University of Twente Student Theses


Impact of shrimp pond wastewater on the estuaries and the issue of salinity intrusion in the Quang Tri Province

Krutwagen, M. (2007) Impact of shrimp pond wastewater on the estuaries and the issue of salinity intrusion in the Quang Tri Province.

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Abstract:Quang Tri Province is located in the central part of Vietnam. Quang Tri has very special geographic characteristics, with mountains in the west and a very flat east side. The east side has a coastal zone which has two main rivers, the Ben Hai river and the Thach Han river. These two rivers have many tributaries and finish in the South China Sea. The two estuaries of these rivers, Cua Tung and Cua Viet are very good sites for aquaculture to take place, because of the brackish environment. That’s the main reason that many shrimp farms are located near or at the estuaries. Shrimp production could be a very good economic resource for the Quang Tri Province, but the last couple of years problems are occurring at the shrimp farms concerning diseases. In 2006 at some farms up to 80% of the production of shrimps was lost. The main reason for the diseases to occur is that the farmers take in water directly from the river. The water quality of the rivers are often not suitable for shrimp farming. The water gets polluted by industries, agriculture and shrimp ponds themselves. Water is taken in at the beginning of each production period, but it is also taken in more frequently during production because of the high evaporation at that time, which effects the salinity rate of the water in the ponds. Salt water can only be taken in at high tides, but at high tides the polluted water that is discharged by farms at the end of a harvesting period tends to flow back upstream of the river. In this research a literature study is done about similar problems that occurred years ago in Thailand, Indonesia, Bangladesh and China. In these countries the problems have largely been solved. This information in combination with new research information about water quality problems, provided enough information about possible measures. The measures have been evaluated with the help of a Multi-Criteria Analysis. And as the best result the combination of better management, a fresh water reservoir and a reservoir with a culture in it seemed to be the most suitable. Though after the fieldtrip of November 2007, it became clear that because of the wide diversity of the structure of shrimp farming communities, a closed circuit biofilter seemed to be more useful for the smaller communities. Better management will include, better equipment for water quality measurement, simple tools to prevent external factors to affect the shrimp ponds, and policies by the government to be able to make a better structure for the shrimp farming in the province. In this research the problems and the possible impact of solutions would be modeled in the MIKE11 model, but unfortunately because of the delay of the fieldtrip in which a lot of important data was gathered, time didn’t allow me to use the model for this thesis already. So this should be done in the next project for this case. The recommendations are to make a complete quantitative analysis with more and specific data about the water quality around the shrimp ponds, to make a study about the quantitative impact of all the proposed measures, Simple measures should be applied immediately and step by step the Quang Tri province should work towards a stable economic environment for the brackish aquaculture, this will require a lot of effort from the government, but also from the farmers.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering BSc (56952)
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