నైరూప్య

Odour Control in Fresh Water Fish Farm using Living Cells of Chlorella vulgaris

ONIANWAH Fidelis Ifeanyichukwu

The menace of odour from fish farms culminated to this study. Previous research works done showed that the major odorous substances from fish farms are ammonia, carbon dioxide and volatile organic compounds all of which are toxic in aquaculture. These compounds are excreted by fish or are products of feed degradation in aquaculture resulting to aquarium pollution. This research is aimed at reducing the concentration of these substances using a microalga; Chlorella vulgaris. This alga was isolated from the pond wastewater using a BG medium described by Mark and Cane. To a fish tank of size 150 × 150 × 150 m3 containing 200 litres of pond water and 200 fish was added 250 mL of Chlorella vulgaris culture and allowed to stand for four hours (4 h). The pond water was made up to 500 litres and incubated for eight days. The control was subjected to the same conditions but without application of the isolate. The ammonia concentration was measured every two days starting from day zero. At the end of eight days incubation, ammonia and VOCs concentrations were reduced to 0.23 and 0.53 mg/L respectively compared to the untreated pond (control) of 23.5 and 1.94 mmg/L respectively. Besides, nitrate and total organic carbon reduction were observed at the end of eight days incubation (33.04 and 2.32 mg/L respectively as against control concentrations of 55.72 and 13.66 mg/L respectively). This is attributed to possible utilization as nitrogen and carbon sources for the growing alga. Oxygen generated during photosynthesis also facilitates the oxidation of ammonia to nitrite and nitrate thereby increasing the nitrate level. The study showed that chlorella which is a known live food in aquaculture can also be used to control aquarium odour as well as improve the quality of the pond water.