Browsing by Author "Jayaweera, M"

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item: Article-Abstract
Are Green jobs sustainable for Sri Lankan Economy?
Jayaweera, M; Manatunge, JMA; Witharana, A
It is imperative that Sri Lanka grasps the concepts of green jobs to meet the most vital but intricate challenge of the 21st Century, which is the transformation to a sustainable and a low-carbon economy. Such a transformation or a paradigm shift, which can be gradual or rapid depending on the circumstances, will undoubtedly have a considerable positive effect on the way we produce and/or consume goods and services. The speed at which this transformation would occur is likely to accelerate in the near future as there is a trend of global transition from a traditional to a low-carbon economy, in order to attain sustainable economies. Such trends will help create an array of different forms of green jobs across many sectors, and most probably can become a catalyst for further development. The International Labour Organization (ILO) has defined green jobs as “Jobs created when they help in reducing the negative environmental impacts ultimately leading to environmentally, economically and socially sustainable enterprises and economies”. Green jobs, in general, stand on two pillars: decent work and environmental sustainability. Thus, green jobs can be defined as decent work that contributes to environmental sustainability. In a broader sense decent work needs to address the core of international labour standards such as freedom of association and effective recognition of the right to collective bargaining, elimination of all forms of forced or compulsory labour, effective abolition of child labour, elimination of discrimination in respect of employment and occupation, occupational health and safety, etc. whilst aligning to laws applicable to Sri Lanka. Environmental sustainability addresses issues such as effectively combating climate change, pollution prevention and control, conservation of eco-systems and biodiversity etc. (ILO, 2007).
item: Article-Abstract
Career management strategies among IT professionals in offshore outsourced IT firms in Sri Lanka
Wickramasinghe, V; Jayaweera, M
Purpose – The purpose of this paper is explore career management strategies used by information technology (IT) professionals full-time employed in offshore outsourced IT firms in Sri Lanka; and to evaluate those against hierarchical plateau, job content plateau, firm size, and individual demographic characteristics that may predict the use. Design/methodology/approach – Survey methodology was used and a random sample of 119 IT professionals responded. Multiple regression was used for the data analysis. Findings – Career management strategies used by IT professionals could be broadly categorised into four areas. Hierarchical career plateau and age significantly predict the use of career strategies. Originality/value – The study provides useful information for both practitioners and academics to better understand career strategies used by IT professionals in managing their own careers and factors that predict the use of career strategies
item: Article-Full-text
Career management strategies among IT professionals in offshore outsourced IT firms in Sri Lanka
(Emerald Group Publishing Limited, 2011) Wickramasinghe, V; Jayaweera, M
Purpose – The purpose of this paper is explore career management strategies used by information technology (IT) professionals full-time employed in offshore outsourced IT firms in Sri Lanka; and to evaluate those against hierarchical plateau, job content plateau, firm size, and individual demographic characteristics that may predict the use. Design/methodology/approach – Survey methodology was used and a random sample of 119 IT professionals responded. Multiple regression was used for the data analysis. Findings – Career management strategies used by IT professionals could be broadly categorised into four areas. Hierarchical career plateau and age significantly predict the use of career strategies. Originality/value – The study provides useful information for both practitioners and academics to better understand career strategies used by IT professionals in managing their own careers and factors that predict the use of career strategies.
item: Thesis-Abstract
Comparison and performance evaluation of direct aerobic submerged attached growth and anaerobic cum aerobic submerged attached growth systems, for factory sewage
Suraweera, PS; Jayaweera, M; Manatunge, J
Most factories located outside of BOI industrial zones in Sri Lanka do not have proper sewage treatment systems. Due to the high number of employees, these factories are always encountered with the problem of handling large quantities of low strength sewage generated from lavatories, canteens and kitchens. In such factories sewage is usually handled using conventional septic tank - soakage pit systems. Such systems are commonly found infested with insects, and promote further breeding. They cause nuisance due to obnoxious odor, and is a major cause for severe ground and surface water pollution. It has been noted that these factories have critical problems of handling sewage during rainy season, especially when the factory is located in areas with high ground water table such as a marshy land or near a surface water body. The activated sludge suspended growth aerobic systems designed to treat sewage in most of the factories have various operational problems which increase the operator involvement and therefore the plants performance are operator dependent. Activated sludge suspended growth aerobic systems are more susceptible for sludge bulking which leads to poor effluent quality and the unbulking process is very difficult and ~time consuming. In addition to this, the several parameters such as SVI, MLVSS, etc have to be monitored carefully in the conventional activated sludge systems for the proper operation and the maintenance which increase the operational and the maintenance cost. The maintenance departments of factories always request a trouble free sewage treatment plant to minimize their involvement in operation of the plant. Therefore the submerged attached growth aerobic systems are becoming the most appropriate system as an alternative of the activated sludge system for treating low strength effluent, sewage from factories. A leading company in Sri Lanka which provides turnkey solutions for waste water and sewage has introduced submerged attached growth aerobic and anaerobic treatment systems to overcome above issues ..Depending on the affordability of the client and the space availability they have introduce submerged attached growth aerobic systems in two ways. (a) Direct aerobic submerged attached growth systems where sewage is treated only with aerobic treatment (b) Anaerobic cum submerged attached growth aerobic systems where sewage is treated with anaerobic process prior to aerobic treatment. However no proper study has been carried out to find out the most appropriate submerged attached growth system to treat sewage generated from factories. Research suggested that the anaerobic cum submerged attached growth aerobic system is more suitable for treating factory sewage than direct aerobic submerged attached growth system in terms of quantity of sludge wasting and lower operational and maintenance cost which results to a lower unit cost per m3 of treated water.
item: Thesis-Abstract
Comparison and performance evaluation of submerged attached growth aerobic system versus suspended growth aerobic systems designed for factory sewage
Athukorala, IASL; Jayaweera, M; Manatunge, J
Most factories found in Sri Lanka do not have proper sewage treatment systems and due to the high number of employees these factories are always encountered with the problem of handling large quantities of low strength sewage generated from lavatories, canteens and kitchens. In such factories sewage is usually handled using conventional septic tank - soakage pit systems. Such systems are commonly found infested with insects, and promote further breeding. They cause nuisance due to obnoxious odor, and is a major cause for severe ground and surface water pollution. It has been noted that these factories have critical problems of handling sewage during rainy season, especially when the factory is located in areas with high ground water table such as a marshy land or near a surface water body. However, some factories consist of a conventional activated sludge system and a higher percentage of activated sludge processes found in these factories are in the malfunctional stage due to the least attention by the factory management. The activated sludge systems require a very high attention for the proper operation. The major problem of such factories is the giving of the least priority for the above issue and therefore the allocation of competent personal to operate plant is neglected. ,.' Therefore, their key demand is to provide them a treatment system to treat sewage with minimal operational difficulties and minimal labour involvement to overcome above problem. This research was therefore carried out with the following objectives to fulfill the above requirement. The broad objective is the study and compare the performance of aerobic attached growth and aerobic. suspended growth processes designed for factory sewage and recommend the most appropriate treatment regime for the factory sewage with regard to less operational and maintenance issues. Therefore, BOD removal efficiency and nitrogen removal efficiency have been compared for both processes in order to evaluate the performance of the each process. The estimation of sludge wasting, appropriation of process control parameters and operational issues in both processes are studied for the justification of the operational feasibility of each process. The land utilization and operational and maintenance cost have been estimated to identify the economical feasibility of each process. This study has proved that the BOD removal efficiencies of each process are equal and the nitrogen removal percentages are 43 % and 37% in attached growth process and suspended growth process respectively. Sludge production is 27 % less in attached growth process and thereby sludge handling is easy and esthetically good. The operational issues have been proved less in attached growth process. Annual operational and maintenance cost for the attached growth aerobic process is 30 % less over suspended growth aerobic process. Land requirement (foot print) is 13 % less in attached growth process over suspended growth process. Unit cost Rsl m3 of treated water for attached growth process has been proved that 32% less. Therefore, submerged attached growth system is, recommended as a less complicated, trouble free method for treatment of the factory sewage.
item: Thesis-Abstract
Conservation of masbedda (Gymnemasylvestre R.Br.) through propagation
Kumara, KKIUA; Subasinghe, S; Jayaweera, M
Several activities could be undertaken aimed at conservation and sustainable use of medicinal plants. Some of them are undertaken directly at locations where plants are naturally occurring. while others are less direct, such as commercial cultivation systems. Cultivation of medicinal plants is particularly important for species, which already have a good market demand. Gymnema sylvestre is one such rare medicinal plant. Therefore, the present study was aimed at developing cost effective and simple propagation techniques for Gymnema sylvestre. Investigations on both sex-ual and vegetative means of propagation of Gymnema have been carried out, at the Faculty of Agriculture, University of Ruhuna, Mapalana, Kamburupitiya from October 2002 to November 2003. Viable, uniform seeds were screened and used for seed propagation studies. The effect of sowing media on germination of Gymnema seeds has been investigated using four kinds of sowing media; sand, coir dust, a mixture of top soil and sand (1:1) and a mixture of sand top soil and coir dust (1: 1:1). Seeds were stored in an open system under room temperature (30°C) and germination percentage was recorded at 15-day intervals. This was to find out the effect of storage period on germination of seeds. Complete Randomized Design was used for the experiments with five replicates, each contained ten seeds. Germination percentage was calculated and the experiments were repeated to confirm the results. For vegetative propagation studies, three separate experiments were carried out using stem cuttings. Double nodal semi-hard wood cuttings were rooted in polybags filled with different rooting media including sand, a mixture of sand and top soil (1: 1), a mixture of sand, top soil and compost (1:1:1) and top soil alone to investigate the effect of media on rooting. Hard wood, semi-hard wood and soft wood cuttings were planted in polybags filled with a mixture of sand, top soil and compost (1:1:1), to determine the effect of maturity of cuttings on rooting. Effect of watering on rooting of cuttings was investigated using semi-hard wood cuttings planted in polybags contained a potting mixture of sand, top soil and compost (l:1: 1) with three watering frequencies. Complete Randomized Design was used for the studies with ten replicates. Number of roots, root length and root biomass accumulation were measured at the end of 6,10 and 14 weeks after planting. Results showed that germination percentage of seeds was significantly (p≤0.05) high (92 %) in coir dust, whereas the lowest germination percentage (28 %) was observed from top soil media. There were no significant (p ≤ 0.05) differences in germination of seeds throughout the first two months of storage under normal condition. Results of the vegetative propagation studies revealed that a mixture of sand, top soil and compost (1:1:1) was the most suitable rooting media for Gymnema cuttings, whereas the semi-hard wood cuttings rooted significantly (p ≤ 0.05) higher than the hard wood and soft wood cuttings. With regard to the watering frequency, cuttings watered once in two days rooted and performed significantly (p≤ 0.05) better than the other treatments. Results can be concluded that Gymnema sylvestre can be propagated by means of both sexual and asexual methods. Semi-hard wood cuttings, which appear to be more amenable to rooting and potting mixture of sand, top soil, and compost watered once in two days, showed the best results, while high germination percentage of seeds could be obtained within first two months of storage.
item: Article-Full-text
Consumption of chilled water stored in a PET bottle multiple times: are we quenching thirst or gulping phthalates?
(2021) Jayaweera, M; Perera, H; Dhanushika, G; Gunawardane, B
The statistics forecast that the production of polyethylene terephthalate (PET) bottles worldwide in 2016 was about 485 billion, and the same in 2021, has been approximately 583 billion. Although such productions in many countries have the ear of prominent political and social leaders, high production rates still reign the global market. In parallel, revered scientists globally conflate plausible and incontrovertible medical canons against the use of PET bottles for the protection of public health.
item: Thesis-Abstract
Development of environmental management guidelines for Sri Lankan golf courses
(2016-05-26) Abeysuriya, TD; Rathnayake, N; Jayaweera, M
Golf is a precision sport and it is expected that there will be a trend in increasing the number of golfers playing in Sri Lanka, and perhaps new Golf courses to cater to the increasing demand, particularly among tourists, with the major development drive maintained by the government. Even though a golf course can contribute to the sustainability of the ecosystem, it may lead to many environmental risks associated with the activities of the golf courses, unless there are safeguards to protect the environment through proper environmental policies and practices, which can be adopted by all stakeholders, including the staff, clients and visitors of the Golf Course. To achieve the international standards while minimizing the environmental risks associated with them, it is necessary to have an environmental management system for golf courses. Even though the Government of Sri Lanka requires Environmental Imapact Assessments to be carried out for new Golf Courses, there are no monitoring regulations for operation of Golf Courses. Interviews with management staff of the Colombo Golf Club revealed that there is no proper environmental guideline for the golf courses in Sri Lanka at present. It is imperative to develop an environmental guideline and self assessment method suitable for adoption for Golf Courses in Sri Lanka, to ensure proper practices during the operation of the courses before any further damage is done to the environment. This study was carried out to develop an environmental guideline for Sri Lankan golf courses and a self assessment method in order to assist the management of the courses to evaluate their own operations against benchmarks and identify weak areas and take corrective actions where necessary. Review of literature revealed that there are diverse methods adopted by golf courses in USA, UK, Canada and Australia in order to minimize environmental risks caused by Golf Course operations. Having understood the commitment to safeguard the environment in golf courses by the developed countries, it was decided to develop a questionnaire to assess the situation with respect to various aspects of the operation of golf courses relevant to Sri Lanka, and provide guidelines for improvement of the weak areas. General information regarding the operations was collected by using a general questionnaire. After evaluating the methods used in the developed countries, it was decided that the most appropriate method suitable for adoption for the Sri Lankan situation was the Environmental Quotient Questionnaire method for self assessment used by the Unites States Air Force (USAF) and guidelines for preparation of a supporting document such as the Breckland Pines Golf Course Environmental Management Plan. The model questionnaire was prepared with 50 questions in ten subcategories, based on the relevant environmental aspects. The aspects covered were: policy, planning, wildlife & wildlife habitats, clubhouse operations, pest control, pesticide use, fertilizer use, water quality & use, safety and education & awareness. Even though the USAF self assessment method used equal weightages for all environmental aspects, it was decided to factor-in the importance of the aspects of the overall environmental profile of the local situation by giving weights to each category. Since all questions were of the type with three possible answers (yes/no/partial), the weights assigned to each aspect were reflected in the final total marks by varying the number of questions in each category. The number of questions was adjusted several times in order to achieve the intended purpose of capturing the importance as well as the status of environmental management of the golf courses. Thus, after several modifications, the model of the ECQ questionnaire was developed to a satisfactory level to be tested using field data. The final assessment of the Golf Course was obtained as a percentage of the possible 100% if all 50 questions yielded positive answers, as two results - the actual ECQ (only 'yes' answers) and potential ECQ ('yes' and 'partial' answers). This questionnaire was tested with the data of Royal Colombo Golf Course (RCGC) and after minor modifications based on the results of the test, it was used to assess the other golf courses in the country. Benchmark values were also proposed for the status of the Golf Course depending on the ECQ values as per the table below. Total Yes or Partial response Environmental compatibility Level 90% - 100% Advance 70% - 89% Showing Progress 40% - 69% Getting Started 39% or Less Urgent action needed The results of the assessment were compared to the actual status of the Golf courses as perceived by the employees and users of the courses, and were found to be comparable, which showed that the ECQ provided a reliable assessment of the environmental status of the Golf Course, and helped to identify the weak areas that needed urgent attention as well as long term improvements. Ten environmental best practice guidelines were prepared under the topics of policy, planning, wildlife & wildlife habitats, clubhouse operations, pest control, pesticide use, fertilizer use, water quality & use, safety and education & awareness, in order to help the Golf Course management to prepare their own Environmental Management Plans for present and future courses. The final recommendation is to use the ECQ method to assess the current status of existing courses, prepare an environmental management plan for each golf course using the guidelines and to monitor the golf courses annually with the self assessment method, in order to continually improve the ECQ and thus enhance the environmental performance of the Golf Course.
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Grappling with COVID-19 by imposing and lifting non-pharmaceutical interventions in Sri Lanka: A modeling perspective
(Elsevier, 2021) Jayaweera, M; Dannangoda, C; Dilshan, D; Dissanayake, J; Perera, H; Manatunge, J; Gunawardana, B
Jayaweera, M., Dannangoda, C., Dilshan, D., Dissanayake, J., Perera, H., Manatunge, J., & Gunawardana, B. (2021). Grappling with COVID-19 by imposing and lifting non-pharmaceutical interventions in Sri Lanka: A modeling perspective. Infectious Disease Modelling, 6, 820–831. https://doi.org/10.1016/j.idm.2021.06.004
item: Conference-Abstract
Investigation of Zinc removal capacities of different sorbent materials to be used in constructed wetlands
Witharana, A; Jayaweera, M; Manatunge, JMA
It has been found over the past couple of years that health hazards associated with heavy metals have been on the rise, particularly the chronic diseases. Lack of tertiary treatment of wastewater may have contributed to this emergent problem, mainly due to the high costs involved in the removal of heavy metals. Constructed wetlands have therefore received great attention as a tertiary treatment method or a polishing technique of wastewater due to its low construction and operation costs. However, finding a low-cost sorbent material to be used as the wetland filter material, which can be used as an alternative to activated carbon, has been a problem for decades. Therefore, the present study focuses on applicability of low-cost sorbent materials: viz., clay tile, brick, saw dust and rice husks, as filter mediums. Laboratory-scale experiments were performed with a synthetic Zinc solution. Results revealed that clay tile material has the highest adsorption capacity (47.6 mg/g) and removal efficiency, (98%), while brick (37.0 mg/g, 86%), sawdust (20.4 mg/g, 80%) and rice husks (15.8 mg/g, 64%) have relatively low adsorption capacities and removal efficiencies, respectively. The separation factor of equilibrium (RL) indicates favourable isotherms (0< RL<1) for all tested sorbent materials. Among the studied materials clay tile, brick and rice husks are good adsorbents for Zinc (n>2) while sawdust is a moderately difficult material for adsorption of Zinc (n <2).
item: Conference-Full-text
Long term performance of a constructed wetland planted with Typha angustifolia
(Department of Civil Engineering, University of Moratuwa, 2011-12) Jayaweera, M; Witharana, A; Ratnayake, N
Constructed wetlands are often utilized for wastewater treatment' including removal of metals. The removal mechanism is phytoremeditation, in which plants are manipulated to immobilize the pollutants. Physico-chemical properties of substrate and its potential tor removal of pollutants also effects the performance of constructed wetlands. Many engineering studies of treatment by wetlands use a black box approach.This paper discusses the Zn uptake by Tvpha angustifoha and its distribution within the shoot (leaves and stem) and root. This was investigated by introducing different operation conditions to the constructed wetland during acclimatization with nutrients, and gradual variation of Zn loading with incremental increases. The relative changes in the substrate (clay tile) were also investigated by means of XRD, FT-IR and SEM analysis. The results revealed that the clay tile is a promising adsorption material for Zn. In addition,Typha angustifolia is found to contribute to metal trapping into the senescing plants via rhizodeposition and act as a catalyst for biochemical reactions. The interesting feature noted in the wetland was that after nearly two years of operation, almost all clay tiles around the rhizosphere of Typha angustifolia were disintegrated completely, back to the original clay, suggesting that nature helps to sustain the plants by providing an environment with less toxicity. lt could be concluded that the long term adaptation of wetland plants to heavy-metal rich environments would not help the sequestration process, and they cannot be considered to be heavy metal sinks in the aquatic system once this stage is reached.
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Management of municipal solid waste open dumps immediately after the collapse: An integrated approach from Meethotamulla open dump, Sri Lanka
(Elsevier, 2019) Jayaweera, M; Gunawardana, B; Gunawardana, M; Karunawardena, A; Dias, V; Premasiri, S; Dissanayake, J; Manatunge, J; Wijeratne, N; Karunarathne, D; Thilakasiri, S
Meethotamulla open dump (MOD) of Sri Lanka that has received about 290,000 metric tons of mixed MSW annually collapsed on 14th April 2017 with massive devastation. An integrated approach was attempted to control further collapse with the deployment of drone-assisted and stand-alone instrumentation. The collapsed dump was analyzed for attributes, including contours, heights, wetness, temperature levels, tension cracks, landfill gases, fire, explosion, and asphyxiation hazards with 24-h surveillance after one day of the collapse. The mode of MOD failure was implicated to be deep-seated (rotational) slope failure. A short-term plan, consisting of 12 activities was prepared and successfully implemented. The activities of the short-term plan were carried out at the dumpsite until the water level fluctuations <5 cm, inundation of the toe area receded completely, the horizontal displacement of surface markers <20 mm, lower explosive levels of CH4 and CO less than 5 and 12%, respectively, O2 level improved up to 21%, and temperature variation of the collapsed face <2 C. The short-term plan was halted when the factor of safety for slope failure of the critical face improved from 0.807 to 1.286 ensuring no signs of a subsequent collapse of the MOD. An early warning system was established in the case of an imminent collapse. This integrated approach, to our knowledge, is the first study instituted, and this holistic management effort could be easily replicated to avoid disasters from slope failures of landfills or open dumps that may occur elsewhere.
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Migration of phthalates from PET water bottle in events of repeated uses and associated risk assessment
(2020) Jayaweera, M; Perera, H; Bandara, N; Danushika, G; Gunawardana, B; Somaratne, C; Manatunge, J; Zoysa, K; Thathsara, T
Phthalates are widely used as a plasticizer in manufacturing polyethylene terephthalate (PET) bottles to improve softness, flexibility, durability, longevity, and workability. Phthalates are known in instigating profound human health hazards. In many developing countries, lack of proper disposal facilities established for empty PET bottles and the absence of legislation on reuse invariably persuade people to reuse them for storing potable water. An experiment was conducted with two commercial brands of PET bottles to explore the potential of phthalate migration when domestically refilled and reused in multiple times at two temperature conditions. Temperatures of ambient (27 ± 2 °C) and warm (60 ± 2 °C) were selected as the refilling temperatures because of the common practice by people. For both brands, only bis(2-ethylhexyl) phthalate (DEHP) levels were detected in refilled water in every event of reuse. For both brands, mean DEHP levels migrated to water at 60 ± 2 °C were significantly higher (p < 0.05) compared to those at 27 ± 2 °C. Risk analyses carried out on human health suggested that there exist no definite acute or chronic health risks when the refilled water is consumed continuously for 30 years for both temperatures. Still, such risks were higher for the consumption of refilled water of warm temperatures than those of ambient temperature. However, this study elucidates that DEHP migration would be at an alarming rate when the events of reuse of a single bottle increase so that regulations banning the reuse of empty PET bottles are paramount, especially for developing countries.
item: Thesis-Abstract
Modelling of growth cycle of water hyacinth : an application to Bolgoda Lake
Fernando, PUD; Jayaweera, M
Water hyacinth (Eichhornia crassipes (Mart). Sohns) is considered as a problematic aquatic weed in many lakes, irrigation canals, stagnant ponds, waterways and semi-wet areas in Sri Lanka. Bolgoda Lake is one of the freshwater bodies in Sri Lanka, which has been severely affected by excessive growth of water hyacinth thereby clogging the water ways and hence adversely affecting water quality. This study was conducted to determine the growth characteristic of water hyacinth under influence of natural, physical and chemical factors in Bolgoda Lake. The parameters considered in the study were as follows: biomass in dry weight, biomass production per day, phosphorus and nitrogen contents in plant tissues, phosphorus and nitrogen contents in the water body, pH, temperature, and salinity. The luxuriant growth of water hyacinth was observed during the study period, which occurred with the temperature ranging between 26-32 °C, pH from 6.67-7.76, salinity from 0-1.5 ppt and water nutrients from 4.6-17.4 mg Nil, 0.18-0.70 mg N03-NIl and 0.14-0.93 mg P/I and 0.02-0.16 mg P04-PIl respectively. Under such conditions, results revealed that hyacinth plants produced a biomass yield of 20 -1800 g dry weight/m' and the number of plants increased from 21 to 412 per m2 for the entire study period of 14 weeks with doubling time of around 13-15 days. The biomass production rate varied from 2.10-75.25 g dry weight/or' per day. Results of heavy metal uptake experiment suggest that rhizofiltration (metal absorption into roots) and phytoextraction (concentrate into the harvestable parts of roots or shoots) are the key mechanisms for removal of heavy metals from the aqueous phase. Phytoextraction was more responsible in translocating heavy metals to aboveground parts in initial few weeks and rhizofiltration became prominent at the later stages in which more metals are bound to below-ground parts. Once the heavy metal binding was complete, harvesting was suggested at the end of the 13th week during which more metals were adsorbed only to root zone. From this study it was shown that there exists a massive proliferation of water hyacinth stands in Bolgoda Lake with a great influence of nitrogen, phosphorus, pH and temperature. However, there has been a significant perishment of the existing stands of the vegetation from time to time due to the exposure to saline waters entering from the tidal action. A numerical model was developed to simulate the growth of water hyacinth in Bolgoda Lake, Sri Lanka. The model was first applied to experimental data from Sato and Kondo, (1981). Secondly, it was used to evaluate the management options to control the growth of water hyacinth in Bolgoda Lake. Model application showed how the model could be used to evaluates the management options to control the growth of water hyacinth and to reduce the available nutrients in the system. These options include harvest strategies (initial density and harvesting interval) and harvest rate. The maximum yield of 329 g / m2 dry weight was obtained when the rate of harvest was analogous to the initial density (at 100 g dry wt/rrr') in that the water hyacinths were harvested at a uniform rate every 20 days. The continuous harvesting is the major objective criteria to remove available nutrients in the water body and to control the excessive growth of water hyacinth in Bolgoda Lake.
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Prediction of dissolved oxygen in harbours using artificial neural networks: an application to the port of Colombo
Dayanthi, WKCN; Jayaweera, M
Maintenance of high dissolved oxygen (DO) level in harbours is highly important as it could give rise to catastrophic effects if it is depleted affecting day- to- day port functions such as dredging activities and other maintenance work. The depletion of DO results not only in toxic gases such as methane and hydrogen sulfide but also in accumulation of wastes. Frequent monitoring of DO is therefore imperative, but makes practical difficulties due to ship movements and other activities. Hence, prediction of DO with an empirical model using Artificial Neural Networks (ANNs) was done with success with an application to the Port of Colombo (PoC). This model aims to lessen the frequency of monitoring DO and to foresee the responses of the system due to environmental changes. The performances of ANNs were compared with Multiple Linear Regression (MLR) . Monthly values of 14 water quality parameters at several depths for the period of four years from 1997 to year 2000 were collected. The values of weather parameters of rainfall and wind velocity for the corresponding period were also collected. The neural network possessing 7 inputs and 45 hidden neurons, performed well giving rise to correlation coefficient (R) as 0.87 and 0.67 for calibration and verification respectively. The inputs are temperature, depth and five rainfall intensities (including values on four immediate previous days). A sensitivity analysis was carried out to assess the potentials of small changes in each input on the neural network output. MLR model with 7 input variables indicated R to be 0.45 for calibration after several transformations. The temperature was the most influential variable among the ANN inputs affecting the output. In conclusion, it could be inferred that the ANN model is capable of predicting DO in PoC considerably well compared with MLR.
item: Article-Abstract
Reshaping dental practice in the face of the COVID-19 pandemic: Leapfrogging to dentronics
(Nova Science Publishers., 2021) Jayaweera, M; Amarasinghe, H; Johnson, NW
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Study of Occupational Noise Levels ofIndustries and Hearing Impairment ofWorkers in Western Province
Peiris DLA; Jayaweera, M
Occupational noise should be given due concern as it can cause psychological and physiological damage on human beings. Out of the physiological effects of noise, the hearing impairment is important as it is permanent damage and there is no medical treatment to cure it. At present, Industrial Safety Division of the Labour Department receives complaints in respect of occupational noise problems from workforces of various industries in Sri Lanka. However there is no proper legislation pertaining to occupational noise aspects in Sri Lanka. Therefore it is vital to have proper remedial measures on occupational noise to abate the noise in the factory premises and to prevent hearing loss in the workers exposed to excessive noise. In view of understanding the gaps and drawbacks of the present situation on occupational noise, the literature survey on legislations/ guidelines on occupational noise was carried out for twenty seven countries and the remedial measures in those legislations/ guidelines were identified. This study mainly focuses on the noise levels of industries and hearing impairment of workers in Western Province. In the field work, equivalent continuous noise level was measured for eighty factories during the working hours. The factories were categorized in to four groups depending on the measured noise levels. They are noise level equal or above 90 dBA, equal or above 85 and less than 90 dBA, equal or above 80 and less than 85 dBA, and less than 80 dBA. Hundred and forty workers were tested for audiometry to find out Hearing Threshold Levels {HTL), from each exposure group over 80 dBA and in a reference group, in accordance to ISO 8253 of 1984. Measured HTL was prepared according to hearing impairment equations of ISO 1999 of 1990 and age correction was also applied to the data according to ISO 7029 of 1984. Audiometric chart was prepared with the means of HTL in samples. Means of HI levels in each sample were compared. The hypothesis test was applied to test whether the sample mean for HI really exceeds 25 dB. The difference of sample means and reference group means were tested for significance of 95 percent confidence level. Percentage of workers HI levels equal or above 25dB, equal or above 30dB and equal or above 35 dB were compared for samples. Hearing impairment of workers for all groups were compared for duration of exposure. From the analysis it was found that when greater the exposure level, higher the risk of hearing impairment. In Leq > 90 dBA group, the population mean of HI level with 95% confidence level exceed 25 dB. The Leq > 90 dBA group was exceptional and showed significant difference of means at ninety nine percent confidence level in respect of other groups. Ln conclusion from this study it could be recommended that a value less than 90 dBA to be the appropriate permissible equivalent noise level for a period of eight hour exposure per day.
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The Role of Neochetina Eichhorniae and Neochetina Bruchi on biological control of water hyacinth in Sri Lanka
Kasige, AP; Gamage, NPD; Jayaweera, M
One of the major scourges accompanying water resource development in Sri Lanka is the explosive proliferation of water hyacinths (Eichhornia crassipes). A better sustainable solution to manage the infestations seems to be biological control and the main biological control agent used in many parts of the world including Sri Lanka is reported to be the weevil [(Neochetina eichhorniae Warner) (Coleoptera; Curculionidae)]. Fernando and Room used the weevil N eichhorniae for the first time in Sri Lanka in 1988. Although some 15 years have elapsed since the first release, infestation in the areas in which the weevil was released is as high as in the areas in which Neichhorniae was not released. The present study therefore focuses on the evaluation of the role of N eichhorniae and Nbruchi on controlling water hyacinth and is designed to evaluate the optimum weevil densities required to cause significant damage to the plants. Healthy plants of height 21 ern ±l were cultured in 6 and 4 fiberglass tanks respectively for a period of 8 weeks to complete one life cycle of weevil. Different weevil densities were used, varied from 1,3, 6,10 and 15 weevils per plant, and the control with no weevils. In case of Nbruchi the first 3 treatment levels were tested with the control. Field monitoring carried out in eight locations within the Western province and showed the average maximum weevil density in natural conditions as 2 per plant. The success of biological control using Neichhorniae will ultimately rely on host plant quality and the habitat conditions to establish a healthy population of weevil densities. Results showed that the treatments with weevil numbers less than 3 of Neichhorniae per plant did not significantly change (p>O.Ol) the water hyacinth stands, but 3 weevils per plant of Nbruchi was the best option in sustainable management. Densities of 10 of Nieichhorniae and 6 of Nbruchi were subjected to complete eradication of the plant.
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Urban watercourses in Peril: Implications of phthalic acid esters on aquatic ecosystems caused by urban sprawl
(Multidisciplinary Digital Publishing Institute, 2019) Jayaweera, M; Danushika, G; Bandara, N; Dissanayake, J; Gunawardana, B; Manatunge, J; Zoysa, K
Urban sprawl worldwide warrants the use of large quantities of industrial and household products containing phthalic acid esters (PAEs) resulting in adverse impacts on the quality of aquatic life in urban watercourses. The presence of six PAEs (dimethyl phthalate (DMP), diethyl phthalate (DEP), di(n-butyl) phthalate (DBP), benzyl butyl phthalate (BBP), bis(2-ethylhexyl) phthalate (DEHP), and di(n-octyl) phthalate (DnOP)) in 22 shallow urban watercourses in Colombo and suburbs of Sri Lanka was investigated. The average concentrations of DEP, DBP, BBP, and DEHP in all watercourses varied between 2.5–265.0, 1.0–32.0, 61–108, and 12–165 g/L, respectively. DMP and DnOP were below the limits of quantification (DMP-0.5 g/L, DnOP-1.0 g/L) for all watercourses. DEHP was the most abundant PAE in many watercourses. The significant factors affecting the ubiquitous presence of PAEs in watercourses are the inherent properties of each PAE, presence of industrial and household products with great potential for the migration of PAEs in the sub-catchments, and quality of the receiving water. The contamination levels of PAEs in most of the watercourses are alarmingly high, as evidenced by higher concentrations of DEHP and DBP than those of Canadian permissible levels for the protection of aquatic life (16 and 19 g/L). This study was the first effort in Sri Lanka to investigate the presence of PAEs in urban watercourses.
item: Conference-Full-text
Zinc adsorption by lowcost sorbent materials: clay tile, Brick, sawdust and rice husk
(2013-11-19) Witharana, A; Jayaweera, M; Manatunge, JMA
It has been found over the past couple of years rapid growth of population, industrialization and urbanization has first and foremost contributed to the severe water pollution in both surface and ground water. The health hazards associated with heavy metals have been on the rise, particularly the chronic diseases. Lack of tertiary treatment of wastewater may have contributed to this emergent problem, adsorption process is considered as the best available water treatment method and activated carbon has proven to be the best sorbent material which can be used in removing wide variety of pollutants. However, usage of this activated carbon becomes restrict due to its high cost and regeneration cost. Therefore, the present study focuses on low-cost sorbent materials: viz., clay tile, brick, sawdust and rice husks. Laboratory-scale experiments were performed with a synthetic Zinc solution. Results revealed that clay tile material has the highest adsorption capacity (47.6 mg/g) and removal efficiency, (98%), while brick (37.0 mg/g, 86%), sawdust (20.4 mg/g, 80%) and rice husks (15.8 mg/g, 64%) have relatively low adsorption capacities and removal efficiencies, respectively. The separation factor of equilibrium (RL) indicates favourable isotherms (0< RL<1) for all tested sorbent materials. Among the studied materials clay tile, brick and rice husks are good adsorbent for Zinc (n>2) while sawdust is a moderately difficult material for adsorption of Zinc (n <2).