Minimizing the water pollution in Kandy Lake by
Minimizing the water pollution in Kandy Lake by using Natural water purification Technologies EMM-2020 Centre for Environmental Studies University of Peradeniya H. M. Y. L. P. Herath, Tharindu Rajapaksa (MBCS) *Department of Environmental Mgt, Rajarata University of Sri Lanka, ** London Metropolitan University INTRODUCTION The Kandy Lake which was built in 1807 is a magnificent legacy that speaks of a bygone era and transforms the hill capital into a place of beauty. This was a creation of the last king of Kandy, Sri Wickrama Rajasinghe (1798 -1815). The water is being collected from all around the mountains around the lake. Further, water from the entire drainage system is being collected to the Kandy lake. In earlier days, the water which came from the drainage system was not this much polluted. Even the king, queens, Bikkus used this water for their day today essentials. But the current situation is totally different. In 2009, a massive fish die-off was reported in the Kandy Lake. The maximum number if dead fish was as high as 150 fish per day. As per the literature gathered the researchers were able to identify that dissolved Oxygen, nutrients, heavy metals could have caused the die off the fish. And the ultimate solution is to purify the water before letting them to flow to the Kandy Lake. Chemical pre treatment, coagulation, sedimentation, membrane filtration and ultra violet disinfections are some options available to produce good quality water. Further, methods like reverse osmosis are the available technology to produce good quality water. But these systems are costly to maintain and not efficient for a massive load of water. Hence the objective of this research is to present natural water purification technologies which are feasible for this water body. METHODS Collection of primary data was a challenge for the researchers. And hence the researchers identified observations as the most suitable primary data collection methodology for this research the several observations were carried out to gather the data. The observations were targeted on the • Water Catchment Area of the Kandy Lake. • Drainage System Around the Kandy Lake. • Wastewater sources which is flown towards the lake. • Sources of other water pollution (Kandy Lake) Secondary data were collected via the reports, maps which are publicly available on the internet. Furthermore the researchers gathered the data related to the irrigation system via the regional irrigation department who is responsible for the management and the maintenance of the Kandy Lake. Since the researchers were focused on the non- numerical data to carry out this study the main approach was qualitative. CONCLUSIONS RESULTS AND DISCUSSION The Kandy Lake has a complex catchment area, which consists of urban centres, densely populated residential areas, hospitals, hotels, restaurants, market places, public transport destinations and a number of government and private sector institutions. As a result, the Kandy Lake water is polluted due to solid and liquid waste generated and disposed without any treatment from point and non-point sources. Water quality of the Kandy Lake has been maintained to a certain standard due to its close proximity to the Dalada Maligawa (Temple of the tooth relic). There are many hotels, restaurants and private hospitals around the lake. Wastewater discharges from these locations into the lake are monitored in order to protect the lake. But it cannot be controlled and continues waste disposal is progressing. Kandy Lake which is in the heart of the Kandy adds beauty to the Kandy City. But since this lake is surrounded by the hills almost all the waters from these hills are flown towards this. And now the water is highly polluted with dissolved heavy metals, irons and other sedimented substances. But artificial purification of the waters costs a lot. Hence to prevent the water pollution in the Kandy Lake researchers have recommended a natural water purification methodology which filters the water by sedimentation , along with bio-purification at no cost at all. The researchers are suggesting a two-step natural water purification system to the Kandy Lake. In this system two small tanks will be constructed at the end of the canal. Where the water which is flown towards the lake will first go to these two tanks before entering the main lake. Main purpose of the first tank (sedimentation tank) is sedimentation of the suspended and colloidal materials by gravity. It needs enough stability time to settle down the particles. The time taken of the sediments depends on quality of raw water, which may carry particles of different size. During sedimentation process, most the colloidal particles settle at the bottom strata of the water column. And then the water is passed to the Bio-purification tank which contain Eichhornia crassipes, Salvinia molesta (water hysinth) and hydrilla verticillata plant with number of small fish. Water comes from second sedimentation tank passes through this tank (Biological purification unit) sequentially. Plants absorb most of the ions especially nitrogenous compounds. Further the fish and plants helps to increase the quality of water by reducing, excess of nutrients(Nitrates, Phosphates) etc. In this micro ecosystem by fish, helps to regulate excessive plant growth. Finally, the naturally purified water will be directed to the Kandy Lake. REFERENCES Balke, K. -D. & Yan Zhu, 2008. NCBI. [Online] Available at: https: //www. ncbi. nlm. nih. gov/pmc/articles/PMC 2266879/ [Accessed 17 10 2020]. Crites, R. W. , S. C. Reed & R. K. Bastian, 2000. Land Treatment Systems for Municipal and Industrial Wastes. s. l. : s. n. Crites, R. W. & G. Tchobanoglous, 1998. Small and Decentralized Wastewater Management Systems. s. l. : Mc. Graw Hill. Weerasinghe, K. D. N. , R. U. K. Piyadasa & S. H. Ferrer, 2006. Natural water purification system for local community. SUSTAINABLE DEVELOPMENT OF WATER RESOURCES, WATER SUPPLY AND ENVIRONMENTAL SANITATION. Furthermore, the water passes through the permeable soil dams will naturally recharge the water. So, this natural purification system acts as an infiltration basin and purifies the water which enters the Kandy lake. ACKNOWLEDGEMENT This research study would not have been a success without the tremendous support received from the regional office of the irrigation department to collect the secondary data related to the Kandy lake and the surrounded irrigation system. Besides we’d like to thank the University of Peradeniya and the organizing committee of the EMM 2020 Conference for giving us the opportunity to present our research in the conference. Finally, I would like to thank all our friends and our families for their understanding and support.
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