Master of Science in Environmental Engineering & Management

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Browsing Master of Science in Environmental Engineering & Management by Subject "CIVIL ENGINEERING - Thesis"

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    item: Thesis-Abstract
    Development of a model to select the optimum sedimentation process in surface water treatment
    (2014-08-08) Liyanage, WW; Ratnayake, N
    In the water treatment process, sedimentation is used to remove suspended particles from raw water, and sedimentation tanks have become a common structure at water treatment plants. Generally sedimentation tanks are made of reinforced concrete and may be rectangular, square or circular in plan. With the advancement of technology, there are a number of sedimentation techniques now available. Some sedimentation tanks require coagulation and flocculation separately prior to the water enters the tank, while others provide the flocculation process within the tank by creating a velocity gradient using hydraulic or mechanical forces. The detention time of sedimentation tanks varies from thirty minutes to six hours depending on the sedimentation technique. This makes the sedimentation tank the largest and heaviest structure in the conventional water treatment plant. According to the data available with the drinking water industry, construction cost for sedimentation tank and flocculator is about 25% to 35% of the total construction (civil works) cost of the water treatment plant. Good engineering design should be economical. Unfortunately, based on experience in the potable water industry, the selection of the sedimentation technique mainly depends on the designer’s experience and not based on an analysis of all relevant conditions affecting the economy of the tank throughout the design horizon. Considering the operational cost, most local Engineers select sedimentation tanks operated by natural forces by gravitation and natural aggregation. A literature survey was carried out to find out the design practices on Plain Sedimentation, Clarifiers and Plate/Tube settlers. A field survey was also carried out to collect information on the construction and operation & maintenance costs of the tanks available within NWSDB. Furthermore a number of detailed designs were carried out to prepare cost estimates in order to supplement the collected data. Based on this study, relationships were developed for cost functions and a method has been developed for the selection of an economical sedimentation technique depending on the capacity of the water treatment plant.
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    item: Thesis-Abstract
    Root causes for the failures of existing sewerage system in Colombo Municiple Council area
    (2014-08-08) Kumudu Lal, LB; Ratnayake, N
    The ageing Colombo Sewerage system has been deteriorating over the years and the system was unable to cater to the increased demand and led to many environmental issues. Therefore, certain improvements were carried out in the last 3 decades to address the prevailed issues. But, sewer pipeline stoppages and collapses were increasing gradually with the dilapidated condition of the system, even with the newly introduced improvements. Collapses, blocks and chokes are experienced regularly in the system. This has led to overflows and short-circuiting which has caused serious pollution in water bodies and the environment as a whole. As most of the major collapses and overflows had not been attended to and not been given necessary priority due to various constraints, the situation became critical day by day, so that life styles of the public have been badly affected. Though a few studies have been conducted to develop the existing sewerage system in Sri Lanka by various non government organizations, the expectations were not achieved successfully and some issues still remain. Only a few recommendations of these researches were implemented. Therefore, it is vital to identify the issues in the existing Sewerage Systems in Colombo Municipal Area, to improve it into a smooth running, environmental friendly sewerage system. Thus, there is a need to conduct a research to explore the root causes for the failures of the existing sewerage system. The case study research approach was used to investigate the research problem, by interviewing key stakeholders, including the Engineers, within a selected administrative district. Further, a questionnaire survey was carried out among the other five administrative districts in the CMC areas to observe whether the identified root causes through the case study are similar and common to the other districts too. This study revealed that there are several types of failures in the existing sewerage system. The related root causes for the failures were further disclosed after evaluating the common reasons for the failures. Furthermore, it was observed that the root causes for the failures are common and acceptable to the entire sewerage system in CMC area through the survey. Further it is recognized that these root causes are generated in all three stages; design, construction and maintenance. Finally, good practices to improve the existing sewerage system are also explored through this study.
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    item: Thesis-Abstract
    Study on CBOS capability for sustainable management of rural water supply schemes
    Wijesundara, TWMLP; Ratnayake, N
    Sixty per cent (60%) of the rural population living in the country does not have access to safe and adequate water supply facilities. The rural population is 75% of the total population as per the 2001 census records. The lack of access to safe drinking water directly relates to health, bygiene and income generation of rural community in Sri Lanka. Target Ten of the Millennium development Goals (MDGs) is to "halve, by 2015, the portion of population without sustainable access to safe drinking water and basic sanitation". If this target to be achieved, development of natural water supply, sanitation and hygiene are required as more than 70% of poor living in rural areas. This has promoted the government and donors to increase user involvement in water supply sector. In the past two decades many rural water supply projects have been implemented with donor assistance. Experience gained from those projects had provided guidance towards implementation policies in rural water supply and sanitation. The challenge facing the water sector today is how to scale up these experiences in order to meet the MDGs. Increased financing is clearly needed, but that alone will not meet the challenge. Client capacity to ensure the sustainability of investments is equally important as evident from the experience of many failures made by rural water supply schemes during the last two decades. Therefore development of policies and strategies is needed with the understanding that water supply is a service and the user community should be considered as the core of sustainability. The rural water supply projects were implemented successfully with community involvement during the construction phase with less emphasis on operation and management. However, during the operation and maintenance period, these projects had faced problems and consequently some of these schemes were abandoned within a period of 5 years or less. The policy for the rural water supply and sanitation sector has recognized the value of water and the need for institutional arrangement for the efficient management of facilities with community participation and the stakeholders. According to the Rural Water Policy, the users should be encouraged to own and manage the facilities and assets. There are seventy-nine community water supply schemes in the Monaragala district including five small towns implemented by the ADB assisted 3rd project completed in the years 2003 to 2005 with community involvement. The community should undertake O&M as per the project policies. Though the ADB assisted 3rd project paid attention to sustainability from the start, there are many examples of CBOs failing in O&M. Further criticism from some local government bodies and the National Water Supply and Drainage Board devalued the capacity of CBOs to undertake O&M of completed WSS. There is strong evidence that supporting agencies are not giving assistance to the CBOs during D&M and the CBOs with committed staff exist many years as if in construction stage. Technical, financial and managerial activities of water supply schemes are directly related to sustainable D&M. Therefore it is needed to assess the CBO's capability in managing water supply schemes with respect to technical, financial, institutional, social and environmental sustainability during he operational stage, in order to ensure sustainability of the project. Even though some indicators for measuring the overall performance of rural water supply schemes have been developed, a structured methodology is needed to assess the capability of the CBO's in the above aspects. to assess capabilities of the CBOs for sustainable rural water management a study was undertaken in the Monaragala and Badulla districts selecting eleven water supply schemes managed by the CBOs. The research focused on the CBOs capability in five main areas for sustainability of water supply schemes; 1) Technical sustainability, 2) Financial sustainability, 3) institutional sustainability, 4) Social sustainability, 5) Environmental sustainability. Data were collected from eleven water supply schemes maintained by CBOs by interviewing consumers \ and officers on a questionnaire and a structured format respectively. These values were compared with the acceptable values of the indicators in order to assess the technical, financial,institutional, social, environmental and overall sustainability of each scheme.sub indicators of each area were analyzed to assess the capability of the CBOs. Qualitative and quantitative analysis of the structured interviews provided insight into the views of the community and officers of the CBOs. The results obtained this way were tested against the situational observations of each scheme in order to check the validity of the specially developed methodology. The more salient findings were; According to the results of the developed methodology only one scheme was found a failure which was Wila Oya Vilage WSS and the sustainability of Athimale WSS cannot be assured and need urgent attention for the improvement of performance indicators related to financial sustainability and all the other schemes are on the sustainable track with respect to the management of the CBOs. It is identified in the assessment using the developed methodology, most of the CBOs are capable of managing WSS assuring technical, financial, institutional, Social and Environmental sustainability; Inappropriate filtration facilities implemented due to financial constraints, water quality variation and reduction in extraction capacity of deep production bore hole wells being impediments for the capability of the CBOs for sustainable rural water management. The methodology developed in this study to assess sustainability of WSS covers almost all the important areas of managing WSS by the CBOs. The indicators to be evaluated in the methodology should be assessed from the views of both officers of the CBO and the sample of consumers. The results of the assessment using this methodology in the study recommend that the CBOs are capable of managing WSSs with an assurance of sustainability. The methodology can be implemented for other WSSs managed by the CBOs to assess the capability of the CBO in managing WSS and also can be adopted for future projects implementation policies. In the study it was identified that it was necessary to establish a support service mechanism for the CBOs during the O&M.