."

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