Master of Science in Environmental Management

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Browsing Master of Science in Environmental Management by Author "Jayaweera, M"

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    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.
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    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.