THE ENVIRONMENTAL IMPACTS OF INTENSIVE SHRIMP FARMING IN TAM GIANG LAGOON: IMPORTANCE WASTEWATER TREATMENT SYSTEM

This paper investigated the effects of intensive shrimp farming on environment in Tam Giang lagoon and the potential strategies for sustainable management of water pollutant discharged into the lagoon. Shrimp farming has developed rapidly in recent years in the Tam Giang lagoon area in Thua Thien Hue province, Vietnam. Shrimp is the main species farmed, contributing to 65% of all aquaculture products and has brought significant economic benefits to the local community. Although shrimp farming generated quick initial income to the fishing community in the lagoon, the lack of proper planning and poor water management resulted in the discharge of large volumes of effluent into the lagoon system. Besides, farmers using nutrient rich commercial feed and keeping high stocking densities lead to eutrophication, caused mainly by uneaten feed and fish excretion. The increase of commercial feed, chemicals and medicines including advertised substances was used in shrimp farming systems with a aim to gain more income. There are additional impacts on the natural ecological system, such as species diversity, reduction in dissolved oxygen levels as well as an increase in toxic gases (NH 3 and H 2 S) and carbon pollution in the lagoon areas. The integrated wastewater treatment has also been suggested in this study. The system includes three stages (i) toxic gas removal and oxygen level enhancement by mechanical treatment; (ii) biodegradation of organic matter use local fish; and (iii) reuse nutrients to produce aquatic biomass using locally available molluscs and seaweed.