Master of Science in Environmental Management

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Browsing Master of Science in Environmental Management by Author "Jayaweera MW"

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    item: Thesis-Full-text
    Defluoridation of potable water in CKDu prevalent areas enriched with hardness using modified-fly ash functionalized with iron oxide
    (2020) Priyadarshani EAC; Jayaweera MW; Gunawardana WB
    Chronic Kidney Disease of Unknown Etiology is a major health issue reported in countries around the equator including Sri Lanka, Tunisia, Andra Pradesh India, and El Salvador. In Sri Lanka, CKDu is prevalent in the North-Central Province and now it is being progressed in the dry zone. The exact causal factor for the disease is not known yet where scientists now mainly suspect that the multiple ion interaction in potable groundwater may be the root cause for the disease. Further, fluoride ion concentration is higher in CKDu prevalent areas and the interaction of fluoride ion with other constituents (Cd, As, Al, hardness) is mainly suspected as the cause for the disease. The synergistic effect of hardness and fluoride on the CKDu had been discussed in many studies worldwide where the prevalence of other ions is very less, and it is below the WHO maximum allowed concentrations. The hardness and fluoride distribution are relatively higher in CKDu prevalent areas in Sri Lanka and the nephrotoxicity of hardness and fluoride in their mutual presence is proven by experiments with mice. Our preliminary studies found that there is no CKDu when the hardness and fluoride concentrations of water are below 200.00 mg/L and 0.47 mg/L, respectively. Therefore, this study was carried out to remove the hardness and fluoride concentrations of water to the level of 200.00mg/L and 0.47mg/L, respectively. Initially, a divalent cation exchange column was designed using a commercially available cation exchange resin, ECO A, to remove excessive hardness level up to 200.00mg/L. The eluent from the cation exchange column was further treated for defluoridation. Coal derived fly ash was further modified using the hydrothermal method. The Modified Fly Ash (MFA) was further treated with Fe (III) Chloride to generate positive charges on the surface. FTIR, SEM, EDX, confirmed the incorporation of Fe into MFA and, the defluoridation ability of Fe functionalized MFA. FTIR spectra (400cm-1 – 600cm-1 region) showed the incorporation of Fe into MFA. The average crystalline size obtained from XRD analysis was 23.3nm and the synthesized material was in nanoscale. The batch experiments showed that 1.3g of the Fe functionalized MFA resulted in the maximum defluoridation for a 100.00 ml of water sample containing 200.00 mg/L hardness and 2.00 mg/L fluoride within 40 minutes of contact time at pH 6. The material gave optimum defluoridation at pH 6 and therefore there is no need of altering the pH of water for the defluoridation. The adsorption data fitted with the Langmuir adsorption isotherm where the maximum adsorption capacity was 10.00mg/g. The separation factor for the Langmuir adsorption was 1.23 and therefore the Langmuir adsorption is favorable. The reaction followed pseudo second order kinetics. Regeneration studies of the Fe functionalized MFA showed that iii NaOH was the best regeneration agent and the material was exhausted after two regeneration cycles. The material synthesize cost to purify water for a five-member family for three months was LKR 6923.07 (37.52USD) and the cost for the regeneration was LKR 174.46 (0.95USD). Therefore, the synthesized material is ideal and cost effective to remove fluoride in potable ground water in CKDu prevalent areas.
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    item: Thesis-Full-text
    Evaluating the performance of subsurface horizontal flow constructed wetland for tertiary treatment of sanitary landfill leachate
    Jeganathan SSD; Jayaweera MW
    The difficulty in detecting and quantifying the typical composition characteristics of landfill leachate, limit successful treatment of it. High quality effluent that can be discharged to surface waters could be achieved by using the two stage leachate treatment systems with a constructed wetland at the final stage. This pilot scale study was conducted with the aim of evaluating the tertiary treatment of pre-treated leachate obtained from Sanitary Landfill located at Dompe, by a subsurface horizontal flow constructed wetland comprising Phragmites karka and Calicut tiles as substrate. The removal efficiency of BOD5, COD, TSS, NO3--N and PO43--P was evaluated. The study period was from June to August 2017. Sixty liters of diluted pre-treated leachate (i.e. Containing 80% of the pre-treated leachate by volume) was fed per day with a hydraulic retention time of 1 day. Concentration based average removal efficiency of the system was 63% for BOD5, 62% for COD, 96% for TSS, 49.11% for NO3- -N and 85.28% for PO43--P. Long term research is necessary to examine the effects of continuous feeding and shock loadings on the growth response of Phragmites karka.
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    item: Thesis-Abstract
    Treatment of textile wastewater containing dye stuff by fenton oxidation process and adsorption
    (2021) Parimalarajah D; Jayaweera MW
    Environmental pollution is the most severe global issue threatening our ecosystem in the current scenario. Pollution is present in every strata of the earth, and the negative effects associated with it are a major source of concern in the modern era. Textile industry hazardous effluents are regarded as one of the major contributors to water pollutants discharged untreated into bodies of water. The discharged effluents from these industries have been demonstrated to bear a high pollution load (high dissolved solids, COD, colour and chloride content) with poor biodegradability. Therefore, untreated textile wastewater causes severe damage to the environment if discharged without treatment. Many techniques like electrochemical coagulation, reverse osmosis, nanofiltration, adsorption using activated materials etc., draw attention to treatment. With traditional approaches, treating textile wastewater, which is of great strength and complexity, has become a significant challenge. Advanced oxidation processes represent a powerful treatment for refractory and toxic pollutants in textile wastewaters. The present investigation is focused on COD removal, using Fenton oxidation and combined treatment with materials of TiO 2 , Commercial activated carbon and TiO 2 impregnated activated carbon (AT). Initial COD level of 2100mg/l decrease up to 710 mg/l through Fenton oxidation process. Further to discharge treated wastewater into the water body (<250mg/l) is achieved with 8g of TiO 2 ,7 g of CAC, and 6g of TiO 2 impregnated AC. CAC was selected as the best material economically for post-treatment. Many factors influenced the degradation rate in the Fenton process, such as initial hydrogen peroxide concentrations(0.65ml/l), initial iron concentration (1.5 g/l) and pH (2-3). CAC gave maximum COD removal at pH 2. The data were fitted to the Langmuir adsorption isotherm, with a maximum adsorption capacity of 8.16 mg/g and monolayer dye adsorption to the material. The Langmuir adsorption separation factor was 0.033, indicating that the Langmuir adsorption is favourable. The reaction proceeded in a pseudo-second-order, implying chemisorption to the substance. The optimum regeneration agent was found to be NaOH, and the material was exhausted after two regeneration cycles. From the results Fenton with CAC adsorption is most efficient treatment method at higher dye concentrations and for textile industry effluent.