Browsing by Author "Vithanage, M."

Now showing 1 - 6 of 6

Anammox bacteria in treating ammonium rich wastewater: Recent perspective and appraisal
(Bioresource Technology, 2021) Weralupitiya, C.; Wanigatunge, R.; Joseph, S.; Athapattu, B. C.; Lee, T. H.; Kumar Biswas, J.; Ginige, M. P.; Shiung Lam, S.; Senthil Kumar, P.; Vithanage, M.
The discovery of anammox process has provided eco-friendly and low-cost means of treating ammonia rich wastewater with remarkable efficiency. Furthermore, recent studies have shown that the possibility of operating the anammox process under low temperatures and high organic matter contents broadening the application of the anammox process. However, short doubling time and extensive levels of sensitivity towards nutrients and environmental alterations such as salinity and temperature are the limitations in practical applications of the anammox process. This review article provides the recent yet comprehensive viewpoint on anammox bacteria and the key perspectives in applying them as an efficient strategy for wastewater treatment.
Cyanotoxins uptake and accumulation in crops: Phytotoxicity and implications on human health
(Toxicon, 2022) Weralupitiya, C.; Wanigatunge, R. P.; Gunawardana, D.; Vithanage, M.; Magana-Arachchi, D.
The invasive nature of cyanotoxin-producing cyanobacteria and the adverse effects concerning their toxic impacts have gained heightened scientific attention of late. The persistence of cyanotoxins in irrigation water leads to bioaccumulation in plants, the development of phytotoxic effects, and the threat of groundwater contamination. The accumulation of cyanotoxins in plants is caused by several factors leading to severe toxic effects, including reduced plant growth and seed germination, enhanced oxidative stress, lowered rate of mineral uptake, decreased photosynthetic efficiency, and loss of chlorophyll content. The uptake and accumulation of cyanotoxins in plants can be concentration-dependent, as reported in a myriad of studies. Even though several studies have reported phytotoxic effects of cyanotoxin contamination, field-related studies reporting phytotoxic effects are particularly inadequate. Paradoxically, at realistic conditions, some plants are reported to be tolerant of cyanotoxins. Furthermore, the breadth of adverse impacts of cyanotoxins on human health is significant. Cyanotoxins cause major health effects including cancer, oxidative stress, organelle dysfunction, DNA damage, and enzyme inhibition. This review intends to present compelling arguments on microcystins (MCs), cylindrospermopsins (CYN), β-N-methylamino-L-alanine (BMAA), and anatoxin-a (ANTX-a), their uptake and accumulation in crop plants, phytotoxic effects on plants, and potential health implications to humans. The accumulation of cyanotoxins implants cultivated as food crops, resulting in phytotoxic effects and adverse impacts on human health are serious issues that require scientific inputs to be addressed.
Efficient dye removal from wastewater by using expired rice grain derived biochar: A sustainable solution for water purification
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Ranaweera, D. M. S. U.; Vithanage, M.; Ranaweera, S. A.
The accumulation of waste dyes in aquatic systems poses significant risks to human and animal health due to their hazardous and carcinogenic nature. Dyes also interfere with photosynthesis by reducing sunlight penetration in deep water. Although various methods have been developed to remove color contaminants from aqueous systems, there remains a need for cost-effective, environmentally friendly, and efficient adsorbents. Over 350,000 kg of expired rice is disposed of annually from warehouses in Sri Lanka. Because of the rich composition of nutrients in rice, they can be used as raw material to produce biochar. In this study, the remediation of Methylene Blue (MB) from simulated wastewater using biochar produced by pyrolysis of expired rice grains was investigated. Two types of biochar were prepared: non-modified (NMRG) and modified (MRG) through KOH activation. The efficiency of MB removal by these variants was evaluated. FT-IR spectra confirmed the modification of the rice biochar surface with various functional groups through alkali treatment, and Scanning Electron Microscopy (SEM) micrographs showed the opening of meso and macropores in the biochar due to KOH activation. Batch adsorption studies were conducted to determine the effects of MB concentration, pH, temperature, and contact time on MB removal. The optimum pH was found to be pH 4 for both NMRG and MRG, with an optimum contact time of 2 hours. The maximum MB adsorption was observed for a 2000 ppm MB solution at an optimum temperature of 30 °C. Experimental results indicated that MRG exhibited the highest adsorption capacity of approximately 169.93 mg/g with an 84.97% removal rate, while NMRG showed an adsorption capacity of 41.75 mg/g with a 20.88% removal rate. Thermodynamic parameters such as enthalpy change (ΔH), entropy change (ΔS), and Gibb’s free energy (ΔG) were evaluated for both adsorbates. The ΔS and ΔH values for NMRG were 0.01 kJ mol⁻¹ K⁻¹ and 5.25 kJ mol⁻¹, respectively, whereas, for MRG, these values were 0.13 kJ mol⁻¹ K⁻¹ and 8.55 kJ mol⁻¹, indicating an increase in randomness during adsorption. The enthalpy values revealed the endothermic nature of the process, with MB uptake enthalpy for NMRG and MRG at 5.25 kJ mol⁻¹ and 8.55 kJ mol⁻¹, respectively. The Gibbs free energy for MRG was a large negative value (-30.45 kJ mol⁻¹), while for NMRG, it was a small positive value (8.89 kJ mol⁻¹), suggesting that adsorption was mainly governed by chemisorption. The Intra-Particle Diffusion model indicated that adsorption occurred through both intra- and inter-particle diffusion. The Toth isotherm and the Redlich-Peterson models were identified as the best-fit models for NMRG and MRG, with R² values of 0.99.
Internet Gaming Disorder: Prevalence and Associated Gaming Motivations among an Advanced Level Student Population from the Colombo Educational Zone
(Faculty of Medicine, University of Kelaniya, Sri Lanka, 2021) Manchanayake, M.; Malsirini, M.; Vithanage, M.; Jayawardene, D.
Introduction: Internet Gaming Disorder (IGD) is on the rise among adolescents owing to increasing technology usage amid the COVID-19 pandemic. It is linked to anxiety, depression, disordered sleep, and poor academic performance. Understanding the motivations that drive gaming addiction can enable early identification of at-risk individuals. Objective: We aimed to identify the gaming motives underpinning IGD among an urban Advanced Level student population. Methods: A cross-sectional study was conducted among 395 students aged 16-18 years, selected via random cluster sampling from four Type-1 AB schools in the Colombo Educational Zone. The validated Internet Gaming Disorder Scale Short-Form was used to assess IGD, and cases were diagnosed if >5 items in the scale were scored 4/5 or more. Seven gaming motives, namely Social, Escape, Competition, Coping, Skill Development, Fantasy and Recreation were explored via the Motives for Online Gaming Questionnaire. Results: Most of the students (81.5%, n=322) identified themselves as gamers. Among them, the prevalence of IGD was 6.21% (95% CI=3.58-8.85) which was significantly higher (p<0.05) among males and those who played games for >6h daily during weekdays. All the motives correlated significantly (p<0.001) with IGD although Escape showed the strongest correlation (Spearman’s Rs=0.616). Escape and Fantasy were associated with higher odds and Competition was associated with lower odds of having IGD in binary logic regression analysis. Conclusion: IGD is an emerging public health challenge which predominantly affects male gamers. Escapism and Fantasy is higher while competitiveness is lower among disordered gamers. These motivations should be considered in the psychological screening of potential cases.
Removal of Ciprofloxacin from aquatic environments using Pristine and KOH activated waste rice biochar
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Vishwani, L. L. D.; Ranaweera, S. A.; Vithanage, M.
Ciprofloxacin (CPX) is an antibiotic used to treat many bacterial infections and is considered as a water pollutant, which induces antibiotic resistance. This study aimed to remove CPX from water using pristine (WRBC-P) and KOH-activated (WRBC-A) waste rice biochar derived at 500 ˚C. WRBC-P was prepared by pyrolysis of expired rice grains at a 5 ˚C/min heating rate. KOH activation was carried out using WRBC-P to obtain WRBC-A. Both biochar samples were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM). The data indicates that the activation improves the pore structure and the surface area of biochar. Removal of CPX by both biochar variants was studied in batch experiments. The edge experiments were conducted by varying the pH from pH 3 to 10, kinetics experiments at different time intervals up to 24 h and the isotherm studies at different initial CPX concentrations (2-25 mg/L) in the presence of 1 g/L dosage of biochar at 25 ˚C. Variations in CPX concentrations before and after adsorption studies were determined using UV-visible spectroscopy measuring absorbance at 277 nm λmax using a Quartz cuvette. The maximum adsorption capacity of CPX was observed at pH 7.3 for both WRBC-P and WRBC-A. After 12 hours of equilibrium time, the maximum adsorption capacities were 1.45 mg/g and 6.15 mg/g for WRBC-P and WRBC-A respectively. The fractional power model was the best-fitted model for the kinetic data obtained for both WRBC-P and WRBC-A. This explains that the rate of the adsorption of CPX on biochar depends on the concentration of CPX to non-integral power. This reflects that the CPX adsorption takes place via a complex mechanism with intermediate formation. Isotherm data confirms that the adsorption of CPX is a two-way process for both WRBC-P and WRBC-A. Hill isotherm model was fitted with cooperative binding between CPX and biochar showing a monolayer formation for the first part of the data set. After that, the Freundlich model was equipped with the multilayer adsorption of CPX on the biochar surface. Overall, experimental data suggested that the incorporation of CPX onto both WRBC-P and WRBC-A is mainly driven by both chemical and physical forces. CPX adsorption was a favorable process at room temperature and in the 7-8 pH range after 12 hours of contact time. WRBC-A demonstrated four times higher CPX removal capacity than that of WRBC-P indicating KOH activation as an efficient route to improve the adsorption capacity of biochar for the removal of CPX.
Risk factors for endemic chronic kidney disease of unknown etiology in Sri Lanka: Retrospect of water security in the dry zone
(Science of the Total Environment, 2021) Hettithanthri, O.; Sandanayake, S.; Magana-Arachchi, D.; Wanigatunge, R.; Rajapaksha, A. U.; Zeng, X.; Shi, Q.; Guo, H.; Vithanage, M.
The prevalence of chronic kidney disease of unknown etiology (CKDu) is receiving considerable attention due to the serious threat to human health throughout the world. However, the roles of geo-socio-environmental factors in the prevalence of the CKDu endemic areas are still unknown. Sri Lanka is one of the countries most seriously affected by CKDu, where 10 out of 25 districts have been identified as the areas with the high prevalence of CKDu (10–20%). This review summarizes the geographical distribution of CKDu and its probable geochemical, behavioral, sociological, and environmental risk factors based on research related to hydrogeochemical influences on CKDu in Sri Lanka. More than 98% of CKDu patients have consumed groundwater as their primary water source in daily life, indicating the interactions of geogenic contaminants (such as F−, total dissolved solids, Hofmeister ions) in groundwater is responsible for the disease. Apart from the hydrogeochemical factors, mycotoxins, cyanotoxins, use of some herbal medicines, dehydration, and exposure to agrochemicals were alleged as risk factors. Sociological factors, including poverty, living habits and anthropogenic activities, may also provoke the emergence of CKDu. Therefore, the interaction of geo-socio environmental risk factors should be sociologically and scientifically considered to prevent the prevalence of CKDu. Future in-depth studies are required to reveal the individual role of each of the postulated etiological factors, possibly using machine learning and advanced statistics.