Browsing by Author "Yatawara, M. D. M. D. W. M. M. K."

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Assessment of cytotoxic and genotoxic effects on Mahaweli river surface water samples contaminated with Gohagoda landfill leachate using Allium cepa bioassay
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Abhayarathna, I. D.; Yatawara, M. D. M. D. W. M. M. K.
Landfill leachate that potentially contains toxic compounds harms humans and the environment. Therefore, landfill leachate must be appropriately treated and disposed to avoid its environmental damage. However, conventional physicochemical analysis alone may not be adequate to evaluate the biological effects, therefore, conducting bioassay toxicity tests and traditional methods would be more appropriate. The present study assessed the potential toxic effect of Mahaweli River surface water samples contaminated with Gohagoda landfill leachate by a plant-based bioassay, Allium cepa. Moreover, the physio-chemical parameters have been tested. Surface water samples were collected from the river where the leachate was released into the Mahaweli River from the leachate outlet on five occasions, covering wet and dry seasons from September 2023 to January 2024. The A. cepa root tips were exposed to collected samples and the bioassay was carried out according to a standard method with some modifications. Aged tap water was used as the control. The statistical analyses were performed as appropriate in MINITAB-19. The study revealed that the A. cepa bioassay indicated significant cytogenotoxic effects on the leachate contaminated surface water compared to the control, evidenced by a percentage decrease in mitotic index (44.60%, 48.81%, 20.99%, 44.41% and 16.91%), the higher number of total nuclear abnormalities (165.20‰, 159.70‰, 154.20‰, 182.86‰ and 162.26‰), and higher number of chromosomal aberrations (352.40‰, 328.10‰, 258.00‰, 254.08‰ and 291.90‰). The presence of toxic substances in the leachate contaminated surface water, suggests a clear cytotoxic effect on exposed organisms. This is further supported by observing various nuclear abnormalities such as bi nuclei, micronuclei, and nuclear buds, predominantly in samples collected from leachate contaminated water, compared to control. These abnormalities indicate genetic damage and potential mutagenic effects, likely stemming from the discharge of leachate into the Mahaweli River. Moreover, chromosomal aberrations, including vagrant chromosomes, chromosomal bridges, and spindle disturbances, underscore the genotoxicity of the leachate. These abnormalities reflect structural changes in chromosomes and spindle apparatus, which can lead to disruptions in cell division and genetic instability. The significantly higher occurrence of these aberrations in leachate contaminated samples compared to control water samples highlights the detrimental impact of leachate contamination on the environment. All the COD and BOD5 values obtained for the leachate-contaminated water exceed the CEA tolerance limit values for all five sampling events. The findings highlight that the leachate discharged directly and significantly impacts the water quality at the leachate discharging point of the Mahaweli River. Further research is recommended to confirm the toxic effects of drained leachate on sensitive aquatic organisms in the Mahaweli River since they provide a better understanding of the risks associated with drained leachate. In addition, strict leachate management measures are recommended to minimize river contamination with this leachate.
Comparative study of the percentage degradability of food wrapping polythene films manufactured from different virgin materials
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Abeywickrama, M. S. J.; Yatawara, M. D. M. D. W. M. M. K.
The polythene industry in Sri Lanka is being shifted towards the use of compostable raw materials to manufacture food wrapping - films (lunch sheets) after the prohibition of films which are less than 20 microns. Nevertheless, no studies have been carried out to assess the degradability of such films in natural conditions. The present study was therefore focused on assessing the percentage degradability in ambient air, soil and compost of three types of films F001, F002 and F003 available in supermarkets and films manufactured from Poly-L-Lactic Acid (PLLA) (28%) + dimethyl ester (38%) + starch (26%) + auxiliaries (8%) (F004), Poly Lactic Acid (PLA) (F005) and Poly Butylene Adipate Terephthalate (PBAT) (F006). The material properties; tensile strength (MD-machine direction & TD-transverse direction), % elongation, moisture and water absorption of all the films (n=10 for each test) were analyzed at the beginning of the experiment. Half of each film type (n=144) was immersed in food waste contaminated water while the other half (n=144) was used as controls without subjecting to any processes. One third of the food waste contaminated films (n=28) was kept in ambient air while another one third was buried at 10 cm depth in soil. The remaining one third was buried in compost. The same procedure was carried out for control films. The percentage degradability was assessed after two and four months’ time interval and the percentage degradability was calculated with respect to weight losses of films with time. The highest MD and TD tensile strengths (25 Nm-2 and 12 Nm-2) were shown by F001 and the highest MD and TD elongations (148 mm and 175 mm) were shown by F002 respectively. In addition, all films showed 85-88% water absorption. The food waste contaminated F005 kept in ambient air showed 0.56% degradability after 4 months and it was not significant from its control (p> 0.05; ANOVA). Nevertheless, the food waste contaminated F006 showed 94% (non-contaminated- 77%) degradability in soil followed by F005 (92%; non-contaminated-65%) and F002 (89%; non-contaminated-82%). The non-contaminated films showed cracks, distortions, de-coloration, irregular patches etc. and the severity of such morphological changes was increased in food contaminated films buried in soil. Nevertheless, the non-contaminated F005 showed 61% (37%-contaminated) degradability in compost followed by F002 (42%). The results further revealed that the films contaminated with foods (buried in soil) degraded more than the other types. The overall results conclude that food wrapping polythene available in supermarkets were more or less similar to the films manufactured from known virgin materials (PLA and PBAT) except F004 and showed a significant degradation potential within four months
Do meteorological parameters have an impact on dust nuisance problem in the vicinity of Lakvijaya coal fired power plant in Sri Lanka?
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Hasmiya, A. J. F.; Yatawara, M. D. M. D. W. M. M. K.
Storing coal and piling up the resultant ash in open yards is a common practice in many thermal power plant operations in developing countries which may lead to dust nuisance problem in the vicinity of the power plants. However, meteorological parameters may have an influence on the dispersion and deposition of dust particles from pollution sources. The present study assessed the changes in dustfall rate with meteorological parameters (rainfall, atmospheric temperature and wind speed and direction) in an area between 500 m and 3 km from Lakvijaya coal fired power plant (LCPP) in Kalpitiya Divisional Secretariat Division from June to November 2019. Sampling sites included eight (08) locations covering all the directions of LCPP in the study area. Dust falls were collected and analysed according to ASTM D1739 methods. The meteorological parameters were collected from the Department of Meteorology. Monthly mean dustfall rate of the study area was statistically analysed with each meteorological parameters concerned over the study period. According to the results, dustfall rates varied significantly during the study, with the highest recorded in July (437.00 ± 208.00 mg m-2 day-1) and the lowest in November (54.10 ± 15.00 mg m-2 day-1). Rainfall exhibited an inverse trend to dustfall, increasing substantially from 26.2 mm in June to 638.4 mm in October. Temperature decreased gradually from 30.1°C in June to a minimum of 27.3°C in October. However, the statistical analysis revealed that, dustfall rate had a moderate positive correlation with atmospheric temperature (r = 0.312, p = 0.031) and a moderate negative correlation with rainfall (r = -0.312, p = 0.031) and the correlation with wind direction and wind speed were not statistically significant. Therefore, according to the study, within the study period, changes in atmospheric temperature and rainfall had an impact on variations in dustfall rates in the study area. Also, the LCPP could be a significant source of dust in the study area as the dust collected near the coal yard was dominated by coal dust. It is recommended to carry out further research to find out in which way rain reduces and atmospheric temperature promotes dustfall rate in the study area.
Effect of CaCO3 on mechanical properties and degradability of polythene manufactured from low density polyethylene
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Abeywickrama, M. S. J .; Yatawara, M. D. M. D. W. M. M. K.
One of the major drawbacks of polythene manufactured from low density polyethylene is its poor degradability in the environment. The present study was therefore planned to assess how the addition of CaCO3 effect on the mechanical properties and on the degradability in ambient air, soil and in compost. Two types of polythene films, one with 100% polyethylene (P001) and another with 86% polyethylene + 14% CaCO3 (P002) were manufactured by a film extruder machine. The mechanical properties including thickness, tensile strength, elongation, moisture and water absorption of the two types of films were analyzed at the beginning of the experiment (n=10 for each test). Half of each film (n=144) was immersed in food waste contaminated water while the other half (n=144) was used as the control. One third of each of food waste contaminated film (n=28) was kept in ambient air while another one third was buried at 10 cm depth in soil. The remaining one third was buried in compost. The same procedure was carried out for control films. The percentage degradability was assessed after two and four months’ time intervals and the percentage degradability was calculated with respect to weight losses of films with time. A significant reduction of machine direction (MD) and transverse direction (TD) of both tensile strengths and elongations were shown by P002 (p< 0.05; student t-test). In addition, P001 showed 0.20% moisture content while P002 showed 0.01% moisture. Both films showed 0.03 mm initial thickness and P002 showed a significantly highest water absorption. The food waste contaminated P002 kept in ambient air showed 0.13% degradability while P001 showed 0.12% degradability after 4 months. Nevertheless, the food waste contaminated P002 showed 2.4% (non-contaminated- 2.1%) degradability while the food waste contaminated P001 showed 0.8% (non-contaminated- 0.6%) in soil. The food waste contaminated P002 showed 0.8% (non-contaminated- 0.7%) degradability while the food waste contaminated P001 showed 0.5% (non-contaminated- 0.3%) in compost. Nevertheless, transparency reduction and dark spots were also observed from food waste contaminated P002 buried in both soil and compost. The results further revealed that the films contaminated with foods (buried in both soil and compost) degraded more than those of the non-contaminated films but their percentage degradability were less than 2.5% by 04 months. The overall results conclude that CaCO3 was able to significantly reduce the mechanical properties; but unable to increase the degradability in the environment. Therefore, the present study implies that the addition of CaCO3 to polyethylene only makes the manufacture cost effective
Effect of Selected Aquatic Macrophytes in Controlling Some Human Enteric Pathogens of Sewage Sludge Collected from Common Waste Water Treatment Plant at Biyagama EPZ.
(In: Proceedings of the International Postgraduate Research Conference 2017 (IPRC – 2017), Faculty of Graduate Studies, University of Kelaniya, Sri Lanka., 2017) Kodituwakku, K. A. R. K.; Yatawara, M. D. M. D. W. M. M. K.
The macrophyte based constructed wetlands (CWs) are economically feasible, easy to manage and an effective phyto-remediation method to treat sewage sludge safely. These wetlands have also been used for the removal of human enteric pathogens from sewage sludge. The present study assessed the effect of Eichhornia crassipes, Salvinia molesta and Pistia stratiotes in controlling fecal coliform and Salmonella in sewage sludge collected from the Common Waste Water Treatment Plant (CWWTP), EPZ Biyagama in dry and wet seasons. Equal weights of acclimatized young plants of each species were placed in three preset batch type CWs simultaneously. Controls were maintained and triplicates of all treatments were continued for 28 days. Sludge samples were analyzed weekly for fecal coliform and Salmonellafollowing USEPA standard methods. Data were analyzed using MINITAB (version 14.12.0). According to the results, the fecal coliform content in raw sludge did not show a significant difference between dry (3.1 × 104 MPN/g (dry weight) and wet (3.7× 104 MPN/g (dry weight) seasons (Two-sample T-test; p=0.670). CWs that contained different macrophytes lowered the initial fecal coliform content after the 3rd week in the dry season. Nevertheless, a gradual reduction of fecal coliform content was observed in wet season in all CWs that contained macrophytes. On the other hand, the controls lowered the fecal coliform content up to 2nd week and then increased in both dry and wet seasons. When compared all three macrophyte treatments, a significant reduction of fecal coliform content on day 28 was shown by the CWs that contained S. molesta in both seasons (One-way ANOVA; p= 0.003 in wet season and p= 0.004 in dry season). Salmonella was not recorded in either raw or treated sludge in CWs. Altogether, the results suggested that CWs consist of S. molesta have a high potential to lower the level of fecal coliform in sewage sludge generated at CWWTP at Biyagama EPZ.