Pilot and farm-scale microbial and chemical treatment of waste. Technical Report (CARD 023/06 VIE)

A range of strategies are needed to ensure flexible and effective treatment of waste from catfish ponds at a range of different types of operations and throughout the year. A diverse range of chemical, microbial and biochemical products may be suited for this purpose, including a number that are commercially available, but their efficacy has not been independently tested. The soil bacteria, Pseudomonas stutzeri, was isolated from catfish ponds and tested for its ability to reduce NH4-N loads in waste water. In laboratory tests at Cantho University promising denitrification activity was obtained but this could not be reliably reproduced in studies at Murdoch University or in tests at CLRRI. Commercially available preparations for waste water treatment were found to be variably effective, but the most promising materials assessed were the biological preparations from plant materials, Yucca extract and crushed Moringa oleifera seeds. Ozone treatment of the wastewater appears to have a limited role in oxygenation of the wastewater and reducing NH4-N. Aquatic plants with or without fish such as tilapia were promising options for improving water quality in settling ponds. Despite the diverse range of approaches examined no single technology was developed to a point where scale-up to field or operational scale was feasible.