Improvement of water quality of outflows from ponds to waterways. Technical Report CARD Project VIE/06/023

V.P. Cao; R.W. Bell

In the Mekong Delta of Vietnam, water quality is critically important for human health and wellbeing as well as ecosystem function. Catfish farming in the Mekong Delta, which is mostly confined to the provinces of An Giang, Cantho, Dop Lap and Vinh Long, is considered to be a significant source of water pollution in those provinces. A survey of 240 catfish farmers in An Giang and Cantho provinces, and of Clarias fish farmers in Cantho Province confirmed that discharge of waste water and solid waste from these operations is directly to public water sources in canals and rivers in over 75 % of cases. Water consumers in the areas where catfish ponds are prevalent had a strong perception that catfish pond discharge was the major cause of degraded water quality. Water sampling at 2 points of discharge in An Giang over a 5-month period confirmed that discharge causes canal water to exceed discharge standards for COD, TSS and NH4. However, even background levels were generally above the levels set for household use in Vietnam. Two case studies showed that passing Clarias fishpond waste water or water laden with catfish waste through rice fields improved its quality substantially, by decreasing TSS, COD, BOD, N and P. Coupled with evidence that catfish and Clarias fish pond wastes can be an effective partial replacement of rice fertiliser requirements, these results indicate that recycling solid waste and waste water from fishponds could be promoted as an effective technology for improving quality of public water ways. The recent decline in density of active catfish ponds in the Mekong Delta, during to poor profitability, may be having a beneficial effect on water quality.

Improvement of water quality of outflows from ponds to waterways. Technical Report CARD Project VIE/06/023

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