Browsing by Author "Wanniarachchi, D.D.C."

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    Detection of Dhool Number in Black Tea Manufacturing with Image Processing Techniques
    (Uva Wellassa University of Sri Lanka, 2016) Saranka, S.; Kartheeswaran, T.; Wanniarachchi, D.D.C.; Wanniarachchi, W.K.I.L.
    The possibility to use digital images of tea particles as a tool to monitor fermentation of black tea processing is studied in this project. Copper green colour is the predicted colour used to measure the degree of fermentation; therefore, determining the fermentation level by observing the copper green using naked eye is error prone and affects the complete product outcome. Black tea processing takes several batches per day, and from each batch, there are three types of particles obtain after Roll breaker processes. According to the size of the particles these are named as dhool 1, dhool 2, and dhool 3. The duration of fermentation is varied by dhool number for a given batch due to varied sizes of tea particles. Therefore, it is important to identify the dhool number for a given digital image. The method used in this project is divided in to three main phases, image pre-processing, identification of the dhool number, and prediction of the fermentation level. image processing techniques are used to extract features of tea leaves and Support Vector Machine (SVM) is used as the classifier to train the system and obtain accuracy in each stage. The results indicate higher accuracy in predicting the dhool 1 which is over 77% accurate while dhools 2 and 3 indicated accuracy levels of 69% and 73% respectively. Therefore, image processing techniques can be successfully used to predict the dhool number of a given batch of tea processing. Keywords: Fermentation, Image processing, SVM
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    Development of light weight bricks using red clay and rice-husk
    (Uva Wellassa University of Sri Lanka, 2015) Vyshnavi, G.; Pitawala, J.; Wanniarachchi, D.D.C.; Pitawala, H.M.T.G.A.
    Bricks are one of the oldest building materials that can be made at relatively low cost. They have been in continual use for more than 5000 years and still used in Sri Lanka, because of their many advantages (El-Mahllawy et al., 2013). Mud bricks, burned bricks and cement bricks are types of bricks using in construction purposes (Society of Civil Engineers, 1996). The composition of red clay minerals used in brick production is SiO2 (60.67%), Al2O3 (15.18%) and Fe2O3 (7.61%) (Hettiarachchi et al., 2010). Certain admixtures such as rice-husks, sawdust, etc. are added to brick raw mixtures to produce different effects such as color, high strength, or low weight in the finished product. Admixtures consists of organic matter are burned out when bricks undergo firing. Cons equently, porous bricks are produced. This permits the control of the bulk density of brick products and help in producing lighter bricks with low material cost. In this research work, bricks are made using red clay and 5 wt. % of rice-husk or 5 wt. % of rice-husk ash as admixtures. The fabricated bricks were analyzed to measure material properties such as compressive strength, weight, volume, density, water absorption, and color changes during firing process. Results are then compared with the values obtained from commercial bricks. Methodology Preparation of prototype bricks The dimensions of the bricks studied in this project were 25% of the commercial brick dimensions. Accordingly, length.41/4” (10.79 cm) x width 23/4” (6.98 cm) x height 11/4” (3.17 cm) mold was used to make prototype bricks. Bricks were made with both premixed clay (obtained from brick makers) and dried clay with rice husk. Procedure 1 (Premixed Clay) The amount of water added to the clay material was unknown as it was obtained as a wet sample from the brick makers. The purpose of making bricks with this premix is to set standards for tensile strength and weight of the bricks similar to market quality bricks. Accordingly, five brick blocks were made with premixed clay (500 g). These bricks are labeled as sample 1. Procedure 2 (Dried Clay) Clay material and rice-husk sample were dried until a constant weight was obtained (2-3 days). Then dried clay and a known amount of water were mixed to produce bricks to be used as the control (sample 2) to compare the effect of rice husk. The same amount of clay and water were mixed with either five percent of rice-husk (sample 3) or rice-husk ash (sample 4). In each case, five bricks were made. All the brick samples were dried under sunlight for four days. Firing process of the bricks was done using a common rice-husk burning kiln or using an electrical furnace at 1000 C during this research. All bricks were tested for compressive strength, weight, volume, density, water absorption, and color changes. Bricks made with rice husk (sample 3 and 4) were compared against premix samples (sample 1) and bricks made without rice husk (sample 2). Results and Discussion Density of the prototype bricks The dimensions and weight of the bricks were recorded for all samples before and after firing. These data were used to calculate the volume and density of bricks. According to the results, volumes of unfired bricks samples are almost equal, but after firing the bricks have different values for volume due to evaporation of water and burning of organic matter during firing process. The lowest density was recoded for sample with rice husk (3) compared to the control sample (2). Also addition of rice husk in sample 3 resulted in lower density compared to the sample with rice husk ash (4). This observation is in agreement with the expected trend in density where rice husk burning will result higher loss in weight compared to rice husk ash.
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    In-vitro Study on Geosmin and 2-Methylisoborneol Producing Four Species of Native Cyanobacteria
    (Uva Wellassa University of Sri Lanka, 2019) Ganegoda, S.S.; Wijesekara, W.M.A.; Chinthaka, S.D.M.; Wanniarachchi, D.D.C.; Manage, P.M.
    The production of odiferous metabolites, such as Geosmin and 2-methlyisoborneol (2- MIB) cause muddy and moldy taste and odor in water is a major limitation in safe and adequate provision of potable waters in worldwide. The biological functions of these odorants have not known, and cyanobacteria are the major producers of Geosmin and 2- MIB in natural waters as a result of their secondary metabolites. Objective of the current study was to investigate four laboratory cultured cyanobacteria’s ability to produce Geosmin and 2- MIB. Production of Geosmin and 2- MIB was studied using native cyanobacteria isolated from Unnichchi tank in Baticolloa district, Jayanthi tank in Ampara district and Padawiya tank in Anuradhapura district where taste and odour issues are prevailing. Isolation of cyanobacteria was carried out using dilution and spread plate method by maintaining cultures in BG 11 medium with antibiotics. The cultures were identified as Oscillatoria sp., Psudoanabena sp., Lyngbya sp., and Nostoc sp. using the 16s rRNA sequencing. 10 ml aliquots of two months old axenic cultures were subjected to Solid Phase Micro Extraction (SPME) and Gas Chromatography Mass Spectrometry (GC/MS) analysis with BG 11 culture medium as control. The concentration of Geosmin produced from the cyanobacteria were ranged between 10.8 ng/L to 162.6 ng/L whereas 2- MIB levels ranged from 50.8 ng/L to 532.5 ng/L. Axenic cultures of Nostoc sp. recorded the highest Geosmin level (162.6 ng/L) and highest 2- MIB level was detected from Psudoanabena sp. (532.5 ng/L). Further Nostoc sp. recorded a significant high level of 2- MIB level (379.6 ng/L) compared to Oscillatoria sp. and Lynbya sp. (p < 0.05). It can be concluded that above species are commonly available cyanobacteria species in Sri Lankan water bodies and popular Geosmin and 2- MIB producers.
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    Kaolin - based Filter Material to Remove Textile Dyes in Water
    (Uva Wellassa University of Sri Lanka, 2018) Imalka, H.T.R.; Wanniarachchi, D.D.C.
    In this research, the adsorption capabilities of four kaolin - based filter materials for dye removal was tested and locally available kaolin (collected from Meetiyagoda, Sri Lanka) is the main component of these four materials. First filter material (M1) is based only on kaolin. Second filter material (M2) is based on kaolin and activated carbon (5% w/w). Third filter material (M3) is based on kaolin and calcium hydroxide (5% w/w). Fourth filter material (M4) is based on kaolin and calcined eggshells (5% w/w). Pellets of each material had average diameter (2 mm) and average length (4 mm). Methylene blue (MB) was used as a model dye to understand properties of filter materials and also the adsorption capabilities of materials were tested with an industrial dye. The effect of dark (Reagent bottles were covered by aluminum foils) and light conditions (light box consisting of 20W, CFL bulb was used due to potential photocatalytic pathways possible), effect of initial concentration, effect of contact time for adsorption of MB and industrial dye was tested in this study. M3 has the highest MB removal efficiency (37.29%) and M1 has the highest industrial removal efficiency (13.69%) in light conditions. The removal efficiencies under dark conditions are considerably lower for all four filter materials. Next, adsorption of MB onto M3 was found to follow Freundlich isotherm (r2 = 0.96, n = 1.96, KF = 0.06 Lg-1) than Langmuir isotherm (r2L = 0.95, q max= 0.20 mg g-1). Furthermore, MB adsorption was found to follow pseudo-second order kinetics (R2 = 0.99, k2 = 1.11 x 10-2 g mg-1 min-1). Adsorption of industrial dye onto M1 was found to follow Langmuir isotherm (r2L=0.89, qmax = 0.34).In conclusion, the study reveals M3 can be used to remove MB and M1 can be used to remove industrial dye in water more efficiently. Unlike activated carbon, kaolin based materials can be reused several times and can prevent the secondary pollution due to adsorbents.
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    Statistical Analysis of Determinants of Black Tea Quality
    (Uva Wellassa University of Sri Lanka, 2018) Tharaga, S.; Kumari, K.W.S.N.; Wanniarachchi, D.D.C.
    Tea is the world most popular beverage. It has very good market both locally and internationally.Sri Lankan tea is world renowned for high quality and taste. However, in the recent past, Sri Lanka has lost the top ranking and now in rank third in the world market. Therefore, ensuring the export of quality tea is essential for the regaining the top ranking.In this study, a literature survey was conducted to identify the factors affecting the quality of black tea.Some identified factors are fermentation time, temperature, moisture and humidity content of leaves. These will impact quality parameters such as Theaflavine, Thearubigin, Tea liquor color and brightness.In this paper, a statistical analysis was conducted to identify the extent to which fermentation time and temperature will impact with Theaflavin, Thearubigin, and total color of the tea infusion by using correlation and regression (simple and multiple). An analysis was conducted using 17 reported data where each data point is the average of a triplicate. According to correlation analysis, relationships are available among time, temperature and Theaflavin. When the fermentation time increases, Theaflavin content decreases. When the temperature decreases, Theaflavin content increases.However,the impact of temperature on Theaflavin is not significant as in the observed analysis (P = 0.966).A similar study was carried out to find relationship between Thearubigin versus temperature and fermentation time. The results reveal that the thearubigin is not significantly related with temperature (P = 0.189) and fermentation time (P = 0.844).Tea infusion color is highly related to the time than temperature (P = 0.098),It can be concluded that the Theaflavin and tea liquor color is significantly depending on fermentation time, where thearubigin is depending on temperature.
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    Study on Relative reactivity and Toxicity of Metal-Glyphosate Complexes
    (Uva Wellassa University of Sri Lanka, 2016) Liyanage, D.N.; Jayarathna, R.A.; Wanniarachchi, D.D.C.
    Glyphosate (Gip), (C31-1,1\10,13), N-(phosphonomethyl)glycin is a non-selective, post emergence organophosphorus herbicide. Metal-glyphosate complexes can be formed via coordination of amine, carboxylate, and phosphonate functional groups in glyphosate with di/tri valent metal ions in surface water. However, adequate studies on toxicity of metal¬glyphosate complexes are not yet conducted. Furthermore, glyphosate metal complexes are suspected to cause chronic kidney disease in Sri Lanka. The goal of this study is to compare relative reactivity of metal ions towards glyphosate and toxicity of metal¬glyphosate complexes. Therefore, metal-glyphosate complexes which has a higher potential to contaminate the surface water can be identified. Complexes were synthesized for Cu, Fe and Ca ions and characterized with FTIR and UV-Visible spectroscopy. Solubility was measured for these complexes and suggests higher solubility for Cu-Glp. However, the fastest complex formation was observed for formation of Ca-Glp followed by Fe- Glp and Cu- Glp. Fish embryo toxicity (FET) test results indicates metal-glyphosate complexes have a higher toxicity compared to individual metal ions and the highest toxicity was reported for Cu-Glp complex. Keywords: Glyphosate, Metal glyphosate complexes, Toxicity, Glyphosate-metal reaction rates