"Tra fish" or catfish production has been on the rise in many provinces in the Mekong Delta, Vietnam, and has brought significant profits to commercial fish farmers. However, it has also caused considerable pollution to surface water sources in the areas where catfish culture has taken place as the waste generated from pond fish breeding has been dumped into outside surface water bodies without proper treatment. As a result, the organic matter content (measured by the Chemical Oxygen Demand (COD) parameter) in these bodies has increased substantially, exceeding the legal surface water quality standards in Vietnam and adversely affecting the water bodies as well as threatening the livelihood of the fish producers.

This study examined the environmental consequences arising from pond "Tra" fish breeding in the Mekong Delta and explored technically and economically feasible wastewater treatment options for bringing water pollution down to an acceptable level in accordance with Vietnamese environmental standards. The research results showed that the farmers’ practice of exchanging water between fishponds and outside water bodies was one of the main causes of surface water pollution in Tra fish-breeding areas. Water sample analysis results indicated that the COD concentration in Tra pond water was 34 mg/l, exceeding the limit of <10 mg/l according to Vietnam’s surface water quality standards (TCVN 5942-1995, Class A). The pollution load rate in terms of COD per kilogram of fish produced was 0.098. To cope with the pollution situation more effectively, some technical pollution control options were proposed, of which the trickling filter technology was found to be the most cost-effective. Some policy recommendations to address the environmental pollution caused by pond Tra fish production in the Mekong Delta are also given.