Browsing by Author "Wijeyekoon, SLJ"

Now showing 1 - 12 of 12

item: Conference-Extended-Abstract
Advance oxidation of high strength wastewaters as a suppleme~tary treatment option for enhanced biological treatment
(2007) Raamshangar, K; Wijeyekoon, SLJ; Rathnasiri, PG
High organic strength wastewaters from food industry, distilleries, breweries etc. are conventionally treated by anaerobic digestion due to low sludge production, derivation of biogas and low operating costs. However anaerobic process is extremely slow and hence requires large space and therefore capital cost intensive. On the other hand, aerobic treatment is rapid, efficient with stable end products yet the considerable sludge formation is a major disadvantage. Chemical oxidation is extremely rapid, easy to control and able to oxidize non bio degradable substances but its widespread application is restricted primarily due to cost consideration. Therefore an integrated approach to high strength wastewater treatment by taking advantage of the merits of anaerobic, aerobic and chemical oxidation is an attractive option to develop a sustainable, efficient, intensive and rapid treatment technology for the treatment of high strength industrial effluents.
item: Thesis-Abstract
Cleaner production options for skim rubber industry - a case study
Yasaratna, PDTN; Wijeyekoon, SLJ; Peiris, S
Rubber processing factories generate large amount of wastewater containing organic pollutants and various process chemicals. Rubber processing factory effluents exhibit high BOD (Biochemical Oxygen Demand), COD (Chemical Oxygen Demand), ammonia, and suspended solid concentrations. Except for a few, most rubber processing factories in Sri Lanka do not adequately treat the effluents before discharge either due to high cost of treatment or use of inefficient methods for treatment. Due to the low operating margins of this vital industry, that utilizes a waste product as raw material, an introduction A of expensive pollution control methods would lead to the collapse of the industry. In centrifuging plants the serum water contains 2.5% to 10.0% m/m.(I) dry rubber. Direct coagulation of this skim latex is not easy, because the colloid stability is enhanced by the high content of ammonia and protein containing substances, and by the small size of the dispersed rubber particles. One method of coagulation is by the addition of sulphuric acid where the skim is left to coagulate spontaneously. Then the coagulum is processed by conventional means, and made in to thick crepe. The technology used in the selected factory for the case study, the production procedure is in primitive stage and this result in low productivity with high environmental damage. The industry discharges large volume of waste water and effluents consisting of 34 000 litres of serum and 4 000 litres of wastewater per day. Though the company has a large Treatment plant, the effectiveness of it is totally inadequate due its high retention time. Few methodologies were used to find out the environmental damage by this factory, quantify the wastes and ways of maximum utilization of resources. Walk through audits; develop process flow charts, materials balance sheet, chemical analysis of raw material and the effluent and brainstorming are such methodologies. The application of Cleaner Production (CP), apart from reducing pollution load brings in many other benefits to this type of industry, which include resource conservation, improvement in work environment, product quality improvement etc. Cleaner production is not only concerned with technology, but also with management, labour, organization and health and safety. Cleaner production solutions will help to improve the industry's financial bottom line and mitigate environmental damage through helping the industry to survive. Fifteen cleaner production options were identified during the study. Waste free latex, de-arnrnoniation, avoidance o~ntaminates, control use of chemicals, improvement of coagulation process, technology improvement for skim separation, resource recovery, repair and maintenance, good house keeping, better storing of finished goods, modifying the air drying process, introduce proper drainage system for wastewater flowing, change the power generating system, and better scheduling are the identified CP options in the factory. Based on technical feasibility, financial viability and environmental desirability, an overall qualitative analysis was carried out for these options. According to the analysis the Proper mixing of skim latex with chemicals (Sulphuric acid), minimize rubber in waste streams, mechanized the skimming process, good house keeping practices (Introduce proper drainage system for w. water ,separate and reuse water and storing finished goods )and de-ammoniating options were prioritised. The proposed pollution prevention ana pollution control measures would help to improve the environmental performance of skim rubber processing factories and grant resource conservation benefits to the industry.
item: Conference-Extended-Abstract
Comparative performance of bio filter packing materials for waste gas treatment
(2009) Wijayawardhana, AJ; Wijeyekoon, SLJ; Walpalage, S; Amarasinghe, ADUS
A study was conducted to evaluate the removal efficiency of NH3 and H2S emitted from an industrial waste gas source by biofiltration. Four types of packing material were used and NH3 and H2S in the contaminated air stream, ranged between 43-90 ppm and 70-100 ppm respectively. The experiments were carried out over an effective period of 45 .days. Results indicate that 100% removal efficiencies of NH3 and H2S can be achieved for coconut fiber/tobacco compost and peat/wood chips mediums.
item: Article-Abstract
Design and performance of an industrial scale biofilter for odorous gas treatment
(2016-05-24) Wijayawardhana, AJ; Wijeyekoon, SLJ; Walpalage, S; Amarasinghe, ADUS
Odorous gas treatment is a challenging task due to the difficulties in identifying odor specific gases and their varied characteristics. A bio filter was designed for the treatment of waste gas stream from a tobacco leaf processing factory that discharged a high temperature gas stream from drying chambers with characteristics of tobacco odor. Major constituents of the foul smelling gas (gas flow rate of 1160 - 2100 rn'lr1) were identified and quantified using thin film micro sensors and was found to constitute mainly ammonia (60 - 80 ppm (v/v)) and hydrogen sulfide (80 -100 ppm (v/v)) after pre-treatment. A bio filter unit (11.65 m3 in volume) with a mixture of coconut fiber and compost as filter media was used to treat the odorous gases which eliminated the hydrogen sulfide completely while removing more than 80% of ammonia at the EBRT of 36 (s), producing a non odorous gas stream. The pH (6.5-7.5) and moisture (60 -65%) were kept at optimum levels to facilitate microbial growth and minimal pressure drops within the system. This paper details design, construction, operation, performance monitoring aspects involved in bio filtration in an industrial scale application and recommend many practical engineering solutions in its application.
item: Conference-Full-text
Environmental management options for skim rubber industry
(2005) Yasaratna, PDTN; Wijeyekoon, SLJ; Peiris, S
Natural rubber processing factories generate large amount of wastewater containing organic pollutants and various process chemicals. The effluents exhibit high BOD, COD, NH4+-N and suspended solid concentrations. The discharge of untreated effluents into streams or paddy fields result in the emission of obnoxious odour and low pH levels. The acidic effluent is found to cause damage to crops especially to paddy and coconut. Except for a few, most rubber processing factories do not treat the effluent prior to disposal due to high capital and recurrent costs involved for end of the pipe treatment. Therefore sustainable environmental management dictates the adoption of Cleaner Production (CP) strategies to meet environmental regulations and reduce treatment costs.
item: Conference-Extended-Abstract
Full scale bio filter ammonia removal performance during filter maturation
(2009) Wijayawardhana, AJ; Wijeyekoon, SLJ; Walpalage, S; Amarasinghe, ADUS
An industrial bio filter of 23 m3 in capacity, packed with a coconut fiber filter medium inoculated with compost of 12 m3 in volume was operated for a period of 45 days. Performance was monitored at gas flow rates of 1160 m3h-1 to 2100 m3h-1 to identify the removal efficiencies under varying conditions during filter maturation. Maximum elimination capacity of 5.9 gm-3h-1 was reached for an inlet loading of 1.8 gm-3h-1 for ammonia. Filter maturation periods were unexpectedly very short due to initial physical adsorption.
item: Conference-Extended-Abstract
Kinetic coefficients for anaerobically pretreated crepe rubber effluent and optimization of activated sludge process by kinetic modeling
(2003) Wijeyekoon, SLJ; Hettiarachchi, IU; Senewiratne, WMG
Factorv efl:1uents from raw rubber processing facilities exhibit very high biochemical oxygen demand (BOD). ammonia and suspended solids and therefore arc amenable for biological wastewater treatment. The Rubber Research Institute of Sri Lanka developed. pilot tested and commissioned a novel treatment system consisting of anaerobic digestion followed by aerobic stabilization and finally chemical precipitation and sand filtration. However. investigations have revealed that treatment plant design could be further optimized to enhance performance and reduce capital, operational and maintenance cost.
item: Thesis-Abstract
Recovery of silver (Ag) from photo processing effluent by chemical and electro-winning methods
Rohitha, LPS; Wijeyekoon, SLJ
Industries such as mining and industrial minerals, metallurgical, photo processing, textile, leather and chemical produce wastewater containing heavy metals that are hazardous to man and the environment. Photo processing waste effluents arise from X-ray, lithographic and photo processing operations. The photosensitive medium used in these operations is an emulsion of fine Ag halide matrix in gelatin. During fixing, the Ag" is removed by the fixer solution. The developer and bleach solutions also contain the Ag heavy metal. The recovery of Ag" from such wastewater may be done by electro-winning, metallic replacement, evaporation, ion exchange, reverse osmosis and electrodialysis. The aim of this research was to investigate the application of electro-winning technique for selective removal of Ag metals from photo processing effluent. The laboratory scale electro-winning cell was a beaker of 12.7 cm in diameter and having a capacity of 250 ml. The anode was of stainless steel of size 7.5 x 4.5 cm2. A carbon plate of 1 cm thick (7.5 x 4.5 cm2") of 99.5% carbon was used as the cathode. The circuit consisted of an electrolyte bath a precision type milli-ammeter and an adjustable resistant in series, and a voltmeter connected across the electrodes in the bath. During the electrolysis, samples were taken after 5, 10, 15, 30, 60, 120 & 180 minutes intervals respectively at each of the current density values corresponding to 10, 20, 30, 35, 40, 45, 50, 55, 65, 70, 75, 80, 90, 100 & 110 From each solution three aliquots were pipeted out & analyzed In the electro-chemical method the electrowinned solution was filtered and the residue was treated with. Ammonium Nitrate reagent In the third approach the photo processing effluent was subjected to electro-winning process using a current: voltage ratio of 2.2 to 2.8. In the first approach, industrial photo processing effluent having 2400-Pfm of Ag was subjected to electro-winning technique at current density of 82 mA/cm2. However in three hours, only 14 % of Ag was deposited on the cathode and considerable amount of precipitate was visible at the bottom of the cell. This black precipitate resembled typical AgS precipitate and is thought to be formed due to oxidation of S203 to elemental sulfur that preferentially binds with Ag". The interference from S drastically reduced the recovery potential of Ag at the investigated process condition thus rendering the process technically aid economically non viable. In the second approach, the same effluent was subjected to an electro chemical method giving 14 % of Ag deposition on cathode and 72 % of Ag was extracted from chemical methods. However the use of number of expensive chemicals and heating make this method economically less attractive. The use of very low voltage with a current: voltage ratio of 2.2-2.8 does not provide sufficient energy for oxidation of S203 thus avoiding S interference on Ag" reduction. Under this process condition, a remarkable Ag recovery of 86% was achieved at the current density of 82 mA/cm2. The developed process conditions prove the technical feasibility of electro winning for Ag recovery and stimulate further investigations into optimization of cell configurations for industrial application.
item: Thesis-Abstract
Removal of nutrients (N and P) and heavy metals (Fe, Al, Mn and Ni) from industrial wastewaters by phytoremediation using water hyacinth (Eichhornia crassipes) under different nutritional conditions
(2014-07-07) Kasturiarachchi, JC; Jayaweera, MW; Wijeyekoon, SLJ; Hirimburegama, K
This study was investigated the utilization of phytoremediation strategies to remove nitrogen, phosphorus and heavy metals (Fe, Al, M n and Ni) from wastewaters by water hyacinth {Eichhornia crassipes [Mart.] Solms). Batch studies were conducted for 15 weeks using fiberglass tanks in which healthy young plants were grown for a period of 15 weeks under different nutrient concentrations o f 2-fold (56 T N mg/1 a nd 15.4 T P mg/1), 1-fold (28 T N mg/1 a n d 7.7 T P mg/1), 1/2-fold (14 T N mg/1 a n d 3.85 TP mg/1), 1/4-fold (7 T N mg/1 a n d 1.93 T P mg/1), 1/8-fold (3.5 T N mg/1 a n d 0.96 TP mg/1) and control (without nutrients). In each week plants, water and sediments were analysed for TN and TP. The phytoremediation potential of heavy metal removal was determined at above nutrient concentrations with the addition of the constant heavy metal concentrations (Fe-9.27mg/1, Al-5.62mg/1, Mn- 0.92 mg/1and Ni-0.21mg/1) in fiberglass tanks. Plant, water and sediment were analyzed for heavy metals during the 15 weeks of culture period. A mass balance was conducted to investigate the phytoremediation efficiencies and to determine the different mechanisms governing nutrient and heavy metal removal from the wastewaters. Our results manifested that hyacinth could be effectively utilized in constructed wetlands to phytoremediate N rich wastewaters than P. Plant uptake was the major TN and TP removal mechanism during the initial periods. Accumulation of a high content of nitrogen in plant tissues due to plant uptake and denitrification was found to be the key mechanisms involved in the efficient removal of nitrogen at the latter part of the study period. Plant uptake of phosphorus and chemical precipitation together with adsorption on to the detritus are the key mechanisms of phosphorus removal. However the phosphorus removal seems to be not high with that of nitrogen indicating that hyacinth systems are not ideal for phosphorus removal from wastewaters. In conclusion, very young plants having seems to be ideal to commence a constructed wetland after a period of acclimatization and approximately 56-63 days of hydraulic retention time is recommended for optimum phytoremediation of nitrogen as well as phosphorus. Phytoremediation of Fe largely due to the process of rhizofiltration and the chemical precipitation followed by flocculation and sedimentation were the key Fe removal mechanisms during the first few weeks of the study. Plants grown in the control set-up showed a highest phytoremediation efficiency of 47% during optimum growth at the 6th week with a highest accumulation of 6707 Fe mg/kg dry weight. Root effluxing of Fe to the waste waters at intermittent periods and with time was a key mechanism of avoiding Fe phytotoxicity in water hyacinth. It can be concluded from this study that water hyacinth is an ideal plant for a batch removal of low polluting Fe rich industrial wastewaters under completely nutrient poor conditions. Very young plants are ideal to commence a constructed wet land after a period of acclimatization and approximately 42 days hydraulic retention time is recommended for optimum phytoremediation. Phytoextraction was the key Mn removal mechanism and root effluxing of Mn was observed intermittently possibly to avoid any phytotoxicity caused by an excessive accumulation of Mn in hyacinths. Hyacinths cultured in the 1/8-fold set-up showed a highest accumulation of 1133 Mn mg/kg dry weight with an optimum removal of 79% at the 9th week. Hence very young plants inhabiting waterbodies containing approximately 3.5 TN mg/1 a n d 0.96 TP mg/1 seems to be more ideal for a batch removal of low polluting Mn rich wastewaters in constructed wetlands. Acclimatization of the plants is necessary for at least 1 week prior to the removal of Mn and then approximately 63 days hydraulic retention time is recommended to optimize phytoremediation. Chemical precipitation followed by flocculation and sedimentation with phytoremediation mainly due to rhizofiltration were the key Al removal mechanisms Control and 1/8-fold set-ups showed higher phytoremediation efficiencies of 63% and 54%, respectively with maximum accumulations of 4278 Al mg/kg dry weight and 4224 Al mg/kg dry weight, respectively. Therefore young plants of completely nutrient starved adult hyacinths seems to be more ideal for a batch removal of low polluting Al rich industrial wastewaters in pilot scale constructed wetlands. A hydraulic retention time of approximately 28 days is recommended for optimum removal after a period of acclimatization of the young plants. The results manifested that hyacinths are essentially Ni excluders since higher levels of Ni were detected in water throughout the study.
item: Conference-Abstract
Resource recovery from photographic waste by electro-winning
(2006) Wijeyekoon, SLJ; Rohitha, LPS; Fernando, WLW; Dissanayaka, DMDOK; Karunarathna, S
Industries such as mining and industrial minerals, metallurgical, photographic, textile, leather and chemical produce wastewater containing heavy metals that are hazardous to man and the environment. Indiscriminate discharge of these effluents pollutes natural resources and disturbs vital eco systems. On the other hand most heavy metals in these effluents are rare in nature and hence are expensive industrial raw materials. Therefore a sustainable pollution control option for these industries should aim at resource recovery. Successful isolation of heavy metals from wastewaters will not only render such effluents non hazardous but also make waste management an attractive proposition, thus leading to multiple benefits in terms of resource conservation, pollution control and treatment cost savings. Photographic waste effluents arise from X-ray, lithographic and photographic operations. The photosensitive medium used in these operations is an emulsion of fine Ag halide matrix in gelatin. During fixing, the Ag+ is removed by the fixer solution. The developer and bleach solutions also contain the Ag heavy metal. The recovery of Ag" from such wastewater may be done by electro-winning, metallic replacement, evaporation, ion exchange, reverse osmosis and electro-dialysis. However many process parameters of these methods are not readily available and opportunities exist for optimization of methods to improve removal efficiencies. The aim of this research was to investigate the application of electro-winning technique for selective removal of Ag metals from photographic wastewater. The advantages of the application of electro-winning technique are no hazardous sludge generation, isolation of pure elements, no pretreatment requirement and l
item: Conference-Extended-Abstract
Treatment of silver (Ag) containing effluents using electrodialysis
(2004) Botheju, PDC; Wijeyekoon, SLJ; Jayaweera, MW; Dissanayaka, DMDOk
Electrodialytic recovery of Ag+ ions from industrial effluents (basically photographic effluent.s~ was.",) investigated with the aim of reclaiming and recycling of the metal Ag, mainly considering the fact that Ag being a very valuable metal and also a toxic heavy metal. Eco-toxicity of this kind of metal elements is well recognized and supposed to be due to their bio concentration and bioaccumulation nature associated with various food chains. On the other hand, in a highly competitive market and environmental conscious society, it is very important to recover these metals in more economically and environmentally sound means, than the conventional approach of disposing these effluents into common sewage lines with or without metal recovery using old electrolysis techniques. A recent study carried out in the Rathmalana- Moratuwa area, revealed that, a significant amount of ground water wells situated in this area are polluted with Ag and other heavy metals, beyond the normal acceptable levels. (Heavy metal levels of groundwater in Ratmalana-Moratuwa industrial area, A comprehensive survey carried out in 2002 by Dayani Gunawardana ). Thus the necessity of a cleaner, greener and economically viable local technology for the treatment of metal contaminated wastewaters is crucial at the moment, when comparing with conventional, inefficient and less economical treatment options
item: Thesis-Abstract
Zero effluent solution for detergent industry
Dayananda, DH; Jayaweera, MW; Wijeyekoon, SLJ
Reuse of industrial wastewater is an important strategy for reducing freshwater consumption and wastewater generation as well as minimizing the potential impact of effluent on the environment. From an economic perspective, wastewater reuse reduces the costs of freshwater consumption and wastewater disposalWastewater is to be adequately treated prior to disposal. Surfactants including detergents are refractory organics that resist conventional treatment methods and therefore need an advance wastewater treatment. However, the cost of wastewater regeneration and treatment rises exponentially with increasing contaminant removal efficiency. In order to balance these competing cost factors wastewater disposal costs vs. wastewater regeneration and treatment cost has to be considered.This case study of the zero effluent solution provides experience in cost effective management of eff1uent as a resource, with minimizing the potential impact of eff1uent on the environment. The overall objective was to recycle wastewater as a resource for liquid detergent manufacturing process. Special attention is being given to control of unpleasant odour, maximization of reuse of surfactants and establishment of proper hygienic conditions in treated eff1uentThe results of wastewater characterization showed that the concentration of the organic matter is very high, expressed as COD ranging from 6,200 mg/1 to 34,400 mg/1, while the biodegradable portion was very low, since BOD/COD ratio was low. These values indicate that organic compounds are not easily subjected to biological treatment. In order to ensure the maximum reuse of surfactants and other important chemicals only physical treatments were adopted. They were aeration, filtration followed by UV disinfection. Two major limiting factors in the case of reuse wastewater were identified specific to this case study. (ie. Unfavorable odour experienced in collection sumps and contaminated with pathogenic micro organisms.) The proposed treatment can successfully solve these issues ensuring maximum reuse of important constituents in the eff1uent. More than this, it can reduce TSS up to 5!-l particle size, which is more beneficial in reuse for production process. The treated eff1uent is best foruse in coloured products.