Browsing by Author "Manatunge, JMA"

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item: Thesis-Abstract
An Integrated management plan to sustain the restoration of Lunawa lake
Gunawardena, GDSD; Manatunge, JMA
Lunawa Lake, located in the western coastal belt south of Colombo (Sri Lanka) is a small lagoon of 20 ha. with a catchment area of 6.15 km2 Industrial effluent discharged through the storm water drainage system connected to the lake and urbanization had converted the Lunawa Lake into one of the most polluted lakes in Sri Lanka. Encroachment of drainage canals by the inhabitants and sand bar formation at the mouth of the lagoon had caused serious flood problems in the catchment during rainy season. Lunawa Environment Improvement and Community Development Project which is being implemented with JICA fundings helps to convert the polluted Lunawa Lake from an eyesore to an environmentally attractive lake and alleviates flood damage through an improved storm water drainage system. Apart from the engineering works, series of community upgrading activities have also been carried out to uplift the quality of life of the low-income inhabitants of the catchment. The maintenance of the improved lake system is of prime importance for sustainability of the project. The water quality monitoring reveals the signs of gradual transformation of the polluted lake into a more acceptable water body and this is more so evident by the emerging aquatic life and flocking of birds in the lake. This research intends to provide overall insights on Canal and lake water pollution sources in terms of point and non point including identification of stake holders involvement in the Lunawa Lake basin area those who may change the quality of basin environment towards the direction of positive or negative sides as a result of their direct or indirect interventions. The ultimate intention of this research is to fInd out an Action Plan to form a well-defined integrated type stake holders' initiated "Lake Basin Management Plan to Sustain the Restored Lunawa Lake Basin" iii
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Are Green jobs sustainable for Sri Lankan Economy?
Jayaweera, M; Manatunge, JMA; Witharana, A
It is imperative that Sri Lanka grasps the concepts of green jobs to meet the most vital but intricate challenge of the 21st Century, which is the transformation to a sustainable and a low-carbon economy. Such a transformation or a paradigm shift, which can be gradual or rapid depending on the circumstances, will undoubtedly have a considerable positive effect on the way we produce and/or consume goods and services. The speed at which this transformation would occur is likely to accelerate in the near future as there is a trend of global transition from a traditional to a low-carbon economy, in order to attain sustainable economies. Such trends will help create an array of different forms of green jobs across many sectors, and most probably can become a catalyst for further development. The International Labour Organization (ILO) has defined green jobs as “Jobs created when they help in reducing the negative environmental impacts ultimately leading to environmentally, economically and socially sustainable enterprises and economies”. Green jobs, in general, stand on two pillars: decent work and environmental sustainability. Thus, green jobs can be defined as decent work that contributes to environmental sustainability. In a broader sense decent work needs to address the core of international labour standards such as freedom of association and effective recognition of the right to collective bargaining, elimination of all forms of forced or compulsory labour, effective abolition of child labour, elimination of discrimination in respect of employment and occupation, occupational health and safety, etc. whilst aligning to laws applicable to Sri Lanka. Environmental sustainability addresses issues such as effectively combating climate change, pollution prevention and control, conservation of eco-systems and biodiversity etc. (ILO, 2007).
item: Thesis-Full-text
Attitude of affected households towards the mode of compensation and possible issues due to land acquisition for expressway projects in Sri Lanka
Dharmawardhana, HMT; Manatunge, JMA
Road and highway projects are intended to either build new roads or widen or improve existing ones. Opening up a corridor for a new road requires more space resulting land acquisition and the resultant negative impacts are usually more severe than in road rehabilitation or upgrading. In this thesis, the methodology is discussed in two phases. In the first phase, data were collected using a questionnaire from the households who were affected due to the land acquisition for Southern Expressway and Extension of Southern Expressway. The survey was conducted from 20th May to 17th June 2017. Altogether 86 affected households were selected and interviews who were resettled in Matara and Colombo districts. In the second phase, quantitative data was collected from secondary data sources such as databases available at Government Institutions, published books, journals, and newspaper, etc. Attitudes of the affected households depend on their expectations. If the expectations are fulfilled as they wish, affected people are satisfied with what they received. Almost all the affected households are concerned about the amount of compensation. Because they should find new land to re-build their residence/housing unit or continue livelihoods or bear dedicatory assets. In the selected sample of the present study, 27% of the affected households expressed their satisfaction regarding the amount of compensation. Around 43% of the affected households gave affirmative answers (i.e., yes), while 57% did not answer positively on impacts related to developing of social infrastructures. Further to that, nearly 50% of the affected households had a satisfied attitude on the development of transportation facilities within their new settlements. Around 33% of the affected households had a positive attitude on improving the quality of living, especially among those who were interviewed in the Colombo district. This is due to around 28% of affected households did not face the risk of flooding twice a year after resettlement. Remaining 5% of the affected households were squatters who received 10 perch land by the government. These may create a positive attitude in the minds of the affected households on improving the quality of living when they were adapting to the new location. Nearly, 72% of the affected households, loss of relatives, neighbours and/or friends were the most cited negative social impacts of the project. The opinions of the people were significant and they mentioned that the social relationship among relatives, neighbours, and friends who were isolated. When adapting to the new location, the difficulties that they experienced due to isolation has been one of the factors which caused negative or positive attitudes in the minds of people. v Around 80% of affected households were affected by property loss, such as the acquisition of residential and commercial buildings, shops, and stores. Wells, gates, part of roofs and parapet walls were peripherals that were lost together with the buildings. When the affected households are pushed away, they have to build their life from scratch when adapting to another location than the original place. The living standard and living quality of the affected households were deteriorated due to project activities. Most obviously, the amount of compensation may be insufficient to fulfill their expected requirements. Therefore, the projects should pay particular attention to people with vulnerable conditions (21% woman-headed families) when monitoring and evaluating their situation for their living pattern and income restoration. The government policies are geared to pay adequate compensation regarding money and other provisions for landowners to be able to meet their resettlement requirements based on the criteria given. However, most of the projects have adopted their compensation methods based on the market value. The market value is not sufficient to rebuild their standard of living to a level that was there before the acquisition. Therefore, when valuing the properties of the affected people, replacement cost is the most appropriate one.
item: Thesis-Abstract
Attitudes of site personnel towards waste management of building construction projects in Sri Lanka
Jayaweerarathna, JPKN; Manatunge, JMA
Waste management is a very widely known subject and it has served with many aspects of research areas already carried out to avoid waste in construction industry. But the problem still remains as this is very severe problem to the construction industry in terms of cost and time involvement to the waste reduction efforts and the cost of wasted materials. Although the designers, planners and managers trying to develop various means of waste reduction efforts, finally the people who are actually engaged with the work have more influence towards the outcomes of waste management. Therefore the examination of their attitudes regarding this concept is worthwhile to the successfulness of this effort. In Sri Lanka it is hard to find any widely published research that, has addressed attitudes and behavioural factors of site personnel towards waste management of construction industry. Since the construction is a highly labour intensive trade of work, the attitudes and behaviours of individuals involved in the construction work influence its growth and performance. This research intends to provide insights of what attitudes and behaviours have the more significance towards waste management of building construction industry in Sri Lanka. Further the individuals who ,are actually work at construction sites or the operatives of the construction work were selected for this research, since they are the more influential cluster of the construction works towards waste management. The ultimate intention of this research is to find out the important attitudes of site personnel towards waste management in Sri Lankan Building construction industry to overcome the negative attitudes for a successful project waste management
item: Article-Abstract
Control of algal blooms in reservoirs with a curtain: a numerical analysis
Asaeda, T; Pham, HS; Priyantha, DGN; Manatunge, JMA; Hocking, GC
Two vertical curtains, having depths to cover the epilimnion thickness, were installed across the Terauchi Dam Reservoir in the western island of Japan to curtail the nutrient supply from nutrient-rich inflows to the downstream epilimnion of the reservoir. The withdrawal level was also regulated to keep the downstream epilimnion away from the nutrient supply. This method markedly reduced algal blooming in the reservoir downstream of the curtains during spring and summer. The physical and biological processes in the reservoir ecosystem were analysed using the 2-D reservoir model DYRESM and chemical and biological submodels, to predict the water quality and algal species composition in the reservoir. The horizontal variability was maintained in the model by dividing the horizontal layer into parcels. Temperature, chlorophyll-a, soluble phosphorus, nitrate, ammonium, dissolved oxygen, biochemical oxygen demand, internal nitrogen, internal phosphorus were considered as state variables in the model. The simulated results revealed the mechanism of how algal blooming is reduced, during early spring high algal concentrations consume large amounts of nutrients, which reduces the nutrient supply to the downstream zone of the reservoir, whereas during late spring and summer, nutrient dispersion from the upstream epilimnion to the downstream epilimnion is curtailed by the curtains, markedly reducing algal blooming in the downstream zone.
item: Article-Abstract
Dealing with algal toxins and dissolved organics in drinking water
Ratnayake, N; Manatunge, JMA; Hapuarachchi, DP
Several types of cyanotoxins found in surface water bodies are recognized as having human health effects, whereas taste and odor affect the palatability of water and give rise to public complaints. Conventional water treatment unit operations may be effective in removing the cyanobacteria cells, but cyanotoxins and dissolved organics are not targeted for removal by them. Special treatment units need to be introduced to deal with these substances and attention paid to the process design as many operational issues may be encountered. We used a water supply project in the Eastern Province of Sri Lanka as a case study to investigate the performance of unit operations in water reatment plants for which the source is shallow surface water sources with high inflows of nutrients. The present case study was designed to evaluate the efficacy of prechlorination, activated carbon adsorption, dissolved air flotation (DAF), filtration and disinfection in removal of cyanotoxins, and taste and odor causing dissolved organic substances from the source water. Raw water quality was evaluated using algal concentration, algal toxin concentration, and chemical oxygen demand. To evaluate the efficacy of treatment operations, the sequence of initial unit operation was changed on each day as with prechlorination and with powdered activated carbon (PAC), with prechlorination and without PAC, without prechlorination and with PAC, and without prechlorination and without PAC. In addition, laboratory analysis was done to obtain adsorption isotherms using three types of different PAC. The primary findings of our study were that PAC was effective in removal of Microcystin and chemical oxygen demand (COD) but needs to be optimized by providing sufficient contact time, and prechlorination does not improve the performance, whereas postchlorination is effective in removing any traces of Microcystin left after PAC. 001: 10.10611 (ASCE)HZ.21S3-SS1S.0000114. © 2012 American Society of Civil Engineers.
item: Article-Abstract
Effect of inlet morphometry changes on natural sensitivity and flushing time of the Koggala lagoon, Sri Lanka
Gunaratne, GL; Tanaka, N; Amarasekara, P; Priyadarshana, T; Manatunge, JMA
The changes of natural sensitivity in terms of lagoon morphometry, particularly the inlet morphometry and flushing properties of the Koggala lagoon, Sri Lanka, are presented in this paper. The morphometric assessment is based on analysis and consideration of morphometric characteristics for three scenarios of the lagoon, namely: (I) before the construction of the old groyne system or time period before 1996 (Koggala Scenario I-KS I); (2) existing situation or time period after 2007 (Koggala Scenario 2-KS2); and (3) future scenario with respect to proposed groyne interventions for the mouth width of 20 m, as proposed by Gunaratne et al. (J Environ Sci 22(6):813-819, 2010) (Koggala Scenario 3-KS3). The morphometric assessment provides a simple means of defining natural sensitivity or vulnerability of individual scenarios of Koggala lagoon to external loads and anthropogenic activities. We found that KS I and KS3 scenarios are relatively more sensitive than KS2, whereas KSI has the highest natural sensitivity, and KS2 has the lowest natural sensitivity or the most robust conditions. In quantifying the tidal flushing of Koggala lagoon, the concept ofThe changes of natural sensitivity in terms of lagoon morphometry, particularly the inlet morphometry and flushing properties of the Koggala lagoon, Sri Lanka, are presented in this paper. The morphometric assessment is based on analysis and consideration of morphometric characteristics for three scenarios of the lagoon, namely: (I) before the construction of the old groyne system or time period before 1996 (Koggala Scenario I-KS I); (2) existing situation or time period after 2007 (Koggala Scenario 2-KS2); and (3) future scenario with respect to proposed groyne interventions for the mouth width of 20 m, as proposed by Gunaratne et al. (J Environ Sci 22(6):813-819, 2010) (Koggala Scenario 3-KS3). The morphometric assessment provides a simple means of defining natural sensitivity or vulnerability of individual scenarios of Koggala lagoon to external loads and anthropogenic activities. We found that KS I and KS3 scenarios are relatively more sensitive than KS2, whereas KSI has the highest natural sensitivity, and KS2 has the lowest natural sensitivity or the most robust conditions. In quantifying the tidal flushing of Koggala lagoon, the concept of The changes of natural sensitivity in terms of lagoon morphometry, particularly the inlet morphometry and flushing properties of the Koggala lagoon, Sri Lanka, are presented in this paper. The morphometric assessment is based on analysis and consideration of morphometric characteristics for three scenarios of the lagoon, namely: (I) before the construction of the old groyne system or time period before 1996 (Koggala Scenario I-KS I); (2) existing situation or time period after 2007 (Koggala Scenario 2-KS2); and (3) future scenario with respect to proposed groyne interventions for the mouth width of 20 m, as proposed by Gunaratne et al. (J Environ Sci 22(6):813-819, 2010) (Koggala Scenario 3-KS3). The morphometric assessment provides a simple means of defining natural sensitivity or vulnerability of individual scenarios of Koggala lagoon to external loads and anthropogenic activities. We found that KS I and KS3 scenarios are relatively more sensitive than KS2, whereas KSI has the highest natural sensitivity, and KS2 has the lowest natural sensitivity or the most robust conditions. In quantifying the tidal flushing of Koggala lagoon, the concept of flushing half-life (Tso% h) was adapted as the optimum measure of flushing time. Flushing half-life was calculated for KS2 and KS3 scenarios. The flushing half-life ranges from 9 to 37 h (1.5 days) for KS2 and from 12 to 72 h (3 days) for KS3. Flushing half-life suggests that the exchange rate between the lagoon and the ocean is controlled by the balance between fresh water inflow and the seawater inflow. Applications of the morphometric classification and flushing half-life presented in this article can be used to help guide management and policy-making decisions for the coastal environment of Koggala lagoon and other coastal water bodies of Sri Lanka.
item: Article-Abstract
Evaluation of Performance of a Sludge Blanket Clarifier
Illangasinghe, WK; Ratnayake, N; Manatunge, JMA; Jayasuriya, N
Maintaining a stable blanket is essential for operation of a Sludge Blanket Clarifier. However, operators have to use their judgement to assess the stability and performance of the blanket, due to lack of information about their performance indicators. Main objective of this study was to observe the effect of the coagulant dose on the stability and performance of the sludge blanket. The characteristic ‘Sludge Cohesion Co-efficient’ (SCC) defined as the upward velocity needed to expand the sludge blanket to double its initial volume was selected as a suitable indicator of the stability of the sludge blanket. Tests were done on 33 sludge samples prepared with a Bentonite suspension and PACL as the coagulant. Raw water turbidity, PACL dose, supernatant turbidity and SCC of each sample were recorded. Results showed that there is an optimum coagulant dose that produces the highest SCC, which varies with raw water turbidity. With increasing raw water turbidity, optimum coagulant dose for SCC is the same as the Jar Test optimum, up to approximately 300NTU. Thereafter the optimum dosage for SCC is lower than the Jar Test optimum. A correlation can be established between the Jar Test and SCC optimum PACL doses.
item: Thesis-Full-text
Fate and transport of glyphosate and degradation byproducts: implications for remediation at ckdu endemic areas in sri lanka
Gunarathna, AASU; Manatunge, JMA; Gunawardana, WB
Glyphosate, which is commercially available as Roundup®, was the widely used herbicide in Sri Lanka until 2015 and is suspected to be one of the causal factors for Chronic Kidney Disease of unknown etiology (CKDu). This research, therefore, focuses on investigation of glyphosate and Aminomethylphosphonic acid (AMPA), the major degradation product of glyphosate, immobilization in top soil and subsequent mobilization to water and their effective and efficient removal. A field study and a series of mesocosm studies were performed to investigate the immobilization of glyphosate in the top soil and the mobilization of glyphosate and AMPA to water. Further, a long term batch experimental study was carried out to study the degradation of glyphosate in water in the absence and presence of hardness, for 240 days. Finally, the applicability of Ozonation process for glyphosate removal from water was studied using batch experiments. Glyphosate and AMPA were analyzed using LC/MS and GC/MS. It was evident that glyphosate persistence in the environment was high, especially due to the sorption of glyphosate to soil. Mobilization of glyphosate to water was minimal and it was catalyzed by the event of first precipitation after the application of glyphosate and application of Triple Super Phosphate (TSP) to the soil. Furthermore, glyphosate degradation was hindered and its persistence was increased due to the presence of hardness in water and surfactants in commercial grade glyphosate. Ozonation process rapidly degraded the glyphosate present in water both in the absence and presence of hardness to levels less than 700 µg/L which is the USEPA Maximum Contaminant Level for drinking water. In conclusion, this study provides the insight that the dominant mechanism of glyphosate in the environment is adsorption of glyphosate to the topsoil and mobilization to water is minimal. Further, Ozonation is an effective and efficient method to remove glyphosate in water in CKDu prevalent areas despite the presence of hardness and surfactants.
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Impact of rubble mound groyne structural interventions in restoration of Koggala lagoon, Sri Lanka; numerical modelling approach
Gunaratne, LG; Tanaka, N; Amarasekara, GP; Priyadarshana, T; Manatunge, JMA
Physical processes of the lagoon are influenced by structural interventions. Understanding the complex reality of physical processes sometimes difficult with field observations thus a model provides a simplified abstract view. Two dimensional hydrodynamic model is used to describe, restoration efforts to Koggala lagoon, a combined freshwater and estuarine complex of rich ecosystem on the southern coast of Sri Lanka. The lagoon mouth was naturally closed by a sand bar which controlled the seawater intrusion. Due to large-scale sand removal at lagoon mouth, formation of the sandbar shifted towards the lagoon. After the removal of natural sand barrier, rubble mound groyne structures were built to avoid sand deposition in the lagoon and to protect the highway bridge from the sea wave attack. Construction of the groyne resulted in the lagoon mouth being permanently open which in turn led to many environmental problems with saline intrusion. The aim of this study is to evaluate the current situation of the lagoon and propose alternative structural interventions for minimization of seawater intrusion and subsequently improve lagoon ecosystem. Hydrological parameters were investigated and mathematical models for hydrodynamic behavior of the lagoon were applied in order to describe the lagoon physical processes and flow characteristics. Existing rubble mound structures were redesigned in order to minimize the seawater intrusion. Numerical simulations were carried out for two different mouth widths (40 m and 20 m) with appropriate structural interventions. Existing salting factor for the lagoon is 0.68 and numerical simulation results showed salting factor for 40 m and 20 m openings are 0.61 and 0.54 respectively. This shows the mouth width can be reduced up to 20 m in order to obtain a slating factor close to 0.5, which indicates the predominant influence of fresh water which in turn leads lagoon to a fresh water ecosystem.
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Improving the performance of unit operations of water treatment plants where irrigation tanks are used as the source
Hapuarachchi, HADP; Ratnayake, N; Manatunge, JMA
Worldwide, increasing demand for drinking water to cater to the increasing urban population has led to the use of lakes and reservoirs with unprotected catchments as sources of public water supplies. These water bodies receive drainage water containing large amount of nutrients, mostly from intensive agricultural practices, resulting in algal blooms, which have become a growing environmental problem. Conventional treatment used for surface water may not always produce satisfactory quality water in these situations. In addition, the increasing occurrence of toxins produced by cyanobacteria in such water bodies has become an important public health issue. “Eastern Coastal Towns of Ampara District (ECTAD) Water Supply Project”, where the raw water source is an irrigation tank with high inflows of nutrients was used as a case study. Coagulation, flocculation, dissolved air floatation (DAF), rapid gravity filtration and disinfection are the unit operations that have been designed and constructed, while Pre-chlorination and Powdered Activated Carbon (PAC) adsorption are also currently used in this water treatment plant, which have been introduced to treat taste an odour problems encountered after commissioning the plant. The case study was carried out to evaluate the efficacy of pre-chlorination, activated carbon adsorption, Dissolved Air Flotation, filtration and disinfection in removal of cyanotoxins, taste and odor causing dissolved organic substances and colour causing substances such as iron and manganese from the source water, in order to provide satisfactory potable water. The samples were collected at the source, and the inlet and outlets of each unit operations. Samples were collected in the morning and afternoon to capture the diurnal variations in quality. It was decided to carry out four trials during two dry seasons and two wet seasons since the raw water quality reports showed that the quality was significantly varied seasonally. It was found from this study that raw water in Konduwatuwana Tank has high cyanobacteria content and Microcystis aeruginosa is the predominant specie. Main findings of our study were that PAC was effective in removal of Microcystin as well as dissolved organic substances, but needs to be optimized by providing sufficient contact time, and pre-chlorination does not improve the performance. The results of this study were generalized using water quality data of irrigation tanks in Gal oya cascade system, several irrigation tanks in the Kala Oya Basin and another few selected irrigation tanks in the North Central Province (not in the Kala Oya Basin).
item: Thesis-Abstract
Investigation of zinc removal capacities of different sorbent materials to be used in constructed wetlands
Witharana, WAU; Manatunge, JMA
There is an increasing demand for better water quality in order to safeguard public health, the social security and accomplish environmental integrity. It has been found over the past couple of years that health hazards associated with heavy metal have been on the rise, particularly the chronic health problems due to the ingestion or consumption of even low doses of heavy metal-rich waters. Accumulation of such metals is reported mainly due to non-treatment or poor treatment of industrial wastewaters. Lack of tertiary treatment may have attributed to this growing problem and hence the environmental pollution. Constructed wetlands have therefore received great attention in the recent past as a tertiary treatment method or a polishing technique due to low construction and operation costs, minimum maintenance and also as an environmental friendly system. However, finding a low-cost sorbent material which can be used as an alternative to activated carbon has been a problem for decades in wastewater treatment industry, especially in developing countries. Therefore, the present study focuses on the applicability of low-cost sorbent materials that can be used in constructed wetlands as a filter medium. The focus was on four sorbent materials: tile, brick, saw dust and rice husks, which were selected based on their local availability. Laboratory-scale experiments were performed to investigate their maximum adsorption capacity and removal efficiency with a synthetic Zinc solution. The Results revealed that tile material has the highest adsorption capacity (47.6 mg/g) and removal efficiency, (98%) while brick (37.0 mg/g, 86%), sawdust (20.4 mg/g, 80%) and rice husks (15.8 mg/g, 64%) have relatively low adsorption capacities and removal efficiencies, respectively. The percentage removal of Zinc by all the four sorbent materials increased with an increase of contact time. The kinetics of adsorption were relatively fast for all tested low-cost materials. The equilibrium data were correlated with both Langmuir and Freundlich isotherms. Adsorption isotherms are well described by Langmuir isotherms. The separation factor of equilibrium (RL) indicates favourable isotherms (0< RL >1) for all tested materials. Characterization of four sorbent materials was done by undertaking SEM, XRD and FTIR analyses. It can be concluded from the results that, the low-cost sorbent materials that were tested can be an attractive substitute for activated carbon in removing Zn from industrial wastewaters. Keywords: adsorption isotherms, constructed wetlands, sorbent material, Zinc
item: Conference-Abstract
Investigation of Zinc removal capacities of different sorbent materials to be used in constructed wetlands
Witharana, A; Jayaweera, M; Manatunge, JMA
It has been found over the past couple of years that health hazards associated with heavy metals have been on the rise, particularly the chronic diseases. Lack of tertiary treatment of wastewater may have contributed to this emergent problem, mainly due to the high costs involved in the removal of heavy metals. Constructed wetlands have therefore received great attention as a tertiary treatment method or a polishing technique of wastewater due to its low construction and operation costs. However, finding a low-cost sorbent material to be used as the wetland filter material, which can be used as an alternative to activated carbon, has been a problem for decades. Therefore, the present study focuses on applicability of low-cost sorbent materials: viz., clay tile, brick, saw dust and rice husks, as filter mediums. Laboratory-scale experiments were performed with a synthetic Zinc solution. Results revealed that clay tile material has the highest adsorption capacity (47.6 mg/g) and removal efficiency, (98%), while brick (37.0 mg/g, 86%), sawdust (20.4 mg/g, 80%) and rice husks (15.8 mg/g, 64%) have relatively low adsorption capacities and removal efficiencies, respectively. The separation factor of equilibrium (RL) indicates favourable isotherms (0< RL<1) for all tested sorbent materials. Among the studied materials clay tile, brick and rice husks are good adsorbents for Zinc (n>2) while sawdust is a moderately difficult material for adsorption of Zinc (n <2).
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Mechanisms of Manganese Removal from Wastewaters in Constructed Wetlands Comprising Water Hyacinth (Eichhomnia crassipes (Mart.) Solms) Grown under Different Nutrient Conditions
Kularatne, RKA; Kasturiarachchi, JC; Manatunge, JMA; Wijeykoon, SLJ
This article discusses key mechanisms involved in removing 1 mg/L Mn from synthetic wastewaters in constructed wetlands comprising water hyacinth (Eichhornia crassipes (Mart.) Solms) grown under different nutrient levels of 1-fold (28 mg/L and 7.7 mg/L of total nitrogen and total phosphorus, respectively), 2-fold, 1/4-fold, and 1/8-fold. A mass balance was carried out to evaluate the key removal mechanisms. Phytoremediation mainly due to phytoextraction substantially contributed to manganese removal. However, chemical precipitation was absent, suggesting that manganese has a higher solubility in the given average pH (6.2 to 7.1) conditions in constructed wetlands. Bacterial mediated immobilization mechanisms also did not contribute to manganese removal. Sediments constituted a minor sink to manganese, implying that manganese has a poor adsorption potential. Constructed wetlands comprising water hyacinth are effective at removing manganese from wastewaters despite the fact that the plants are grown under higher or lower nutrient conditions. Water Environ. Res., 81, 165 (2009).
item: Thesis-Full-text
Phthalic acid esters in urban watercourses of Colombo and their treatment
(2019) Danushika, UAAG; Jayaweera, MW; Bandara, NJGJ; Manatunge, JMA
Urbanization of many cities with industrial, commercial, and residential areas in the world takes place at an unprecedented scale. Di-2 Ethylhexyl Phthalate (DEHP) is commonly used as a plasticizer in a number of industries which has become a precursor to cause DEHP contamination of watercourses through untreated or partially treated industrial wastewater effluents. Such contamination may result in bioaccumulation and bio-concentration in biota, so that it will adversely affect humans through the food chains. The presence of six PAEs (dimethyl phthalate (DMP), diethyl phthalate (DEP), di (n-butyl) phthalate (DBP), benzyl butyl phthalate (BBP), bis(2-ethylhexyl) phthalate (DEHP), and di(n-octyl) phthalate (DnOP)) in 22 shallow urban watercourses in Colombo and suburbs of Sri Lanka was investigated and the effect on fish community was analyzed. EPA 8061A method was used in analyzing PAE concentrations in samples and Gas Chromatography / Mass Spectrometer was used. Titanium dioxide (TiCb) and Modified Coal-derived Fly Ash (MCFA) were successfully synthesized and characterized using Fourier-Transform Infrared Spectroscopy, Environmental Scanning Electron Microscopy, and X-ray diffraction. Effectiveness and efficiency of TiC>2 and MCFA in the removal of DEHP from wastewaters was identified. According to the results obtained, the average concentrations of DEP, DBP, BBP, and DEHP in all watercourses varied between 2.5-265.0, 1.0-32.0, 61-108, and 12— 165 pg/L, respectively. DMP and DnOP values were below the limits of quantification (DMP-0.5 pg/L, DnOP-l.O pg/L) for all watercourses. DEHP was the most abundant PAE in many watercourses. The significant factors affecting the ubiquitous presence of PAEs in watercourses are the inherent properties of each PAEs, the presence of industrial and household products with great potential for the migration of PAEs in the sub-catchments, and the quality of receiving water. The contamination levels of PAEs in most of the watercourses are alarmingly high, as evidenced by higher concentrations of DEHP and DBP than those of Canadian permissible levels for the protection of aquatic life (16 and 19 pg/L). iii Isolated lakes which are not adjoining to urban industries, showed depleted adverse effects, most of the urban lakes were observed a significant potential for adverse effects on fish. Thus, the ecological risk of PAEs in urban watercourses in Sri Lankan environments should be considered. TiC>2 nanoparticles were used to remove DEHP through photocatalysis. The photocatalysis with TiC>2 for the destruction of DEHP was found to be a promising technique in removing DEHP from industrial wastewaters. The most economical dosage of TiC>2 would be one gram and it needs to be photocatalysed for a period greater than 44 minutes for complying with the permissible level stipulated for DEHP (16 pg/L) for the protection of aquatic life. The cost of the photocatalysis with Ti02 was around Rs.120 and the cost could be further reduced when the material (TiC>2) is reused for subsequent usage. Even TiC>2 was reused for five times, inherent properties for photocatalysis were not changed. An initial level of 171 pg/L of DEHP was successfully removed with 98% efficiency by three grams of MCFA dosage and consequently, regenerated with NaOH twice for the effective use. The maximum monolayer adsorption capacity of MCFA was 63.6 pg/g of DEHP. MCFA is a potential candidate for the effective removal of DEHP from industrial wastewaters as its raw materials are readily available.
item: Thesis-Abstract
Removal of chromium in aqueous solutions using powdered activated carbon treated with humic acid
Sooriyabandara, BH; Weerasooriya, R; Manatunge, JMA
Because of its toxicity, Chromium (VI) causes water pollution and threatens to the environment. Its solubility in nature is strongly inf1uenced by adsorption process. Relatively few studies have focused on adsorption properties onto the Powdered Activated Carbon (PAC). In this work. the PAC and humic acid treated PAC adsorption properties were compared.This study proposed humic acid treated Powdered Activated Carbon as a low cost adsorbent for removal of Chromium from aqueous solution. Adsorption of Cr (VI) by PAC was conducted using batch tests. The int1uence of pH, contact time, initial Chromium concentration on removal of Chromium (VI) was investigated. This test was also repeated with humic acid treated PAC. The optimum initial pH for maximum adsorption of Cr (VI) from aqueous solution was found to be 4.0. The removal efficiency was found to be correlated with the initial Cr (VI) concentration, ionic strength, as well as the contact time between the Chromium (VI) and the adsorbent. For humic acids treated PAC, the optimum adsorption also was found at 4.0. Therefore acidic medium is favorable to the Chromium removal.According to the experimental data obtained from this study, the percentage metal removal increased with increasing PAC dosage at the same initial metal concentration. After using humic acid treated PAC increased the metal removal percentage with same adsorbent dosage.When the effluent is in acidic medium, the PAC is more suitable as the adsorbent while the humic acid treated PAC is more suitable for basic effluent.
item: Conference-Full-text
Water balance and renewal time of rekawa lagoon, Sri Lanka; a restorative approach
(2013-11-19) Gunaratne, GL; Priyadarshana, T; Manatunge, JMA; Tanaka, N; Yasuda, S
Rekawa Lagoon is a chocked and shallow coastal water body located in the southern coast of Sri Lanka. It is relatively unusual in that the major freshwater input, Kirama-oya river connects through the constricted channel much closer to the inlet at seaward end. A causeway was constructed, around 700 m from the lagoon inlet to the inland, across the constricted channel with an effort to link a secluded Kapuhenwala village with the rest of the area which in turn greatly reduced the volume and speed of water entering and leaving the lagoon system. Construction of the causeway led to many environmental problems with poor flushing efficiency and hampering to and fro movement of the prawns in the lagoon. The aim of this study was to evaluate the present situation and propose alternative management scenarios for improvement of water flow and lagoon ecosystem. The implications of different development stages of the causeway were discussed in terms of field measurements supported by modeling to describe the water balance and the water renewal time. The alternative of modifying the existing causeway was proposed to increase the free water flow at the inlet that favors recruitment of juvenile shrimp species.
item: Conference-Full-text
Zinc adsorption by lowcost sorbent materials: clay tile, Brick, sawdust and rice husk
(2013-11-19) Witharana, A; Jayaweera, M; Manatunge, JMA
It has been found over the past couple of years rapid growth of population, industrialization and urbanization has first and foremost contributed to the severe water pollution in both surface and ground water. The health hazards associated with heavy metals have been on the rise, particularly the chronic diseases. Lack of tertiary treatment of wastewater may have contributed to this emergent problem, adsorption process is considered as the best available water treatment method and activated carbon has proven to be the best sorbent material which can be used in removing wide variety of pollutants. However, usage of this activated carbon becomes restrict due to its high cost and regeneration cost. Therefore, the present study focuses on low-cost sorbent materials: viz., clay tile, brick, sawdust and rice husks. Laboratory-scale experiments were performed with a synthetic Zinc solution. Results revealed that clay tile material has the highest adsorption capacity (47.6 mg/g) and removal efficiency, (98%), while brick (37.0 mg/g, 86%), sawdust (20.4 mg/g, 80%) and rice husks (15.8 mg/g, 64%) have relatively low adsorption capacities and removal efficiencies, respectively. The separation factor of equilibrium (RL) indicates favourable isotherms (0< RL<1) for all tested sorbent materials. Among the studied materials clay tile, brick and rice husks are good adsorbent for Zinc (n>2) while sawdust is a moderately difficult material for adsorption of Zinc (n <2).