Browsing by Author "Gunatilake, S.K."

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Comparative study on the adsorptive behavior of As (III) and Cr (III) ions from aqueous solution on to sawdust and rice husk biochar
(Research Centre for Social Sciences, Faculty of Social Sciences, University of Kelaniya, Sri Lanka, 2016) Gunatilake, S.K.
Sorption capacity of two different biochar (saw dust and rice straw) was evaluated in the recovery of arsenic and chromium from aqueous solutions. Biochar from rice straw and saw dust were obtained from pyrolysis of biomass at 400◦C. The optimum sorption conditions were studied for different concentrated monometallic system. Sorption studies were performed at different pH, contracting time and different initial metal ion concentration in the batch mode. The optimum pH was 3 for recovery of As(III) and 5-7 for Cr(III). Kinetic studies yielded an optimum equilibrium time of 50 minutes with an adsorbent dose of 1 g/L and initial concentration ∼20 mg/L for both ions. Metal ions in aqueous solution were transported to biochar surface through adsorption and intra-particle diffusion process. Experimental data for both metal ions were fitted a Langmuir model with R2 value for As(III) 0.969, 0.879 for saw dust and rice straw respectively while 0.971, 0.99 for Cr(III) ions. The Freundlich constant, KF values for removal of As(III) and Cr(III) ions by saw dust and rice straw were 0.9127, 0.8951 and 0.944, 0.844 respectively. The 1/n value for arsenic and chromium ions obtained from saw dust and rice straw were 0.209, 028 and 0.862, 0.84 respectively and indicate the normal sorption of As(III) and Cr(III). The values indicated the affinity of the sorbent towards the uptake of both ions and adsorptions of the metal ions were favorable. According to FTIR analysis As(III) as well as Cr(III) metal ions bound to active sites of the biosorbents in different biochars through either electrostatic attraction or complexation mechanism. The electrostatic attraction between metal ion and carbonate group and complexation mechanism between electron donor atoms (O and N) are occurred. These results indicated that carbonyl, hydroxyl, amine and halides are the main adsorption sites in saw dust and rice straw biochar and these functional groups complexes with As(III) and Cr(III) ions in the aqueous solution and changed the chemical environment of the functional groups in the biochar. The results showed that rice straw and saw dust biomass can be used to remove Arsenic and Chromium ions from aqueous phase.
Farmers’ knowledge, perception, and practices on agrochemical usage in upper Uma Oya and Kumbukkan Oya watersheds in Sri Lanka
(Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Sumudumali, R.G.I.; Piyathilake, I.D.U.H.; Randika, J.L.P.C.; Jayawardana, J.M.C.K.; Udayakumara, E.P.N.; Gunatilake, S.K.
Pesticides are widely used to reduce pre- and post-harvest losses in cultivations due to the pest infestations. A semi-structured questionnaire survey and key informant interviews were carried out to compare the patterns of pesticide usage, perception and knowledge of farmers in one of the main vegetables growing areas of upper Uma Oya and main field crop cultivated areas of upper Kumbukkan Oya watershed in Sri Lanka. The primary data were collected covering two main seasons (Yala and Maha of 2019/2020) in Uma Oya (n = 61) and Kumbukkan Oya (n = 65) watersheds. The cultivated major crops in Uma Oya watershed area are potato, bean, tomato and cabbage whereas rice, cowpea, and maize are grown in Kumbukkan Oya watershed. According to the results, active ingredients of 26 insecticides, 21 fungicides, 17 herbicides were used by farmers for their cultivations in both sampling areas. The most frequently used pesticides were insecticides (51.2%) followed by fungicides (45.8%) and herbicides (3.0%) in Uma Oya watershed while in Kumbukkan Oya watershed herbicides usage (44.4%) was followed by insecticides (36.0%) and fungicides (19.6%). More than 50% of farmers in Uma Oya watershed mainly used five insecticides namely Abamectin, Carbosulfan, Chlorantraniliprole 20% + Thiamethoxam 20%, Profenofos, three fungicides of Chlorothalonil, Mancozeb, Propineb and only three types of herbicides. More than 80% of the farmers in the Kumbukkan Oya watershed used to utilize herbicides of MCPA 600 g/l and MCPA 400 g/l as major pesticides. Most of these active ingredients used in this study were belong to the World Health Organization hazard classification class “U” which is unlikely to present an acute hazard. Highly used insecticides Abamectin, Carbosulfan, Profenofos MCPA 600 g/l and MCPA belongs to WHO hazard class II (moderately hazardous) chemicals while fungicide Chlorothalonil belongs to hazard class III (slightly hazardous) chemicals. There is no significant difference observed in mixing (χ2 = 2.567, α = 0.05) and selecting the pesticides (χ2 = 0.403, α = 0.05) in both regions. Nearly 67.5% of the respondents applied a mixture of different chemicals because they believe such mixtures save their time (20.6%) and unsure about the pesticide strength of controlling pests and diseases (34.2%). Farmers selected pesticides mainly based on the information provided by the pesticide retail shop owners or dealers (72.2%). Meanwhile, only 7.1% of farmers seek advice from agricultural instructors/extension officers on pest management decisions. Only 31.0% of respondents had training on the correct use of pesticides and such training were conducted by private sector organizations involved in pesticide marketing. Most of the farmers washed their pesticide sprayers in their field (62%) while 23% washed in the irrigation canal and 13% washed in nearby waterways. Eight percent of farmers carelessly disposed of the pesticide leftovers and containers in the open fields. The findings indicated pesticide application in the study areas represents a potential risk for the environment and farmers.
Improvement of the Existing Integrated Leachate Treatment System in Gohagoda Dumpsite in Kandy in Sri Lanka
(Research Centre for Social Sciences, Faculty of Social Sciences, University of Kelaniya, Sri Lanka, 2016) Dissanayake, H.M.K.P.; Gunatilake, S.K.; Basnayake, B.F.A.
Kandy is the hill capital of Sri Lanka having nearly 1,375,382 populations. Generated solid waste within the Kandy city is disposed in the Gohagoda dumpsite since 1960. Leachate generating from dumpsite is polluted surrounding water bodies since long time. Therefore, an integrated leachate treatment system (LTS) had been established by Ecotech Lanka Limited with the collaboration of University of Peradeniya and Kandy Municipal Council (KMC) to rehabilitate the dumpsite. This research was conducted to evaluate the performance of available system and investigate methods to improve the quality of LTS through laboratory scale experiments. Samples were obtained from 13 pre-defined points on weekly basis for three months and analyzed for pH, Salinity, Total Dissolved Solid (TDS), Electrical Conductivity (EC), Dissolved Oxygen (DO), Total Solid (TS), Total Volatile Solid (TVS), Total Suspended Solid (TSS), Total Volatile Solid (TVS), Biochemical Oxygen Demand (BOD), Heavy metals to determine water quality of surrounding area. It was clearly monitored that the LTS not functioned properly and laboratory scale experiments were conducted to treat the effluents to meet the Central Environmental Authority (CEA) standards by using sand and charcoal filters with addition of clay and alum. Average pH, EC, Salinity, DO, BOD, TS, TDS, TSS, VS,VSS were 7.24, 22.74mS, 12.71%o, 0.31mg/L, 15977.57 mg/L, 29537.04 mg/L, 12437.5 mg/L, 10796.25mg/L, 10942.08mg/L and 3250 mg/L respectively. Pb, Mn, Ni and Zn concentrations were 0.3l, 7.4, 0.202 and 0.07mg/L respectively. Using the sand filter, EC and salinity removal efficiency were increased upto 24.92% and 27.58%, while the charcoal filter EC, salinity, TDS were 39.52%, 39.62% and 39.54% respectively. More than 8.53% of EC, 10.41% of salinity, 9.89% of TDS and 26.81% of DO were removed by adding 3g of clay. Alum showed maximum TDS removing efficiency with 0.2g/100ml dosage. pH in the system could be reduced upto 6.63. TDS, DO and BOD were reduced upto 9,120 mg/L, 0.38mg/L and 21,900mg/L respectively. Reactor composite liner permeability is reduced with the time after operation. Therefore LTS should be rehabilitated according to the improvement and further studies should be needed to confirm the findings.