Engineer : Journal of the Institution of Engineers, Sri Lanka
[0 followers] Follow
Open Access journal
ISSN (Print) 1800-1122
Published by Sri Lanka Journals Online [45 journals]
- Streamflow, Suspended Solids, and Turbidity Characteristics of the Gin
River, Sri Lanka
Abstract: Human induced impacts on the river systems result in decrease in water quality, which is generally reflected by an increase of particulate matter in rivers. Turbidity and suspended solids are part of physical and aesthetic parameters and good indicators of other pollutants that are carried as sediment in suspension. Study objectives were to define the relation between turbidity and total suspended solid (TSS) concentration in Gin river at Baddegama (6°11'23" N, 80°11'53" E) in developing an estimation technique for TSS load, and to reveal how turbidity and TSS load vary with the streamflow. Linear regression model developed between turbidity and TSS concentration showed strong positive correlation (R2 = 0.98). Results strongly suggest turbidity is a suitable monitoring parameter for TSS, where TSS evaluation is crucial when logistical and financial constraints make TSS sampling impractical. Mean daily TSS loads in the Gin river at Baddegama during 2000-2009 were modeled in the study using load-discharge rating curve for estimating constituent loads in rivers. Relatively strong relationship (R2 = 0.85) was observed between the rating curve estimated and observed TSS loads. Estimated TSS loads were having substantial temporal variation and generally peaked in May and October, coinciding with the high flows. Turbidity which ranged between 2.3 NTU (Nephelometric Turbidity Units) and 195 NTU significantly exceeded the maximum permissible limits of the water quality standards set for the potable water as well the inland waters of Sri Lanka. Since there was no specific water quality standards developed for TSS in Sri Lanka to compare with the present values, TSS concentrations were compared with the permissible total solid levels. TSS concentrations which ranged between 2.4 mg/l and 204 mg/l were well below the maximum permissible total solid level cited in the Sri Lanka standards for potable water. Understanding on this turbidity and TSS characteristics in Gin river flow might be useful for water managers and planners to adjust operations accordingly at water treatment plants.
DOI : http://dx.doi.org/10.4038/engineer.v46i4.6809 ENGINEER, Vol. 46, No.04, pp. 43-51, 2013
Published on None
- Peak Electricity Demand Prediction Model for Sri Lanka Power System
Abstract: Accurate prediction of daily peak electricity demand is a requirement for service reliability, system stability and operating performance of a power system in the field of electrical engineering. This has now become a very important factor for Sri Lanka power system, since the available power plants are to be dispatched in an economical and reliable manner especially during the peak demand period of the chronological load profile. Therefore the prediction of next day peak electricity demand to an acceptable accuracy is useful for the system control centre (SCC) of the Ceylon Electricity Board (CEB). However, presently the unit commitment to meet the next day peak electricity demand is being mostly done by the system control engineers based on their past experience in the field of operation with respect to the day, period and other factors. This research paper carefully identifies sensitive elements which affect the daily peak demand of Sri Lanka power system and develop two forecasting models, namely linear statistical “Multiple Regression” and feed forward “Artificial Neural Network”. Both models were developed and fine-tuned using recorded peak demands of Sri Lanka power system from year 2008 to 2011 taken from the SCC of CEB and tested for the calendar year 2012 and also for the first few months of 2013. Artificial Neural Network model was found to be the best fit model for the prediction of daily peak demand of Sri Lanka power system with the lowest Mean Absolute Percentage Error (MAPE).
DOI : http://dx.doi.org/10.4038/engineer.v46i4.6810 ENGINEER, Vol. 46, No.04, pp. 53-60, 2013 Published on None
- Floating Wetlands for Management of Algal Washout from Waste Stabilization
Pond Effluent: Case Study at Hikkaduwa Waste Stabilization Ponds
Abstract: Waste stabilization ponds are advantageous waste water treatment processes, especially for developing countries. Nevertheless, in spite of the well known advantages of the implementation of the stabilization pond system, the effluent of this system has a significant amount of algae and high nutrients. Disposing this effluent with high contents algae and nutrients to the receiving waters can hinder the water reuse for a wide range of different applications, it is essential to look for a post treatment method that can provide considerable removal of algae, nutrients and organic matter from the effluent and at the same time, assure that the treatment system as a whole will maintain the advantages of the pond treatment processes. In this context, this research study was planned and intended to introduce a floating treatment wetland in which water hyacinth plants (Eichhornia crassipes) were used as macrophyte or vegetation in the part of the maturation pond area to control algae and nutrients in the effluent. With the application of the floating wetland the removal efficiencies were found to have increased in the maturation pond in terms of BOD and COD from 13.3% to 62.9% and 13.6% to 57.5%, respectively. In the case of TP and TN there were no significant reductions achieved prior to the establishment of the wetland but, reductions of 74.8% for TP and 55.8% for TN were achieved since the establishment of floating wetland. It was also possible to achieve a reduction of algal cell densities of 900 units/ml to zero unit/ml for the algal species of Spirulina and for Oscillatoria, the reduction was from 290 units/ml to 0 units/ml. In case of Chlorella and Pandorina, density reductions were 830,000 units/ml to 68,000 units/ml and 4300 units/ml to 280 units/ml respectively. Accordingly, the reduction efficiencies for Spirulina, Oscilltoria, Chlorella and Pandorina were reported to be improved from 31.8% to 100% and 4.5% to 100%, 34.2% to 91.8% and 42.2% to 93.5%, respectively. Application of this research can therefore be possible to polish waste stabilization pond effluent economically in order to re-use for various beneficial uses except potable use.
DOI : http://dx.doi.org/10.4038/engineer.v46i4.6811 ENGINEER, Vol. 46, No.04, pp. 63-74, 2013 Published on None
- Estimation of Sediment Trap Efficiency in Reservoirs - an Experimental
Abstract: Reservoir sedimentation has become one of the major problems facing water resources development projects in many countries around the world. However, only a limited number of studies have been reported in this field, particularly addressing the trap efficiency of reservoirs. In addition, even the available studies in this area have considered only few parameters governing reservoir sedimentation. As a result, the available knowledge on trap efficiency is not very well defined. The Brune curve  is being widely used for estimating trap efficiency of reservoirs at present, but it has several limitations, as it considers only the reservoir capacity and inflow ratio for estimating the trap efficiency. The objective of this study is to formulate an improved methodology for estimating reservoir sedimentation through laboratory experiments. A small-scale laboratory model was set-up to represent a reservoir and a series of tests were conducted by varying the inflow rate, inflow sediment concentration, reservoir capacity and the outflow rate. The experimental results were compared with values obtained from available theories and it was found that they are not very much in agreement with many of the existing theories which are mostly based on a limited number of parameters. A comprehensive data analysis was performed using dimensional analysis to develop an improved relationship to estimate reservoir sedimentation incorporating many parameters governing the problem. However, the applicability of the proposed method is still limited only to reservoirs with continuous spilling conditions. In addition, only one type of sediment gradation (d50) was used in the experimental runs and thus, the effect of sediment sizes is not well represented in this method. However, the relationship developed in this study could be further improved by conducting more experimental runs by varying few other parameters which have not been considered in the present study.
ENGINEER, Vol. 48, No.02, pp. 43-49 2015 Published on None
- Spread Sheet Solutions in Irrigation Canal Modeling Help to Achieve Better
Operational Performance in Major Irrigation Schemes
Abstract: Levels of Operational performance in Major Irrigation Schemes have become a major concern to the scheme operators and scheme managers. To achieve better levels of performance a situation analysis close to reality is needed when they schedule their irrigation deliveries in the canals. Various methods are being practiced by the system operators in their scheduling processes. Most of the methods are not in conformity with the scheme objectives and water rights of the farmers. So there is a vacuum demanding a better solution which can be applied as a tool for planning and monitoring irrigation schedules taking in to account the instantaneous changes in climatic and cropping conditions.In order to fulfill the above requirements, a mathematical model was developed using spread sheets and Visual Basic Applications. This model creates irrigation schedules for Primary, Secondary and Tertiary canals by considering instantaneous conditions such as cropping data, metrological data, reservoir levels and canal properties.This model was tried out in the Mahaweli System C during six consecutive cultivation seasons and a better water productivity could be obtained. Mahaweli System C covers cultivated paddy (Rice) land of 24,100 ha and this model covered 16,772 ha of that land area..ENGINEER, Vol. 48, No.02, pp. 51-64 2015 Published on None
- A Design Nomogram for a Horizontally-Fractured Geothermal Reservoir to
determine the Production Temperature
Abstract: The paper presents a graphical technique for the rapid analysis of the complex, nonlinear equation that describes the variation of the production temperature of a horizontally fractured geothermal well. The nomogram presented for the evaluation of the production temperature incorporates the mass flow rate, fracture width, fracture length, number of conductive fractures, host rock temperature, and the production time. The range of the fracture length considered in the nomogram varies from 100 m to 1000 m whereas host rock temperature can be selected from a range of 1000C to 2600C. The production temperature predicted by the nomogram agrees well with the analytical solution. The most attractive feature of the proposed technique is its extreme simplicity and speed of operation.
ENGINEER, Vol. 48, No.02, pp. 35-41 2015 Published on None
- Implications of Micro-Tunnelling on Wastewater Pipeline Constructions : a
case study from Muscat Wastewater System: Al Khuwair Project
Abstract: Al Khuwair is a sub city located in Muscat in the Sultanate of Oman. It is presently growing rapidly with illustrious highways, modern housing complexes, commercial centres, hospitals, schools etc., being built. Even though the local population represents around 60% of the total population, developing infrastructure is an essential need in order to cater to the needs of both the local and foreign migrant population and also the tourists. The present trend of development of the city indicates that Al Khuwair would provide a considerable proportion of the Muscat’s wealth. The yellow tankers roaming around the city are not uncommon in AlKhuwair even though it might surprise the visitors at their first glance. They enter every house and restaurant at least once a month in order to empty the septic tanks of those properties. It is also not uncommon to see overflowing septic tanks emitting in tolerable odours when tankers fail to arrive promptly to empty the overflowing septic tanks. The aim of the paper is to present the actual experience from Muscat Waste water Project that has been implemented in order to overcome the above mentioned most critical issue. It highlights the problems which surfaced with regard to pipe deviations, deflections and pipe cracking that occurred during the micro tunneling of 1000mm diameter polycrete wastewater pipes. The attempts made to provide technical solutions for the deficiencies and possible alternatives to overcome the defective situations are comprehensively discussed in the paper.
ENGINEER, Vol. 48, No.02, pp. 25-33 2015 Published on None
- FROM THE EDITOR Vol.48(2)
Abstract: No abstract availableENGINEER, Vol. 48, No.02, pp. iii 2015 Published on None
- Strategies for Prevention of Delayed Ettringite Formation in large
Abstract: With many large scale civil engineering construction projects being undertaken, there is a possibility to find large concrete pours in thick members. Due to the hydration process, temperatures in concrete will increase during early stages and when the temperature exceeds 700C, Delayed Ettringite Formation (DEF) can take place. DEF can have adverse long term effects when moisture is present leading to severe cracking of the concrete as it ages. Thus the key to prevent DEF is to control the maximum temperature that concrete could reach during early stages. Mineral additives like fly ash can play a major role in this regard. This paper presents several strategies to mitigate DEF, including the selection of limiting values for member thicknesses that could be cast with different mixes and grades of concrete in different climatic regions in Sri Lanka.
ENGINEER, Vol. 48, No.02, pp. 1-13 2015 Published on None
- Beneficiary Participation in Formulating Social Safeguard Management
Programmes – Experience from Dam Safety and Water Resources Planning
Project of Sri Lanka
Abstract: The Social Safeguard Management Programme (SSMP) has become a key component of irrigation related rehabilitation projects. This paper reviews a renewed approach to developing SSMP that has been adopted in the rehabilitation of four reservoirs coming under the DSWRPP, where water releases had to be suspended temporarily to enable the rehabilitation. The SSMP has been designed in such a way that livelihood support assistance is provided to 8,344 affected families in the downstream communities. The conduct of Social Impact Assessment and the development of Livelihood Support Assistance (LSA) plans are illustrated. The LSA plan has four sub plans namely Wage Assistance Plan, Alternative Crops Plan, Domestic Water Use Plan and Gender Action Plan. The affected people have contributed to the economy by working in the rehabilitation work and saving foreign exchange by cultivating alternative crops. The paper presents ample evidence of the level of contentment and happiness of the farmers at the end of the programme, they being made responsible for the development and implementation of the LSA plans. The main argument offered in this article is that the programmes to assess and mitigate socio-economic impacts should primarily take into account the perspectives of the people without exclusively relying on specialists or technocrats.ENGINEER, Vol. 48, No.02, pp. 15-23 2015 Published on None