Browsing by Author "Ariyadasa, TU"

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item: Conference-Full-text
Assessment of the potential of co2 sequestration from cement flue gas using locally isolated microalgae
(IEEE, 2020-07) Wijayasekera, SCN; Cooray, BY; Premaratne, M; Ariyadasa, TU; Weeraddana, C; Edussooriya, CUS; Abeysooriya, RP
Carbon dioxide (CO2) emissions are rapidly escalating due to industrialization and urbanization worldwide, resulting in many long-term adverse effects such as global warming. Industrial flue gases which contain 3-30% CO2 (v/v) are a major constituent of global CO2 emissions. Employing microalgae for biological fixation of CO2 from flue gas is a prospective strategy for the reduction of CO2 emissions since microalgae have the capability of utilizing inorganic carbon to rapidly generate biomass via photosynthesis. In the current study, the locally isolated microalgal strains Chlorella sp. and Desmodesmus sp. were employed to assess the CO2 sequestration potential from simulated flue gas, comparable to the emissions from the cement industry. The gross calorific values (GCVs) were determined to evaluate the potential of employing microalgal biomass for co-firing processes. Desmodesmus sp. showed the highest CO2 tolerance, as it exhibited a biomass productivity and CO2 fixation rate of 1.17 g L-1 and 0.26 g L-1 day-1 respectively under undiluted flue gas (15.50% CO2). However, the GCVs of Chlorella sp. biomass were higher than Desmodesmus sp. biomass under all flue gas dilutions. Nonetheless, the GCVs of Desmodesmus sp. were in the range of 23.277-24.202 MJ/kg, comparable to biomass typically used in co-firing applications.
item: Article-Full-text
Astaxanthin accumulation in the green microalga Haematococcus pluvialis: Effect of initial phosphate concentration and stepwise/continuous light stress
(2020) Liyanaarachchi, VC; Nishshanka, GKH; Premaratne, RGMM; Ariyadasa, TU; Nimarshana, PHV; Malik, A
Nutrient composition and light stress significantly affect the productivity of astaxanthin in Haemotococcus pluvialis. Hence, the present study aimed to investigate the effect of initial phosphate concentration and two distinct light regimes on astaxanthin accumulation in H. pluvialis. In the green stage, microalgae were cultivated in different initial phosphate concentrations under 2000 lx and a 12:12 h photoperiod. To initiate astaxanthin accumulation, an increased light intensity of 5000 lx was provided using two methods; (i) stepwise light stress, where a 12:12 h photoperiod was provided for 14 days, followed by 14 days of continuous illumination, and (ii) continuous illumination for 28 days. Phosphate limitation and continuous light stress were favourable to enhance cellular astaxanthin accumulation, which reached 7% by weight. The highest astaxanthin concentration of 27.0 ± 1.9 mg/L and lowest specific light energy consumption of 32.9 ± 2.3 kW h/g astaxanthin were reported in cultures grown in 41 mg/L phosphate under continuous light stress.
item: Conference-Full-text
Biodegradation of natural rubber latex by a novel bacterial species isolated from soil
(IEEE, 2016-05) Hapuarachchi, SNS; Kariyapper, SR; Gunawardana, MBDMD; Egodage, S; Ariyadasa, TU; Jayasekara, AGBP; Bandara, HMND; Amarasinghe, YWR
A natural rubber degrading bacteria Paenibacillus lautus was isolated from soil samples of a rubber plantation in Sri Lanka. The strain was able to decompose natural rubber latex by adhesively growing on its surface using NR latex as the sole carbon source. The staining test performed using Schiff's reagent confirmed the degradation of NR latex. The Fourier Transform Infrared Spectroscopy further verified the result by showing the reduction of C=C double bonds and the presence of carboxylic acids and ketones in the polymer chain. The surface erosion images of the latex overlay surfaces obtained from scanning electron microscopy also validated the degradation process.
item: Article-Full-text
Biodegradation of reactive yellow EXF dye: optimization of physiochemical parameters and analysis of degradation products
(Springer Science+Business Media, 2022) Madhushika, HG; Ariyadasa, TU; Gunawardena, SHP
Biological decolourization of textile dyes is getting more attention as a cost-effective and environmentally friendly technique. Bacterial strain Proteus mirabilis has been identified as an effective decolourizer of Reactive Yellow EXF dye. Laboratory-scale experiments were carried out to study effects of physicochemical parameters (pH, temperature, concentration of dye, agitation and sources of carbon) for the maximum decolourization, and the structural changes caused in the dye due to biological treatments were investigated. Maximum decolourization of the dye was observed at 40 °C and pH 7–8. The highest percentage colour removal of more than 95% at 48 h of incubation was observed in the medium containing 5 g/l yeast extract as the carbon source. Further, this bacterial strain could tolerate high concentrations of dye and decolourize dye solutions of 500 mg/l. Ultraviolet–visible spectra and high-performance liquid chromatography analyses clearly indicated changes in dye structures due to treatment. Compounds formed due to degradation of the dye under static and shaking conditions were analysed using gas chromatography–mass spectrophotometry and found to be non-toxic and benign.
item: Article-Full-text
Cultivation of microalgae in palm oil mill effluent (POME) for astaxanthin production and simultaneous phycoremediation
(Elsevier, 2021) Fernando, JSR; Premaratne, M; Dinalankara, DMSD; Perera, GLNJ; Ariyadasa, TU
Haematococcus pluvialis and Chromochloris zofingiensis are freshwater microalgae exploited to produce the high-value carotenoid, astaxanthin. Nonetheless, a copious amount of freshwater is consumed for microalgae cultivation, thereby raising concerns regarding sustainable astaxanthin production. Characterization of palm oil mill effluent (POME) obtained from a commercial facility in southern Sri Lanka revealed high concentrations of total nitrogen (TN), total phosphorous (TP) and low concentrations of heavy metals, thus showcasing the potential of POME as an alternative growth media for astaxanthin production. Hence, H. pluvialis and C. zofingiensis were cultivated in 2.5%, 5.0% and 7.5% POME with the aim of producing astaxanthin, reducing freshwater consumption, and simultaneous phycoremediation. H. pluvialis exhibited better adaptability to higher POME concentrations, with its maximum astaxanthin yield (22.43 mg/L) achieved in 7.5% POME, whilst reducing specific freshwater consumption for astaxanthin production by 43%. However, only moderate performance in phycoremediation was achieved, with removal of 50.9% chemical oxygen demand (COD), 49.3% total nitrogen and 69.4% total phosphorous at rates of 3.95 mg/L/d, 0.50 mg/L/d and 0.11 mg/L/d respectively. The heavy metal content in biomass was within permissible limits. Characterization of astaxanthin-extracted residual biomass of H. pluvialis revealed possible applications as protein-rich animal feed or feedstock for biofuel production. Results indicated that POME generated in Sri Lankan palm oil mills has the potential to be utilized for large scale production of microalgal astaxanthin. Nevertheless, pilot-scale experiments, product toxicology evaluation and techno-economic feasibility studies are required prior to implementation of large-scale POME-integrated astaxanthin production facilities.
item: Article-Full-text
Cyanobacteria pigment production in wastewater treated for heavy metal removal
(Elsevier, 2023-11) Thevarajah, B; Nishshanka, GKSH; Premaratne, M; Wasath, WAJ; Nimarshana, PHV; Malik, A; Ariyadasa, TU
Cyanobacterial pigments have an evolving market demand as natural colorants with numerous health benefits and diversified applications. Nevertheless, scaling up cyanobacterial pigment production to meet the market demand is economically unsustainable due to the high upstream processing costs, notably associated with the supply of nutrients during cyanobacteria cultivation. Thus, utilization of wastewater as alternative nutrient sources for cultivation is a potential method to enhance the economic viability and sustainability of pigment production. In wastewater-integrated cyanobacteria cultivation, nutrients are assimilated to produce biomass simultaneous to bioremediation. Nonetheless, the toxic heavy metals present in wastewater may accumulate in cyanobacteria and adversely affect biomass valorization. Therefore, the use of suitable heavy metal removal techniques is essential prior to integration of wastewater with the upstream process of cyanobacterial pigment production in view of improving product safety. Accordingly, the current review discusses primary literature on pigment biosynthesis and heavy metal accumulation in cyanobacteria cultured in wastewater and details physicochemical, electrochemical, and biological treatment methods available for heavy metal removal from wastewater prior to cyanobacteria cultivation. The suitability of heavy metal removal methods is analyzed with respect to various technical and economic aspects, including selective heavy metal removal, minimizing nutrient loss, and incremental capital/operating costs. Moreover, future perspectives in the research domain are discussed, with emphasis on the requirement for techno-economic assessments, life cycle analysis, product safety assessment, and public perception. Thus, the current review comprehensively analyses strategies for heavy metal removal from wastewater prior to its integration with the upstream process of cyanobacterial pigment production.
item: Conference-Full-text
Decolourization of reactive red exf dye by isolated strain proteus mirabilis
(IEEE, 2018-05) Madhushika, HG; Ariyadasa, TU; Gunawardena, SHP; Chathuranga, D
Decolourization of textile dye containing effluent is a very difficult and challenging task textile industries have to face. Biological dye decolourization techniques can be effectively used in textile effluent treatments as an environmental friendly solution for the pollution created by coloured effluents. During the current study, Reactive Red EXF dye decolourization potential of isolated bacterial strain, Proteus mirabilis was studied. Dye decolourisation was most effective under static conditions and reached 94% decolourization after 72 hours of incubation. Optimum dye decolourization was observed at pH 7-7.5 range and at 40 oC temperature.
item: Thesis-Full-text
Decolourization of textile dyes and textile industry effluent in a fixed bed biofilm reactor using native microorganisms
(2021) Madhushika, HG; Gunawardena, SHP; Ariyadasa, TU
Textile and apparel industry produces huge quantities of wastewater with unfixed dyes, which generate colour and toxicity in discharged water, creating environmental pollution. Physical and chemical effluent decolourization techniques are widely used at present to remove colour in effluents in textile industries, however, they have several drawbacks and therefore not productive. Compared to physical and chemical methods, biological treatments have gained much attention globally as environmental-friendly and cost-effective techniques to decolourize textile industry effluent. Hence, in this work, decolourization potential of textile dyes by microbial strains, which were isolated from local-environment, and their applicability in industrial wastewater decolourization were investigated. Five bacterial strains, with dye decolourizing potential were isolated from an effluent treatment facility of a local textile industry and identified using 16S rRNA gene sequencing analysis. Ability of these strains to decolourize selected textile dyes as individual strains and in a bacterial consortium was investigated using free bacterial cells cultured in 250 ml Erlenmeyer flasks containing 100 ml of decolourization media. Out of the isolated bacteria, Proteus mirabilis showed the highest capability to decolourize all dyes and was able to decolourize 50 ppm dye solutions of Yellow EXF, Red EXF, Blue EXF, Black WNN and Rhodamine under static conditions at 35 °C. Colour removal of 96, 94, 83, 95 and 30% respectively was observed after 72 h of treatment when decolourization media was inoculated with 2% (v/v) of bacterial culture. The developed bacterial consortium composed of Proteus mirabilis, Morganella morganii and Enterobacter cloacae, decolourized more than 90% of all four reactive dyes and 36% of Rhodamine dye after 72 h of incubation. Furthermore, the developed bacterial consortium was able to decolourize more than 83% of the synthetic dye mixture and 60% of the textile industry effluent, respectively after 46 h and 138 h of incubation at 35 oC temperature under static condition. Effects of physico-chemical parameters (pH, temperature, concentration of dye, agitation and sources of carbon) for biological decolourization of dyes were studied in batch cultures with free cells. It was observed that dye decolourization was more effective under oxygen-limited, static conditions than shaking conditions and the maximum decolourization of dyes was observed at 40 oC and pH 7-8 in the media containing yeast extract as the carbon source. Dye decolourization was further investigated in a fixed bed biofilm reactor where the biofilm was composed with the developed bacterial consortium. Decolourization of the synthetic dye mixture was done with three different concentrations of yeast extract in the feed and more than 90% decolourization of the synthetic dye mixture was observed when the concentration was 2 and 1 g/l in batch operation of the reactor. However, even when the concentration was reduced to 0.25 g/l, 75% decolourization of synthetic dye mixture was achieved in both batch and continuous operation of the reactor. Results showed that dye decolourization was more effective with attached cells (bacterial consortium) in the reactor than with free cells (used in flasks). Stability of the dense microbial communities in biofilms and their ability to survive and degrade dyes at extreme conditions could be the reason for observed high colour removals in the decolourization studies conducted in the reactor. Structural changes occurred in dyes due to biological treatments were studied using ultraviolet-visible spectral and high-performance liquid chromatography analyses. Metabolites formed due to biological degradation were analyzed using gas chromatography-mass spectrophotometry and found to be non-toxic and benign. A maximum of 45% colour removal was observed when the diluted textile effluent was treated in the fixed bed biofilm reactor operated in continuous mode whereas 70% colour removal was achieved in 48 h with undiluted textile wastewater treated in batch mode. This shows the ability of the developed bacterial consortium to endure in highly complex and toxic environment in the fixed bed biofilm reactor and the potential application in textile industry wastewater treatment.
item: Conference-Full-text
Development of a novel preprocessing method for removal of chlorophyll from microalgae
(IEEE, 2020-07) Kulasinghe, YM; Ariyadasa, TU; Weeraddana, C; Edussooriya, CUS; Abeysooriya, RP
Microalgal lipid is a potential feedstock of bioenergy in recent years. Rapid growth rate and high lipid content in microalgae are foremost factors to compete with first and second-generation biofuels. However, high levels of chlorophyll in feedstock limit its large scale application. Chlorophyll makes oil more susceptible to photo-oxidation, decreases the storage stability, causes low-quality oil with a dull and dark color and decreases the transesterification efficiency and combustion efficiency of biodiesel. This study aimed to develop a novel preprocessing method (i) to identify the best solvent ratios (ii) temperature and (iii) reaction time for chlorophyll removal from the selected microalgae to synthesize high-quality biofuel. The species Mychonastes homospaera isolated from Beire Lake, Colombo, SriLanka was employed to study chlorophyll removal. The doubling time and the lipid accumulation in the isolated microalgae were 2.89 d and 58 % (w/w). According to the results the best solvent ratio (NaOH: ethanol), temperature and reaction time were reported as 7:3, 60 0C and 90 min respectively.
item: Article-Full-text
Effect of a dark-colored substrate on the production of phycocyanin by the cyanobacterium Phormidium sp
(Elsevier, 2023-07-15) Mastropetros, SG; Pispas, K; Zagklis, D; Tsigkou, K; Ali, SS; Ariyadasa, TU; Kornaros, M
As the biotechnological production of valuable compounds has recently gathered research interest, more and more photosynthetic microorganisms are being examined for the synthesis of proteins, fatty acids, pigments, and other biopolymers. In this work, a local isolate (lagoons of Western Greece), of the blue-green cyanobacterium Phormidium sp., was evaluated. Its cultures were considered to be promising for the recovery of the phycobiliprotein, called phycocyanin, even during mixotrophic growth. Interestingly, phycocyanin accumulation was favored by substrates with a low organic load. In order to minimize substrate cost, anaerobic digestion effluent was used as a nutrient and organic carbon source, replacing a synthetic medium containing glucose, to meet the cyanobacterium’s nutrient needs. The results from the cultures containing liquid digestate were surprising, as its addition at low concentrations not only allowed Phormidium sp. to grow but also enhanced the phycocyanin synthesis. The experiments that exhibited a notable phycocyanin production showed a final biomass concentration that barely exceeded 0.7 g L􀀀 1 regardless of the nature of the substrate. When Phormidium sp. was inoculated in a pure synthetic medium with 1 g L􀀀 1 of glucose, phycocyanin concentration approached 10 mg L􀀀 1, while it was measured being 1.75 times higher in the culture containing 10% v/v anaerobic effluent, due to greater cellular accumulation. The present work comes as evidence of the successful bioremediation of digestate accompanied by the production of a high added-value pigment, leading to the removal of organic carbon, total nitrogen, and phosphorous in percentages of 60%, 90%, and 40% respectively
item: Conference-Abstract
Effect of different pretreatment methods on lipid yield and biodiesel quality of Desmodesmus sp. isolated from Sri Lanka
Maduwanthi, C; Nuwanthika, C; Withanage, P; Sandani, WP; Ariyadasa, TU
The present study investigates the growth rate and the effect of different pretreatment methods on lipid yield and biodiesel quality produced from Desmodesmus sp. isolated from Beira Lake, Colombo, Sri Lanka. Desmodesmus sp. was cultivated using photobioreactors providing the optimum cultivation conditions and growth was determined by measuring the optical density and direct cell count of the culture. Four different physical cell disruption methods including manual grinding, autoclaving, microwaving and water bath heating were carried out using chlorophyll removed microalgae biomass to investigate the effect of pretreatment on lipid yield and biodiesel quality. The highest lipid yield was obtained as 31.46 % for Desmodesmus sp. using water bath heating method. However, there was no significant impact on lipid yield after employing different cell disruption methods. In addition, chlorophyll removal reduced the lipid yield and increased the quality of the biodiesel produced from Desmodesmus sp. Furthermore, chlorophyll removal and cell disruption enhanced the quality of biodiesel by increasing the saturated fatty acid and monounsaturated fatty acid contents. Moreover, cetane number, higher heating value and iodine value of the biodiesel were within the acceptable range according to biodiesel quality standards. Therefore, Desmodesmus sp. can be identified as a potential source for microalgae biodiesel production
item: Conference-Extended-Abstract
Employing indigenous microalgae for third generation biofuel production
(Department of Chemical and Process Engineering, University of Moratuwa, 2019) Maduwanthi, MKC; Nuwanthika, WHC; Withanage, PK; Ariyadasa, TU; Rathnasiri, PG
Microalgae have been identified as a potential source for biofuel production by the researches. Cell disruption and chlorophyll removal of microalgae biomass are the most critical factors, which determine the lipid extraction yield and the biodiesel quality. Thus, the chlorophyll removal and cell disruption before lipid extraction is a mandatory step for the microalgae biodiesel production. This research investigated the growth rate and different pretreatment methods on lipid yield for selected microalgae species. Desmodesmus sp., Scenedesmus sp. & Closteriopsis sp. are the selected indigenous microalgae species, which were isolated from the Beira Lake, Colombo, Sri Lanka. Desmodesmus sp has shown the highest growth rate compared to other two species. Moreover, most suitable cell disruption method, which gave the highest lipid yield for each species were different.
item: Conference-Abstract
Enhancing the sustainability of microalgae biomass generation for production of alpha-linolenic acid via integration of reverse osmosis (ro) reject streams
(Department of Chemical & Process Engineering University of Moratuwa., 2023-08-17) Wickramasinghe, S; Ovitigala, M; Ariyadasa, TU; Walpalage, S; Gunawardena, S; Narayana, M; Gunasekera, M
Industrial reverse osmosis (RO) reject streams are a significant source of pollution in surface water bodies and requires effective treatment. Microalgae-based treatment of RO reject streams is an interesting approach as it generates valuable biomass concurrent to bioremediation. This approach also enhances the sustainability of microalgae biomass production by eliminating the requirement of external nutrient supply and reducing the freshwater footprint. However, there is a significant gap in research on utilization of RO reject streams generated by food/pharmaceutical industries for synthesis of microalgaebased high-value bioproducts. The current study was performed to ascertain the potential of using RO reject streams from the local food (RO1) and pharmaceutical (RO2) industries to cultivate Desmodesmus sp. for synthesis of alpha-linolenic acid. Accordingly, a screening experiment was conducted by growth of Desmodesmus sp. in RO1 and RO2 under dilutions of 25%, 50%, 75% and 100% (undiluted sample). Results showed that the highest biomass yields were obtained in 100% RO1 and 100% RO2. Thereafter, Desmodesmus sp. was cultured in 100% RO1 and 100% RO2 using photobioreactors with Modified Bold’s Basal media (3N-BBM) used as the control. Results showed that the use of RO reject streams resulted in a positive effect on the growth and biochemical composition of Desmodesmus sp. The high lipid content in biomass showcased that the use of RO reject streams could enhance the sustainability of microalgae-based alpha-linolenic acid production. However, further research is needed to study the toxicology effects and assess the techno-economic feasibility of using RO reject as the growth media.
item: Conference-Abstract
Integration of food industry wastewater for cultivation of desmodesmus sp. to synthesize alpha-linolenic acid
(Department of Chemical & Process Engineering University of Moratuwa., 2023-08-17) Gamage, GDNC; Hannadige, SKHN; Ariyadasa, TU; Walpalage, S; Gunawardena, S; Narayana, M; Gunasekera, M
Microalgae biomass production for food and fuel applications necessitates the use of resources such as water and nutrients, raising sustainability concerns. This study aimed to integrate food industry wastewaters as a source of nutrients and water for microalgae cultivation while simultaneously performing bioremediation. Nonetheless, wastewaterbased microalgae cultivation requires the identification of suitable wastewater streams, nutrient loads, and appropriate media sterilization methods to prevent culture failure due to contamination. In the current study, the microalga Desmodesmus sp. was cultivated in wastewater-based media for synthesis of the nutritionally-valuable alpha-linolenic acid. This study is the first in literature wherein a comparative assessment was performed between autoclaving and filtration as methods for wastewater sterilization. A screening experiment for Desmodesmus sp. growth was performed using brewery wastewater (BrW), coconut processing industry wastewater (CW) and biscuit wastewater (BiW) obtained from the food industry, under 25%, 50%, 75%, and 100% (undiluted) concentrations. Undiluted BiW was the most suitable media, as it resulted in the highest final biomass yields. Thereafter, undiluted BiW sterilized by autoclaving and filtration was used to culture Desmodesmus sp. in photobioreactors with Modified Bold’s Basal Media used as the control. BiW showed higher biomass yields and specific growth rate compared to the control. A higher lipid productivity of 16.78 mg L d was exhibited in autoclaved medium as compared to 9.92 mg L d in the filtered medium. Thus, BiW sterilized via autoclaving was identified as a promising growth medium for alpha linolenic acid production from a circular economic perspective.
item: Conference-Extended-Abstract
Investigation of the effect of solar irradiation and temperature on biomass production of h. pluvialis in photobioreactors under outdoor cultivation in Sri Lanka
(Department of Chemical & Process Engineering University of Moratuwa, 2020-03) Perera, ULMSM; Muthunayake, MKC; Madushanka, KWD; Ariyadasa, TU; Rathnasiri, PG
Complicated and changeable weather conditions and contamination from fungi, protozoa and bacteria increase difficulties in outdoor microalgae cultivation. In this paper, outdoor microalgae cultivation was investigated in Moratuwa city, Western province Sri Lanka. During December, when both the solar irradiation and temperature is high, the water spray system combined two agro shading nets, each with a shading rate of 40-50% can effectively reduce the temperature to 27±2 0C and control solar irradiation below 13500 lux in the 3 L vertical tubular photobioreactor. Under an initial biomass density of 0.2 g/l and an atmospheric air flowrate of 1 vvm, H. pluvialis had a maximum biomass accumulation of 0.45 g/l and the maximum specific growth rate of 0.020 g/l.day. In addition, reactor system and its design exhibited good performance, implying a potential scale- up opportunity.
item: Conference-Full-text
Investigation of the effect of solar irradiation and temperature on h. pluvialis production in photobioreactors under outdoor cultivation in Sri Lanka
(IEEE, 2021-07) Perera, M; Muthunayaka, K; Madushanka, D; Liyanaarachchi, VC; Premaratne, M; Ariyadasa, TU; Adhikariwatte, W; Rathnayake, M; Hemachandra, K
The complicated and varying weather conditions and contamination from fungi, protozoa, and bacteria are major problems associated with outdoor microalgae cultivation. In this study, outdoor microalgae cultivation was investigated in a 3.2 L vertical tubular photobioreactor in Moratuwa, Sri Lanka. During December, when both the solar irradiation and temperature were high, the water spray system in combination with two agro shading nets (each with a shading rate of 40-50%) could effectively reduce the temperature to 2±2 0C and control solar irradiation below 13500 lux. Under an initial biomass density of 0.2875 g/L and an atmospheric air flow rate of 1 vvm, Haematococcus pluvialis showcased a maximum biomass accumulation of 0.45 g/L and the maximum productivity of 20 mg/L/day. In addition, the reactor system and its design exhibited good performance, implying a potential scale-up opportunity. However, operation under outdoor conditions showed slightly poorer performance due to the light inhibition effect.
item: Conference-Full-text
Investigation of the efficiency of dairy wastewater treatment using lipid-degrading bacterial strains
(IEEE, 2018-05) Sandaruwani, A; Kumarasinghe, C; Samarakoon, D; Ariyadasa, TU; Gunawardena, SHP; Chathuranga, D
Dairy industry is considered as the largest producer of wastewater in the food industry in many countries. Dairy wastewater contains high concentrations of nutrients, organic and inorganic constituent. Therefore, discharging untreated/partially treated dairy wastewater causes serious environmental problems. Biological treatment methods show the highest efficiency for treating dairy wastewater. Aim of the present study was to identify indigenous bacteria capable of degrading dairy wastewater efficiently. Bacterial isolates were tested individually and in combinations using synthetic wastewater medium, incubated at 30 °C, for 2 days and Chemical Oxygen Demand (COD), pH, free fatty acid content, cell growth rate and the lipase activity were obtained at 6 hr time intervals for 36 hours. All the tested bacteria along with the consortium exhibited lipid degradation as well as removal of organic matter. Pseudomonas aeruginosa showed the highest activity in lipid degradation and COD reduction to 250mgO2/ltr at 12 hours.
item: Conference-Full-text
A mathematical model to predict the microalgal growth in an open pond cultivation
(IEEE, 2018-05) Rammuni, MN; Ariyadasa, TU; Nimarshana, PHV; Attalage, RA; Chathuranga, D
Cultivation is the paramount step of microalgae bioprocessing as a concentrated and flourished biomass broth will result in higher recoveries of its metabolites. But there is scarce model development for the prediction of microalgae biomass productivity in outdoor cultivation systems under the fluctuations of process conditions. Hence, this study develops a mathematical model based on the first principles with a nonlinear approach to forecast the microalgae growth in open ponds under non-optimal cultivation conditions in respect of the location. The model accounts for the effect of temperature, solar irradiance level, availability of nutrients in the cultivation medium and the effect of local climatic conditions over the microalgae growth. The model is validated against the experimental results from literature data and model analyses have been proceeded to determine the effect of variations in process parameters on the microalgae biomass yield.
item: Article-Full-text
Microalgae : a promising bioresource for a sustainable future
(2021) Ariyadasa, TU
Microalgae are highly diverse unicellular photosynthetic organisms found in aquatic environments. Microalgae produce oxygen during their proliferation, contributing to nearly 50% of the total oxygen production in the world. Concurrently, microalgae consume carbon dioxide in the atmosphere, thereby serving as carbon sinks to alleviate the effects of global warming. In comparison to terrestrial plants, microalgae exhibit rapid growth rates, higher photosynthetic efficiency, shorter harvesting time and higher biomass productivities. Moreover, they do not require arable land or potable water to facilitate their growth, hence becoming a more sustainable feedstock as compared to conventional crops. Altogether, microalgae have been identified as a bioresource with great industrial potential due to their ability to accumulate commercially valuable metabolites that can be extracted and subsequently processed into diverse bioproducts such as biofuels, pharmaceuticals/nutraceuticals, biofertilizer and animal feed.
item: Article-Full-text
Nitrogen-limited cultivation of locally isolated desmodesmus sp. For sequestration of CO2from simulated cement flue gas and generation of feedstock for biofuel production
(Elsevier, 2021) Premaratne, M; Liyanaarachchi, VC; Nishshanka, GKSH; Nimarshana, PHV; Ariyadasa, TU
Biological CO2 sequestration from flue gas using microalgae has emerged as a promising alternative to conventional carbon capture technologies, since it concurrently generates valuable biomass which can be utilized to produce biofuels. In the current study, the locally isolated microalga Desmodesmus sp. was utilized for sequestration of CO2 from gas mixtures simulating undiluted cement flue gas (1x), and cement flue gas diluted by two-fold (1/2x), four-fold (1/4x) and eight-fold (1/8x). The current study aimed to assess the feasibility of maintaining high CO2 sequestration rates in nitrogen-limited culture media while simultaneously producing biomass rich in target metabolites for biofuel production. Accordingly, Bold’s Basal Medium (BBM) and BBM with three times the standard nitrate concentration (3N-BBM) were employed as culture media for nitrogen limited and nitrogen replete experiments respectively. The highest CO2 fixation rates were demonstrated in undiluted flue gas containing 15.50% CO2. Moreover, the average CO2 fixation rate of Desmodesmus sp. over the 8-day cultivation period (0.21 ± 0.02 g/L/d) was not significantly reduced in nitrate limited media (BBM). Nitrate limited cultivation in undiluted flue gas enhanced the accumulation of carbohydrates in microalgae (32.44 ± 0.45% and 327.65 ± 23.39 mg/L), although the increment in lipid content was not as significant as expected (41.54 ± 1.13% and 419.57 ± 31.52 mg/L). Biodiesel properties of microalgal lipids were within the limits of the ASTM D6751–12 standard. Higher heating values of microalgae biomass were in the range of 21.97–23.17 MJ/kg. Nonetheless, pilot scale studies using actual flue gas are essential prior to microalgal biofuel production and simultaneous CO2 sequestration.